I have an 87 lt 250r and I have a problem. When I got the bike it ran like a champ, I seized ngine and had to bore out the cylinder and put a new top end in. Once I buttoned it up I started it and after an hour it had blown the cylinder gasket and was sucking air making the engine weind out when idling. So I took it apart to find out I had a crack in the sleeve. So I took the cylinder and had it re sleeved with a stock sleeve and had the bottom of the cylinder block laid so it was flat. I put it together and it still will not idle. It starts ok but then it slowly wiends out almost to the point where I have to shut it off because I'm afraid it will seize. I'm not sure if it's still sucking air or if it's the carb. Please help me out with some sugestions.

 

what you need to do,or have done is a leak down test to verify you have no other seals leaking,then go on to carb adjusting and jetting.

 

Its leak down test time just like Min said. It sounds like you are sucking air from somewhere.

 

pull mag cover side off and spray carb cleaner around seal behind mag wheel if doesnt bogg out, spray around carb boot . if doesnt bog out go do leak down test. 90 percent of time in my mishaps its been one of those 2 let us know.

 

Good call 1987 Lt250r,or you could use W-D40.if you have a leak the idol will change if you have one.

 

I'm sure it would have been caught, but make sure it's not cracked around either of the 2 base bolts around the reedcage area. With the 87's being thinner there they can crack. Just a thought, but personally I would think a bigger air leak.

 

Mine did that when running alky.