Twin cam pinion

Groily · Post by **Groily** » Mon Apr 27, 2009 2:03 pm

For the last thirty-something years I've been successfully removing twin cam pinions with a puller made of a bar of very chunky mild steel with a pair of 5/16th Cycle bolts into the pinion and a centre bolt of 3/8 BSF plus ball bearing in the hollow bit to ensure no harm to the oil pump drives. Never had even the hint of a problem - easy in fact.
Several times over the past few weeks I've attempted to get the exhaust cam pinion off a shot 650 motor in the shed.
I can now see why that camshaft was the only thing left attached to the motor.
First time, I tightened the centre bolt to the point that my 2 stalwart Cycle bolts stripped all their threads with a hell of a bang (luckily leaving the pinions' females intact).
Since, I've used a thicker bar - inch thick - and a pair of con-rod studs with double nuts to take the pull. Than which I can't think of anything tougher in my shed.
I have now bent the inch thick bit of bar significantly. I've applied as much heat to the pinion round the shaft as I dare, from a serious MAPP turbo blowlamp and even oxy-acetylene; I've given a whack or three on the centre bolt far in excess of what I'd normally administer to anything. I've left it under tension and with heat too. I've sworn at it a time or two as well, just in case that's what it needed.

Nothing has made any impression, whatsoever. Apart from destroying the tools. It took several tons in the hydraulic press to straighten out the bent bar . . .
I don't know if the thing was put on by a cross-eyed gorilla with a huge hammer, with the key cock-eyed; whether it's got a double dose of loctite and superglue; or what the hell has been done. But I just can't get it off.
Does anyone have any better ideas which don't risk busting the crankcase? Preferably short of machining the pinion off, which would be very non-trivial from the 'safe holding' point of view as the cam is of course in the case?
I'm going to try to make an even more rigid cross piece out of a bit of forged steel if I can drill and tap the stuff - but that's about the only other thing I can think of. I'm not that optimistic as I think it'll be a question of more threads failing, with an obvious risk to the threads in the pinion itself if I'm not careful. There are no obvious impediments - such as the thread for the end nut wrecked and raised and jamming the thing on.
What do you guys reckon?

petert120r · Post by **petert120r** » Mon Apr 27, 2009 6:15 pm

Sounds like the pinion has rust bonded to the camshaft over the aeons. Try immersing it in diesel in a plastic washing bowl or similar for a week and then trying again with an old socket over the camshaft end to protect the thread. Tighten the extractor tool as much as you dare, plenty of heat and a ******* good whack with a club hammer on the central bolt. Good luck!

TommoT · Post by **TommoT** » Mon Apr 27, 2009 6:52 pm

I had the same with a timing pinion on a single (yes I know it's a left hand thread!). In the end I used an angle grinder and cut off a section as close to the axle as I dared. I realize this pinion is much smaller than the one you're attempting to remove, but as a last resort, it's doable! Good luck! (you may need it!)

zwarts · Post by **zwarts** » Tue Apr 28, 2009 1:03 pm

I came across this problem some years ago. A very substantial bar type puller was unable to remove the cam pinion on a twin engine I was working on. The pinion would move slightly and then lock onto the shaft. I suspected that the woodruff key was moving outwards in it's slot and jamming the pinion onto the shaft. Fortunatley the owner of the engine had access to spark erosion facilities which were used to remove most of the key - the pinion then pulled easily, as they normally do !

Groily · Post by **Groily** » Tue Apr 28, 2009 1:12 pm

Thanks very much gents.

Made better puller, but no joy at all - and this one is REALLY chunky! I said the first one was an inch - well, I lied, it was only 21mm thick. And it bent. This one is 30mm thick and not bendable.

However, had tried diesel, and also coca-cola, following the advice of a lifeboat man who said it had been known to work on screws on marine motors, which get well stuck.

With a 9/16th centre bolt with a 1/2 in square milled on to take a massive ratchet bar, something was going to break and it wasn't going to be the tool. Something did . . . there seemed to be movement, oh joy! But, the end of the tool's centre bolt had mushroomed in the cam recess and with a huge noise cracked one half of the dog end for the oil pump. And I thought it was the thing starting to come. Disappointment or what!

So, the best bit being damaged, decided to grind the boss off the pinion along with the remains of the camshaft end. After much messing, and getting the 3/4in thick pinion boss down to about 3/8th, the thing came off with a lot of muscle power. The key had part sheared and smeared, and the pinion and the shaft were effectively welded together. Could have happened when the motor blew I suppose, if the valve train had been stopped dead by a piston when a rod broke (that much I know happened to it) and the timing pinion carried on a fraction. Hadn't checked the valve timing as the rest of the motor was in bits already, but now pretty sure the pinion was out of position from looking at the remains.

Shame, and a waste of bits, but at least the cases are intact. The pinion wouldn't have been much good anyway as it would have been mighty hard to get a good fit ever again looking at the extent of the smearing and scoring, although the camshaft would have cleaned up.

A least I know why the thing wouldn't come off. Goes under the Live and Learn heading I suppose.