No Start. Need some help.

[jlsparky7]

2002 Blaster, TORS removed, FMF pipe 260 main stock pilot, Powder coated frame (grounds are good), Top end has 3-5 small rides on it, K&N air filter with lid no snorkel, boysen reeds, new coil last year.

Last time we went riding it was bogging pretty bad and would die at idle. We cleaned the carb completely as well as the air filter (air filter was very dirty) and added fresh gas (amsoil interceptor 40:1). It helped a little but something was still wrong.

Yesterday we compression tested it and we only got 60psi. Took the head off and there was a black mark of oil were it looked like the head gasket was leaking so we got a new head gasket. Compression tested it again and got 75 psi. However with the new gasket it wouldn't start at all. The piston and rings went in fairly easily but the cylinder walls were not scared at all, looked like a new top end (which it pretty much is) the piston has a small set of scratches which looked like normal wear and tear to me (boring and honing was done by lakes motor sports which has a good reputation). Both rod bearings and crank bearings were good with minimal side to side slop and no up and down slop at all. Checked spark multiple times and it was good and put in 2 new plugs with no luck. Fresh gas, complete carb rebuild, new reed cage gasket, reeds seemed good but bent out the slightest bit (maybe 1 mm). Plug does get wet when trying to start.

I don't know what else to try. Cleaned ALL the electrical connections with electrical cleaner. Only thing I can think of thats left is maybe the flywheel key broke? Any ideas? Ill let you know if ive tried it. I don't get how the compression could be so low with a pretty much brand new top end. It wasn't rode during winter and had 2-3 rides on the new top end last season. Always ridden in 50-80 degree temps, never lower.

 

[blastapole]

Check your ring gaps. If the sleeve went on easy, then it might be bored a size bigger than your piston.

I have had this happen on a 4 stroke. It ran but smoked and ran like crap.

If your not sure how to check ring gaps take the rings off the piston and put them into the cylinder. Put feeler gauges in the gap of the ring and add them up.

 

[jlsparky7]

Check your ring gaps. If the sleeve went on easy, then it might be bored a size bigger than your piston.

I have had this happen on a 4 stroke. It ran but smoked and ran like crap.

If your not sure how to check ring gaps take the rings off the piston and put them into the cylinder. Put feeler gauges in the gap of the ring and add them up.

The quad ran awesome for the first 3 rides. How would the ring gap change when it just sat there all winter?

Not trying to be a dick or anything. Ill try it next time I go up to work on the quad. Its 3 hours north of me.

 

[yfz450bence]

The quad ran awesome for the first 3 rides. How would the ring gap change when it just sat there all winter?

Not trying to be a dick or anything. Ill try it next time I go up to work on the quad. Its 3 hours north of me.

if you did the compression test right, which im sure you did, than something changed because it will never start with 70psi, anything under 120 and its going down hill from there, somethings wrong with the top end, you dont need to look any further, how does the pistion look just under the lower ring? is it dark? any sign of blow by under that lower ring? if so thats the problem, bore is too big or the rings worn out. bad reeds can make it extremely hard to start, but with 70psi i would rule that out, checking the flywheel key isnt a bad idea, but even if it broke that would screw up timing not compression.

 

[jlsparky7]

if you did the compression test right, which im sure you did, than something changed because it will never start with 70psi, anything under 120 and its going down hill from there, somethings wrong with the top end, you dont need to look any further, how does the pistion look just under the lower ring? is it dark? any sign of blow by under that lower ring? if so thats the problem, bore is too big or the rings worn out.

I did the compression test as right as I could (obviously couldn't warm it up first). Heres the weird part I forgot to mention. We compression tested another blaster that was there and it only read 90 warm and 80 cold. However we tested another quad that was there (old honda 3 wheeler) and it came to 135psi. So I know its not the tester.

How could the other blaster run flawless and start no problems and have power with only 90psi hot? also how could the top end already be gone?

There was one part about 1 inch by 1/2 inch on the lower 1/2 of the piston that had small scuffs on it but nothing major. The rest was fine. no signs of blow by or leaks.

 

[yfz450bence]

hmmm, 90 just seems too low on a good running blaster, testing them cold is how you should do it. you gave full throttle and kicked till you coudnt get any more psi out of it right? make sure your using the longer threaded part of the adapter of the compression tester, threads should be the length of the spark plug, theres usually a shorter adapter for mowers and what not, make sure your not using the shorter one, i know it sounds dumb, but trying to eliminate some things. with 90 psi you can literly use your hand without much hassle. a good running blaster wont have 90 psi, somethings not right there.

 

[jlsparky7]

hmmm, 90 just seems too low on a good running blaster, testing them cold is how you should do it. you gave full throttle and kicked till you coudnt get any more psi out of it right? make sure your using the longer threaded part of the adapter of the compression tester, threads should be the length of the spark plug, theres usually a shorter adapter for mowers and what not, make sure your not using the shorter one, i know it sounds dumb, but trying to eliminate some things. with 90 psi you can literly use your hand without much hassle. a good running blaster wont have 90 psi, somethings not right there.

The adapter was slightly shorter than the plug but it was the only one threaded the same. It was only like 1/4 inch shorter. It was at WOT and I kicked until the needle stopped moving and then some. How could it need a rebuild already? They must have messed up the hone if that is the problem.

 

[yfz450bence]

The adapter was slightly shorter than the plug but it was the only one threaded the same. It was only like 1/4 inch shorter. It was at WOT and I kicked until the needle stopped moving and then some. How could it need a rebuild already? They must have messed up the hone if that is the problem.

idk, but like said checking the ring gap should tell you something, also piston to cylinder clearance should be no more than .005 or if wiseco it can be a tad more, .003 is recomended for wiseco pistons

 

[jlsparky7]

What should the ring gap be? The rings/piston were definitely MUCH easier to install this time then they were last time.

 

[jeepinncreepin]

measure your jug bore times that by .04 theres your ring gap

 

[jeepinncreepin]

ring gap should be around .12 if your bore is 3 inches 3x.04=.12

 

[jeepinncreepin]

sounds like you need new rings to me if anything you can get oversized rings but i dont know how to go about measurements for them

 

[jlsparky7]

measure your jug bore times that by .04 theres your ring gap

ring gap should be around .12 if your bore is 3 inches 3x.04=.12

The bore is .020 over. Not sure what that translates to in inches or mm.

sounds like you need new rings to me if anything you can get oversized rings but i dont know how to go about measurements for them

Maybe new rings will work. Cylinder and piston seem fine :-/