engine machining question

[agentpineapple]

a spanish friend has asked me if i know anyone who can bore out his cb750 engine, he's based in the east end, he's been quoted £80 a cylinder....
he's got some oversized high comp pistons and needs to go from 61mm to 65mm, so anyone got any reccomendations?

[turbo_billy]

That sounds steep. I know when I had the CBX barrels done it was £20 a barrel for bore and hone. Even with the extra meat that has to come off for the big bore he is fitting I wouldn`t expect more than double that. Can`t help you with an alternative though as the guy who did mine has closed up shop.

[lloydie]

That sounds steep. I know when I had the CBX barrels done it was £20 a barrel for bore and hone. Even with the extra meat that has to come off for the big bore he is fitting I wouldn`t expect more than double that. Can`t help you with an alternative though as the guy who did mine has closed up shop.

i had my old rg done for £50 for both barrels but that was 15 years ago .
i think he just needs to shop around .

[tony.mon]

Try Dartford Rebore, they're in, erm, Dartford.
Wherever you go, they'll need the pistons.
Insist they bore to min clearance, with each piston matched to it's bore.

[edds11]

it's the little things like tony's last comment that make a difference between an engine rebuild and a good engine rebuild. it the small things that matter. and if you ask the machinist what tony says then you will get a better job because it shows you know what you want, and he will do it sign of a good engineer.









still think me's a mango wurzel though

[bluestoesonnose]

Can't be bothered to argue but there are ways and means and your not telling the complete story

[agentpineapple]

Can't be bothered to argue but there are ways and means and your not telling the complete story

have i missed something?????????

[Z28DUNC]

a spanish friend has asked me if i know anyone who can bore out his cb750 engine, he's based in the east end, he's been quoted £80 a cylinder....
he's got some oversized high comp pistons and needs to go from 61mm to 65mm, so anyone got any reccomendations?

What your paying for there is the number of cuts. To go from 61mm to 65mm they've got to do say 7 or 8 cuts. A normal rebore of say .5mm might only take 2 cuts. Hence the higher price, more machining.

Anyway if your mates after another quote try Board Bros at Clapham junction.

Out of interest who's quoted him £80 a cylinder?

[agentpineapple]

a spanish friend has asked me if i know anyone who can bore out his cb750 engine, he's based in the east end, he's been quoted £80 a cylinder....
he's got some oversized high comp pistons and needs to go from 61mm to 65mm, so anyone got any reccomendations?

What your paying for there is the number of cuts. To go from 61mm to 65mm they've got to do say 7 or 8 cuts. A normal rebore of say .5mm might only take 2 cuts. Hence the higher price, more machining.

Anyway if your mates after another quote try Board Bros at Clapham junction.

Out of interest who's quoted him £80 a cylinder?

not sure who quoted him mate, whoever it was must be reasonably local to him in east london, i'll pass on the info to him, thanks for the heads up guys, jose is a bike mechanic by trade, he trained in barcelona, and worked for a race team in spain before moving to the uk, he said if he had the tools he would be able to do it himself but the workshop he works at only has general tools nothing specialised.....he a nice guy and always willing to help out....

[tony.mon]

An il4 has vertical cylinders, and so can be clamped to the table without problems, then bored vertically down.
TBH you spend more time clamping them down than machining, really.
The main machining is coarse and you can take off a fair bit at a time/pass, but the finishing cuts need to be much more careful.

It's those that need to be near size, then hone out to spec.
Unless you have a very expensive bore grinder.....

Your Storm is a lot more problematic, as the cylinders are at 45 degrees to the vertical, so you need a table which can be adjusted in the x or y axis, can't recall which is which now, years since I had a decent mill at my disposal.

I've used people who block and chock it up at an angle, but I'm never convinced it's true when chocked...

[edds11]

or you just take the barrels

[AMCQ46]

or you just take the barrels

problem is they are integral with the upper crank case

[edds11]

just checked that, thought it sounded funny.....deeeeer, 2 stroke days effecting my judgement.

[AMCQ46]

cant beat the smoke haze of a stroker..........which reminds me I need to get my little KH125 bored out for its oversize piston......the last bit of the rebuild, but I put it back together with the old scuffed piston to make sure I had got it fully running before I wasted any money on a rebore.

[edds11]

rebuild with the old piston and take it for a run, then rebuild it oversize and take it for a run and kid yourself how much quicker it is and how that was 'such a good buy'