I have an 86 Trail boss 250, I have a problem with it not wanting to Idle.
I have rebuilt the Top End (new Piston, Rings and Honed Cylinder), Compression is very good but once it is running, It goes from a Hi Idle - (the Pilot Screw has almost no effect where it is adjusted) to stalling when We switch riders or just come to a stop.
I too was told to check for an air/ Vacuum leak thru the crankcase but am finding it hard to find ways to block off the Intake and Exhaust ports properly. Should I just take it to the Dealer and "Bend over" and close my eyes.
Thanks
Timmy from Connecticut

 

it does sound like you have an air leak if its high idling and then dropping off. some people use a can of staring fluid to spray around like the crank seal on the clutch or maybe the intake boot. (this spray is highly flammable so maybe use wd-40 or other) if the bike idles up while spraying then you have an air leak. check your intake boot for cracks as well to suck air in. just an idea for ya.

 

to block off the intake get a pcv cap that fits inside the rubber intake boot..tighten the clamp around it...

for the exhaust cut a piece of inner tube to act like a gasket and get a peice of 1/4" metal and drill the two holes for the studs..put the piece of tube between the cylinder and the 1/4" metal and tighten the nuts on the studs. then do a leakdown test.

 

Clean the carb very well and blow out with compressed air. Sounds like a dirty carb

 

if its idling high like mentioned it has an air leak somewhere.

 

Hi Guy's
Thanks for the Help, I have gone thru the Carb like 10 - 15 times, removed the Pilot Jet, complete disassemble, Set Float Level, Main Jet, Slider is seated all the way down, and reassemble of Carb.
Removed the Rubber Carb flange, I have a Spare engine (seized, Bad Piston) that I removed the Carb Flange, put a small amount of sealant and installed to the Intake side. My Exhaust flange and pipe are wet, I figured it was oil residue ?
I will have to remove the Pull starter and side cover to see if there's movement at the Crank.
I would assume the Crank Bearing's and seals are bad right now as it is a 1986.
How easy is it to change the Crank Bearings ? I have seen how the Seals could be pulled out using the "Sheet Metal Screw" trick but how are the bearings Removed ??
Should I just bring it to a Dealer at this point ?
Thanks again
Timmy from Connecticut

 

Well I did it, I Replaced Both Crank Shaft Seals and my 250 TrailBoss. It runs and Idles perfect. Starts right up and goes to Idle. I did it with the engine in the Frame.
I used the Clymer Repair Manual and Polaris TrailBoss Scrambler Magnum Clutch Puller tool I got off eBay ($ 58.00 Total), Had a Flywheel Puller, got 3 - 6mm x 3.5" bolts for that and used the old # 40 drill into the old Seals, screwed in a small sheet metal screw and pulled out the old ones.
I kind of took the long road around the real problem.
If you have worked the top end and it won't Idle - Change the Crank seals, Both of them.
Timmy from Connecticut