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Discussion Starter #1
I have a 1987 Trail Boss 4x4 that has been driving me nuts for over a year. I'm pretty good at fixing things, bikes, boats, tractors, but I'm stumped on this one.
Maybe someone can point me in the right direction.
First, it's almost brand new. It was used very little, and stored in a garage for 25 years. The brakes were gummed up, mud wasp nests everywhere. So I took it all apart, cleaned everything, rebuilt the carb, changed the crank seals, fixed the brakes, put acid in the new unused battery, changed the gas, topped up the 2 stroke oil, and it started. And died. Repeat 1000 times. Well it seems like it.
It won't rev up cold at all, but idles without the air box if I partially block the carb intake. If I can get it hot enough, it will run at high rpms only. If I let off the throttle halfway, it dies and seems to flood. If I hold the throttle open all the way and crank it 10 seconds or so, it starts and runs unless I let off the throttle.The compression is 125-130. The choke on or off makes no difference.
I'd buy a new carb, but I'm not sure that's the problem .I've rebuilt lots of carbs, this one is dead simple. Oh, I've tried spraying wd-40 everywhere, makes no difference in rpm. Any ideas would be appreciated.
 

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trail boss

try cleaning the idle jet,its recessed so you may have missed it,its about a inch deep in the bottom on the carb once you take the cover off,takes a flat head to remove it,there 4 small holes on the side,clean those out with a piece of wire.
 

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Discussion Starter #3
Bingo!

It was the pilot jet! I missed cleaning it and it was blocked, especially the 4 holes. Thanks for the tip. If you have a service manual, it's page 7.123. Runs a little cold blooded still, but fine once warmed up. I'll try adjusting the pilot jet a little. I set it at 1 1/2 turns from closed.
 

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I see you got it fixed but another common problem for poor idling, especially on bikes that sat for a long time is bad crankshaft seals.
 
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