Hey all,

my 95 polaris xplorer 400. wont start.... i went on the trails 2 weeks ago and it just started popping and backfiring and eventually died.... and since then i cant get it started.... so i cleaned the carb, changed fuel filter, changed spark plug and still no go...

But today i did a compression test, and the first runs were 90 PSI..... which is low.... should be around 120-140PSI so i put a little oil in the hole, and ran the test again, and i got 120PSI.....

so basically, that mean that my piston rings are shot. (because 2 strokes dont have valves)//

any thoughts of how to fix it.... or other suggestions.... BTW, after i put the new spark plug in, i was still dry when i took if out after cranking on it for a while....

thanks

 

you hit iot on the head w/ the low compression. needs a top end job for sure. the popping and back firing came from it being too lean maybe which it meansd a possiable melt down. time to pull it apart to see.

 

Yeah, i figured it was too lean, and the rubber boot from the carb to the airbox has big tears in it... and it was missing some of the foam pre-cleaners...

i will be tearing it apart on Saturday too see whats the problem...

 

yea shes getting way tooo much air by the sounds. sounds like maybe a partial melt down.

 

<div class="FTQUOTE"><begin quote>Originally posted by: stendori

yea shes getting way tooo much air by the sounds. sounds like maybe a partial melt down.</end quote></div>

Now when you say melt down, what exactly could need replacing?

 

Ok.... everything in my engine seems the be ok.... all the bearing and crank.... and head.

so, must i bore or hone the cylinder.... or can i just put a new piston/ring set in.....


and how do i know what size to do?

 

IF you need a intake boot i think i have an extra, get a .010 over wiseco, bore to match. fix that boot, check pilot and main jet. i also remember you asking about a counterbalancer in another post thats the dipstick under the carb make sure that has clean oil in it

 

if you only have 90 psi and theres no scouring on the cylinder walls or hole in the piston then chances are you need a fresh top end meaning maybe a .010 over bore and hone w/ new piston and rings. you need specail tools and specs. to know this. i would fine out the specs and take it to a machine shop for a professional to do the work . at the least new rings and a hone job is in order. just my .02

 

thanks, will start calling the shops on monday

 

well i sent my cylinder away to get bored out today.... then i can order a new piston ring set, when i know the exact size to get...

but i was looking at the engine head, and i noticed some metal "bumps" on it.....

heres a pic...



the engine shop said i could just scrape it away with steel wool, but now i am wondering where it came from and how long it was in there..... Like i said, i checked everything out, even the crank, and nothing was loose or worn, and i saw no metal fragments