RX125 Tuning - Jetting

[Muzzab]

Any 2-smoke experts have any tips on Jetting a RX125.

The main jet my bucket came with did not appear to have a number on it.
I changed it to the one from my parts bike, which I assumed would be the standard size. To see if it made any difference. I don't think it did.
The one in it now is a 125. It starts and runs fine and gets up to about 130kmph on a good day, which I think is not too bad for nearly 30 year old bike with a 100kg rider. But am curious to know if a 125 jet is considered big or small. The bike hits its powerband at about 6000 rpm and pulls to about 8500 rpm.

If anyone has a selection of jets for a RX125 surplus to their requirements I'd be keen to get some to experiment with.

Cheers
Muzza

[all4A50s]

have you looked at adding an expansion chamber. I'm running an Rx125 engine and increased the power band so it kicks in just above 4 thou and tops out at 9 thou.

Have you looked art lifting the needle?

[Muzzab]

have you looked at adding an expansion chamber. I'm running an Rx125 engine and increased the power band so it kicks in just above 4 thou and tops out at 9 thou.

Have you looked art lifting the needle?

I should have said it has a chamber. The clip on the needle is one from the bottom, if I move it down and lift the needle what should I notice? I'd be pleased if I could get the power starting a bit sooner.
What size jet are you running?

[SHELRACING]

Two strokes are fussy at the best of times, depending on the carb, pipe you are running, petrol, the two stroke oil, mixture ratio... Blah blah. Taking my RX from Taumarunui to Auckland Requires a jetting change.

Idle mixture is adjusted by the AIR (not Idle) screw on the front or back of the carb

Mid range mixture is adjusted by moving the the needle up and down on the clip

The top end mixture, maybe the last quarter of the throttle is controlled by the main jet.

Set your mixtures in order Idle, Mid range, Main. Changing anything suggested previously may effect your jetting

125 is probably a good start for the main. Keep an eye on your plug it should be a brown colour for correct mixture. Careful not to run too lean (grey Plug)

I'd say you were doing very well to be getting 130kmh. That would be faster than you could ride on a kart track.....

Good luck

[Muzzab]

Two strokes are fussy at the best of times, depending on the carb, pipe you are running, petrol, the two stroke oil, mixture ratio... Blah blah. Taking my RX from Taumarunui to Auckland Requires a jetting change.

Idle mixture is adjusted by the AIR (not Idle) screw on the front or back of the carb

Mid range mixture is adjusted by moving the the needle up and down on the clip

The top end mixture, maybe the last quarter of the throttle is controlled by the main jet.

Set your mixtures in order Idle, Mid range, Main. Changing anything suggested previously may effect your jetting

125 is probably a good start for the main. Keep an eye on your plug it should be a brown colour for correct mixture. Careful not to run too lean (grey Plug)

I'd say you were doing very well to be getting 130kmh. That would be faster than you could ride on a kart track.....

Good luck

Thanks for that, The bike starts and idles fine, so I will adjust the needle to see what happens in the mid range. I'm not entirely sure how accurate the speedo is, most of my racing has been this year over at Ruapuna and a few days at the local Kart Track. The bike is to high geared for the Kart track and gets to 80-90kmph by the end of the straight and just into 4th gear.

[Undertow]

Sounds like your RX is doing pretty well, I'm only 70kg and mine occassionally hits 135km/h.

Sorry, if I hijack the thread but does anyone happen to have a full exhaust for an RX?

[F5 Dave]

ok I'm going to piss all over this. No one on earth will be able to tell you what jets to run in your modified bike. There is no shortcut. You have to experiment.

ok 2nd; write this down & refer to everytime you think of 2 stroke carb tuning;

-The jets are in relation to throttle position.

Do not use phrases like 'midrange' that implies revs. These are not CV carbs.

Full open is where you run the bike on a long track & mainjet will be how you experiment using jets from same manufacturer (ie genuine mikuni or Keihin jets have logos on them). One step at a time. Then once that is set (at least on the day) consider how the bike works on less than open throttle.

[Muzzab]

ok I'm going to piss all over this. No one on earth will be able to tell you what jets to run in your modified bike. There is no shortcut. You have to experiment.

ok 2nd; write this down & refer to everytime you think of 2 stroke carb tuning;

-The jets are in relation to throttle position.

