Its finially time for me to rebuild the top end. ( Low compression, and seem to be getting gas in the bottom of the crankcase.) I have the specs on the cylinder size etc... but how do you tell if you need just the standard piston size and rings? Do you have to use a caliper to check the cylinder? Looks like you can buy the top end rebuild kit and they have a standard size, and a few sizes larger if it has to be bored out. I have never rebuilt a top end, but I am going to try it. Doesn't look like rocket science!

 

Cylinder needs to be measured compared to stock bore with a micrometer and depending on shape of cylinder (scored,gouged,or just worn) will need to be bored to the CLOSEST oversize that will clean up the cylinder without taking too much material. DONT waste your money on a stock piston as cylinder will be worn too far!! If you plan on doing most of the work yourself,take the cylinder to a reputable shop and let them check what size you need,order the parts and have it bored. Then you can install it. After installation premix the first tank of gas 50-1 ratio oil to gas to help break-in. Its not "rocket science" but needs to be done right or your money goes up in a puff of smoke! I bore cylinders weekly for customer takeout and if you take your time,the job is pretty cut and dry! Good luck OPT

 

started takeing things apart tonight to get the engine out. The exhaust tube that comes directly off the engine was full of gas, and before I was getting gas out of the wiring harness that goes into the crank case. Is this from keep trying to start it and I flooded it, or is there probely more problems than a top end rebuild? Maybe crankcase seal bad also? why would the exhaust have so much gas in it?

 

This is a common problem when the needle and seat go bad in the carb.It will dump gas into the engine and exhaust.Chances are it washed out the rings so if you have the stuff go ahead and do a top end but DO rebuild the carb too.

 

Got the top end all pulled apart tonight. That sounds right, the crankcase is full of gas too.
Will get top end all rebuilt, and will get a carb kit too! This thing has had me puzzled. It ran fine last I drove it, and it has been parked in the garage for a while and when i go to start it it wont work. I had gas comeing out of the wiring harness that goes into the block! So far the cylinder doesn't look to bad but I will have it checked to see if it needs bored or not. I'm still learning!

 

remember to shut the petcock off when parking it.

 

I got my cylinder all pulled apart and it looks great with no gouges at all. It also measures what the standard should. I ordered a piston kit for the standard cylinder, but it looks real slick and glassy.....should this cylinder wall be roughed up so the new rings will seat better??? Just what someone suggested to me. I need your opinions. Thanks!

 

You need to hone the cylinder or the rings won't seat properly. You can get a hone at any auto parts store. If you have an Autozone near you, they have a loan-a-tool service, so you don't have to buy it.

 

I just did my wifes 98 trailblazer. Bring the cylinder to your cycle shop, have them bore the cylinder to the specs of the new piston you're planing on installing. I used a weisco piston and rings that I bought right at the place that did the bore. Get all new gaskets as well. It was my first top end rebuild as well and it wasnt hard at all. A few things I learned-arrow on the piston points towards the front of the bike. Looking at the rings the side of the ring that has the writing on it is the top.

 

make SURE u don't need a bore job!!! if not, have the cycle shop hone
it with a ridged hone, if they don't have one find another shop!!! should
cost about 10 bucks or so. this is the reconmended way to hone the
cylinder!! also I like wiseco pistons too!!