still laggy

[lt250racer]

i have an 85 lt250r and recently it has been laggy, worst when tring to move from a stop. Now, i have recently taken the top apart, the piston and rings look fine and last week i installed an whole new reed assembly, when i put it back togather I it ran alittle better but is still very laggy and dosent like to hit the powerband very well. any thoughts... ...please help.

[Banshee]

Sounds like your sucking air somewhere. Have you pressure tested the motor. If you haven't I would take it to a shop that can pressure test it and see what results you get.

[370banshee]

eyah you might have an air leak. does it run good when you grab the throttle with the clutch in?? usually vacuum leaks do that because they lean it out so much. if i were you i'd say don't ride it. that is unless you'd like a piston you can see through!

[Banshee]

Another way to test for an air leak is to spray WD-40 or Carb cleaner around the motor and carb if the motor revs up you have a leak and you should be able to find were by spraying around the rev up should be immediate

[370banshee]

man i knew i was forgettting to tell him something!!!! yeah jasons right try the carb cleaner thing. oh yeah it works on anything with an engine not just 2 strokes. i've diaged plenty of crappy carb base plate gaskets on small block chevys the same way

[lt250racer]

air leak huh? are you talking about the crank case vacume? Where would the most likely place for the leak be?, by the way it runs great at idle and idles fine, and when the clutch is in it will rev good as well, but as soon as i try to get it moving from a stop (or when a load is applied), it will just about stall.

[jwalkerblack]

Hello,
I think I am having the same type of problem as you and any assistance would be greatly appreciated!
I have an 87 Lt250R, it was a great running machine up till this year. I replaced the entire clutch assembly including arm and cable, kickstarter springs etc., and installed an fmf powercore silencer instead of the answer s-11 that was on it when I purchased it. The machine will start in one or two kicks, but will only stay running if you give it a little throttle. If you put it into gear, you have good acceleration in every gear until about half throttle then it bogs down and will stall if you don't let off or engage the clutch giving it some throttle to keep it running?
I have tried adjusting the carb's fuel/air ratio and idle control with no luck (replaced the float and float valve, because if you turn the gas to off it will run like it is supposed to until it runs out of gas)?
It has a 38 mm Keihin carb that was also on it when I purchased it, it has been cleaned, jets and everything appear to be good and I had no problems from this carb last year, the only power change has been the different aftermarket silencer.
So I have read how to go about checking for a vaccuum leak in this forum (thank you), is the carb boots and head area the only place that these can occur and does this sound like the problem?

[370banshee]

iwould try the carb cleaner thing on any top end gaskets. if you can't find it it's time for a leakdown test. if it's in teh bottom end i'd look at crank seals. they can suck air on the stator side or oil on the clutch side.

[jwalkerblack]

Hello,

I checked the head gasket, carb boots, and reed cage gaskets for a vaccuum leak with WD-40 like stated and got no increase in revs.
So how do you perform a leak down test, is this something that you need special tools for or does your dealer have to do it? What will the leak down test tell you?
I installed a new clutch and that is when this problem started, could something have gone wrong, especially during the radiator refill process where you have to tilt the machine to each side to get rid of air bubbles?
How about electrical components could it be a weak coil or something?
It starts second kick with no problems, but you have to keep giving it just a hint of throttle for it to stay running and then of course in gear it bogs down and wants to stall?
I appreciate all the help!!
Thanks,
Keith

[jwalkerblack]

I forgot to mention that when you turn the gas off in gear it runs like a raped ape like it is supposed to until the gas of course runs out?
I don't know if this helps or not, but just figured I had better say it since I had missed putting it in the first time?
I have another carb I am going to also try in the morning and see, it is a honda keihin 34 mm that I have not got the right set up for (still has the honda throttle assembly attached as that is how the carbs came on them), but if it makes any type of difference then I guess it might be the carb???
I will let you know how that goes giving you time to tell me about the leak down test when you get a chance.
Thanks Again