2001 CR125 jetting - continued

[morg_nz]

thought i'd resurrect this post following my first mx race at the weekend. Join the MOMCC club and went along to my first club day yesterday. Really enjoyed the racing - it was definately an eye opener. I already knew I wasn't very quick, but the track showed me just how slow I was. Even though I was racing mostly 450's in the novice class (vs my cr125), I thought I would have stood a bit of a chance given how tight the track was. But I got smoked, as I just couldnt find any power out of the corners. Now I know that 99% of that is probably down to my riding ability, but until I've got more practice i'll try and find some power in the bike (its a good workman that blames his tools ay? :-) )

So I think the bike is running quite rich (I got side tracked from my last efforts to sort this out while I fixed the clutch), as it has no power down low, and seems to be spitting quite a bit of black oil out the pipe (i'm running a deps fatty pipe with a FMF shorty on the back, and motul oil at 1:50). I've had the carb apart and this is what I found:


................ Currently in Bike .....................Factory Specs
Main...................350........................ ............................360
Pilot....................32.5..................... ..............................50
Needle Clip..........3rd from top.......................................3rd from top
Needle................6BEG21-68..........................................6BEG20-69

Any ideas on what I might need to do to get it running better - oh and im not interested/concerned in top speed, just looking for some speed/response down low.


Anywhoms, I really enjoyed the racing so will be doing as much as I can! Just trying to sus out a place to practice at the moment - just looking for a flat paddock that I can practice some drills in like cornering and starts etc.

[Rupe]

thought i'd resurrect this post following my first mx race at the weekend. Join the MOMCC club and went along to my first club day yesterday. Really enjoyed the racing - it was definately an eye opener. I already knew I wasn't very quick, but the track showed me just how slow I was. Even though I was racing mostly 450's in the novice class (vs my cr125), I thought I would have stood a bit of a chance given how tight the track was. But I got smoked, as I just couldnt find any power out of the corners. Now I know that 99% of that is probably down to my riding ability, but until I've got more practice i'll try and find some power in the bike (its a good workman that blames his tools ay? :-) )

So I think the bike is running quite rich (I got side tracked from my last efforts to sort this out while I fixed the clutch), as it has no power down low, and seems to be spitting quite a bit of black oil out the pipe (i'm running a deps fatty pipe with a FMF shorty on the back, and motul oil at 1:50). I've had the carb apart and this is what I found:


................ Currently in Bike .....................Factory Specs
Main...................350........................ ............................360
Pilot....................32.5..................... ..............................50
Needle Clip..........3rd from top.......................................3rd from top
Needle................6BEG21-68..........................................6BEG20-69

Any ideas on what I might need to do to get it running better - oh and im not interested/concerned in top speed, just looking for some speed/response down low.


Anywhoms, I really enjoyed the racing so will be doing as much as I can! Just trying to sus out a place to practice at the moment - just looking for a flat paddock that I can practice some drills in like cornering and starts etc.

Wouldn't run a 125cc mx bike at 50:1 myself. Don't forget your jetting mixture is air-fuel, not oil-fuel as most get confused and mess around with the pre-mix ratio...this won't help

[morg_nz]

oh not trying to fix jetting that way - its just its easier to do the maths for 50 to 1 in my head than 40 to 1 lol! maybe i should just write it on the bottle?

[noobi]

250ml of oil per 10L of fuel = 40:1

[CRF119]

OK if you want to make a CR125 really sing and you are planning on keeping it here is what ive done and do for all of my mates.

I tell them to buy a race Expansion chamber and matching rear pipe, most of the time there front pipe is dented and rusty any way. (not a shorty they are crap a 125 is ment to rev not have bottom end power) You should pick a up a FMF or Pro Ciruit for a round $600 for both.

V-Force 3 carbon reeds make a huge differance huge gains can be had from this even more then the pipe. (dont bother with boysen i dont find them as good)

Thats the easy part next is the hard part, On my bike i bored the carby out 2mm polished before the slide and left the other side matt finnish to help with fuel mixture. You can nearly double the size of the reed block intake also the rubber joiner between the carb and reed block can be made alot larger and alow to flow easier. If you are still after more you can have the engine reported and Electrosil plated in Aus.

After this it will need a full tune by sombody that can tune and not just guess. ( I tune 2 strokes for a job so i have done mine and about 4 others) this can take over a day to get perfect.

Always run 98, good 2 stroke oil and at least 40:1

When i sold my 02 CR125 to jump to my CRF450 the guy that brought it sold his near new 06 CRF250 to by it as it was faster.