Do not use phrases like 'midrange' that implies revs. These are not CV carbs.

Full open is where you run the bike on a long track & mainjet will be how you experiment using jets from same manufacturer (ie genuine mikuni or Keihin jets have logos on them). One step at a time. Then once that is set (at least on the day) consider how the bike works on less than open throttle.

Thanks for that, This is kind of where I started, what range of jets should I buy? I'm assuming I'd only want to go bigger, but wanted to get an idea of whether the 125 was nearing the maximum practicle size. Any suggestions?
130? 140? 150? Cheers Muzza

[Muzzab]

Sounds like your RX is doing pretty well, I'm only 70kg and mine occassionally hits 135km/h.

Sorry, if I hijack the thread but does anyone happen to have a full exhaust for an RX?

Are you after a standard one? or a chamber? I have a standard RX125 chrome
exhaust and a rusty header. I do not know if the exhaust is any good as the bike it is off was seized when I brought it. It would cost more to freight to Auckland from here than what it is worth.

Cheers
Muzza

[SHELRACING]

You're quite correct Dave and i didn't quite word my response correctly. I would conceed you and a few others on this site are more experienced than me. No need to be rude tho.

I have seen standard RX's running on a 120 jet so suggested a 125 a good place to start if the bike appeared to be running ok which it does. As I suggested there are many cosiderations to two stroke jetting. My RX is actuall running on quite a bit higher jetting than 125, and it took me quite a while and a bit of Help from TZ350 to get things right

What I meant by my poorly worded response was throttle position.
Idle screw = stop to 1/8-1/4 throttle position
Needle = 1/4 to 3/4 throttle position
Main jet - 3/4 - full throttle position

Please correct me if I am wrong, You should check your mixture at each of these throttle positions, I used this is the method to solve several mixture related problems on my RX.

One thing I am sure of is to regularly check the Plug. Especially if you change anything, even your 2 stroke oil.

[Muzzab]

So...quite a bit higher jetting than 125 means ????? This is the bit of info I'm after. The plan was to push it out till it went overly rich and then step it back.
I just wanted to get an idea of what would be a large jet for a Rx125.

[bucketracer]

.

Some pictures that might help explain things.

.

[SHELRACING]

So...quite a bit higher jetting than 125 means ????? This is the bit of info I'm after. The plan was to push it out till it went overly rich and then step it back.
I just wanted to get an idea of what would be a large jet for a Rx125.

Well as F5 commented I couldn't presume to tell you the correct jet for your bike. the jet sizes in my bike would not work in yours because of the various modifications in my bike. You have to experiment. I had my bike running. To a similar point to yours then brought 3 jet sizes either side of that and experimented from there.

Remember the main jet is affected by approx the last quarter of throttle movement. So that's the throttle position to run the bike and check the mixture.

[Buckets4Me]

So...quite a bit higher jetting than 125 means ????? This is the bit of info I'm after. The plan was to push it out till it went overly rich and then step it back.
I just wanted to get an idea of what would be a large jet for a Rx125.

haha just to throw a spanner in the works :jerry:

and I know the gp's are a different beast :bleh:

but you MAY need to go down in jets just as much as you may need to go up :jerry:

TZ's bike ran better and 20% more HP after droping a few jet sizes (and advancing the ignition) about a 110 main I think and 20 hp :bleh:

if you run to rich you controll detonation better but loose power
the leaner you run the closer to the right fuel ration and more HP (unless you run to lean then you start to loose HP again water cooled engines are easier to get closer. Better cooling)

BUT and a big BUT the hotter the engine runs and the more chance of detonation

saying all that the standard gp125 engine starts with a main jet around 85-90 ?? and your rx had a 120 in it

good luck and dont blow the engine up :jerry:

so to answer you question it's big compared to my gp125 and small compared to shelracing ?

[all4A50s]

After talking this over with a couple of people, the main question I got asked was why are you starting with the jetting so start off with? The could see the attraction (of trying to simply get more in to the combustion chamber), but felt that an expansion chamber would make a much bigger and immediate improvement than changing the jets. I noticed a couple of good deals on TM for suitable donors using 1/2 a 250 2-stroke exhaust.

