so i have a stock 87 suzuki lt230e quadrunner (66mm bore) and was wondering what the bore tollerances were? how far can you bore these cylinders? Ive seen tons of 66.50, 67 and even a few 68mm pistons for these motors. I want to bore it and still be safe and reliable and i plan putting a stage 1 cam in it also..

 

The rod is the weak link, not the jug. You can bore it to 68 and be fine. You could even get a big bore kit and go 70 and 71.

Stage 1 what?

 

rod? and were can you find the big bore kits?

 

why is the connecting rod the weakest part? i would think 68 would make the sleeve very thin?

 

Guys have been boring these out to 68 for decades. Wiseco has offered 68s for decades. 2mm overbore is pretty standard on any engine. Some engines go 3mm over... it just depends on the sleeve. I've never heard of any issues from 2mm overbores on 230 engines. I have seen broken rods though.

The rods are so notoriously weak, that I pretty much assume they're all bad.





16mm small end stretches and the big end bearings wear out causing the rod to flop in every direction.

The good news is these engines will run great with almost no compression, smoking like tar wagons, and with big chucks of metal in the engine.

Here's what's left of the rod thrust bearings in one engine:



The engine ran fine... until a bit of metal clogged the gears. Had to roll the quad backwards to free it up and ride again.

But if you hang a big heavy piston on the rod and suddenly let off the gas after revving it to the moon, this happens:

 

wow thats insain lol so i can have the cylinder bored to 68mm and buy a 68mm wiseco piston and everything will still be ok or should i go again and replace the rod and bearings? how much of a chore is it to do that ive only rebuilt top end on 4wheelers nothing in the crank? and another ? when i have it bored does it need to be bored a hair over 68 to alow for ring room?
thanks

 

If the reason you want to bore it out is because it was smoking, then the odds are almost certain the rod is in no condition to make a race engine. It was probably smoking because the rod let the piston flop and rock around, which scratches the bore and wears out the oil rings. So, if it was smoking, it will smoke again.

I'd probably go with a 67.5mm and find a guy to bore it real tight and do a great job. Then plan on doing it again in a year or two. You might get lucky and it lasts longer.

Wiseco pistons are crazy heavy. Its like the engineers went to great lengths to design the most massive piston they could think of. I'd try to shave off as much weight as I could.



The black areas are safe places to grind on. Also grind out the inside of the wrist pin some. You might save 5-10 grams. Not much, but its something.

 

im just looking for a little more out of it so ill probley do the 67.5mm bore and find a lighter piston like a Namura or something. so i can have it bored ecactly to 67.5mm? i found a namuar piston says its oversized to 67.47mm is that to allow room for the rings? .002/3 is plenty of room?

 

As far as engines go, its not bad, but its a big job to change any rod... even an easy one like the 230.

Call this guy MrCrankshaft ATV Crankshaft repair site.

You have to split the cases and send him the crank.

Me, I'd just rebuild what you have and deal with the smoking. Its $250 per bore job so you spend that much and get 1-2yrs out of it.

If you change rods, well now you have the option of a longer rod. Or, you could go with a 250S rod, which is longer and bigger. But then you would have to get a 69.5 or bigger piston and a 250S jug.... Hard to find parts. If you pop out the crank, suddenly you have all kinds of choices.

Call Vince and see what he thinks you should do.

 

That sounds like a good idea. Yeah, that would be to allow for thermal expansion of the piston. Forged pistons expand more than cast. It should say on the papers that come with the piston how big the bore should be. It should also tell the ring gap. Don't forget to set the ring gap!

Get something with 10.25:1 compression. There's a big power boost there.