Help!!!!!!!!!!!!!!!!!!! running lean

[cr250brider]

I think its your crank seal on ignition side.

it didnt make difference wen i sprayed cleaner inside cover, or wen cover was off running, and its a new seal

 

[whenfoxforks-ruled]

Have you tried a bigger pilot?

 

[cr250brider]

Have you tried a bigger pilot?

thats my next step, i bought two of them, i just cant mess with it yet, i ended up in er for staph infection. trying to get over that.

 

[cr250brider]

ok, im outta hospital, i pulled carb again, cleaned again, backflushed all passages with carb cleaner and air pressure. I have installed a #60 pilot jet.

i ran engine, made it idle, sounds good. good throttle response, revs smoothly when moving the throttle all the way to wot.

so i checked the throttle at part throttle and same response as before. i start to crack throttle and just as i get to 1/8 of throttle, engine revs really high. i know this makes no sense. but heres an example of when this would be a problem. I am slow riding the woods trails and when i hold throttle at this point the bike would rev really high. and not even on part throttle. wat the heck.


i am about to put a completely rebuilt bike on the sale list.
i know i cant get all my money back but if i can get some ill be happy.

 

[ellandoh]

wow, well we can see youre frustrated, dont give in on the dirt just yet!!

if i was you i might try a new needle as my next step

 

[cr250brider]

wow, well we can see youre frustrated, dont give in on the dirt just yet!!

if i was you i might try a new needle as my next step

and what should i try?, what needle #? i heard of a 1368? but not sure. ,

this thing is crazy, it only revs like this at part throttle. its so crazy. thanks everyone for all their thoughts.

 

[ellandoh]

well i wouldnt know what # but i would go to FMF website they have jetting recommends for bikes with their products. the only reason i say this is because i hear needles and seats can wear over time and the throttle range it is having problems is in the pilot and needle circuit range. it is not sucking air somewhere else if you can crack it 1/2 to full throttle with no problems. so your carb is leaking air at little opening or starving it of fuel at little opening. 20$ worth of brass in the carb with new jets, needle and seat will eliminate the possibility it is starving for fuel.

 

[dirt bike dave]

Sounds like maybe the power valve is sticking open.

There is an inspection plug on the left side of the cylinder, which covers the end of the power valve shaft. When the power valve opens, the shaft rotates 90*. I think the power valve closed the notch in the shaft lines up with 'L' on the cylinder, and when it rotate opens the slot lines up with an 'H'.

Run the motor with the bike in neutral and the inspection plug open, and see if the power valve is opening and closing properly.

If the powervalve is stuck open, the bike could run horrible under load and seem to be jetted wrong at low rpm, but run fine at high rpm. Under no load and no throttle, it would probably rev high.

FWIW, on your CR250 when you put the cylinder back on you have to be very careful that the pin in the cases that operates the power valve lines up exactly right with a fork at the bottom right hand corner of the cylinder. If you mess up this step, the power valve will not operate properly.

 

[ellandoh]

^^^^ding ding ding. theres your winner. if it ran good before you took the jug off thats the ticket

 

[cr250brider]

^^^^ding ding ding. theres your winner. if it ran good before you took the jug off thats the ticket

well, i bought the bike and tore it apart, I cant say that it ran good before i took apart. I have removed the plug on the cyl while running and all is working fine. I did make sure the valve pin and fork lined up perfectly, and when engine off the mark is straight up and when engine running it moves very nicely and smoothly.

so this rules out power valve.
thanks

 

[whenfoxforks-ruled]

A 60 pilot is crazy big on a 250. If it works/helps though?

 

[cr250brider]

ok, i have tried 2 different pilots, a 58 and a 60 and this thing still is so unrideable. i took carb off and went thru and thru, and no restrictions. I took reed cage off and inspected.

this thing has boyesen pro reeds in it. the engine is completley stock including carb. only mods are pipes. would the reeds have anything to do with it running this way????? thanks, just searching for answers.

 

[1998RM250]

Hey man didn't get ro read the whole thread, but I'm having problems like this on my bike. Sketchy throttle response, it just randomly goes lean and revs. There has to be an air leak somewhere, it's drivin me crazy too man cuz its unrideable. I'm sure it would blow up in no time running so lean, and when i ask people around here for advice all they say is buy a new 4 stroke, yeah right!

 

[cr250brider]

Hey man didn't get ro read the whole thread, but I'm having problems like this on my bike. Sketchy throttle response, it just randomly goes lean and revs. There has to be an air leak somewhere, it's drivin me crazy too man cuz its unrideable. I'm sure it would blow up in no time running so lean, and when i ask people around here for advice all they say is buy a new 4 stroke, yeah right!

what carb are you running?

