Low Compression? Please help

[redhatman]

Hey guys, I am having a lot of difficulties with my Blaster. Its a 2002, supposedly has the hot rod crank, has Motion pro twist throttle, tors out, oil blocked off, idle kit, DG exhaust sytem, mixed 32:1 - 92 octane.

I was driving it the evening I bought it last weeked and about 30 minutes of runtime on it it started bogging and backfiring. I decided to shut it off, loaded it up and brought it home. I changed the plug with brand new ones several different times, and still wont run.

So far:
-Cleaned the carb twice by two different people, everything looks fine
-Checked reeds, resealed gasket
-Fixed exhaust leak out of engine
-Fresh Fuel
-New Plug
-Tightened the thing down that gives electricity to the plug so its nice and grounded
-Tors Out
-Cleaned air filter
-Cleaned Air box
-Took off panel to check flywheel, no play in it
-Has good spark
-Reset Carb to 1.5 turns out

The only thing left I believe would be compression, right? It is hard starting if I dont give up by the time it fires. While running it seems to run decent.

I noticed that if I put it in gear and try to push it, it will move fairly easily. For instance if I tilt my trailer down it will roll off in gear.

What else could I check? Whats the cheapest way to rebuild if I need to? I have no clue if this was bored out yet or not, and the guy I bought it from was as dumb as a brick.

Thanks a ton,
-Pat

[trx]

it sounds like you have a electrical issue with your coil or cdi

i would check for bad grounds and what is the compression at right know

[Suz_Madness]

yea just because you see spark doesnt exactly mean its a good spark, check the compression and leakdown if you have the tools....

[redhatman]

Compression was reading around 90 on the first couple kicks, then steadily at about 60...Not sure though being the gauge would jump when I kicked it and go back to zero after i let off. I had to read it as I kicked.

How do I know if I have a "good spark" What should the voltage read? Also....How do I go about boring it out? Does the sleeve come out easily? Are there any guides as to how to measure the values and identify what to do? I will call NAPA tomorrow and ask if they can machine the sleeve.

I bring it to a machine shop right?

[trx]

okay this is what to do

1.there is no vavles or guides on a 2 stroke motor this a head and cylnder and the bottom end

2.take the cylinder into a shop the whole thing and have them bore it to the next size u dont need to take the sleeve out at all they do the bore and HONE aswill then slap a new piston in it clean the head of carbon and break it in and rip

[NightBiker07]

get the piston first so they can match the bore to the piston.

[FPMXer]

Originally Posted by redhatman

Compression was reading around 90 on the first couple kicks, then steadily at about 60...Not sure though being the gauge would jump when I kicked it and go back to zero after i let off. I had to read it as I kicked.

How do I know if I have a "good spark" What should the voltage read? Also....How do I go about boring it out? Does the sleeve come out easily? Are there any guides as to how to measure the values and identify what to do? I will call NAPA tomorrow and ask if they can machine the sleeve.

I bring it to a machine shop right?

When you did the compression test was the tester threaded tight?? Could be the cause of the pressure loss. Also did you hold the throttle wide open during the test? If both were done and you still lost pressure you could have a blown head or base gasket allowing the charge to vacate the cylinder while kicking the bike. I would make sure all the nuts and bolts on the cylinder and head are torqued. If all that is good then yes you need rings at the least. NAPA won't be able to help you as they only deal with automobile parts.

[kxrider]

ok i see that no one touched base with this so ill give it a wack if ur bike is in gear and u can tilt ur trailer and it will roll off check ur clutch but as far as compression try tighting all tha head bolts next try replacing tha head gasket and if still a problem then jus pull tha cyl and check tha walls for scaring if none then put another piston in there

[redhatman]

Originally Posted by FPMXer

When you did the compression test was the tester threaded tight?? Could be the cause of the pressure loss. Also did you hold the throttle wide open during the test? If both were done and you still lost pressure you could have a blown head or base gasket allowing the charge to vacate the cylinder while kicking the bike. I would make sure all the nuts and bolts on the cylinder and head are torqued. If all that is good then yes you need rings at the least. NAPA won't be able to help you as they only deal with automobile parts.

Yes it was threaded, how else would I put it in the spark plug hole?

How would it be completely air tight? At idle there is a gap in the carb.

Sorry, but your entire post didnt make sense to me.

[lt250racer]

Alright.......

To do the compression testing you should hold your throttle open while kicking several times in a row, like 4-5 times. The gauge should have a constant reading that will not go higher with more kicks. The gauge will not lose pressure unless
there is a leak in the top end. (the top end of a two stroke engine is a sealed) The only way you will lose this compression is thru:
The compression tester threads
The Head gasket
The piston rings

I would reccomond you build/buy a leak down tester, Then check your entire engine for a quality seal.

To me it sounds like your problem is either a :head gasket" or "a New Top End: - time for the nenxt size piston with a rebore