The next questions was has he cleaned up his ports to warrant changing the jets? As it is worth spending sometime with a demel type tool and simply cleaning up the casting first, trying it out with the needle set at different levels. Or in other words taking one step at a time, and saving your money for later when you have identified where to best to go next.

If its any help this is the process i am following with my bucket (an RX125 engine in a RG50 rolling chassis).

Identified engine and frame I wanted/could afford/had access to

The fun of fitting something into something that shouldn't, including riding position, fairing, etc

Sorted out suitable exhaust expansion chamber

Worked out gearing (sprocket size(s)) suitable for where I am racing.

Sorted out tyres i am happy with/have access to.

Got the bike to run reliable

Had fun with some paint.

and am now working on porting, needle height, etc

and then if I need to jetting.

[Muzzab]

After talking this over with a couple of people, the main question I got asked was why are you starting with the jetting so start off with? The could see the attraction (of trying to simply get more in to the combustion chamber), but felt that an expansion chamber would make a much bigger and immediate improvement than changing the jets. I noticed a couple of good deals on TM for suitable donors using 1/2 a 250 2-stroke exhaust.

The next questions was has he cleaned up his ports to warrant changing the jets? As it is worth spending sometime with a demel type tool and simply cleaning up the casting first, trying it out with the needle set at different levels. Or in other words taking one step at a time, and saving your money for later when you have identified where to best to go next.

If its any help this is the process i am following with my bucket (an RX125 engine in a RG50 rolling chassis).

Identified engine and frame I wanted/could afford/had access to

The fun of fitting something into something that shouldn't, including riding position, fairing, etc

Sorted out suitable exhaust expansion chamber

Worked out gearing (sprocket size(s)) suitable for where I am racing.

Sorted out tyres i am happy with/have access to.

Got the bike to run reliable

Had fun with some paint.

and am now working on porting, needle height, etc

and then if I need to jetting.


Good points made....But who said I was starting with jetting? the bike has a chamber on it, the gearing seems right , it is reliable, it has a custom paint job, I don't want to pull it apart just yet to look at ports (but this will happen), so having an experiment with the jetting was where I was at. I have no idea if the 125 jet in it is right for it (it could be perfect). But rather than buy jets I don't need, I was looking for a hint as to whether a 125 was at the large end of things. But understand that bikes are all different, so will start with a couple of bigger jets and see what happens.

Cheers
Muzza

[gav]

well, its not a million miles away is it, runs pretty good already. Only way to tell would be to change up one size and try, plug chop would be good too.

[Muzzab]

well, its not a million miles away is it, runs pretty good already. Only way to tell would be to change up one size and try, plug chop would be good too.

Cheers Gav, I'm sure you're right, half the fun is having a tinker. Got the kill switch wired in yesterday, so all set for the Greymouth Street Races now.

Muzza

[SHELRACING]

Yep I agree with B4me and all4a50s.

The jetting is probably the last thing to pay attention to. Be happy with the rest of the setup, Carb, Air filter ( or not) Chamber, porting, ignition etc etc.

Beware tho incorrect ignition timing can cause severe engine damage, so can incorrect mixture better to start slightly rich rather than lean.

[F5 Dave]

Arrgh, now I agree with no one.:mad: [edit except Gav. . . mostly]

I'm not trying to be rude, but please people, stop spouting potentially damaging 'advice'.

You should check the jetting (& ignition timing) whenever you make a significant change.

People are taking off airboxes & putting on chambers & not even considering that the jets will need optimising for the new required fuel rate.

People on Gokart tracks are protected a bit as unlike Ruapuna you aren't full open for ages down the backstraight. But if you are jetted lean it will seize solid. Some engines are tetchy, some are more resilient, but lean enough will ruin an engine.

Ok my two bits of advice;
first check that can be done in the pits (esp with carb swaps) is take the mainjet out & start the bike. The bike should die when full throttle applied. If it revs & revs on wide then the needle is restricting flow upstream of the mainjet. Not common, but not unheard of.

2nd is that I have built two engines running the same carb ignition & pipe & ran a 240 main in one & got down to a 130 in the other. Same engine but one modified with a different inlet style. Made a heck of a difference. Another chap ran a similar inlet & was using 280s.
Sometimes you will need to go down & sometimes up. Bigger is not the only way because you 'need more fuel'. That is ignoring the requirements of the engine.

