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MG Midget and Sprite Technical - My engine update...

So I've been very, very busy recently with work and racers and also rebuilding a bike engine so have had very little time to even look at my own midget. It is the poor sibling.

The engine has finally been picked up by the mechanic guy I use, Shaun Bateman. I simply don't have the space or the time to work on the A Series myself and nor do I have enough intuition to find the root of the problem (not yet!).

Few observations when he picked it up, some of which I already knew about:
- Spigot bush was wrecked
- Peter May 7.5 clutch pressure bush (the bit on the end of the fingers?) has sh*t loads of play in it, probably caused by the fact that the thrust bearing was overthrowing. Significant blue heat marks on the bush and on the thrust bearing so it must have been making contact at the wrong points.
- Certain amount of play in the clutch plate itself..

So seems like some of the engine and gearbox mating wasn't particuarly good by the last garage who put it together (an easy mistake in fairness, especially with aftermarket clutches etc), or it suffered vibration.

Anyway, the block is going to be examined and all the components are going to be balanced, just to make sure it's all good again.

Might be back on the road by early summer, you never know...
Rich Amos (1 Sprite 1 Midget!)

you might have thrown us a picture or two

considering we have to wait forever for the next update

:-)
Bill sdgpm

Hah! I'm riding down to his workshop tomorrow to pick up some bike engine shafts he's taken with him (quite enjoyed having a play with bike bits, he's never done that before!) to do some heavyweight work to I don't have tools for, so I'll take some photos while I'm down there for you people if he has the MG stuff lying about.

One very, very busy job, one race car, two bikes, one very active racing community, one very active biking community.... rapidly learning what it's like to grow older, have too many toys and not enough time...
Rich Amos (1 Sprite 1 Midget!)

Rich

I have plenty

have some (not all) of mine. ;-)

look forrards to seeing the knackered clutch component pictures, they seem to be a facet of Midget/Sprite life lately
Bill sdgpm

Didn't get a chance to do the clutch, but here's the thrust bearing:

http://www.flickr.com/photos/77673728@N00/3353334977/
Rich Amos (1 Sprite 1 Midget!)

That is a horible sight

the fork is holding the carbon thrust offcentre which is one reason it is wearing out

if you are going to persist with 1940s engineering do make sure you get the fork lining up so the thrust sits as close as possible to central on the input haft

or concentricalise

A shot of the clutch cover too please, when you've time of course!
Bill sdgpm

Wasn't me doing it. I think that fork has been thrown all over the place what with the vibrations etc. Anyway, yes, I will look at a concentric but I need to find out how much is wrong with the engine first as my wallet isn't endless....

Clutch cover, I think, has been chucked. Or I didn't see it at the garage...
Rich Amos (1 Sprite 1 Midget!)

Also, I assume it could have been thrown 'off center' by the wobbly bush on the clutch, or vice versa. Chicken and egg, all I want to do is get the engine fixed!
Rich Amos (1 Sprite 1 Midget!)

the engine IS a priority of course but if the fork stays that offset even a Peter May or Morry Minor centre roller bearing will soon give up the ghost.

You may think you had overthrow but in fact the eccentric running will break diaphragms even on moderate movements such as the normal designed fork will give

Think about it, the fingers on the diaphragm work to release the pressure plate but only on the "offset side" of the bearing. It has to have a bad effect on the preesure fingers, snap! the spring plate snaps

I did my CSC on less than a ton, so did Guy

when you're ready to think the unthinkable gizza shout and we can get you helped on the way

PM does a very snazzy front bearing seal doodah that fits the present fork carrier location and it isnt much more than a revitalised front cover, drilled and tapped to mount the CSC on to it. I'm sure a similar adaptation can be home brewed...

as to why the clutch showed signs of high hotness, look no further, I reckon the offset dunnit!
Bill sdgpm

Oh the fork isn't staying! I replace the fork every time I split the engine/gearbox. It's just whether it gets a new fork... or it gets a different thrower such as a concentric.
Rich Amos (1 Sprite 1 Midget!)

On a positive note, it's likely not overthrown. Which is good. That's one shaft not necessarily buggered.
Rich Amos (1 Sprite 1 Midget!)

This thread was discussed between 13/03/2009 and 14/03/2009

MG Midget and Sprite Technical index

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