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I'm trying to restore a 1978 GTL 500 and am having trouble removing the primary drive pinion from the crankshaft. I have tried two different gear pullers, and neither one has been able to loosen the pinion. The gear clearance to the back of the casing is also too tight to get the jaws securely behind it. Any suggestions on what other tools or methods can be used to get it free?

On a related question: From reading other posts, it seems that loose cam discs (preventing top-end lubrication) was a major problem for the parallel-twins. What other issues have been known to cause problems? I'm willing to get them all fixed, but if there's no need to split the casing, it would save me from fighting the pinion (and the two other gears with the same tight clearance issue).

I have no direct exp with pulling this specific gear but heat with a propane torch or heat gun on the hub, making sure to not heat the shaft will usually make things come apart easier. The gear will grow as it's heated and there will be poor heat transfer to the shaft for about 5 minues or so. You need to act quick to make sure the shaft doesn't heat up and defeat the heating of the gear. A few taps on the gear puller shaft while the puller is under tension also may help.

Driver31

Can't remember how exactly we got them off (+20 years ago) but sure we had to adapt some tools and apply force

Gasket between cyl and head was critical.
Two types were used : ordinary headgasket (later) or the bevel-type sunken cylinder (bad).
Oil going to the head was always a problem.
Solved it by machining extra dowel and o-ring.
Take care when tightening the head : the M8 bolt at the rear could snap the head.
Discussed the use of a alu bush with o-rings to connect the two cams but my partner in crime isn't among us any more.

Hope this helps.
cu
joseph

I finished restoring a parrallel twin late last summer (78 500 Desmo Sport) and found that the primary drive gear was tight on the taper and keyway.

We warmed it with one of those electric paint stripper guns (less aggressive than a propane torch). When we put it back together we put some WD40 on the taper to get it to seat ok.

When we started looking at the disassembled engine, we found a few problems that needed fiixing:

Both of the core plugs inside the camshafts were loose. We found that we could machine the inside of the cam (it wasnt that hard) on the lasthe and made up aluminium plugs to fill the holes properly. These meet in the middle of the cam sprocket so they cant come out.

On three engines that I have looked at the screw in oil pressure releif valve was finger tight, could unscrew, etc. We loctited and lockwired it in place.

On removing the grub screw for the sludge traps in the crank, we found that it was full of crap and needed clearing out.

Several of the rebates in the crankcases designed to take the sealing O rings for the oil system, were incorrectly milled. Most were too deep for the size of O ring normally used, by about 0.5mm. We milled them deeper and fitted oversized O rings - now no oil leaks!

Check the bolt just in front of the left cyclinder - this contains a restrictor for the oil supply to the head. Mine had a bit of swarf in it restricting flow.

If you need more help drop me an e-mail [email protected] and I will do my best to help.

I am just waiting for the better weather to be able to start using it now!

Chris

I have absolutly no experience with a parallel twin and have never laid a spanner to one. However reading your post the best accesorry to a 2 or 3 legged puller is a chain grip made by vise grip. It`s built like a vise grip but has a chain coming off it that can be wrapped around the legs of the puller and snapped shut holding the legs in place and making it impossible for them to slip out or move. As much force as you can muster can then be applied to the puller with out fear of the puller slipping off. They are the type of tool you never knew you needed till you had one and then can`t do without it.
I was sniffing around the net one day and stumbled across a site that was dedicated to parallel twins. I could be wrong but I think it was French or European based but it was wealth of information and very interesting. I`ve Googled it just now but come up with nothing. I know it`s not much help but maybe some one out there knows of the site and can point you in the right direction. Had lots of pit falls to watch for, common problems and the like.