Is it worth it to do this? engine tech needed.

[andersonee4]

the local honda shop says if i bring them the engine they can seat the valves and hone the cylinder for 100 bucks. give or take a few. I also think they can bore it? does that sound normal? do honda shops usually bore cylinders? if so i want to buy a rocky piston on ebay. Are all of their pistons high performance? they all seem to be dome topped. Furthermore how large of a piston do i buy. they have 30 and 40 thou over. There is only a few but how do i know what size to get? Thanks ahead of time.

[dcreel]

Have you checked the bore size you have now? You normally have to check the bore size you have and the condition of the cylinder before you buy the correct size piston.

[andersonee4]

well i am assuming that it is 74mm because it is the factory piston to my knowledge. ... Were there variances in the factory?

[HuffieVA]

Its not the best idea to assume anything on a 25+ year old small engine unless you have personal knowledge of its history, but like Doug said you need to know the actual size of the existing bore and if it will need bored making it a new size there is really no way to tell until you have it apart.

[andersonee4]

Ok, thanks. Is it typical for small engine shops to be able to bore them out? Or is that a specialty thing

[audioworks04]

Yes, it is very typical, smaller shops normally sub out the work to a machine shop, but still will have the tools and know how to tell you what you need. I would take them the cylinder and head and see what they have to say about it. You wouldnt have to go with a high compression piston, but most people would, just be sure that you run 91 octane in it after that. I would recommend a forged piston such as a wiseco over a cast piston, but the price will be higher.

[HuffieVA]

It all depends on what equipment they have, because of the expense of the equipment they often outsource to a local machine shop

[andersonee4]

Cool thanks guys. I called an engine shop today, and they said it was 35 for the first oversize (.25 mm) and 10 every size over. Thats not bad. I will be putting a high compression piston in it. Anyone have experience with the rocky pistons? they are all nos, and i cant get a new one from any manufacturer. Will there need to be any other mods to the engine to be able to run the high compression piston? Does it need to be jetted, or different carb? I am new to this so forgive my ignorance.

[Dirtcrasher]

Nah, not unless you change the exhaust or open up the airbox lid.

The shop can use an inside bore gauge in any position and see how much it needs to be bored. They need the piston first before they bore so the can keep the tolerances in check.

Even my local shop has a "power hone" that apparently they can go up a few sizes; But when it's really out of round, they send it to a machine shop.

[andersonee4]

Well this is what i did. I was able to get ahold of a 1mm over piston, high compression. I took the jug off and the piston out. Well, they were immaculate condition. I took it into a machine shop and he told me that the piston and jug were minimal wear. I told him about my piston purchase. He said, i can bore it out to 1mm over. I had the specs and original piston there. Since i was this far, even though the piston and cylinder walls were good, i still chose to put in the high comp piston. Once i get the piston in the mail, i will bring it in to him and he will get me all set up. I am also dropping the head off at honda to have the valves re-seated. The exhaust valve was leaking a little bit. So with these two mods, it should be a pretty fresh engine. And its gonna run be about a 100 bucks for everything, except the piston of course. So i am happy with that. Is there any aftermarket exhaust that will work, or do i pretty much have to fab something onto the head pipe? I like the sounds of power core iv's.