[Muzzab]

Arrgh, now I agree with no one.:mad: [edit except Gav. . . mostly]

I'm not trying to be rude, but please people, stop spouting potentially damaging 'advice'.

You should check the jetting (& ignition timing) whenever you make a significant change.

People are taking off airboxes & putting on chambers & not even considering that the jets will need optimising for the new required fuel rate.

People on Gokart tracks are protected a bit as unlike Ruapuna you aren't full open for ages down the backstraight. But if you are jetted lean it will seize solid. Some engines are tetchy, some are more resilient, but lean enough will ruin an engine.

Ok my two bits of advice;
first check that can be done in the pits (esp with carb swaps) is take the mainjet out & start the bike. The bike should die when full throttle applied. If it revs & revs on wide then the needle is restricting flow upstream of the mainjet. Not common, but not unheard of.

2nd is that I have built two engines running the same carb ignition & pipe & ran a 240 main in one & got down to a 130 in the other. Same engine but one modified with a different inlet style. Made a heck of a difference. Another chap ran a similar inlet & was using 280s.
Sometimes you will need to go down & sometimes up. Bigger is not the only way because you 'need more fuel'. That is ignoring the requirements of the engine.

Thanks again....you have answered my question, that a 125 main jet is not large in the scope of things. I want to make the bike run rich rather than lean for the reasons you mention. I'm new to this and want to learn what I should notice by changing jets etc, hopefully one day I'll go out on the practice laps and come back in knowing that for "todays" conditions I need to go up or down a jet size, Cheers Muzza

[Buckets4Me]

just a quick note :yawn:

had my 2 bikes a JC on sunday for a dyno run and tune
fist bike th gp125 didn't need much of anything
started with the timing and found we had it spot on
then the jetting and had to drop it 1 jet size (had raised it years ago as I thought it was leaning out at pukekohe)

then got on to the 50
I new it was lean and the timing was out
so started by retarding the timing and it lost power
advanced it and it gaind power so keeped going till it stoped getting more power and started to drop off again :2thumbsup

then tried the jetting and found that what was wonce way lean was the best you could get not to lean and not to rich (for the room temp etc)

so now it's back to the track to see how it goes

and as another side note jetting sizes are 97.5 for the gp125
and about 107.5 for the 50

jetting and timing is where you should start and finish and go backto everytime you change anything

dont be cheap

[F5 Dave]

. . . jetting and timing is where you should start and finish and go backto everytime you change anything . . .

Now there is something I can agree with!!

[all4A50s]

Arrgh, now I agree with no one.:mad: [edit except Gav. . . mostly]

I'm not trying to be rude, but please people, stop spouting potentially damaging 'advice'.

You should check the jetting (& ignition timing) whenever you make a significant change.

People are taking off airboxes & putting on chambers & not even considering that the jets will need optimising for the new required fuel rate.

People on Gokart tracks are protected a bit as unlike Ruapuna you aren't full open for ages down the backstraight. But if are jetted lean it will seize solid. Some engines are tetchy, some are more resilient, but lean enough will ruin an engine.

you Ok my two bits of advice;
first check that can be done in the pits (esp with carb swaps) is take the mainjet out & start the bike. The bike should die when full throttle applied. If it revs & revs on wide then the needle is restricting flow upstream of the mainjet. Not common, but not unheard of.

2nd is that I have built two engines running the same carb ignition & pipe & ran a 240 main in one & got down to a 130 in the other. Same engine but one modified with a different inlet style. Made a heck of a difference. Another chap ran a similar inlet & was using 280s.
Sometimes you will need to go down & sometimes up. Bigger is not the only way because you 'need more fuel'. That is ignoring the requirements of the engine.

I was taught to do one thing at a time and changing the jetting should be done last. Identifying what the engine is actually doing (i,e flat spot at 1/2 of full throttle) first, then change the jets to try and rectify to what you want. I always try to remember that the companies have made/designed the beasts have already spend a considerable amount of money in development.

