MK1 rear crank gear knock - again

[camstevens]

Hi All
I just completed a successful BA gearbox overhaul (thanks to great support from Geoff Brown), working beautifully. After a lovely ride to Bowl of Brooklands and back, the rear crank gear released and started knocking again (I know the sound by now!).
Once I lift myself out of the depression I have been thrust into I will seek to get this sorted.......I inserted a new key and used green loctite, which had been successful for a while but I guess the level of interference has been compromised to the extent that I need to do somenting different. It may also depend on whether the wear is predominantly on the gear or on the shaft.

A solution may be to replace the gear(s). If this is a viable approach, much gears be "paired", or can just the one be replaced? Can new gears be procured? Is there another approach?

Regards
Cam

[nevhunter]

Those gears have to be a tight fit on each shaft. If it's just relying on the key it won't go long. Nev

[camstevens]

Thanks Nev
I'll need to dive in and measure things up. I imagine the term "pairing" of the gears would tend to mean that the two gears have worn together at the same rate? I would have thought wear on the gears would be minimal in any case. Does anyone have the spec measurements for interference?

Cam

[nevhunter]

They are heat treated and the GROUND to eliminate any warpage effect. Maybe they are in matched pairs originally a HOT motor will be running more clearance than when cold. There's a lot of "fighting" going on between 2 linked flywheels. There's all that gubbins attached to them to reduce noise. . The biggest worry is not tight enough fit on the respective shafts. to prevent the KEY hammering. Nev

[simon.holyfield]

I wonder if electronic ignition would help the knock - they knock even if the shafts is in good nick, and some of this "fighting" must be down to uneven firing caused by clearances (wear) in the distributor.

What do you think?

[camstevens]

Hi Simon
I'm sure that imbalance would not help, but my issue is somewhat worse the teeth themselves knocking....when the gear/shaft slips it's a horrible nasty noise.....one suggesting imminent damage

Cam

[simon.holyfield]

Hi Simon
I'm sure that imbalance would not help, but my issue is somewhat worse the teeth themselves knocking....when the gear/shaft slips it's a horrible nasty noise.....one suggesting imminent damage

Cam

Understood - I appreciate I was taking the thread a bit off - topic!

[nevhunter]

Firing pulses are of a small order compared with torsional harmonics when you essentially couple TWO engines together by a set of gears each with it's own flywheel.. Nev

[camstevens]

Hi
My focus is on rectifying the problem. Patch-ups are not a good approach because of the potential damage (if it happens a long way from home, you're stuck). I'll get the gear off and measure things up.......maybe a replacement gear that's less worn, or maybe repair the existing gear with metalspray (or similar) and ream out to size.

Cam

[nevhunter]

Couldn't agree more but it's not easy to fix properly. OK back then when everything was new. Do you have quite a bit of backlash in the gear teeth them selves? Nev