Timing

mike916sp said:

On my 850 with Boyer igniton the auto advance range is about 20 degrees from tickover to 5000 rpm. The result of this is that if I set the timing at 31 deg at 5000 when it drops back to tickover the timings at about about 10 to 15 deg and the bike just will not tick over smoothly and pops and bangs in the exhaust and sounds terrible.

How do you solve that problem then other than by setting the timing to about 45 deg advance at 5000 rpm when it will then be on about 25 deg at tick over and sounds sweet as a nut

Click to expand...

The original Commando points auto advance unit had a range of *11* degrees, which equates to *22* crankshaft degrees of advance. So the original AA unit advance range (with points correctly timed) would have given an advance range between around *6* deg. BTDC at idle, to 28 deg. BTDC fully advanced.
I can only suggest you re-check your timing marks, as I've never experienced anything like that when using a Boyer on my Commando set to 31 deg BTDC @5000 RPM?

______________________________________
*
Correction

The AA unit range is actually 12 degrees -not 11 as I said, so that's 24 degrees of crank advance, from 4 degrees at idle.

Well that would take us back to:

http://www.accessnorton.com/norton_commando2465.html

when we all seemed to agree the timing was ok on the photo of the cam chain

mike916sp said:

Well that would take us back to:

http://www.accessnorton.com/norton_commando2465.html

when we all seemed to agree the timing was ok on the photo of the cam chain

Click to expand...

But that was more to do with valve timing? And I note what you said about ignition timing then:

mike916sp said:

its done about 38 thousand miles from new as it is (even though the timing more than likely will be out - actually its bound to be as I use the deg marks in the primary to set it and they can be way out) and when all is well it runs like a dream.

Click to expand...

Maybe your rotor mark is off? Or the timing plate is? Or both?
I can only suggest that you use a degree wheel (and piston stop) to verify the timing marks and TDC positions?

Thanks for the advice. I shall get over to the Stafford Classic Bike Show one day this weekend and purchase a degree wheel and give the timing marks a thorough checkover - they may well be the problem.

It should be a good day out and I can't think of a better excuse to go along to the show :wink:

Mike that was cam timing this is Boyer timing.

Yeah realised that after I posted - but to late then - misunderstood LAB's reply

mike916sp said:

Yeah realised that after I posted - but to late then -

Click to expand...

You can edit your messages after you've posted them Mike; look for the 'Edit' button on the R/H side of the message (when logged in)?

L.A.B. said:

I can only suggest you re-check your timing marks, as I've never experienced anything like that when using a Boyer on my Commando set to 31 deg BTDC @5000 RPM?

Click to expand...

The problem is solved. It was a crack on the pick-up unit circuit board which was interferring with the singal from the pick-up coils to the Boyer box. I replaced the pick-up unit with a new one and was then able to set the timing up fine just like I was always able to do.

These things sound so simple when you've found the fault - just half an hour to do the job plus a day of messing about with the LT wiring trying to find the problem in the first place!!

Not only do those stator plates crack, the coils can be loosened by ham-fisted bodgers pushing on the pickup coils to adjust the position/timing, thus resulting in loose coils and pickups which finally results in either very erratic timing (extremely hard to start), or total failure to start even when push-started. This one can be EXTREMELY frustrating to the average guy, because your static timing will be correct, you'll have a good strong spark, but it just bloody won't start!!!