[Muzzab]

I was taught to do one thing at a time and changing the jetting should be done last. Identifying what the engine is actually doing (i,e flat spot at 1/2 of full throttle) first, then change the jets to try and rectify to what you want. I always try to remember that the companies have made/designed the beasts have already spend a considerable amount of money in development.


Fair enough, I'm still wanting to learn that if the bike goes 10kmph an hour faster one day over another and the only thing that has changed is the weather, then I can consider going up or down a jet size to tune it for that days conditions. Cheers Muzza

[Buckets4Me]

I was taught to do one thing at a time and changing the jetting should be done last. Identifying what the engine is actually doing (i,e flat spot at 1/2 of full throttle) first, then change the jets to try and rectify to what you want. I always try to remember that the companies have made/designed the beasts have already spend a considerable amount of money in development.

I was taught that you change one thing then jet it to suit

if you change how much petrol it uses you had better be ready to change how much petrol it gets

ie put a pipe on it that makes more power at xyz revs then it had better have more petrol as well or you go lean (BANG) and you are starting again

I always try to remember that the companies have made/designed the beasts have already spend a considerable amount of money in development.
and thewy should be right as rain till you change something :crazy:
\then you need to makesure it's all still right ie jet it for the pipe
jet it for the carb
jet it for the weather
the more power you make the more it HAS to be RIGHT !!!
you jet it everytime you change anything so that you get the best out of that change

there is no point in putting on a better chamber if you are going to flood the bike with gass
or a bigger carb and stave it of petrol


and if you leave it till last then you end up like me with an engine you dont know where to start from and is only make half what it could (and runs like a dog)

[AndrewStroud]

Fair enough, I'm still wanting to learn that if the bike goes 10kmph an hour faster one day over another and the only thing that has changed is the weather, then I can consider going up or down a jet size to tune it for that days conditions. Cheers Muzza

Interesting, I just Googled tuning an RX 125 and this thread came up :-) On Thursday my son rode a bucket at Mt Wellington with a RX 125 standard motor and std exhaust but had a K&N filter. I rode it and it didn't run that well. It went flat with the throttle wide open but went better when I backed off the throttle a bit. This usually indicates it's lean. It was pretty flat mide range as well so I lifted the needle max by dropping 2 clips and put in a 135 main jet and it went heaps better. AS

[gav]

Really Andrew, an FXR150 is what your boy needs, then you could race it down here in the MotoFXR class! A Brother Suzuki FXR150, done in black and white, awesome!

[Muzzab]

Interesting, I just Googled tuning an RX 125 and this thread came up :-) On Thursday my son rode a bucket at Mt Wellington with a RX 125 standard motor and std exhaust but had a K&N filter. I rode it and it didn't run that well. It went flat with the throttle wide open but went better when I backed off the throttle a bit. This usually indicates it's lean. It was pretty flat mide range as well so I lifted the needle max by dropping 2 clips and put in a 135 main jet and it went heaps better. AS

Good stuff, just out of curiosity what size jet was in it to start with? I was happy with how my RX went today, I think it likes warm sunny days.
Cheers Muzza

[AndrewStroud]

Good stuff, just out of curiosity what size jet was in it to start with? I was happy with how my RX went today, I think it likes warm sunny days.
Cheers Muzza

It started with a 125 which I assume is standard. I suppose it was lean from having a k&n and also through the oil pump being disconnected. Apparently when u run oil with the gas the jets get a fine coating of oil so need to be a fraction bigger. I modified an RD 400F when I was about 16yrs. I spent some time at school reading Graham A Bell's book on tuning 2 strokes, then got right into it with some porting, plainned the head, designed and made chambers. So it's testing the memory a bit but I think I'd quite enjoy getting some more power out of an RX motor. Might look at the squish next as that makes a fair difference. I'd expect u could take off 0.7mm or so. I don't mind the standard pipe at this stage because it's quite.

[AndrewStroud]

Really Andrew, an FXR150 is what your boy needs, then you could race it down here in the MotoFXR class! A Brother Suzuki FXR150, done in black and white, awesome!

