Cam timing FXR150

[kel]

so definitely need to go a bit leaner than 118.
The spark plug looked fine after doing a plug chop, and it feels close but it misses a little up top.Cheers

NO no no, 118 is run in standard motors, you need to go richer. Your best bet is to put it on a dyno with a gas analyzer (best move you can make when it comes to jetting) before the motor blows. The jets are standard Keihin hex jets available from most any bike shop. Seriously you will need to go richer

[richban]

NO no no, 118 is run in standard motors, you need to go richer. Your best bet is to put it on a dyno with a gas analyzer (best move you can make when it comes to jetting) before the motor blows. The jets are standard Keihin hex jets available from most any bike shop. Seriously you will need to go richer

You might be wrong there. This is a power jet carb. On my engine that has more compression and more flow than Hamish has. I run a 118 main. On the 30mm the power jet comes in very early might be worth disconnecting it and having a play. Just remember to go up to a big jet and work you way down. 135 maybe.

[kel]

You might be wrong there. This is a power jet carb.

I hadn't considered he might be running a power jet.
Is four stroke fueling compatible with power jets? Four strokes often use pumpers which is more or less the opposite to power jetting

[Henk]

If the PWK knock offs are a power valve job I'd be interested to hear what people are using to activate them. I have one of those OKO jobbies and the only thing I can think of with my limited knowledge of carbs is that somehow the air bleed I have blocked off is involvled, as for control I guess the answer will be "Get an ignitech"

[kel]

If the PWK knock offs are a power valve job I'd be interested to hear what people are using to activate them. I have one of those OKO jobbies and the only thing I can think of with my limited knowledge of carbs is that somehow the air bleed I have blocked off is involvled, as for control I guess the answer will be "Get an ignitech"

The air bleed on the outlet side is for balancing, the power jet is mounted in the top of the inlet and is activated by air flow. The knock offs we have dont have the power jet. Im lost to how they would work on a four stroke as the pumper richens the mix when you crack open the throttle, the power jet allows for lean main richen up on high revs via the power jet (very basic theory disclaimer)

[hmurphy]

Ok I will go to some bike shops and try get some more then. Yeah the bike has a lot more grunt through mid range but it misses up top and when I start going richer it just pops and splutters even more. The standard motor I was running a 120 instead of 118 because I wanted to run it as rich as possible and it ran fine on the 120.

So it sounds like I will definitely need to run it just a little bit leaner. The power jet must be doing a lot though. Is it really beneficial to disconnect it? I might try that and go for a test ride with a few richer jets.

Cheers.

[RDjase]

If the PWK knock offs are a power valve job I'd be interested to hear what people are using to activate them. I have one of those OKO jobbies and the only thing I can think of with my limited knowledge of carbs is that somehow the air bleed I have blocked off is involvled, as for control I guess the answer will be "Get an ignitech"

The power jet VM Mikunis I have on the RZ are just off air flow, The late TZ carbs have electronic power jet and are controled by the CDI.

I tried some power jets VM's on my LC and found it went better with standard VM carbs. If I had a dyno and heaps of time maybe you could set them up.

Some of the RZ power jet carbs have fixed/pressed in power jets in the float bowl and you can't do much with them. Blanking the pipes off and going bigger main is the best way

This has bugger all to do with a 4T engine but may help

[RDjase]

Ok I will go to some bike shops and try get some more then. Yeah the bike has a lot more grunt through mid range but it misses up top and when I start going richer it just pops and splutters even more. The standard motor I was running a 120 instead of 118 because I wanted to run it as rich as possible and it ran fine on the 120.

So it sounds like I will definitely need to run it just a little bit leaner. The power jet must be doing a lot though. Is it really beneficial to disconnect it? I might try that and go for a test ride with a few richer jets.

Cheers.

I tried a RVG (?) carb on my Sons FXR, seemed OK (ish) down low but when you gave it a big rev you could see the extra fuel pour out the power jet and it would run crap. Didnt do and more with that carb, as I got a 4 Stroke carb that worked heaps better. I think if the RGV had the power jet blanked off it could have worked OK with some more time and jetting

[Shorty_925]

If anyone has used a DRZ250 carb on an FXR i'd be interested to know what jets your running. Ive had not but trouble trying to find the right jets to be using, got a 135 main and 42.5 pilot and has a horrible part in the middle of the rev range. Ive been larger with both main and pilot and mixed and matched and found nothing that works as yet.

Revs out fine on the stand, but on the track its rubbish, coughs and farts, stab the clutch and clears it out.

[kel]

If anyone has used a DRZ250 carb on an FXR i'd be interested to know what jets your running.

What carb does a DRZ run? Im running Mikuni VM32SS pumper and a Keihin PWK knock off. The Mikuni needed the pumper action backed way off as it would cough when hammering the throttle open, it gives a hell of squirt of fuel but now it surges hard when opened. Mikuni mains between 165 and 190 depending on your state of tune

[hmurphy]

I have a Mikuni carb lying around too that I had tried with my stock motor. It also had a pumper on it which I hadn't got round to setting up but it didn't seem to need it much. The carb was pretty awesome and I was running a 165 main jet but getting the jets to test was gonna prove expensive and it was heavy and slightly too large (32mm).
I also struggled to get it to drive out of corners nicely because it seemed to make the ride rough. I was sliding like mad with it. Don't know how this new carb will be but I have been recommended it and so far it is very easy to change jets and work with. The stock carb was so easy to ride with haha, I was lucky to ever get it sliding a little with it.

[Shorty_925]

The carb is a Mikuni TM28 flat slide. Off the very bottom(like riding slowly out onto the track) it is perfect and with a slow build up of speed its fine, give it a handleful and then its coughs. Up very top it runs fine, but kinda anything inbetween its pretty average. The largest main jet ive got at the moment its 145 i think, I know I have a 140 and tried these and the bike ran worse than what it was running the 135 main. The clip on the needle is two off the bottom, and have been suggested to drop it down another. The state of tune is more or less standard, just a little grind for the manifold to match up.

The clutching it was the only way to ride around it and have some speed in the weekend. Will have to go order some larger mains and try them out. And the pilot, leave that as it is?

[F5 Dave]

You can't just compare jet sizes, every bike will be different, but more carbs will have different air correction jets so a 32mikuni will flow gas differently depending how it is set up.

[hmurphy]

Read this and look at the problems and solutions at the bottom...

http://www.4strokes.com/tech/4sjetting.asp

Read this if you want to understand more about how your carb works...

http://www.iwt.com.au/mikunicarb.htm

[kel]

You can't just compare jet sizes, every bike will be different.

Thats your fidley 2 stroke talking.
There are at least four of us running the same jetting on our works FXR's. If they could be any more similar in performance it would be sickening.