Piston Rings - racing only

[RoninZX-10R]

After this years race season I'm going to be stripping my NC30 for a freshen up of all bearings, seals, etc to get her ready for another year of mistreatment

I'll be giving the engine a freshen up as well, can't go too extreme since I'm racing in the 'standard' class over here in Australia, so engine mods like porting, big bore kits, etc aren't allowed. But I have a question after seeing Mike Norman's (G-Force Engine Development) piston drawing for the 450cc engine. He's designed the piston to use 2 piston rings (only 1 compression ring, most bikes use 2 compression rings). Would the removal of the 2nd compression ring have any noticable reduction in friction for a standard engine, or would it be a waste of time and effort?

[Mananon]

I'm far from being an expert Ronin but I'll throw my two cents worth in.
Firstly, I'm not familiar with you're race rules. Wouldn't removal of a ring make the bike none standard, if you're sticking to the letter of the law that is?
Regarding the compression rings in relation to a standard engine with standard pistons, the engineers put two in there for a reason. Removal of one increases the chances of gas passing the remaining ring. I think you'd find the crank breather would be working overtime.
There would be a slight reduction of friction and the heat this creates but I would expect it to be of little or no perceptible benefit. It's also a lot of work to get the pistons out.
If you are allowed to remove stock parts for weight saving, ditch the the backlash gears, starter, go total loss, cut down the sub frame etc. It depends what you're allowed to do.
When you've got it stripped, set everything as near as possible to the recommended tolerances. If you're allowed to, balance everything. A kind of poor mans blueprint if you will.
As I say, I'm no expert but I hope that helps a bit.
Cheers,

[Neosophist]

The Kawasakis did the same, higer compression pistons but running only 1 compression ring.

The manual states that increased oil consumption is likely when running like this.

Also, is it allowed in your class?

The rings do take a lot of power out of the engine, ideally you could do with a dyno run before / after see if theres any changes to the motor, along with how it actaully feels of course.

Are they standard pistons your using though? Not sure if this makes any difference.

[superlite]

The Australian rules are quite strict, but not detailed enough to mention removing rings, etc. Basically bore size, compression, cam shafts and crank cases must be standard (and no total loss). Anything else in the engine department pretty much goes (and is not scrutineered). I wouldn't personnaly do it (for engine longevity), but wouldn't have a problem if other racers went ahead with it.

I seem to recall that this was practiced in Japan (on stock pistons). Plus there was the HRC pistons - but that's a different kettle of fish

[Neosophist]

Mmmm HRC pistons

[RoninZX-10R]

Cheers guys, thanks for the replies. I'm still undecided how far I'll strip the engine, but if the engine looks worn enough that it requires new rings and a hone I'll remove one of the compression rings and re-dyno the bike. But it wouldn't be something I'd want to be doing on a regular basis!!!

[Cammo]

I seem to remember a reputable UK engine builder was doing this with good results. Only downside is that the engine will use more oil, not really a concern for short races.