LCGB Forums

I have a stripped thread on the stud located in a boss at the front of the crankcase, which is used as the lower fastening for the silencer. Have tried to unscrew the stud so I can replace it but, at the moment, it doesn't want to move. Looking down on the boss I can see the top end of the stud so am applying WD40 to this point in the hope it will ease stud removal. Before I do anything stupid am I right in thinking that the stud is not mechanically locked in place so should unscrew if the WD40 does its work.

Could you post a photo just so we know for sure which fastener you mean?

If it is a stud and not a bolt, hitting the stud with a hammer to "shock" the threads can help loosen it up. Use a proper stud puller as well. Something like this:

https://www.amazon.ca/Performance-Tool- ... B0000AXFMG

Struggling to add an image, how do you do it ?

Is the stud screwed into the front end of the right side (as you sit on the scooter) engine pivot bolt lug ?

Yes, that's the one. It's used to secure the tab welded onto the silencer.

My stud is out at present but, to test it, I've just screwed in a 6mm hex head screw from the bottom, using a 10mm spanner.

The screw only goes up until it is level with the top end of the thread on mine - no further. It may be that someone has forced your stud up higher than it was intended to go, and stripped the thread.

Personally, I would be a bit cautious about hitting it with a hammer, as it might damage the lug.

Thanks Al, When I look down on the top of the boss I would say that the top of the stud is about 1/2 millimetre below the top of the boss - like yours I would think. That means it will have to come out of the bottom. The exposed stud threads where the silencer bracket and nuts and washers fit is in a pretty poor condition, such that on a run last Saturday the nut must have come off leaving the silencer to move about the cylinder connection point. Thats why I started this post as the stud is proving extremely difficult to unscrew and I don't want to damage the boss. In fact up to now, after no end of WD40, it won't budge. I tried a bit of tapping on the end of the stud but that hasn't freed it. So now I will have to try a bit of local heat on the boss to expand it away from the stud threads. I just wanted to make sure that these studs were never Loctited in, but I suppose in 1954 when the bike was built Loctite didn't exist.
Was your stud easy to remove ? I really don't want to try brute force or the stud may shear off.

Panic over !. Tried the little blighter this morning and it screwed out easily. Thread was wet so I can only assume that, contrary to my earlier thoughts, the WD40 had finally done its job. Exhaust/silencer now replaced using a Hex Hd 6mm screw screwed up from the bottom of the boss to which I've added a stiff nut on the top side of the boss, so that should keep things in place.

That's good news!
I think there must have been a hexhead screw and a washer in mine, holding the silencer on, before I stripped the scooter right down.
I would have left the stud in there otherwise.
Glad you found a solution, anyway.