Oil pump rear cover threads

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Jansen
Posts: 5
Joined: Wed Mar 10, 2021 7:17 pm
Location: Niedersachsen GERMANY

Re: Oil pump rear cover threads

Post by Jansen »

Spanielsam wrote: Mon Dec 28, 2020 2:35 pm Thanks for your replies, I guess if there is enough meat for a helicoil there will be enough for a M5 stud. The stripped 3BA thread measures around 4.1mm and so I would only be opening it up to around 5mm, my plan is to use M5 socket head setscrews as studs and then locking nuts to fix the blanking plate in place, if that doesnt work the engine will be pulled apart and crank case sent an engineering firm. The leak is too big to ignore and I am worried about the pump sucking in air
sorry I am a bit late to participate in this converstaion.But I just detected a stripped bolt at the pump cover plate on my '52 G80S, exactly as Spanielsam reported back in December. I was looking for the reason why the oil scavenging was erratic or not functioning at all on my bike, causing wet sumping while running. I was about to pull the plunger and found one of the 4 bolts loose due to a stripped thread. Just for a test, I put the loose bolt back in place with a blob of silicone on its thread, and also smeared silicone all around the plate and on the bolt heads in order to cover any possible air leak and -voila- the scavenging worked perfectly again. Apparently the slightest air leak causes the loss of the vacuum needed to suck up the oil from the sump. Now I have to find a way how to repair the stripped thread. I was thinking to do exactly what Spanielsam says, cutting a M5 thread "over" the damaged thread and glue a stud in place with Loctite, and then use a nut to tighten the cover plate. Of course it is a bodge, but sometimes these are the things you need to do to keep the old bikes running. Especially because spring time is here and who wants to strip down the engine now! ;) Cheers, Jan
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