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MG Midget and Sprite Technical - Timing gear alignment

Has anyone had to deal with the timing gears (1275) being out of alignment with the crank gear being too far forward? The factory crank sprocket had 2 shims equalling 0.012" which I have removed but it is still too far forward by what would guess to be about 0.015. I know it's not a lot but on a duplex chain only a few inches long its not ideal. Plus it's an expensive adjustable set so I don't want it wearing unduly. I'm considering having 0.010' ground off the back of the crank sprocket to get it just about bang on. Has anyone else done this or heard of it being done?

Maybe I'm being a bit too fussy, it's not a race engine after all!

Thanks
John Payne

I haven't come across that. Sounds to me that either the sprocket is wrong or the camshaft is too far back.

Is the gasket fitted behind the front plate or is this a dry run build?
Chris at Octarine Services

John
I had the exact same problem with an 1800 engine- .020" out with all the shims removed
Was going to machine the back off the crank sprocket but then the chain would have interfered with the tensioner-
Ended up shiming the front half of the camshaft sprocket out .020" from the rear half and all was well--
It would depend on the brand of sprocket kit you have as to if you can do that though -
Some have the sprocket bolted to the front of the hub,--which is how this one was, but some have the sprocket on the rear and shiming would multiply your problem
Also- the kit I had, had zero camshaft end float and I had to machine the back of the sprocket base a few thou-to get a good fit there as well
What started out as exciting ,opening the packet ended up not so much so but a good final result--Maybe it was made semifinish ready for hand fitting---------or not

I'd go ahead and spin the .012" off your crank sprocket and get it spot on, but if your 1275 has a chain tensioner you'll need to check for clearance there first
Cheers
willy
William Revit

Yes, camshaft all tightened and gasket behind front plate. The timing set is the one with Allen bolts to adjust from Minispares. I’ve used them before on a couple of other engines and they have been fine, though maybe I wasn’t as fussy then!

I’ll probably have a look at a way of shimming the camshaft sprocket out as Willy says but I think perhaps the outer sprocket is behind the centre.
John Payne

I think we* fettled the back of the sprocket to bring it into line.

* Alan Anstead using my file.

Graeme Williams

John, How did you solve this one?

I've hit exactly the same problem today.

Initially, the two sprockets lined up perfectly and everything was fine until I fitted the crank nut, when everything locked up completely.

After much head scratching and investigation, it turned out I'd fitted the crank sprocket the wrong way round and it was fouling the countersunk Allen screws.

With the crank sprocket the right way round, the two sprockets are well out of alignment. Removing the three shims from the crank shaft would reduce the difference by about 50% (can't get the woodruff key out, so might have to cut them off).

However. before I did anything drastic, I tried the old sprockets - guess what - just about the same misalignment! So it has run for around 20,000 miles like that without any signs of wear or undue stress on the sprockets or chain.

Did you shim out the camshaft pulley? If so, where did you get the shims from as they don't appear to be a normal catalogue item.

Graeme - How easy was it to file the sprocket? It looks to me as though it's hardened. I have a neighbour who's always looking for things to do with his lathe and milling machine and I'm sure he'd love to have a go at it if it's not too difficult.

I decided to leave it there for now while I mull things over but any advice or thoughts would be most welcome.

Colin
C Mee

I think I just lived with it Colin. As it was removing the shims meant the chain was very close to the countersunk screws so machining the sprocket would have made it worse. The screws were slightly proud so I ended up grinding them a little to clear the chain. Countersinking them more would have meant they might break through as they are very close to the edge.

I cant believe this thread is almost 18 months old! I've driven the car but not enough to have run it in yet, all sounds fine so far though.
John Payne

I wonder if this is an issue with the thickness of the front plate gasket - a thin gasket would move the camshaft backwards relative to the crank.
Chris at Octarine Services

That is true Chris, a lot of gaskets seem thicker than they used to. I use Payen gaskets so should be decent quality but you can’t always say that these days. A bit late for me now but might be something for Colin to look at?
John Payne

If its any value, I have a minispares adjustable timing set and I found I didn't need any shims. I stripped the engine to replace the cam followers in February (another story) After 7000 miles and 3 trips abroad, it was all fine and there was no chain wear I could discern. I renewed it anyway with a better quality Iwis one.
Bob Beaumont

Problem solved.

I managed to extract the woodruff key and the shims.

The two sprockets now line up perfectly, so all should be well when it's up and running and I'll have peace of mind and won't be worrying about excessive chain wear.

Colin
C Mee

This thread was discussed between 11/12/2018 and 03/05/2020

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