valve timing

[ronnie]

RESULT RESULT !!!!!! Cant believe it ,, the valve timing was well out , all fixed now and the performance is fantastic compared to what i was used to . Tried everything , changed everything to no avail , and all because some numpty put it together wrong . thanks to everybody for there input

[brucek]

Glad the problem is sorted - enjoy the new found performance and watch out for those yellow boxes at the side of the road

[bmcecosse]

Well done indeed - and for having the determination to search out the problem and put it right. It's most unusual - well done for finding it!

[les]

When I saw the state of the camshaft sprocket lockwasher, it confirmed your suspicions to me; anyone who makes a mess like that sure wouldn't worry about the dots lining up. Glad you're sorted.

[win]

Hi all
I have a 1275 Midget engine, I was never quite happy with it, I don't really know why.

The ignition timing always appeared to be too far advanced, to start properly, but never pinked, starting it with the handle, you knew it was advanced. But the engine appeared to run OK.

So I read this thread about a valve timing check, with more than just mild interest.

I have just done the VALVE TIMEING CHECK METHOD.

On No 1, after setting the valves to .010" at TDC on the non firing stroke, turned the engine until No1 is firing, on TDC, checked the gaps, inlet .033" exhaust .072", a difference of .039". Checked using the same method on No4, identical results.

Removed the timing chain cover, the dots look to be exactly in line, as the book shows.

Any comments would be most welcome.

Regards Win

[bmcecosse]

That's quite a difference - they really should be the same within a very few thou..... The dots may not be accurate - the timing check cannot fail. I would move the sprocket round a tooth on the cam sprocket - and then check again. I think it's running a tooth retarded - so I would turn the cam forward one tooth. Be interesting to see what you find !

[win]

I will do that tomrrow, and report back.

[bmcecosse]

By 'cam forward one tooth' - I mean just that, so it would mean moving the chain back one tooth on the cam sprocket ....

[win]

Hi all
To recap, inlet .033"-exhaust .072 with sprocket timing dots in line.
moved camshaft sprocket clockwise one tooth, inlet .066"- exhaust .039".

Looks like mid way would be better.

I know you should never scale, but look at the pic with the rule lining up the dot and center of sprocket, compared to the sketch of the setup, is the key way too far anti clockwise.???
Is making a stepped key, an option, or risk trying a new pair of sprockets.

Or am I completely missing the obvious.

Regards Win[frame][/frame]

[bmcecosse]

Stepped keys are indeed available from Minspares etc. and adjustable sprockets too - but not inexpensive and I think always for Duplex. I would run it as it is now and see how much better it runs ! Thanks for coming back with the results.

[MarkyB]

If you look at the drawing the crankshaft key isn't at 12 o clock.
I'm sure this is what leads to problems as without the book in your hand it doesn't seem quite right.

[bmcecosse]

It's just a guide to alignment - the rocker gap check must be done at TDC - not necessarily with the dots lined up....... I hope that's what has been done ?

[MarkyB]

You are joking surely?
What adjustment is available apart from where the teeth engage the chain?

[bmcecosse]

Offset keys and adjustable sprockets.......

[win]

Checks always done with crank at TDC, I think a 5 degree offset key to advance camshaft should be about right.
Regards Win

[bmcecosse]

I presume you mean 5 degree forward on the original setting ? As I said earlier - I would run it as it is with the cam moved forward one tooth. I think it will run really well like that! As a point - do you know if it is a standard cam in there ??

[win]

Sorry, no idea which cam.
Why not try to get it spot on, or do you think it will run better, one tooth advanced.

[les]

Win, shouldn't your rule pass through the centre of the crankshaft and camshaft sprocket? Looks like the dots would line up then.

[bmcecosse]

By all means try to line it up - but these offset keys are a menace to work with. I do believe it will run really well now you have brought the timing forward. It was retarded - now it is advanced. But it is your choice - you have gone to all this trouble to find out what's wrong, and well done for that, and I can understand why you want to see the job through and get it spot on!

[win]

Well spotted Les, you are correct.
But I had moved to sprocket round one tooth to try and get the valve timing nearer, this gave me my second readings.

Regards Win