I will take a look. But what is 5.5mm in inches? A stock piston is 3.920. So with say 6 thou wall clearance, or 8 it gives you a nice round number.

 

Ok, so this brings up another point. Bridging. The wall thickness looks less on the 730, but its bridged. While the 650 is thicker but not bridged. Maybe this is where Eric says the 720 go out of round? But still the 730 in inches?

 

The stock bore is 100mm (3.937in) and the HPR bore is 105.5mm(4.154in).

Like I said about the picture, the angle is deceiving. While I have not seen the inside of the HPR jug for a long while now, I do remember that every part of the cylinder was thicker then the stock bore.

Without even measuring the HPR cylinder, you can tell that it can be bored over a few times if it were ever needed. But how many on here ever had to bore over there stock cylinder, not to go big bore, just to bore over due to wear?

 

730 wall thickness is same as stock which is right around .300 thousand's. Bore is 4.153.

Why would you put a sleeve in a 730 jug when it can simply be re nikisil'd and honed for $200. This could be done unlimited times and would be way cheaper than sleeving. Am I missing something here??

 

Yjacket, I'd rather you didn't bring my name into this as what happened to me has nothing to do with sleeves and everything to do with valves. My bike was never stronger than with the sleeved cylinder. I'd have no problem recommending one. As for the guy that did my head , thats a different story entirely.

 

Oh no, your not missing anything. But I am. That leaves less than a quarter inch to play with boring the cylinder wall that thin. Good luck with that. This was what I was after, what did the thickness end up. .212!!!!!!

 

Bigdaddys motor failure didnt have anything to do with the rings folding. I think it was a mechanical miss-communitcation on install. Very rare.... Someone correct me if I am wrong.

 

I do believe you're correct. It seems that head or valve failure is automatically associated with big bores now.

 

Come on guys,

Head work, exhaust flow, valve problems, it don't matter and it dont matter if big bore or not.

When the engine overheats, one of the first things to go is the rings. And if it goes 2 revs, you're screwed.
ESPECIALLY if you have VERITICAL DRAG RACING PISTON PORTING: hint, hint.

No you don't need AL sleeves, but you should always have contingency plans.
Sandaholic has an ultimate package quad he may never do anything else to, but he built it precisely, maintains it, and now he enjoys it for what he built it for. It could last forever in that state. He knows more than most as well, way more.

All I was saying is experimenting with nitrous and alkyhol is risky if you don't have but one bore backup plan, given no 1/2" ring spikes.
$1.9K is a lot to me, and evidently not much to you, so forget it. You must have all your bases covered.
But things happen, and you shouldn't be manipulated by chance alone.

With all the experts on this site, an excel spread sheet could be composed (and transmitted on a thread with '...' to space properly) which would contain all the critical differences: so the product(s) could evolve for the better no matter which vendor took sponsership in the future. Every product will have their advantages and disadvantages: some more for flexibility, some reliability, some pure racing, some cost. There should be an optimum config for 95% of users.

Its hard getting tangible real details. But there is little out there I can see. All I can reasonably do is eliminate non conforming alternatives to goals. That's easier: Safety, reliability, cost, maintenance, performance, environment.


Sandaholic:
I've had my F650 rotax since Jan/97, the first month it arrived in USA. And had several super bikes before. This is the first time I've ever needed performance assistance, so its new in that respect. But there's so much overlap with 7 years engineering in over a dozen type auto (and other) industrys consulting. So its new in that its a new objective. I'm never an expert. And I'm always learning. I feel your pain.

 

This may surpise you but you and I were heading the same place. I may have mis-calculated cause I did this in my head but I came up with a .167 wall thickness.................oh but that would be for 105.5mm bore. The experiment in question is a 105.0 bore so there would be a few thousandths more wall thickness. That is between an 1/8 and 3/16 of cylinder wall................