I thought they simply removed the backlash gears to reduce friction in race engines...? Are friction losses even lower with a chain? Not sure about the aprilia thing..

Removing the backlash gears is first step in reducing friction however something many dont realise is that the backlash between the cam + the drive gear needs to then be measured to make sure there is not too much play, on a stock head if the play is too much then the gears need to stay but on a skimmed head the cam carriers can be shimmed up less than the head skim to keep the backlash correct but will still be better than with the backlash gears in place

The camchains benefit as friction is reduced even further, gear driven cams benefit from reliability as a chain cam stretch + chains have been known to jump a tooth or 2 when tensioners fail or chain wears too much

Chain driven cams make it much easier for skimming + dont need to run huge shims which although only very minimal it reduces valve train weight
All the little bits add up

Whats the name of the place down oxford way mate? If you need any help with anything down this way drop me a PM. Know a few people who have had alot of engine work done on thier bikes so may even know about the place.

There was some detail given on the G-Force site about the issues they had boring these cylinders.
I also agree with most if not all of this useful document http://www.brushresearch.com/pdf/GB.pdf

Two Cents Worth:
How are they going to hold the block?
Are they going to make and use a torque plate?
What taper and ovality limits can they produce to?
How many cuts will they take to remove the 1mm?
How thick will the last cut be?
What grit will the final hone be?
Even if I could find someone to answer those questions. I would then want to measure samples of their work with a dial bore gauge and micrometer (certified instruments not Chinese digital verniers) before considering letting them loose.

Having said that, the UK has some of the most advanced automotive facilities in the world (as opposed to where I live at the moment), so I am sure that finding someone capable of doing an excellent job is not difficult, but convincing them to do it for you might be the hard part.
cheers
Blair

Camchain?
A MotoGP engine

http://www.pinterest.com/pin/565694403164473996/

james66 wrote:Removing the backlash gears is first step in reducing friction however something many dont realise is that the backlash between the cam + the drive gear needs to then be measured to make sure there is not too much play, on a stock head if the play is too much then the gears need to stay but on a skimmed head the cam carriers can be shimmed up less than the head skim to keep the backlash correct but will still be better than with the backlash gears in place

The camchains benefit as friction is reduced even further, gear driven cams benefit from reliability as a chain cam stretch + chains have been known to jump a tooth or 2 when tensioners fail or chain wears too much

Chain driven cams make it much easier for skimming + dont need to run huge shims which although only very minimal it reduces valve train weight
All the little bits add up

Excellent, many thanks for that.

I've always preferred the concept of gears to drive 'loaded' parts of the engine such as cams, oil pump and primary drive as given a decent oil supply the reliability is high and wear is kept to a minimum. Look at any truck engine designed in the last 40 years and you'll see most have gear driven everything.

I have no issue with chains, never really had much upset with chains although the auto tensioner on the Mrs bandit had gone weak and stuck barely touching the blade. As such, skipped one tooth altho no damage was done luckily. It's now got an APE manual one which I inspect on occasion but I've never needed to adjust it since installation.

Sorry for the thread-jack.

http://motomatters.com/news/2010/07/31/ ... nd_to.html

Apparently gear driven cams used on the Aprillia were banned as they allow 'the RSV to attain higher revs and allow for more precise cam timing.'

Maybe you could drop Rick Oliver a message or give him a call? His NC30 is kitted with some extra cc ponies (non standard)

james66 wrote:The pistons are omegas,

Something like these



I will be interested to hear how you get on as I will have the same job to do in the future. Fingers crossed you find someone who can do a proper job

Where are you guys finding these pistons???

PLEASE someone share this info!