GL1100 Engine2 1975_gl1000 GL1100 Engine2

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GL1100 Engine2 GL1100 Engine2

Transmission Cover Screws - Corrosion and Removal

The original screws holding this front transmission cover are JIS cross heads, made from cream cheese I think!

Almost invariably, they are corroded into the cover and  the cross wil rip out, even if you use the correct JIS screwdriver on them.

Using an impact driver will almost guarantee this happening, or the heads breaking off.

The heads with the ripped out cross can be drilled off, release oil put on the remains and usually the cover will lift off eventually leaving the stubs of the screws to be removed, with a stud tool if they are really tight in the block.


But sometime you can hit a real problem!


On the left side of the transmission cover ( the right side as looking at the cover from the front of the engine)  the outer screw goes into an 'ear'  cast into the crankcase just to the outside of the water transfer hole. This ear can relatively easily be broken off  the cases if you get heavy handed with the screw removal. I've had crankcases with that fault.

That's not good! Very difficult to remedy by welding as the case around the hole gets distorted, meaning the O ring slot would need to be welded up and re-machined and the face of the block leveled.

That could prove to be expensive and just a tiny fraction taken off that face could see you with gear change problems due to the lack of clearance!


In reality you would be looking for another block, with all the problems that entails.


In the process of rebuilding an engine for a customer I hit this problem, hence this article.

I tried everything I know to release that screw!

It was so corroded into the cover that eventually, after spending three hours at it, I had to use the Dremel with a cutting disc and cut through the cover on both sides of the screw.

Brutal solution! But I had no choice. The cover had to come off to split the cases. You would not believe the corrosion between that screw and the cover.

Fortunately I have a spare cover and once the old one was off all the stubs of the rest of the screws came out fairly easily.


The problem with that particular screw is that the threaded hole in the crankcase ear is open to the elements from the rear. The solution, once you have replaced the screw with a new one, is to back-fill the hole with some epoxy sealer to keep any moisture out.

I find the 'two-part sausage' type that you cut a slice off and nead between your fingers, available in any auto store, to be the easiest to use.


Before replacing the screws, make sure to run a plug/finish tap (6 x1.0mm) down the threads to clear out any corrosion. You might be surprised how much rubbish you remove out of each hole!

Clean out the bolt holes in the cover too, maybe run a drill down them, and make sure that the anti-seize covers the screw right up to the heads.


Be sure that you use a COPPER anti-seize on ALL the screws when replacing them.



Here's a neat idea!


My friend Robin Ray in the USA has put together a stainless steel Allen screw kit, with washers, to replace those ruined OEM screws. He will ship wordwide.


Go HERE to check that kit out.



pictures to follow..

WinGovations Copyright 2016

J G Evans

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