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MG Midget and Sprite Technical - Revs drop/car won't start with clutch depressed

Ok guys here's the issue.

I bought a 1970 1275 midget a few weeks ago, and have been having a great time driving it nearly every day since. It's had an issue with starting though - car cranks slower, voltage drops, I thought the battery was just a bit sad, but I have discovered that it works perfectly when the clutch isn't pushed in (I was taught to start a car with clutch in and gearbox in neutral - I won't be doing this in the Midget in future). After talking to the local Sprite expert on the phone he suggested I start the car, and holding it at 1000rpm, push in the clutch to see how much the revs drop. Well, it dropped to about 800rpm, and his response was that the crankshaft thrust washers are shot.

Searching through the archives here it seems possible that this could be due to the clutch release bearing instead, is this possible? There is no grinding noise or anything like that. I have also noted all the warnings in the archive and will be careful not to hold the car with clutch in to avoid wear. I have yet to try and check for movement in the crank, I will see if I can get to that this afternoon. If it is the clutch release bearing then that would be excellent, as I have a 5 speed Toyota box here waiting to go into the car anyway.

Finally, if it is the crankshaft thrust washers, I was told that these can be replaced with the engine still together, (and even with it still mounted in the car) but that this would be a temporary fix and that really the crank would need to be machined as it would probably have damage that would chew out the new thrust washers. How important/likely is this? I will have the engine out of the car to change the gearbox anyway, so can do it if need be, but would just like to gauge some other opinions.

Any ideas or advice greatly appreciated.

Thanks, Andrew.
AndrewF

Andrew. Get someone to sit in the car and depress and release the clutch while you watch the crankshaft pulley for forward and backward movement. This will give you an indication that the thrust washers are worn.
If you are going to pull the engine anyway, that would be the best time to do the thrust washers and also check for crank damage. If the washers are shot, there will probably be other wear in the engine, bearings, rings etc. so all in all, as it's coming out, it would be a shame to put it back without at least checking it over, seeing as you are putting in a fresh gearbox.
Bernie.
b higginson

I would suspect the carbon release bearing. This is arguably the weakest link in the drivetrain. The A engine has a sturdy lower end, especially compared to the Triumph 1500.
Glenn Mallory

Glenn. That is indeed true, but I bought a 1275 Midget resto project some years ago and the fore and aft movement on the crank pulley had to be seen to be beleived. When I got it stripped I found it had severely mangled the front main cap and what was left of the thrust washers fell out looking like they were made from cooking foil. The P.O. had been driving it like that without knowing anything was amiss.
Anyway, the test I mentioned earlier should give some indication of the state of the washers.

Bernie.
b higginson

It's my feeling that the engine shouldn't be started with the clutch depressed anyway. This places a load on the rear thrust bearing before the oil pressure builds.

-:G:-
Gryf Ketcherside

Usually with the test that Bernie mentions, you need to first lever between the front pulley and the cross member to push the crank back as far as it will go. Then watch to see if there is forward movement again when someone else depresses the clutch.

If there is, and you have caught it soon enough, it may well be sufficient just to drop the sump and replace the thrust washers with the engine in situ. Only in severe cases would it have damaged the crank necessitating a re-grind.

Guy
Guy Weller

Thanks for your thoughts guys. I quickly tried to check for play last night, just by putting my hand down on the pulley and having my fiancee depress the clutch. I hadn't levered the crank back first. I think it may have moved slightly, but certainly not much. How much play is an issue? Is any noticeable play an issue? I think I will lift up the car this afternoon and lever the crank back if I can, and then eyeball it from underneath while she pushes the clutch, as it's difficult to see any movement where it is currently.

Gryf, having read through the archives I will not be starting the Midget with the clutch depressed from now on. I was taught to both depress the clutch and put the car in neutral as a sort of 'doubly safe' method.

I think regardless I will pull the sump when I pull the engine and have a look to check the condition of things. I was keen to rebuild the motor at some point anyway, I guess I might just have to bring it forward. The one thing I haven't done yet with a car is rebuild a motor, what books/manuals would people recomend I buy as a guide and for clearances, bolt torques etc? In the past I've done engine, gearbox and brake conversions, and all sorts of other repairs and rebuilds both bodywork and mechanical so I think I'm up to the job, but I will want some good detailed documentation to be sure I don't miss anything.
AndrewF

Andrew. The Haynes manual is pretty good. It has all the torque settings etc. It has good pictures too and covers all models of our cars. If you can't source one locally, Ebay has them on from time to time.

Bernie.
b higginson

hey andrew,

the haynes, vizards bible (how to tune the BL A-series engine) David stapletons book (Are we allowed to mention the name...LOL) and minia mania on-line tech session and this BBS websight, you will be able to build the engine in your sleep.

byw..the haynes has a minor flaw about the camshaft and oil pump installation....but its simple enough to fiure out and I was fortant to have no less then 10 people walk me thur the hayns flaw

good luck with your build.


Prop
Prop

Ok, I levered the crank best as best I could in the small space with a long screwdriver. When the clutch was depressed there was very definite visible movement, at a guess maybe 1mm or so. I am thinking this definitely means the thrust washers are shot, correct? Correct movement is meant to be ~6thou and shouldn't really be visible right?
AndrewF

I'm ignorant on the A-series, but on my rebuilt 1500 the crank play could be felt but was, as you suggest, not visible at all.

R
Richard 1600 5 speed

This thread was discussed between 17/11/2009 and 20/11/2009

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