Yea an FXR would be good too. With at least 4 of the 7 kids wanting to race I need a bigger shed and lots of bikes. They already do some mx and also race bmx and now looking at buckets.......... It' like starting all over again :(

[koba]

It started with a 125 which I assume is standard. I suppose it was lean from having a k&n and also through the oil pump being disconnected. Apparently when u run oil with the gas the jets get a fine coating of oil so need to be a fraction bigger. I modified an RD 400F when I was about 16yrs. I spent some time at school reading Graham A Bell's book on tuning 2 strokes, then got right into it with some porting, plainned the head, designed and made chambers. So it's testing the memory a bit but I think I'd quite enjoy getting some more power out of an RX motor. Might look at the squish next as that makes a fair difference. I'd expect u could take off 0.7mm or so. I don't mind the standard pipe at this stage because it's quite.

Be sure to check out the ESE thread (http://www.kiwibiker.co.nz/forums/showthread.php?t=86554)the links are great, it has much reference to all the good books too.

[AndrewStroud]

Be sure to check out the ESE thread (http://www.kiwibiker.co.nz/forums/showthread.php?t=86554)the links are great, it has much reference to all the good books too.

Thanks for that.
Man there's plenty of reading to do there. Good stuff though, I'll have another look later. zzzzzz

[Muzzab]

Interesting, I just Googled tuning an RX 125 and this thread came up :-) On Thursday my son rode a bucket at Mt Wellington with a RX 125 standard motor and std exhaust but had a K&N filter. I rode it and it didn't run that well. It went flat with the throttle wide open but went better when I backed off the throttle a bit. This usually indicates it's lean. It was pretty flat mide range as well so I lifted the needle max by dropping 2 clips and put in a 135 main jet and it went heaps better. AS

Brought a 130, 135 and a 140 jet this week. Today I fitted the 135 and dropped the clip on the needle. Can't wait to give real a test. But just giving it a bit of throttle stationary, it seems to rev up much quicker from idle.

Cheers
Muzza

[bucketracer]

Thanks for that.
Man there's plenty of reading to do there. Good stuff though, I'll have another look later. zzzzzz

The links on the ESE thread are re posted in two collections one page 80 the next page 90 and if you use the thread tools tab at the top of the page you can view all the pictures in the thread (13 pages) then click the post key on any picture to read the post that goes with it.

.

[Muzzab]

Here's some pic's of Tickled Pink,

http://www.kiwibiker.co.nz/forums/album.php?albumid=2799&pictureid=32947

http://www.kiwibiker.co.nz/forums/album.php?albumid=2799&pictureid=32948
http://www.kiwibiker.co.nz/forums/album.php?albumid=2799&pictureid=32949
http://www.kiwibiker.co.nz/forums/album.php?albumid=2799&pictureid=32950
http://www.kiwibiker.co.nz/forums/album.php?albumid=2799&pictureid=32951

[AndrewStroud]

Brought a 130, 135 and a 140 jet this week. Today I fitted the 135 and dropped the clip on the needle. Can't wait to give real a test. But just giving it a bit of throttle stationary, it seems to rev up much quicker from idle.

Cheers
Muzza
Let me know how it goes. I suppose we need a straight a little longer than what's at the go cart track to do a reasonable plug chop. Better be my next little exercise as I ended up getting a bit keen last week ( 4 this time of the yr anyway as I should be sorting Superbike instead). I took off cylinder & Steve Bridge took off 0.7 and gave me a bit of solder to check squish. I filed out the exh port some - until I got bored with it (now 26.5 mm from top of cyl and 39mm wide. Checked squish and was still 1.3mm so left out head gasket and Yamabonded it. now 0.8mm squish. Definately more power now though doesn't rev out still with std pipe. Sure it'll be fine for the kids anyway - for now :-)

[Muzzab]

Let me know how it goes. I suppose we need a straight a little longer than what's at the go cart track to do a reasonable plug chop. Better be my next little exercise as I ended up getting a bit keen last week ( 4 this time of the yr anyway as I should be sorting Superbike instead). I took off cylinder & Steve Bridge took off 0.7 and gave me a bit of solder to check squish. I filed out the exh port some - until I got bored with it (now 26.5 mm from top of cyl and 39mm wide. Checked squish and was still 1.3mm so left out head gasket and Yamabonded it. now 0.8mm squish. Definately more power now though doesn't rev out still with std pipe. Sure it'll be fine for the kids anyway - for now :-)

