Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Engine mounting bolts - How tight 1970 T100C

Can anyone tell me how tight the lower engine mount bolt should be on a 1970 500? The one that runs laterally across the engine, just behind the sump plug.

My laptop has died and I can't read my workshop manual.

Am chasing a persistent oil leak in this area. The two steel collars that sit inboard of the lower frame rails seem loose. I can spin them with my fingers. If they are that loose then they aren't bearing on the crankcase and I think the bottom joint is weeping.

I know they leak here but mine is pretty bad.

Maybe they should spin to prevent chafing the alloy casing?

Thanks

Hi,


Nearest I can find in the 'C'-range manual is "Crankcase junction bolts ... 15 lb./ft." or "Crankcase junction studs ... 20 lb./ft." (sic).

However, on the T160 (which essentially isn't any different to any other Triumph in this area), "(Engine mounting bolts) Bottom" is "30/35 lb.ft."




Maybe they aren't the correct length? When I built my '69, I measured the actual gap on the bike and made spacers to fit, rather than relying on the accuracy of some Far Eastern machinist without any responsibility for the quality or purpose of the parts. Also, if you make 'em/have 'em made to your measurements, no chance of you bending the lower frame rails when you tighten the stud/nut?

Hth.

Regards,

I'd just shim them up with washers and tighten the nuts to about 35ft/lbs.

davy

I'd guess that the principle is identical on a 500 to an OIF 750, in which case the nuts (on T140s it is a stud) or nut (if it's a bolt) have to be tightened sufficiently to clamp the spacers firmly between the frame and crankcase lugs. 35ft/lbs seems a good starting point. If 500s have 7/16" stud/bolt, you should be able to tighten a lot more than that safely.

I know its a Triumph, but surely the engine should not be relying on the engine bolts to keep the oil inside it!

Thanks,

It's a single stud with a nut on each end. I gave it a tweak and tightened up one collar. I'll have to shim the other one. The gap is .035" so I don't think I'd get a washer in there.

Thanks for the thoughts.

If the bike has been used with the spacers free to move for some time, chances are they've worn some of the aluminium away from the crankcase lugs, therefore necessitating shims. Normally, if the spacers are free with the nuts slack, just tightening them fully will clamp them up.

My laptop has died and I can't read my workshop manual.

Why I prefer the printed page.

A stainless washer is 46 thou thick so if you loosen both nuts off you should get one in there without too much effort, 11 thou is nothing at that point between the rails.

davy

Hi Davy,


It might be in Oz but that's a weird size. Here in GB, 3/8" and 7/6" i.d. washers - whether stainless or other steel - are punched out of standard 1 mm. (~40 thou.) or 2 mm. (~80 thou.) plate or strip; given how they have to be produced for the producer to make a profit, I'd be surprised if they're different in much of the rest of the world.

Regards,

It seems you have a choice between springing the frame rails out 11 thou or so, or clamping them up 35 thou. I'd choose the latter, as long as the crankcase lugs haven't worn significantly (if they have, making up the difference with shims would seem a good way to go).

Whatever Stuart, but I'm not about to argue with my vernier caliper on your account. I simply picked a stainless washer out of the box and measured it.
6 thou less would be in the OP's favour anyway.

davy