A10 Noisy and running rough

[Splodger]

Hi Mark,
I asked about the camshaft because a too-tight clearance on the exhaust tappet(s) will give you hiccups in the exhaust - popping and banging.
But.... I keep coming back to your original note which read that the bike ran OK for 700 miles or so. Therefore the set -up that you had worked OK with the cam you've got, the valve clearances you had and the carb settings.
So, what's changed?
My suspicions run towards the ignition system you currently use. Perhaps it has a fault? Can you revert to the original mag set-up and see how that works?
Check that vibrations over 700 miles haven't loosened/frayed connections throughout the ignition system, coils and condensers.
As previously posted, rubbish fuel will also give problems. Get some super unleaded or better octane stuff.
Fit new spark plugs as well?

For interest:
Cam   IO   IC   EO   EC
   btdc   abdc   bbdc   atdc
357   51   68   78   37
366   40   62   67   37
334   30   70   65   25
356   42   62   67   37

Set tappet clearances to .020" to check.

There is a 358 hi-liftcam but that was for US market and/or drag-racing lovers.

Yes, you have to split the cases to get the camshaft out, not a five-minute job!

Hope this helps.
            

[Marka10]

Hi Splodger

Thank you, the all the info and experience is very helpful.

I have gone back to the Mag and points and seen no notable difference.

It is defiantly a over fuel problem. The right plug is sooty in minutes and the right plug get flooded and stops firing.

You are right the bike ran reasonable ok for 700mils but was always very rich even after fitting a new monobloc carb and adjusting needle height and pilot air, made little difference always rich.

But after I Helicoiled the plugs it got  worse running really rough and over fuelling, don't know if helicol mad difference.

I opened the inlet valve clearance to 0.015 and it made a small improvement.

Also found some information, amongst paperwork with the bike  from the person who did the rebuild, now deceased. He set the valve timing 1 tooth off ??, I set it correct and made very little difference. See drawing.

Not sure where to go next, don't want to strip engine if not necessary, everything sounds ok at bottom end. Compression good and equal on both cylinders.

This is a definitely a challenge, first classic bike, bit frustrated but enjoying learning.

Cheers
Mark


   

[Marka10]

Looking at the valve timing info you posted it looks like I have

Cam 357

Cheers

mark

[Splodger]

If you've reset the valve timing after the problems began, did you offset the timing mark as indicated in the sketch?
There has been a similar discussion in the past:(https://www.a7a10.net/forum/index.php?topic=8856.0) which addressed timing marks when an A7 pinion had been used.
Read that topic. I'm reluctant to say that this is the problem because if you reset the camshaft position and it is not correct, you may cause damage - you may not but I would suggest caution.
If you reset timing on the cam by one tooth, take the plugs out and turn her over very slowly to check TDC and valve timing degrees.

[Marka10]

Hi Splodger

Do you know the difference between the different CAMs in your list?

will read similar discussion.


Mark

[Marka10]

Hi quickly read the similar discussion I think I need to identify that the all the pinions are correct, not sure how to do this?

[Splodger]

Mark,

Your pinions must be OK for the bike to run 700 miles.
You did write that you lined up the punch marks on the pinions but you didn't get a significant improvement? But... you've got Inlet opening at 700!
That's not right.
If you line up the pinions as indicated in the sketch you showed, what does that achieve with valve timing figures?

With acknowledgment to A10Boy, 'To avoid a valve / piston interface situation, take out the plugs and carefully set the pistons at the bottom of their stroke. Then turn the camshaft until the dot points to the center of the idler, then turn the crankshaft so the pinion dot is also towards the center of the idler pinion. Then slot the idler back in position with the marks correctly lined up.'

More hassle to do this again but if you can get this set right you won't have to address that question ever again.
If you get the valve timing correct(ish) according to one of these:
   IO   IC   EO   EC
   btdc   abdc   bbdc   atdc
357   51   68   78   37
366   40   62   67   37
334   30   70   65   25
356   42   62   67   37

.......then you can discard the valve timing as the cause of 'running rough and noisy' and concentrate on the sparks and carb/fuel/air leaks. And, you'll know which cam is fitted.

[JulianS]

Dots lined up.

[Marka10]

Splodger/Julian

Thank you for information

I will reset the valve timing and measure the valve opening, see picture 1 and see which cam is fitted and get back to you before putting covers back.

They are some numbers on the pinions

Cam pinion - 338
timer pinion - Difficult to read see photo

Cheers

Mark

[Marka10]

Photo 1

[Marka10]

Timer pinion

[Marka10]

Some thoughts:-

Do you know why there are different cam shafts for same machine?

My bike as the alloy head- does this make a difference?

[JulianS]

The early 67 334 the standard iron head cam used until about 1958.

the 67 356 was more sporty and introduced on the Star Twin and fitted on the Super Flash and Road Rocket )and the iron heads from about 1958)

The 67 357, the Spitfire cam, came with the Spitfire scrambler and found its way into the Super Rocket and RGS. It was described as super sports cam and gave the engine more grunt, and in my experience gave a bit more valve train noise.

The 67 358 is rare and according to tuning notes not for the A10.

The was also one called the Polydyne sold by Bob Joyner in the 1960s.

The US companys Megacycle and Harman and Collins also produced a number of different A10 cams.

[Marka10]

Hi Julian

Interesting, thank you.

Are they all  suitable for the A10 Goldflash and the standard carb 250 jet?

Mark

[JulianS]

I have used the 356 and 357 in iron and light alloy heads. Both seemed to go OK.

Used 356 with a big valve light alloy head this year and needed a 400 main jet and 3 1/2 slide needle in 3, S and B air cleaner fitted. Only following the Amal tuning guide will establish the right settings for a particular bike.

Only seen one 358 and from memory looked like it had a smaller diameter base circle.

Never seen a polydyne, Megacycle or Harman and Collins nor spoken to anyone who has used one. I would imagine they would be quite rare.