A10 Noisy and running rough

[Marka10]

Slodger / Julian

Set the valve timing marks up correctly following the intrusions  "A10Boy" Marks on pinions aligned.

Results-

Valve Clearance      IO         IC      EO      EC
IN       EXH          BTDC   ABDC  BBDC  ATDC
0.008   0.010         60        70      90       40
0.020   0.020         50        50      80       30

Any Thoughts

Cheers

Mark

[Splodger]

Mark,

These numbers don't match any cam characteristic so I am assuming that your scrap of paper which shows the timing mark to be one tooth removed may be the key to the set-up you require.
So set up the pinions as before - timing marks matched - but now you need to have the camshaft pinion moved anti-clockwise by one tooth without rotating the idler wheel or crankshaft.
Do this by first aligning all of the timing marks. Then, without letting the camshaft move from its position, take out the idler pinion, rotate the crankshaft clockwise (and idler pinion anticlockwise by association) by one tooth  and replace the idler.
With the idler replaced, if you turn the crankshaft back one toothsworth, you should see the timing marks aligned between crankshaft and idler but the left-hand idler mark will show as your paperwork sketch indicates - one tooth difference between idler and camshaft.
As before, now check valve timing readings. Hopefully, they will reflect numbers which reflect recognisable values.
Fingers crossed!

[JulianS]

I suggest setting the tappets at 0.015 inch and check the timing again.

That is the figure BSA give for checking Super Rocket valve timing in the 1962 Data book. Attached below.

Be aware that the whole of your valve train needs to be perfect condition to get near the factory quoted figures.

Wear on the rocker assembly, the followers, the cam, bearings and bushes and pinion backlash also cause variations. One degree of movement lost at the cam pinion means two degrees out at the crankshaft pinion.

But if it ran OK for the first 800 miles, unless the cam and followers have suffered significant wear in that that time I cannot see that you have a cam problem.

On the compression test - using a simple Gunson tester on my alloy head A10 with Gandini 8.75:1 pistons (actual ratio will be a bit higher as head skimmed due to a warp) and 356 cam - warm engine, throttle open and 4 kicks gives me 160psi.

[Marka10]

Thank you for you replies, I will be an expert by the time I sort this out.

I will set valve timing back one tooth (Splodges suggestion)   and set valve clearance.    0.015"

see if this gets me near to the Cam 357 (inlet valve opening) 51   68

If problem still exists I will check for Air leaks and contact Amal to check carb components specification




My problem is I do not know what work was carried out during engine overhaul, due to the chap been deceased. so they could be worn parts but everything that a can see seem in good condition Pinions bearing (plain) etc have no signs of wear.

I look at the Cam shaft with endoscope and shows no visual signs of wear and there is no lateral or radial movement on the Cam Pinion

the question is, is the inlet valve opening time, which seem more than the setting effecting the over fuelling.

The compression is good about the same as yours Julian


Cheers

Mark

[Splodger]

Mark,

A helpful explanation re difference in A7/A10 crankshaft pinions is attached. Thanks go to cheshirebsa.

[Marka10]

hi Splodger

Thank you for information, really helpful.

Checking the bike against infor the pinions are correct for A10.

I think, from the valve openings the cam shaft is a 357 which is from the supper rocket, so I am wondering if the carburettor is correct for the valve opening going to check with Amal.

Cheers

Mark