I've got a 250r with fmf pipe, boysen reeds, k&n, and running a 12 tooth drive spocket. I've messed with the jetting and I've got it pretty close. The problems I'm having is that in 1st and 2nd gear the 3/4 to full throttle is sputtering like a rich main jet, but 3rd and up run great. The jet needle groove 2-4 seem about the same 5 makes it worse. Jump down on the idle jet it makes it worse. When I jump up on the idle jet it runs slightly worse.
ANY IDEAS??????????

 

I'm having the same problem, just got my 240ct blaster kit installed. It might be the slow jet giving the problem. It is effective from idle to 1/4 throttle. Maybe try going down on size on this.Good luck!!

 

I think I got my needle grooves mixed up as to which is lean and which is rich. I moved my clip up one groove to lean it out and it seemed to help out I might go to the top groove but I,m scared to lean it out to much.

 

I am having the same problem with my 250R. I've narrowed it down to the jet needle andtube. If that's not it, I'm just getting a new carb. If anyone has suggestions, please help.

 

They mentioned this in May dirtwheels. They say it is an airleak. You might want to get the mag. and flip through it. I couldn't find it again to post it.

 

Well thank heavens, I never thought I would get to the bottom of this peculiar behavior, never mind find a support group for it. Did you guys get yours running right? was it an air leak? on the carb?

I had put my stock pipe back on, tried messing with the jetting 3 times now, checked the reed valve, and was going to try some octane boost next because I had also gone to higher compression, but I was bewildered as to why it ran fine in the higher gears. The carb slide was pretty scratched up so I have also ordered a new one thinking it might magically cure it.

Thanks,
Rod 86 250R

 

You guys might want to check into new needles... something with more of a gradual taper to it. Or maybe a slightly longer needle.

 

Hey this is cool someone else has this problem !

Air leaks , I thought, that where the dangerous ones were like the crank seals and stuff that not good news hope that not it.

Under the honda forum (post---atv site) some one suggested looking at :
www.macdizzy.com

He had 250r microfiche downloaded on his site. (Plus a lot of other cool stuff) I got to looking at the carburetor picture under the 2nd part.
The needle set jet on a 87’ has two choices


a r1371n for a pj07a A
and a r1471n for a pj07a B
A 86’ shows a r1469n
A 88’ shows a r1471L
And a 89’ shows a r1474js

My 250r is a 87’ it kind of makes me wonder about that.
I’ll have to check to see what I’ve got. I hope its just a matter of messing with needles.
One of the motorcycle shops in town just got a dyno I'm strongly thinking of doing that when i get a chance.

 

Since the bike runs well after 3rd gear there are a few things to look for, one of which may be an air leak, but I doubt it. Since the engine is running worst when it is at the greatest load (when it needs torque to get going), the most likely answer to the problem would be low compression. Do a compression test before you mess with anything else. If that comes up okay, then check for an airleak.

Easy way to check for an airleak:
Start the bike and let it warm up (ride it a bit so it doesn't load up). Put the bike in neutral and blip the throttle. Allow the bike to return to an idle. If the idle isn't constant, that's a sure sign of an air leak.

If these come up negative, it may be the coil or cdi.

With the modifications you've mentioned, the MOST jetting you will have to do is go DOWN one position on the clip (raising the needle to a richer position) and two to four sizes larger on the mainjet. The stock pilot jet and airscrew will be correct. The correct position for the airscrew is 1 1/2 to 2 turns out, although some R's like a little more (as much as 3 turns out).

If the engine doesn't respond correctly to this jetting -- the problem isn't in the jetting, it's something else.

 

Does anyone have that May Dirtwheels where something to this nature was mentioned? I couldn't find it for sale in my town and now the June is on the stands. I'd really appreciate knowing what was in there, thanks.

Actually it runs better with load; in the higher gears with more resistance it runs fine, and if I accelerate hard through a lower gear it runs better but not good, where if its revving pretty fast already in a low gear and I nail it just sputters like its over revving but it isn't revving all that fast. I have 160 psi so I shouldn't need race gas but I run 96 octane, and tried some octane boost additive to no avail.

In 4th gear (and up) I can't get it to run badly at all, I can bog it and let it rev all the way out be it half throttle or full throttle, so I can't see it being related to carburation at all, and I don't see any air leaks on the carb boots (and it idles fine).

As for the ignition, I have kept it revving (and running badly) for longer than I should have a few times climbing hills when I had to use 3rd all the way up, so I think sooner or later it would catch and run properly but it doesn't, so I think its okay since it always works fine in 4th gear.

Bizarre.

This thing ran fine for 10 years, so it is likely something is worn out in the bottom end/tranny which mysteriously affects it.

Thanks,
Rod 86 250R