so i purchased this 99 traiblazer. i knew it needed some work but didnt realize what i was getting in to. i bought it for my daughter. when i got it home i started going through it to find in needed tie rods, wheel bearings, battery, starter, starter solenoid, crank bearings, piston, repair on the wiring, belt, tires, and some more. so we are supposed to head to our camp this week end and my daughter is excited to ride this thing. so i spent all week taking the motor out and rebulding, and repairing everything else i could find. get the motor back in start it up and let it heat cycle a couple of times. everything seems to be great. so i put everything back to geather to finish the job. now all the plastics are on and this f! thing wont start now. it ran befor the rebuild but was loud and noisy with the crank bearings falling out and it ran after i put the motor in. i didnt ride it befor i put the plastics back on but it started right up with only a couple seconds of cranking and sat there and idled nice. even giving it throttl it sounded nice with no bog or anything. so i bring home my compression guage and check and see only 90 psi of compression. now im upset. so i tear the top end off and lucky no damage to the cylinder. but the rings are stuck in on the pistion. the alignment pins and lined up but the rings absolutly dont move on the piston. what could have caused this? im stumped. i dont want to stick another piston in and have the same problem. i used a wiseco piston.

 

my daughter is very upset she wont have it for our trip this weekend. i feel horible!

 

Who bored the cylinder?? What clearance did they have. Plus did you premix the first tank of gas? OPT

 

tank is pre mixed. i had the boring done by the shop that does all my machine work. but i am wondering if they set up the piston clearence to tight. how can i check that now. i set the rings in the cylinder and meased ring gap and that looks fine. but is piston clearence different for ring gap? does it have anything to do with the wiseco being forged and not cast? i had a ton of oil in the cylinder and case upon assembly. there is only a couple of very slight scoring lines in the cylinder. can barrly feel them with your finger nail. im thinking a hone should get rid of them. but im nervous to stick another piston in there with fear this will happen again with out knowing what caused it.

 

Measure bottom of piston skirt to bottom of cylinder should be between .0015-.002 clearance normally after bore and hone. Or you can just insert piston with out rings in the cylinder and use feeler gauges at bottom of cylinder against the piston to get an idea of what they allowed on the bore. If a .0015 feeler gauge is tight or won't fit in the cylinder then it's possible that could cause ring sticking.Are you sure the rod bearing wasn't damaged,no up and down play on the rod? Plus did you replace the crank seals? OPT

 

yes crank seals are new. no play in rod. just cant belive that could happen only running like 4mins. do wiseco pistons require more clearence than cast pistons?

 

I set them up the same as I did oem cast pistons and never had a problem. I bored to piston size(measured at bottom of piston skirt) and finish honed to where I had between .0015-.002 final clearance,but always broke them in slowly!(.005 clearance is considered worn out on most 2 strokes!) Early on Wiseco used to recommend a certain clearance on pistons,but started to leave this info out on later pistons.(got in hot water I guess?) Noticed this years ago. OPT

 

there was a sheet in the box the said to set clearence to .003
i took the piston off this morining and had a heck of a time geting cir clips out and the piston pin was stuck in the piston. just seems like an auful lot of damage for 4 minutes of running. i mixed the fuel at 50:1 plus i bled the oil pump. and when the quad was started i held the oil pump wide open untill it started smoking real good. theres no way this could of been lack of lubrication could it.

 

If you premixed the fuel,even held the oil pump arm arm to speed oiling to cylinder,then seems like it's down to either the bore job, or you didn't give it time to seat the rings. Double check the piston to cylinder clearance,could be the shops fault. I always started a new engine and let it run until warm(about 5 minutes) then shut it down to let the cylinder and piston cool down,then second crank up I drove for about 10 minutes easy then shut it down. Could be the problem,especially if the piston pin is extremely hard to get out. Could have heated up too quickly. Also if you're sure the rod bearing is ok. OPT

 

One thing I forgot! Did you make sure both rings had the numbers facing up when you installed them on the piston? Some have made this mistake. OPT