engine theory

[BluGixxer]

I don't understand what the bennifit would be , please tell me ?

As for diff part #'s on pistons in mototor, has to do with valve relief and the direction they are installed, aslo in some cases in diesel engines, the diameter of one piston is slightly smaller due to more heat and expansion.
Counter wieghting wouldn't be the biggest issue, you can always add wieghbt rather then subtract. Although you usally want Light rotating mass.
2 stage air compressors use 2 diff sizzed cylinders/pistons on the same crank. Jfyi
All of the mechanical issues can be thought out.
Here is one big issue, if you have 2 drastically diff sized cyclinders, and you adjust compression, one size is makeing more power than the other, at one point in the rpm range you might get them to meet and play happy. But one will always be fighting the other , one wants to speed up and the other slow down. Vibration will tear up the bearings or crack the rods or crank. Not saying it won't run, just not for long.
V8 air compressor that you pull behind a truck to supply air to jackhammers , they use 6 cyl to make power and 2 to compress air, and run at a relativly low rpm. Just something to think about.
As for boreing out cyclinders on multi-cylinder engines, small changes don't affect the performance very much. The bigger the displacemet the less effect, smaller = bigger effect . Machine shops do this to cut corners, speed shops don't. You just would NOT do that on a performance motor !
Its not written about because your not supposed to cut corners like that , and would give you a bad rep.
I belive it was gale banks or callaway who did a lot of R&R about this in the late 60's or 70's. Bottom line if I remeber corectly, all the small discrepencies(cc sizesand small flow rate) could be made up by adjusting carb/FI, and a complete exact motor , cyl to cyl, runner to runner, there was no benifit.
By the way what was the planned expected beniffit from this ?

[SVRACER01]

essentially, yes, both cylinders would probably have to make similar power. which can be fairly simple to do by increasing pressure and putting in some hotter cams on the 650 side

[Turbocharged]

IIRC, the Honda NS400R (V3 2-stroke), has 1 larger diameter cylinder for the rear bank, and 2 smaller diameter cylinders in the front.
I could be wrong, been a long time since I read up on it.

[butcher bergs]

AFAIK the pistons are the same size (81mm), it's just the cylinder spacing that's altered front to back. Interestingly Honda does have different PNs for the front and rear pistons though.

That's because they are two different diameters.

[CBR929RE]

That's because they are two different diameters.

everything I can find says they are all 81mm. the rear bank connecting rods are next to each other on the crank to make the back of the engine narrower while the front bank rods are on each end of the crank.

[SVRACER01]

IIRC, the Honda NS400R (V3 2-stroke), has 1 larger diameter cylinder for the rear bank, and 2 smaller diameter cylinders in the front.
I could be wrong, been a long time since I read up on it.

which raises the question about the RCV. its a V5 but fires like a twin (3 at once and 2 at once) either the pistons on the 3 bank side are smaller to make the same displacement and weight as the the 2 bank or, if they are all the same size pistons, the 3 bank would fire a bigger bang than the 2 bank side.

in either case is essentially the same thing as what my OP was....right?

[Paul_E_D]

Do it Oxx, prove all these guys wrong!

[butcher bergs]

everything I can find says they are all 81mm. the rear bank connecting rods are next to each other on the crank to make the back of the engine narrower while the front bank rods are on each end of the crank.

I read a publication months ago that stated the pistons are different sizes. That's all I am going on. I doubt I still have it but I clearly remember it going into how the engineers were saying that the larger pistons assisted the low end power and as the engine started to spin up, the smaller pistons assisted the top end.

I believe the article was in Cycle World when the VFR was first released. There was a post-article bubble about the engine's design. I'm not saying it is gospel but I do remember reading this information.

[SVRACER01]

Do it Oxx, prove all these guys wrong!

lol

[Carbonzx10]

I've seen it done to an old snowmobile with parts from another, 440 jug on one side 340 on the other. It only ran for a week though.

[SSearchVT]

In theory - it could be done... I would look at a 4 cylinder (V or inline doesn't matter - it's theory...).

The crank (and every other part would need to be changed) so that it was basically 2 pairs of pistons (one small, one large) on the same power stroke. It would run like a twin, but have 4 cylinders...

[Pigman]

Ive heard that some remove 2 pistons out of a GSXR 600 and run them in the SV class....

[SVRACER01]

In theory - it could be done... I would look at a 4 cylinder (V or inline doesn't matter - it's theory...).

The crank (and every other part would need to be changed) so that it was basically 2 pairs of pistons (one small, one large) on the same power stroke. It would run like a twin, but have 4 cylinders...

in order for that to theory to work, i would think it would have to be a crossplane crank like on the R1. not mention getting custom cams and ignition made since the R1 still runs like 4 cyl and fires each cyl individually.

Ive heard that some remove 2 pistons out of a GSXR 600 and run them in the SV class....

i dont see the advantage to that. youre (hypothetically) cutting the power in half (60hp?) and only running 300cc. maybe a 1k. then you would be around 500cc and 75hp, but you still have to drag around all that weight with 2 cyl and try to spin a 4 cyl crank with 2 pistons. id have to see it work though.

[Stromper]

Old technological maxim

Just because you could do something doesn't mean you should do something

[CBR929RE]

Ive heard that some remove 2 pistons out of a GSXR 600 and run them in the SV class....

wouldn't this fall under not running a bike in a lower class? like you can't sleeve down an engine to run the bike in a lower displacement class.

[Degsy]

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Old technological maxim

Just because you could do something doesn't mean you should do something

I'm with Mr. Tin hat.

Bottom line, you could do it. It would last about 2 minutes unless you did a lot of balancing and tuning to make something work.....kinda.