Hi everyone, a quick message to ask for clarification about the above.
If the crankcase marking is -1/2 (ie minus one half of a thousandth of an inch) then what is the ideal marking on the gearwheel?
Is it also -1/2 or should it be +1/2, or something else?
Or have I got it all wrong? I'm assuming that we are talking of an ideal world when the components are new. Clearly the components will in effect be worn!
The engine in question is a "bitser", none of the components started life together.
Many thanks, Roy

Location: Yorkshire

Hi Roy,

If the crankcase is - 1/2 It would have originally had one gear standard, these are not always marked. And one gear marked - 1/2.

As you say used gears may be warn.

Any new gears on offer I would have thought are made to some sort of standard, I'm not sure how that works with + or - engines! But the lack of wear may work well.

I find the best way is to have a number of old gears, and try for the best fit.

Tony.

Location: HUNCOTE on the pig

I agree with Tony, Roy. The markings were relevant 80 years ago when the parts were new. Best to offer up an assortment of timing gears and pick a set that have
minimal backlash but importantly are not too tight.

I use the mix and match method as above, a 2thou feeler gauge fitting between the meshed teeth tells me I have the mixture just right.

Tony, Malcolm and Ruairidh, thanks for your help,I'm hoping that I've got it sorted now.
Roy

Location: Yorkshire

I am currently inspecting a "spare" engine. The crankcase is stamped in the usual place with a T. I have a wild imagination, but no way can I convince myself that it is -1. The T is complete with serifs. My question is, what does T mean? The cam gear is stamped +1/2. There is zero backlash.

Location: Wales

Just bumping this to the top, hoping someone can answer my previous post.

Location: Wales