Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Timing belt trouble

Quoting Richard Wood:-
"Helical timing gears are a lot quieter and really a must. Velocette tried straight cut in the 50's when they introduced the M series. It was found acceptable on prototype engine but the thinner timing cover on production models forced them to use helical gears which solved the problem".

I know helical gears would be quieter but they also impose axial loads on the shafts and/or bearings on which they are mounted, and these loads would have to be accomodated in the design of the complete set-up.

I believe, if the timing cover (it would obviously have to be the early type without the cooling slots) were to be made oil tight by means of a gasket and provided with a filler plug, a drain plug and a level plug so that the lowest gear (i.e. the gear on the crankshaft) could be up to half it's diameter in oil, the gears would then be running in oil.

I believe this would reduce the noise to an acceptable level but this would need to be proven.

Two comments from the peanut gallery...

If the belt is OK other than the hairy edge, I would get out the propane torch and while the motor is on idle, I would singe the hairs off with the torch being careful to not burn the belt material itself. I've done this before and had no issues.

But if those are cracks in the back side of the flat belt, change it out now and move on.

As far as the gear drive goes, I was going to say the same thing about the axial load, but even with straight cut gears running oil, there would be some parasitic drag due to the oil bath and gears. That's why they put windage trays and dry sumps in race motors.

I personally think that straight cut gears on the motor would be way too noisy and would be a constant distraction from the fun of driving the M3W. Guys on small block Chevys take out the timing chains and convert to the gear cam drives mainly to make them sound like a big blower mounted up front. Yes there is probably a tenth of a hp to be gained by gears over the timing chain in the SBC, but it's about the noise. Believe me with just four gears it's way loud.

In the M3W there would be a few more than just four gears.

Again just an outsider's opinion.

I would suggest you contact Matts Machine Shop in South Wales to get a new belt, they are certainly cheaper than Morgan. Ask about the modification kit for the crankshaft drive pulley, bolt and idlers at the same time. If it doesn't already have it, the front cover should have the gasket removed and spacers fitted to give some cooling airflow, also slots in the front cover. The "snake skin" debris in cam belt case area is the release agent from belt manufacture and is normal. Not seen a "hairy" belt like that before, looks like you may have got it just before failure? With all the mods done, Morgan say the belt life is 30,000 miles.

What makes MMC so certain that with the increased ventilation the belt life could be expected to be 30,000 miles.

This can only be an assumption on their part because this figure has yet to be proven.

With regard to the noise Dan I think you may have a vakid point.

Having said that, most british bikes had gears for their camshaft drives and as far as I know, Velocette were the only manufacturer to go to helical timing gears and from memoery I do not think anybody complianed about the noise from the timings sides of engines made by other manufacturers.
(Velocette were always a bit un-conventional, you only have to look at their clutches to see that).
The Vincent had 6 straight cut gears in the timing case and all but the last one (which drove the magneto) were steel.
The majority of the mechanical noise produced by the Vincent twin engine was caused by the strange cantilever cam followers that they had.

Dan states that the noise of timing gears would detract from the pleasure of driving the M3W.
I do not think this would be a major problem as it would be inaudible over the screaming bevel boxes.

I can't hear the stage 1 exhaust over the BB once its warm so I would worry about the gear noise you should be fine

Maybe you should include Moto Guzzi as well although I'm sure I could find others. I appreciate the axial load issue but in a former life I sold many helical gear conversion kits based on that of the OE V7 Sport model (see below), to owners of later models that were fitted with a timing chain. It was assumed this was on the grounds of cost saving. We never had any load issues, indeed I road nearly 100,000 miles on one bike fitted with these gears and without issue, although the original design was to accommodate such.



The lower gear drives the oil pump.

Good one there...

Concerning the use of helical timing gears and Richard's initial reference to the Velocette, I merely stated that as far as I was aware most british bikes had gear driven camshafts and that Velocette were the only manufacturer (to my knowledge) using helical gears.

I have no doubt that Richard (given time) could find many other examples of non-british bikes with helical timing gears.

I can only bow to Richards vast knowledge of motorcycles which is obviously far superior to my own.

Sorry I genuinely didn't mean to offend

Just defending an earlier post I made.