 

[1998RM250]

I believe it is a keihin pwk 38mm tps, this happened after i messed with the needle clip... I tore it apart multiple times and still no answer though, and my needle is only like a few months old.

 

[whenfoxforks-ruled]

Quit thread stealing RM! The 60 pilot is unaffected. And 1 thing about it, both you guys bikes sound like they are sucking air some where they are not supposed to be. If it was a worn or bad rebuild, it would be a rich issue. If it was a cooling leak you would have black plugs and lean /rich conditions. Find the leaks!

 

[cr250brider]

Quit thread stealing RM! The 60 pilot is unaffected. And 1 thing about it, both you guys bikes sound like they are sucking air some where they are not supposed to be. If it was a worn or bad rebuild, it would be a rich issue. If it was a cooling leak you would have black plugs and lean /rich conditions. Find the leaks!

well, thanks for the rude response, i appreciate your info, im not some rookie when rebuilding, and i hav checked everything for air leaks. i just got on here needing help with this OLD type of carb. its a stupid PJ power jet carb. I am changing to a newer pw carb. I will let you know that it runs fine next week. thanks though

 

[whenfoxforks-ruled]

The only remark remotely close to rude was directed at the rm guy? Strange. The carbs, I did the exact same thing. Except I was fighting a rich condition off bottom. Blubbery, and would clear out when held wfo for a few seconds. Putt around for a few seconds and it loads up again. Spooge and fouled plugs. A head leak compounded by a questionable liner installation. Jetting it was a joke, I could not find the sweet spot in the entire throttle range. I am gaining ground on it. If it was a new bike, it would be so much easier to jet, well almost always! Yours in my opinion should be an easier/cheaper fix, unless a major part is defective. The air stryker carb and fixing the head leak has made my bike ridable, with out fouling plugs. BUT, the jetting is still screwy, and off bottom still. OH YEAH, I have a v-force, pc pipe and silencer? Have fun and find the leaks. Vintage Bob

 

[RM_guy]

Hey, Vintage Bob guy, don't drag me into this...

 

[BSWIFT]

Hey, Vintage Bob guy, don't drag me into this...

I had to laugh at this one! :laugh:

In an earlier post, a worn needle and seat could be the cause of the eratic jetting. While an air leak is the obvious conclusion, this has repeatly been ruled out.
Is the float good, not the level but the float. If the float sticks up, you get your lean condition. I'm not sayin', I'm just sayin'.
In Spanky's Carb Jetting, a solid starting point is a must. If this problem is showing at the first part of the throttle opening, it's the pilot circuit. Until this circuit is clear, all other circuits are not worth working on. If you are certain there are no air leaks, the reeds are satisfactory, then you have got to have a float problem or a pluged oriface.

 

[dirt bike dave]

FWIW, I had a '99 CR250 with a carb and & ignition from a '97.

The jetting was 165 main, 55 pilot, 5.0 slide, R1370M needle in middle position, air screw 1 1/8 out. This worked great at 3,000 - 5,000'.

The bike was always very sensitive to air screw adjustments, with 1/8 to 1/4 turn making a noticeable difference in response and hit.

 

[cr250brider]

OK, I bought a 99 cr250 carb , brand new pwk 38mm keihin. I put it on and wow, this bike runs pretty good, very clean and smooth. we rode it for about 15minutes and bam, it happened again. it started to run stupid again. So I let it cool off and I changed the needle position from the 3rd down to the 4th down. I started it and It ran beautiful for about 15minutes and it started again. this thing runs beautiful and then it starts running like it is running out of fuel, real lean. I dont know what to do but sell. any one interested in my rebuilt 250?

 

[2strokerfun]

If it consistently does this only after it runs about 15 minutes, good when cools down until it heats up again, then I'm thinking it is a heat-related air leak. Could be case mating, base gasket, head, or something slightly of true so that it only shows up when engine is warm. I don't have an answer, just a theory... But I'd start with rechecking all torque on case screws, cylinder nuts, head bolts, and reed cage bolts.

 

[whenfoxforks-ruled]

Gas tank cap not venting, or the screen atop the petcock. Send me all your old carbs!

 

[2strokerfun]

Gas tank cap not venting, or the screen atop the petcock. Send me all your old carbs!

Yes, check, had a clogged vent tube do this once. Frustrating as heck to figure it out!