BIG BORE KIT

[Poby]

I need your professional opinion guys. I have a Z900 A4 which I am rebuilding after a Cam chain guide break up, lots of money so far! Anyway a bit of a school boy error when ordering pistons. The old piston was a .5mm oversize (Bore 66.5) and I went and mistakenly bought a 5.0mm oversize wiseco kit (1045cc) doh! So I now need to rebore the sleeves to 71mm as it says “only a rebore required for z900â€Â￾ on the kit. I took it to a respectable engineer (albeit 4 wheel type) and he measured up and the current spec is Sleeve External 73.5mm Internal 66.5mm. When he has rebored it the spec will be External 73.5mm and Internal 71mm leaving a sleeve wall of only 2.5mm.
Questions
Is this normal and will the Sleeve be man enough for the job?
Have any of you guy's done this conversion and is it successful/worth it?
Will I need to mess around with rejetting Carbs etc?
Should I revert back to the .5mm pistons and try and sell the 5.0mm oversize.
Sell the bike bitz and save up to buy one of those sexy ones from Z Power?
Advice greatly appreciated.

[Buckle]

As the americans say "There ain't no substitute for 'cubes, boy"

seriously though, Debben should be able to advise on cylinder wall thickness etc.

Their contact details are on the Links section.

[Steve R]

I would ring SEP engineering up and have a chat with them. I am fitting a 1075 kit to mine and that does need z1000 barrels.
Sep are on the links page.

[FOZ1A]

I believe that 1045 is the max that std barrels can be bored to.Go to Wiseco web site and all the info you need to know is there.

Foz

[grumpuszed1]

big hello from saltash!!!! this has nothing to do with your post i just thought i would welcome another new member to the club, maybe catch up some time?

[Pigford]

My RedZed has 900 barrels running a 1045 Wiseco kit... no probs

[Poby]

Cheers chaps, contacted your man at Debben's and after a bit of a discussion he say "no" - Well not exactly no but he wouldn't advise it for a road bike. His wisdom is that with 2.5mm sleeve thickness it's going to get hot patches and all sorts of probs may occur, alright for a race bike which gets rebuilt after a few shots but not for your common garden zed on the road.
So it's back to the states to get a different set, does anyone want a set of Wiesco 1045's with rings and pins before I put of the dreaded EB, been fitted to crank but that was it.
Grumpuszed1 will catch up with you when I get at least one of my bikes on the road, just waiting for the liquid sunshine to end to get to work on them!

[Thezedsintheshed]

Why dont you just get hold of a Z1000 cylinder block and get it bored out to fit the 1045 piston kit ? This would probably work out at about the cheapest and most effective solution and also leave you enough liner thickness for 2 future rebore sizes if needed , 1075 and 1105 .

[Garn 1]

Poby, the last idea of fitting Z1000 barrels/ sleeves is good, however, I understand it would require some removal of metal from the cases to fit the larger sleeves. That's not an easy job unless the crank-cases are split.

I agree, 71 mm bores in the standard 900 sleeves leaves them a little thin on the side-walls. although I have seen quite a few bored to this measurement.

I think the best idea is to e-bay the big-bore kit (pulling good prices now) and proceed with the 0.5 mm oversize option, if the bore is good and pistons are not worn, re-hone and fit new rings. The bonus is, you don't have to stuff around re-jetting etc.

RegardZ.

[Big Fluff]

Your other and simple option is to bore out the block to 70mm and fit standard Z1000 (1015cc) pistons. The compression ratio will automatically increase giving a tad more oomph

[chrisu]

and I've got a set of std pistons with brand new rings in my shed I might be willing to sell/trade if you really don't want to go down the 1045 route.

[chrisu]

sorry - should have said Z1000 pistons........

[pablo]

Pigford - what's your carb set up for the 1045? I'm just fitting a bored z1000 block to my z900 and wonder whether the standard z900 carbs will do, or whether I should re-jet. Waddya think?

[Pigford]

Hmmmm, if your engine was a bit worn before, and its now got a nice fresh 1045, then it may not necessarily need re-jetting.
This may sound daft, but a new engine will be more efficient & the slight extra displacement often won't mean the carbs need messing with.
Both me old Z1A (that went from 903 to 1015) and the RedZed, (from 1015 to 1045) ran/run OK with the same carb set up, before & after
You could play safe and go up a size or 2, to start with...

[pablo]

I'll stick with the standard for now. Got enough problems caused by knacker'd cam chain. Hrumph, moan, belch.