Jump to content
Sign in to follow this  

Polaris 2stroke dummy has some ?s

Recommended Posts

I need some help with a project of mine thats got me stumped. I bought a 92 trailboss that wasa pile of parts. I put a different bottom end on it that was supposedly good, put a new piston and rings in it and had it bored, cleaned carb, new gaskets and now it wont start. SURPRISE SURPRISE, why cant anything just work. It sputtered once or twice and has spark, but I think it doesnt have enough compression. where could i be losing it all? I took a spray jug with soapy water and sprayed around gaskets and seals but couldnt find a leak. it doesnt have enough compression to blow my finger off the spark plug hole is that normal for a 2stroke? any ideas would be greatly appriciated.

Share this post


Link to post
Share on other sites

needs a 100 pounds to fire 120-115 is usually what a decent motor has

Share this post


Link to post
Share on other sites

quick note, it should allow some blow-by if you are holding your finger on the hole. It wont blow it off but will cause a blow-by leak on your finger if you have good compression. Now i have seen plenty of 2T that will not blow-by your finger that ran fine. You need to compression test, rent from AutoZone. If its not above 90PSI then you need to look at the carb and change the pilot jet, if its not clogged. Jet cleaning...Small piece of safety wire, carb cleaner, high air press, if the jet is super small ie: 22, you can use a single strand of reg power wire.

Share this post


Link to post
Share on other sites

i worked at a polaris dealer for 12 yrs and have built alot of these engines it should blast your finger off i would question the bottom end bec u said the top was all new the only prob off hand is if it was done right what condition was the bottom end and what model did it come from

Share this post


Link to post
Share on other sites

thank you for the advice, I found an old compression tester of my dads and according to it no compression. I overlooked the seal behind the flywheel so I took everything off to get to it and it does appear to be leaking a tiny bit judging by the oil residue on the bottom side of shaft. I dont believe that is the cause of all my compression loss. I did discover today that the used bottom end off ebay has a number of 87-04410 and the one i took off has a #92-10292. the 87 didnt have a shaft for the oil injection, since i opted to mix the oil myself I made a plate and sealed the deal with high temp silicone. Did i do the wrong thing there, is that shaft and the plate in the bottom of it holding the compression in? Is the only way to swap it out by splitting the case? On the 87 before i installed i noticed i could look in and see the gear that runs the oil injection and on the 92 of course i cant see anything in there because of the shaft and plate in the bottom of it. I appreciate all your help so far and am looking forward to any help with my new questions.

Share this post


Link to post
Share on other sites

U need to take the clutch off of the crank and see if u can shake it sounds like the bottom ends not good And the seal would make it run lean ur compression is on top of the piston did u put the piston on right the ring gap goes toward the intake

Share this post


Link to post
Share on other sites

the bottom end seems alright as far as bearings go, it doesnt move when i try to wiggle it. I took the top end off again and checked the rings and piston but they were in right. I poured oil in it after putting it back together and got about 70 psi on the compression gauge. I called the machine shop and old Dewey said he would check the clearences again. I am greatful for all the help, ill update on what i discovered.

Share this post


Link to post
Share on other sites

well that wasnt no help, all I figured out was that it wasnt bored out more than it should hsve been. Still losing my compression and I think its the rings.

Share this post


Link to post
Share on other sites

Did you check the ring gap And do you know any one who had work done by the shop that did your cylinder

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×