i just checked my compression today and it was 55 so i took off the head and cylinder to check on it all and it was all in perfect condition, no scratches on either. may i just need a hone and new rings? also how do i find what size rings i need?
low compression?
- Thread starter BlasterMaster15
- Start date
most likely that is what is wrong if there are no signs of damage. you will need to either measure the piston yourself or just take it to a shop and have them measure the rings and order them. us a micrometer and be precise so you dont end up needing more than the rings and hone
Exactly! Measure it or have it measured. Also, don't buy new rings (and possibly a new piston) until you get it measured. Usually a damaged cylinder will have to be bored out, but even one that looks "OK" inside may have enough wear that it will need to be bored. You'll know for sure once you start measuring.
If you look in the clymers manual it shows proper way to measure. You need to check in six places. Top, middle, bottom. Front to back, side to side. Compare the numbers to determine if it's within specs or needs bore.
Also if you measure only at the very top there will be virtually no wear as the rings stop about 1/8 down from top.
Also if you measure only at the very top there will be virtually no wear as the rings stop about 1/8 down from top.
Doesn't the mic have a mm setting?
Did you do the compression test by kicking it multiple times at full throttle(or remove the carb completely) until the guage was no long increasing? Are you sure the guage isn't leaking?
55psi is awfully low...definitely time for a bore and new piston....I'm not saying a hone and new set of rings won't work, but I have my doubts. At 55psi though, you have some other things that I would look at. It's pretty tough to even have an engine physically run at that compression. When the plug is in, can you push the kicker down with your hand fairly easily?
If everything looks fine, and measrues fine, then i bet you have a stuck ring or 2. Unless your head wasn't torqued to spec or is warped or had no head gasket.
i have a 96 motor in a 2003 frame that i have done a lot of work to. and i just put a new set of 0.40 rings on my 6 month old piston the other day and today i went and got a compression tester and mine only showed 60 psi... i am so frustrated with this motor I'm about ready to sell it ..
Stupid questions I know, but I have to ask, did the bore get a hone, and did you use lots of oil in the ring area at assembly.
Did you check the ring gaps?
We're both piston and bore within specs?
Did you kick until the pressure stabilised?
It would be preferable for you to start your own thread!
Did you check the ring gaps?
We're both piston and bore within specs?
Did you kick until the pressure stabilised?
It would be preferable for you to start your own thread!
no i didn't have the bore honed but it is in real nice shape inside ... yes to lots of oil.. no i didn't check ring gaps ... yes i kicked it till stabilized
this motor was running fine in october and my stator shut down so i replaced it and then it started showing signs of low comp
If you don't hone then new rings won't wear into the bore and you will never have proper compression. That's the whole point of breaking in a new engine. Also, make sure your head gasket isn't leaking.
The crosshatching of the bore achieves a number of things.
It offers an abrasive surface which will cut the rings to shape.
The hatching also attracts oil for extra lubrication to provide sealing of blow by.
There is a chance that compression will improve as the rings wear to fit the bore.
One should always fit the rings into the bore to make sure that the correct size has been supplied and to check the cylinder wear.
It is possible to still try to save the day and pull the top end off and hone the bore, you should be able to re use the rings.
It offers an abrasive surface which will cut the rings to shape.
The hatching also attracts oil for extra lubrication to provide sealing of blow by.
There is a chance that compression will improve as the rings wear to fit the bore.
One should always fit the rings into the bore to make sure that the correct size has been supplied and to check the cylinder wear.
It is possible to still try to save the day and pull the top end off and hone the bore, you should be able to re use the rings.