Ill never forget beating 2 450s in a drag race and the guy said to me thats a fast CR250 lmao

Also by changing your Fuel ratio from 32:1 to say 40:1 the fuel is thinner because you have less oil in it so you will end up with a richer mixture so keep this the same all the time and dont change oil brands. Ive run to 45:1 but didnt notice much gain so went back to 40:1 for more cyclinder protection and bearing protection. You can run less oil in the bigger 2 strokes as they rev less.

[morg_nz]

I've got a DEPS fatty pipe (in mint condition) and FMF shorty silencer which were on the bike when i got it - I paid $2k for it so not really looking to replace them. I'm interested in reeds though - its crossed my mind, but after a quick serach of the net I cant seem to find anyone who sells them - online at least.

What sort of performance can i expect to gain from boring the carb? I take it boring it makes for greater air flow into the cylinder? What about just going for a 38mm carb?

I woudl like to get some more performance out of my bike but I am mindful of how much I want to spend on it. I bought the 2 stroke 125 to learn to ride (well) on, as I think its a bike that needs to be riden properly to go fast. This was made quite evident to me yesterday racing 4 stroke bikes. I will eventually move to a 4 stroke 250, but I want to be nailing the 125 first as I fear I will be too lazy on a 4 stroke otherwise.

OK if you want to make a CR125 really sing and you are planning on keeping it here is what ive done and do for all of my mates.

I tell them to buy a race Expansion chamber and matching rear pipe, most of the time there front pipe is dented and rusty any way. (not a shorty they are crap a 125 is ment to rev not have bottom end power) You should pick a up a FMF or Pro Ciruit for a round $600 for both.

V-Force 3 carbon reeds make a huge differance huge gains can be had from this even more then the pipe. (dont bother with boysen i dont find them as good)

Thats the easy part next is the hard part, On my bike i bored the carby out 2mm polished before the slide and left the other side matt finnish to help with fuel mixture. You can nearly double the size of the reed block intake also the rubber joiner between the carb and reed block can be made alot larger and alow to flow easier. If you are still after more you can have the engine reported and Electrosil plated in Aus.

After this it will need a full tune by sombody that can tune and not just guess. ( I tune 2 strokes for a job so i have done mine and about 4 others) this can take over a day to get perfect.

Always run 98, good 2 stroke oil and at least 40:1

When i sold my 02 CR125 to jump to my CRF450 the guy that brought it sold his near new 06 CRF250 to by it as it was faster.

Ill never forget beating 2 450s in a drag race and the guy said to me thats a fast CR250 lmao

Also by changing your Fuel ratio from 32:1 to say 40:1 the fuel is thinner because you have less oil in it so you will end up with a richer mixture so keep this the same all the time and dont change oil brands. Ive run to 45:1 but didnt notice much gain so went back to 40:1 for more cyclinder protection and bearing protection. You can run less oil in the bigger 2 strokes as they rev less.

[CRF119]

Boyds in hamilton can get you V-Force Reeds. They are dear between 300 and 400. The Reeds you have may be tired anyway so replacing the stock petals mite help a bit. V-Force reeds give better responce in bottom to mid range and a harder pull. The job of the reed is to open when piston goes up and close when it goes down to hold crank pressure if it dosent close fast enough you lose crank pressure so less air fuel mixture will end up in the combustion chamber so there for less power is made. Carbon petals respond faster and V-Force blocks are in a W configuration so you have 4 petals. Standard Reed blocks in CRs have a V reed configuration so only 2 larger slower responding petals there for less performance.

Im working on a 03 CR125 at the moment, We havnt done carby but we have done the rubber manifold and made the std reed block flow %100 more. Had some strange nylon block in this one. It has made a huge differance already and we are yet to get a FMF or Pro circuit system for it. He to tight to buy a reed block as its his first mx bike.

Ask you local store about No toil air filters and No Toil air filter oil to.

As for the carby the more flow the better but id try the other stuff before you do, that its a big job. If a newer model has a larger one and u can get it cheap do it. I dont think id go any biger then 3-4mm over std i only went 2mm

If i were you id inspected the reeds for any clearance issues, if they not closing they are stuffed. Also make sure your power valve is moving freely and is clean. While you are in there cheek how much restriction is in between the carb and the engine. If you havnt done ring/piston in the last 50 hours do that when u do the power valve makes it easier to clean and pull apart etc.