1275 cylinder head

Post by **Stig** » Fri Aug 05, 2005 8:33 am

'scuse me butting in here, but I'd like to know what sort of grinding bits you used too. I've previously tried using some little drill-mounted grinding stones (probably Draper) on a head and all they did was polish the surface. Good for a decoke, but not much cop for porting.

Post by **Alec** » Fri Aug 05, 2005 1:25 pm

Hello Stig,
fisrtly, mounted points are not intended for electric drills, they are far too slow, (die grinders run at about 20, 000rpm) but I know they do work at the expense of rapid wear.
Try an engineers merchant and go for a coarse grit for material removal.

Alec

Post by **Pyoor_Kate** » Fri Aug 05, 2005 9:12 pm

I dunno if it's true for porting stuff, but I've had very effective grinding balls/cylinders for use in drills, and they've been pretty effective - at the expense of very rapid wear. We used one to correct the incorrectly shaped starter-motor-hole on the 1275 backplate (grr) and I used one a long time ago to smooth out the head of a ETZ125 after it's small end bearing disintegrated and the bits of metal that made the cage for the needle rollers got sucked through into the combustion chamber where they were fired at great speed into the head.

Post by **Alec** » Sat Aug 06, 2005 7:04 am

Hello Kate,
but if you were to use a high speed grinder you would see and feel the difference, and also much easier as no real force is required. What is even more effective is a rotary burr, especially if you get the carbide type. They remove serious amounts of metal and last for ever if cared for.
Die grinders are actually available for a relatively modest cost but of course require an air supply. There are electric ones but more expensive than air driven ones.

Alec

Post by **bmcecosse** » Sun Aug 07, 2005 8:14 pm

I think for all the work I do - my £10 leccy drill is just fine ! Yes the stones don't last all that long - but they are about £3 for a packet of 6 all different sizes - down the market - and will NOT be safety rated for a high speed grinder ! Safety tip - wear goggles & mask and use an old vacuum cleaner to suck away the grot dust. I have done some very comprehensive heads in the past this way - but this head was just a clean-up job to 'unsink' the exhaust valves.

Post by **mu0u207b** » Tue Aug 09, 2005 12:52 pm

Sorry guys im still little inexperienced with this grinding lark. Ive got a leccy drill which will rev at fair rate but not sure wat u mean by mounted points and the ackual cutting bits u used. Ive looked at the local hard ware store and they got the miniture grinding and polishing stone sets and also diamond tip grinding bits. Am i barking up the wrong tree. What grinding material should i be looking for, i.e tunsten carbide? Any help guys. Cheers.

Post by **bmcecosse** » Tue Aug 09, 2005 1:11 pm

Tungsten carbide burrs would be excellent - but again designed for high speed die-grinder. These are just cheap grinding stones - 'mounted points' - example is 1" diameter ball mounted on a 1/4" dia shaft - like a lollypop - they also have smaller and larger shapes pink/white/blue all in the pack for about £3. It is NOT the tiny little things sold in Poundland for use with Dremel and similar toys.