Good afternoon!
Firstly, let me appologise if this post is in the wrong section.
Here in the UK we have a Sportsman 4x4 ATV (quad bike) built in 1992. Been ok for a couple of years but now got some real issues when running.
Its a 2 stroke & only gets light use, that probably doesnt help. Starts from cold, no choke/strangler needed. Runs fairly well then looses all power in a couple of minutes & theres clouds of acrid grey smoke pouring out of the exhaust. At the same time, the expansion chamber gets real hot real quick. Am thinking blocked exhaust. Am i on the right path? Whats the best fix?
As a seperate issue, would like to check the carburettor settings. Anyone able to tell me what they are likely to be please.
Many thanks in advance,

Merv!

 

I suppose you're talking about the 93 Sportsman 350. Loosing power in a couple minutes,it could be loosing compression as it warms up. That I'd check first off.Simple adjustment on this carb as it just has an air screw and idle screw. 1.5-2 turns out normally on the air screw and adjust the idle screw to a slow even idle. Exhaust pipe getting too hot? Could be an air leak,lean jetting,oil pump frozen. Several things to check out,but like mentioned check compression first.If it's at least 120 psi or so,a leak down test may be needed.

 

Sound advice indeed! Will get on it first thing in the morning.
Are workshop manuals & Parts lists available for these?
Many thanks Old Polaris Tech.

 

The first Sportsman was the 93 350 if that is what you have.1993 Polaris Sportsman Service Manual PDF Download If not,find your model. Polaris ATV Service Manuals PDF Download Plus don't know if it's to where you can order parts from parts places like these from where you're located.http://www.partzilla.com/parts/searc...ATV/parts.html http://www.cyclepartswarehouse.com/o...aris_atv/parts

 

All rightee! Did the compression test, nothing.... Checked it was fitted correctly & tried again, nothing.... Thought maybe my tester was faulty so put my finger over the hole & hit the button, nothing.... Probably not enough wind out of the plug hole to blow a match out.... That will be the end of that then!

 

Yes sounds like time to tear the top end down,check for any up and down play on the rod. If the bottom ends feels ok,then time to measure the cylinder for the next over size piston and bore job that will clean the cylinder up.

 

Ideal!
That will keep me out of trouble for a day or two.

 

On replacement pistons Wiseco forged pistons are the best if you have access to them.A lot better than the cast pistons that didn't wear as well. ATV Forged Pistons & Performance Parts - Wiseco Piston Inc.

 

Hi all!
Back again after i managed to source the Wiseco Piston as recommended by Old Polaris Tech. Also got a load of Gaskets & we are cracking on with the rebuild. So far, cant see anything missing from being stood for a while.
Anyway, yet another dumb question from across the pond. The head gasket is as you know a pressed component. its got a little lug on the outside, anyone know which way that has to point? to the carb? to the exhaust? Maybe even the stars! It also has what looks like UP cut out in it. So am guessing that must read UP when it is in place. does this sound about right?.
Many thanks all!

 

Yes the "UP" marked side of the head gasket needs to be visible.