Primary cover fixings

[Oscarmark]

Having removed the primary cover from my A10, I noticed that 3 of the stainless Allen type bolts near the front were slightly larger than the rest... It appears that the threads have been damaged on the inner primary cover and a previous owner has tried to overcome this by putting in larger diameter fixings. My problem is, even these will not tighten... Are there any tips or advice?...

Thanks in anticipation.

Mark

[tombeau]

Hi there,
The 3 bolts at the front of the primary chaincase are thicker than the others. They actually thread into the crankcase to attach the chaincase to the engine. Are the threads ok in the crankcase?
Cheers,
iain

[Oscarmark]

Hi Iain,
Thanks for yor quick reply, I would say that the threads are therefore probably damaged on the crankcase. When I removed the bolts it seems that the holes ad been filled with some kind if silicon or mastic
I have to say, I don't remember there being any kind of oil leak?? Maybe I should clean the bolts and do the same when I re-assemble?
Mark

[Topdad]

Hi Mark, as Iain said those 3 are larger . Any resistance at all ? or do they just slip in ? Appears the prev owner didn't know his own strength which with an allen key could be a recipe for disaster! Whilst lookin in the primary case how are the 2 bolts just the other side of the engine sprocket, they should be locked up with wire ,worth checking again , given the proceeding . (If I remember correctly 1 of those 3 allen keys if screwed in to far will lock the crank )  re the threads clean 'em up and try the allen keys again check they are in reasonable shape ie threads not destroyed if still u/s they'll need to be fixed. please remember that anything inserted through those holes can end up in the crankcases thats why I don't like the idea of sillicon or mastic a bit  pushed into the crankcases could end up blocking oilways . Wiser heads than mine will offer ideas but I think you can helicoil insitu ,think you'd have to take the inner primary etc off but sure someone will know ,also anyone know if safe/practical  to use something like locktight bearing seal ,just an idea please wait until one of the real experts comes on ,they'll advise. BobH   

[A10Boy]

Ideally the engine should be stripped. The problem is that to fit a helicoil you need to pass a drill through, followed by a Tap. This will create swarf which will drop into the crankcase and onto the roller bearing below. You would have to remove the sump plate, and I'm not sure you would be able to clean ALL the swarf out of the cases. Hopefully someone has done this and will advise how they cleaned up.

[bsa-bill]

I did similar to one of the two studs behind the bearing ( the ones with safety wire) smaller hole than the front three though.

Used a hand drill as there's not much metal to take out, a good bit of grease helps collect the swarf, same with the tap.

after I used an aerosol up through the sump (not a degreaser obviously) think it might have been 3 in 1 spray to wash down the crankcase.
Not ideal but faced with a stripdown ??, BTW reason for the helicoil was  due to stripping the thread in the hole due to supply of wrong studs, they were way too short  and stripped out the first couple of threads as that was all they had a hold of.
Something to look out for if replacing them

[RichardL]

I could look this up, but I'm thumb typing and being a bit lazy. I wonder if the stripped-out diameter, if completely stripped out.
is close to the helicoil drill size? Controlling the swarf on just the tap would be a lot easier than with the drill.

Richard L.

[alanp]

Yes Richard I did this for a mate who didn't want to strip the engine down. I didn't need to drill the stripped thread out BUT it took a while to tap the new thread for the insert because for safety, to prevent aluminium bits going into the crankcase, I only took a 1/8th turn per tap cut with the tap greased each time and removed the tap each time to be able to retrieve the small amount of aluminium removed each time.
Tiz possible with patience.

[muskrat]

 I don't drill, just go in with the helicoil tap. Fill the flutes of the tap with grease and back out every turn or so replaceing the grease each time. Make sure the crank web isn't behind the hole your operating on. Magnetise the tang break off tool and add grease to catch the tang.
Cheers

[chaterlea25]

Hi All,
Helecoils or similar in my opinion are a no no for this application, there is a danger that they could wind inwards at some time when the screws are being put in ( no way of seeing this  ) and foul the crank
Timeserts are the best in my view , no tangs to break off either

Regards
John

[morris]

If the bolts still more or less hold, I would screw them in with some loctite, don't tighten them to much, and check from time to time that they don't come loose.
Then wait for a rebuild to do a proper job.
If you want to go ahead anyway, be sure to be as square as possible to the crankcase, otherwise they won't go in when the inner and outer cases are on.

And yes Bob, your memory is still OK. If the bolts go in to far (and believe me, a couple of thou is enough) they lock the crank (DAMHIK)

And John has a point also...

[bsa-bill]

If the bolts go in to far (and believe me, a couple of thou is enough) they lock the crank (DAMHIK)

So it's not just me then

be sure to be as square as possible to the crankcase

Good advise Morris  and re doing it with the cases split, but don't be put off having a go if you don't see a teardown happening for some time.
Being as there is a hole there to start with it's not to hard to keep square providing you let the drill or tap find it's own way through, no side pressure left right up or down
Good luck with it