250r Jetting

[beak7707]

i just bought an 87 R with a K&N, ESR 5 pipe and silencer, .020 over piston, and rad vavle. I was wondering where the jetting should be set. I think they have a 152 main when stock, the owner told me he had a 170 in it now. I didnt know if this would be anywhere close or not. I believe the pilot is stock as is the needle. anyone who can help i would appreciate it.

[airheadedduner]

How does it run, whats the plug look like?? Unless we know that we can't help ya.

[AndrewRRR]

Also what carb is it? Stock 34mm PJ?

[beak7707]

Yes it is the stock carb. It doesnt have much low end, and on top end it acts like its running out of gas sometimes. i think the 170 main is just way to big. but i dont know if i should move the needle or change the pilot.

[airheadedduner]

There is a fine line between cutting out and missing. If it acts like its not gettting gas(cutting out) then it is lean. Does it faul plugs, what color is it?? You maybe able to stand to be a touch richer on the pilot and main. I would try moving the needle first being it don't cost you anything and is eaiser. Raising the clip leans it, lowering it richens it. Need to know plug color though.

[beak7707]

The plug looks pretty good, if anything its a little dark. Every now and then it will foul a plug. But i can easily get a few hours out of a plug.

[airheadedduner]

:confused: May be try one step leaner on the main. That sounds odd that it runs like that. It could be, and hope its not, that your carb has gone south. One the stock R carbs the needle seat starts to leak. It will always show rich on the plug. Mine did it to me. I was running a modded 295R on leaner then stock jetting at sea level and it was still showing rich and fauling plugs every few hours. A few hours on a plug is not very good. My buddies go whole seasons without needing to change one.

[beak7707]

I was thinking maybe the carb was junk too. Do you recommend any aftermarket carb? i might just buy s new one.

[AndrewRRR]

Originally posted by beak7707
I was thinking maybe the carb was junk too. Do you recommend any aftermarket carb? i might just buy s new one.

If you ride fast and/or plan to get the quad ported or go to a big bore later, i'd go with a 38mm Keihin PWK Air Stryker. You can pick them up at LRD for $220 including jets and needles for your application. If I were you I'd find out what the problem is first before throwing money at it. Do you know anybody with a carb you can try? Hopefully it is your carb and not ignition.
When you did a plug check did you make sure to put in a new plug, ride around for a few minutes, then do a wide open plug chop in 5th or 6th gear? What pilot jet does it have?

[airheadedduner]

When you did a plug check did you make sure to put in a new plug,
I have been told to use an old plug during a plug chop:confused:

The 38mm AS is a great carb to use. I went with the 35mm PWK for price reasons. It is about 30-40 bucks cheaper and preformed good but will never put out the power the 38 AS will.

If you leave the gas on for a while on the bike will it flood out or drip out the overflow??? Mine would fill the cylinder and bottom end after about 4-5 days:blah: It would also drip out the overflow.

[beak7707]

It still has stock pilot ans needle. It doesnt leak if i leave the fuel on. My friends used to do that and his ran pretty weak. So i have already checked that and it wont leak if its left on. Will the 38mm carb be too much for my mods? Just .020 over, esr pipe, rad vavles, and k&n.

[AndrewRRR]

Originally posted by airheadedduner
I have been told to use an old plug during a plug chop:confused:


I think you are supposed to use a new plug and ride around for a few minutes to get a little color on it, then do a chop. The old plug may already have lots of color built up on it that a lean motor would have to 'burn off' before you could really tell how lean it was.
If you are planning on porting the motor or getting a big bore or stroker I'd go with a 38mm A/S. They have a design that lets them flow like a smaller carb at lower rpms but still be able to feed a hungry engine at high rpms.
If you are planning on leaving it like it is, something a little smaller should work.

[beak7707]

i put a 158 main in the R last night and it runs much better. I dont think it's perfect yet but it was a huge improvement. I called CT and they told me any carb bigger than the stock carb would kill my stock motor. He said until i port and polish or go big bore the stock carb is best. ESR recommended the TMX carb i think its 36 mm.

[AndrewRRR]

Originally posted by beak7707
i put a 158 main in the R last night and it runs much better. I dont think it's perfect yet but it was a huge improvement. I called CT and they told me any carb bigger than the stock carb would kill my stock motor. He said until i port and polish or go big bore the stock carb is best. ESR recommended the TMX carb i think its 36 mm.

It is possible to over-carburate your engine. Back when my R was a 250 with stock porting I ran a 39mm (taper bored PJ) and it ran great. I'm sure a 34 would have given me a little more bottom but this setup ran good for me. If you are planning on getting ported I'd hold off on a carb or maybe go a little bigger than a 36.