h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Apart from increasing the diameter of the bore what else is necessary for a full engine re-bore?
And will the engine be lighter or heavier as a result of a re-bore?

From my extremely limited technical perspective (hell, I ride the thing, someone else can fix it - so much for Zen and the Art of Motorcycle Maintenance) you'd need new pistons etc. I had my GSX750F taken out to an 800 with a lovely set of wiseco pistons. Didn't plan on the rebore, it was deemed necessary after finding one of the cylinders and pistons were mangled...

I'd guess the engine wouldn't weigh much more or less - after all, you're taking out some metal, but also adding some - the pistons need to fill the holes to some extent...

Ahem. Well, perhaps someone else can answer your question in a more satisfactory and undoubtably more correct manner....

Are you in the club? Would you like to join?

Bad

for the info

I don't think I'm a member yet, would love to become one though if you get the time

Usually a rebore won't have as dramatic an effect as going from 750cc to 800cc, that's more an overbore than a rebore!

If I remember correctly different engines can take different numbers of rebores. Usually done at .25 stages. You can tell if it has already been done by looking at the piston crowns which will have the amount of overbore (if any) stamped on them. I think 3 or 4 overbores is usual but may be wrong. Obviously with the pistons and rings being oversize you do get more cc and thus a bitr more power. Work out the cc increase, you will probably have to tell your insurer and the likes of 750cc to 800cc would probably result in an insurance premium hike (depending on local rules and regs for insurance).

Also do remember that you are removing metal from the bore sleeve and thus making it thinner. This is what limits the number of rebores and size of overbore you can have, make it too thin and 'bang' no engine

The engine should be marginally lighter since you are removing the metal from the sleeve and, although as pointed out you have bigger pistons, pistons are not solid and the actual amount of extra metal in the piston to take up the gap is minimal.

If it is a .25 rebore then you almost certainly wont notice any difference on any medium of large engine (well, other than it should start working properly again )

WShy you having the rebore, has the sleeve become worn or scratched?

I was just thinking about rebores and wondering about what they were and what they do to the engine. I have read articles about bikes being rebored (usually in Streetfighter Magazine- where they rebore to them to incredible sizes and dragrace them) in the past and I was just curious about what is involved. And what the bonus might be apart from extra cc's.

Apparently, so I have been told, the inside of my CB's engine is v. smooth so I don't need a rebore at the moment. (Phew!) Just as well really because I need her on the road.

I know that re-bores are a completely different thing to engine bores

TaskMan, would you care to nominate a first, virtual, current bike(s)?



Bad

First bike: Yamaha TY-80 then a Suzuki GP125 for the road

Virtual bike: The Proton 1000cc two-stroke that was featured in Bike magazine last month but I cannae remember any more details

Current bike: Honda CB750 K2

Ya just gotta love a Honda CB. Used to have a 900 bol'd'or meself

Welcome TM.

Hey Bad whadda ya doing at Easter? Fancy a run to Adelaide?

Taskman, my humble apologies - I've only just updated the member page, but you're there now!

I'd love to ride to Adelaide, PR. But I'll probably be waist deep in paperwork and assignments and my thesis. Unfortunately, this year, I will probably have no life. New job, last year of part-time study, that sort of thing. However, I do plan on getting to Sydney at some stage - my mum lives there - so I'd be honoured to buy you a beer at the Australia hotel on the rocks - Scharers lager is one of my favourites...is that how you spell it?

Love your attempt at a smiley, by the way, Taskman...

Never mind Bad Viv and I will be thinking of you while we're away

I look forward to buying you a beer or two while you're in Sydney, twill be my pleasure.