We're going in the Greymouth Street Races this weekend, so will find out if it makes a difference. After this I probably won't be racing for a bit so intend having a look at the ports, I don't know if anything has been done to them previously. I found out recently one of the guys I work with is a bit of an old hand with two strokes and he mentioned "squish". So may get him to show me how to measure it and take it from there.
Cheers Muzza

[F5 Dave]

Yes, very useful for making Orange juice & fitting record amounts of oiled volleyball team members into a mini.:whistle:

Seek you Graham Bells's two stroke tuning book & read it. Do a search, there are links on this site, but ultimately go buy the book, you will reference it again & again. + feel good that you are helping in his retirement.


ohh look the search got easier still with free delivery even.

Best $55 you will spend on your bucket (http://www.fishpond.co.nz/Books/Nonfiction/Transport/Automotive/Repair_Maintenance/9781859606193/?cf=3)

[Muzzab]

Yes, very useful for making Orange juice & fitting record amounts of oiled volleyball team members into a mini.:whistle:

Seek you Graham Bells's two stroke tuning book & read it. Do a search, there are links on this site, but ultimately go buy the book, you will reference it again & again. + feel good that you are helping in his retirement.


ohh look the search got easier still with free delivery even.

Best $55 you will spend on your bucket (http://www.fishpond.co.nz/Books/Nonfiction/Transport/Automotive/Repair_Maintenance/9781859606193/?cf=3)

Funny you should post this, last night while searching squish came across
Graham Bells book on the net (I find this funny as well, my brothers name is Graeme Bell), had a good read about squish. But plenty more to have a look at. I have not had the top off my motor so may find it had already been tinkered with, time will tell. Cheers Muzza

[Muzzab]

Bike got a good testing on Sunday in the Greymouth Street Races. The jetting and needle adjustments seemed to give give the bike more pull from lower revs. It seemed to get off the line better and rev out a bit more. The bike is too high geared for the street circuit though. Will have to get a couple of smaller front sprokets to experiment with. Had a great time, wish I had discovered bucket racing 20 years and fifty pounds earlier.
Cheers Muzza

[Anmic]

Hi Muzza,

Ive just picked one of these little things up to set up as a racer over in Australia. Ive been hunting for onfo on an expansion chamber. What did you end up using for yours?

Cheers,

Anmic

[Muzzab]

Hi Muzza,

Ive just picked one of these little things up to set up as a racer over in Australia. Ive been hunting for onfo on an expansion chamber. What did you end up using for yours?

Cheers,

Anmic


Hi,

This thread is going back a bit, haven't had the RX125 for a while, brought a FXR150 motor and bolted it into
a RGV250 rolling chassis and been playing around with that for a fair while now.

I don't know the origin of the chamber on it, but people had suggested using ones from the likes of RM125 motocross bikes (made to fit of course).

Have fun.

Cheers
Muzza

[TZ350]

First pic is of the RG250 pipe, second pic is the cut-out front section we found we could use as it was very close to the RM specs.

Third pic is the RG/RM spec pipe, fourth pic shows where we cut the flange end off and turned it down in the lathe to fit the GP cylinder. Cutting it here made it easy to re-align the pipe to fit onto the GP.

Last pics are a comparison between the original RG pipe and the RM spec one. Thomas made the RM spec one in the original heavy gauge metal to better withstand the argy bargy of Bucket racing at Mt Wellington.


You will have to follow the link back to the original post to see the pictures.

A RG250 pipe works well and it can easily be modified to 80's RM125 spec found in Bells Book

We got 18 hp using the RG pipe then 22 with the pipe modified to RM spec.

[koba]

You will have to follow the link back to the original post to see the pictures.

A RG250 pipe works well and it can easily be modified to 80's RM125 spec found in Bells Book

We got 18 hp using the RG pipe then 22 with the pipe modified to RM spec.

22 is more than I've ever had... :o

[Anmic]

You will have to follow the link back to the original post to see the pictures.

A RG250 pipe works well and it can easily be modified to 80's RM125 spec found in Bells Book

We got 18 hp using the RG pipe then 22 with the pipe modified to RM spec.



Thanks heaps for the suggestions guys! I'll keep an eye out for an rm pipe then. Did anyone ever try something of a Aprilia RS125?

Cheers,

Anmic