Pro quad riders often say about 3 hp is noticeable to them. Boring your cylinder .020 over will not give you 3 hp, maybe .03 hp. There is no difference in setup between a stock bore engine and an engine bored .040 unless you mean chamfering the ports after you get done boring it, which any half decent machine shop would do anyways.


I prefer Wiseco pistons, they are stronger (I run alcohol) but you do have to do a rather long break in on them, and make sure you warm them up prior to usage, or they will cold seize.

 

yeah im happy with my wiseco pro lite it has wwaayy over its 30 hour's and will still hang with a fairly modded lt500 and im not sold on holes being drilled in my piston anyways i know there there to cool your ports and all i know im most likely wrong about this but it sounds like one of those race goodie's that are fast but with a short life

 

The holes drilled in the skirt are there to PREVENT problems, not create them. The exhaust bridge is bathed in hot exhaust gasses and gets much hotter than the rest of the cylider, therefore it expands more. This is why when the cylinder is bored, the exh bridge must be relieved a couple thousandths. The three holes that are drilled in the skirt will provide for additional lubrication of the exh bridge. Always a good thing.

Holes that are of the proper size and have been deburred afterwards are a benefit to any bridged exh. Additional holes can be drilled(IF room allows) between the exh port and the transfers. Again providing for addtional lubrication on the hottest side of the piston.

The ATC and TRX engines are for all intents and purposes almost identical and can be interchanged indiscriminantly. Shhhhhh, its a super secret but I have '85 ATC cases, '86 tranny, '88 kick starter and clutch cover, '89 counterbalancer...well the rest...lets just say stock sucks...So you can see how easily these engines can be used across the model years. '85-'86 ATC-R and '86-'89 TRX-R's are all interchangeable.

The likely benefit of "small" bore jobs is bringing the tolerances back to spec on a loose engine reducing blowby and etc, which in turn means better power. Small increases in displacement, i.e. the diff between .020 and .040 is negligible and a waste of perfectly good overbores in case of problems like broken rings, spit circlips, etc...

As for cheap increases in power...whats your budget???

 

well im not real poor hehe i was thinkin about useing the topend from the atc and getting the pro x piston and a reed spacer my r spends all its time in the woods of open feild drag raceing