How to up the torque on the baby ninja

[deviant]

It's just the perfect engine, and I have no idea why nobody makes them for sportsbikes?!

honda obviously used to, and may again, particularly now the motogp bike is a v4

the vfr800 is supposed to be replaced by a new vfr1000 next year, and theres rumours that a sports bike (RVF1000) is in the pipeline as well derived from the same motor.

[Boonie]

You're absolutely right. The reasons for not making V4's is the cost of servicing. The RVF/VFR 400's are great bikes but it's the man hours that make them expensive. My mates VFR800 costs £300 for an engine service as opposed to my R1's £127 at a dealer. The complexity of timing the cams, and exhaust system, also mean that development costs are higher and that money has to be recovered, making the bike more expensive than an equivalent competitors IL4 machine.

[mycallsevern]

You're absolutely right. The reasons for not making V4's is the cost of servicing. The RVF/VFR 400's are great bikes but it's the man hours that make them expensive. My mates VFR800 costs £300 for an engine service as opposed to my R1's £127 at a dealer. The complexity of timing the cams, and exhaust system, also mean that development costs are higher and that money has to be recovered, making the bike more expensive than an equivalent competitors IL4 machine.

Damn I was going to say that but had to do some actual work. Bloody job getting in the way again

[Bozzie]

no just servicing, production costs are higher for V4's . Its due to them being more complex than a engine that is one block. Where a V4 is effectively two parralel twins. Its why Honda has had so many diffrent revisions of the V4 and the early VFR750s are poor reliability.(think its the cam drive, don't qoute me on that though)

[Jamz]

no just servicing, production costs are higher for V4's . Its due to them being more complex than a engine that is one block. Where a V4 is effectively two parralel twins. Its why Honda has had so many diffrent revisions of the V4 and the early VFR750s are poor reliability.(think its the cam drive, don't qoute me on that though)

It was, and I quote "a production engineering oversight that allowed clearances in the top end to knock out camshafts" in the '82 and '83 VF750.

They went *bang* because of chocolate cams in other words!

The VFR in '86 had gear driven cams that, well, are the dogs bullocks and simply don't break ever! The 800's have gone back to chain driven cams... Why? As stated - production costs, rather than anything beneficial to the consumer or reliability.

When the new Honda Transatlantic race bikes didn't turn up for Donnington and Ron Haslam put a stock VFR750 on track - finishing 3rd, I believe - the legend was born!

Very short version of the history lesson there for you!

[Ballsout Racing]

To give the ZXR400 engine more torque you would need to change the piston stroke. Adjusting the crank pivot position isn't an option without making a new crank case, but you might be able to change the piston rods to longer ones and extend the barrel length with an additional section and another gasget. You'd end up with say a 430cc engine with maybe a slight drop in maximum rpm (down to 12k revs fo safety reasons) but torque might be up by 15%.

I love my book shelf.

Piston Rods ???, not sure what you mean, did you mean Con Rods ??, if so, lengthening them would make no difference!
The only way of making a longer stroke is to move the crank shaft journal (where the con/rod attaches) further away from the centre line of the crank

[Ballsout Racing]

Ultimatly the middle ground is a sqaure triple, giving what Triumph feel is the best of both worlds. (I think they actually use a long'ish stroke triple for the 675.)

The 675 engines revs are restricted due to the piston speeds, which are apparently much higher than the Jap 600s.(some are suggesting that this is the possible reason for some of the 675 engines using more oil than the Jap 4's) The longer the stroke, the higher the piston speeds at given revs!