Drive train recommendations

Standard & modified running gear

Drive train recommendations

Postby MogDJ » Sat Feb 06, 2016 8:10 pm

Hi guys, an other query that's baffling me which I hope someone can advice me.
When I matched the moggy gearbox to the 1275 engine, everything become tight and locked up and the clutch would not operate. I machined the end of the crankshaft flange to match the original 1098 engine and everything worked ok. However, when I got the engine started, the clutch operates right at the top of the pedal travel, and tended to slip. Any advice on what I need to do to resolve the issue?

Any advice what is the best combination of 1275 engine, With a standard moggy gearbox and which diff would be best. I have 3 diffs and can't remember which I fitted, but I'm keen to get the right combo. Many thanks.
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Re: Drive train recommendations

Postby bmcecosse » Sun Feb 07, 2016 9:54 pm

All depends which flywheel/clutch/release arm/release bearing you used - and is it still mechanical operation? If it's a bog standard 1275 then it doesn't have that much more power than the 1098 engine (what carb did you use?) - and so a 4.22 will still be ok, and a 3.9 final drive better if you can find one at a fair price. The 3.7 final drives are getting to be stupidly expensive now - but you may be lucky!
 









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Re: Drive train recommendations

Postby MogDJ » Tue Mar 29, 2016 7:53 pm

Apologies for the delay in replying, other jobs getting in the way! The flywheel, clutch, release bearing and operating arm are the standard Moggy ones, and is operated by the original design of mechanical linkage. Not sure if I should have machined the end of the crankshaft flange, and I've read that possibly I should fit a spacer to the release bearing or bend the operating arm.
Any definitive advice on the best way forward would be appreciated. Thanks
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Re: Drive train recommendations

Postby bmcecosse » Tue Mar 29, 2016 9:48 pm

What backplate is on the engine? I haven't ever heard of anyone machining the crank flange. There are carbon thrusts with different 'offsets' so I suspect finding one with less off set will be the best way forward.
 









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Re: Drive train recommendations

Postby MM » Wed Mar 30, 2016 5:12 pm

Peep through the little oval inspection hatch in the side of the gearbox and check that you have enough carbon left on the release bearing - it should protrude from its metal backing by a good 4-5mm or so.

If you have a standardish 1275, I wouldn't go any higher diff ratio than a 3.9:1, which is what I currently have on my Traveller (1275cc Midget engine, Minor gearbox, Midget 3.9:1 diff); it is a fairly high ratio for a relatively small engine which gives good enough cruising, while still being low enough to allow easy trundling along in traffic and hill starts - any higher and the engine will struggle to pull away, etc.
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Re: Drive train recommendations

Postby MogDJ » Sat Apr 02, 2016 7:24 am

The backplate is the standard 1098 one that I modified to fit the 1275, to clear the oil pump etc, didn't know at the time that conversion plates were available. The flywheel was also off a 1098, which was re drilled to fit the 1275 crank.
When I fitted a new clutch assembly, thrust washer etc and fitted the gearbox to the 1275 for the first time, everything locked up solid, so after stripping it down again, I noticed that the crankshaft flange on the 1275, was thicker than the one on the 1098 that I had, so I presumed that I had to machine the 1275 one to match the original!! Sounds like the wrong move!!
The pick up has been laid up and not used, so the thrust bearing shouldn't have worn, but I'll check as suggested.
It may be that I'll have to remove the engine and gearbox and start again, but hoping that there is a simpler solution.
Thanks again for all the advice..
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Re: Drive train recommendations

Postby MM » Sat Apr 02, 2016 10:37 am

Perhaps try a longer or shorter clutch release bearing - see link below:
http://www.mg-cars.net/mg-midget-sprite ... 401247.htm

And/or clutch actuator arm? You could even fit a modern style hydraulic clutch actuator combined with roller-bearing release bearing - this sort of thing:

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