G80 Rigid Timing Tip

[Iron Head]

Apologies if this has been reported before but I thought I'd post my recent finding concerning timing that is a different approach to most of the manuals/books I have read. All it simply entails is loosening the magneto sprocket (rather than the drive sprocket) on its taper, finding your 7/16" or 1/2" BTDC (wife's wooden spoon works a treat and can be returned to kitchen once marking is sanded off!) and then rotating the points assembly until release of fag paper. Re-tighten magneto sprocket - job done.

Probably nothing in it versus loosening the drive sprocket but it felt a lot easier this way and, somehow, more accurate.

Iron Head

[clive]

Cannot disagree more. Never worked when I used the magneto sprocket always moved as I tightened it up. For 35 years I have always used the drive sprocket. Amazed you have got it to time right the first time using the mag sprocket.

[Rob Harknett]

Also no mention of setting the AR lever fully advanced.

[Iron Head]

Thanks for the feedback guys and sorry for omitting to mention A/R Rob, good point.

Obviously your experience may be different Clive, and I may well have 'got lucky' but it really was easy to let the magneto sprocket float on the shaft, push it onto the magneto taper once timing was in place and then tighten up. Don't forget the chain/sprocket is being nicely and accurately controlled by the drive sprocket being tight.

The other factor to bear in mind is if you are doing any magneto work with the magneto off the bike then you have undone the magneto sprocket anyway. I don't see the point in removing the drive sprocket as well.

Just my opinion here..........

Iron Head

[56G80S]

Have to say I usually use the drive sprocket and recently varied from this approach and just couldn't get it right.

Part of it was that I usually (when using drive sprocket) get the setting sorted and then gently tap the sprocket onto the taper. This locks on a bit and then do the nut up.

Doing this on the magneto (automatic A/R on SR1) I was wary of damage and probably didn't tap firm enough.

Gave up and went back to what worked well over the years.

Nonetheless the AR unit still not returning to full retard properly and getting a bit of kickback but al least the "real" timing is right. Judicious use of the valve lifter helps minimise the kickback.

Rob - Thanks for your advice on this, I just can't fathom it, it's working smoothly and promptly off the magneto. When fitted (been off and on several times) it's pulling back to half retard rather than staying at fully advanced though. Might just leave it for a bit and get more runs in.

Johnny B

[clive]

Jonny B Have you got the mag chain too tight this can affect the return of the a/r unit. Also worth investing in new springs if you have not already done so.

[Brad]

I had the problem of the AR unit not returning to the full retard position when on the bike and as Clive suggests, the chain was a little too tight. It only took a very small adjustment to free off the AR unit.

[56G80S]

Thanks for the thoughts. I replaced the springs a couple of years ago (they're all bright and shiny still). Rob Harknett had mentioned checking the chain but I have it set OK, there's a very slight tight spot but allowed for that. I'm still using the old chain from when I got the Matchless in mid 1970's as it has minimal wear. I do have a new Regina chain but the one on is a "real" Renolds and running in a greasebath seems to mean that it wears practically not at all by which I mean nearly no stretch.

I've a couple of other things to sort out but will go out for a good run when these are done and see what difference that makes.

Thanks again.

Johnny B

[clive]

I had the problem of the AR unit not returning to the full retard position when on the bike and as Clive suggests, the chain was a little too tight. It only took a very small adjustment to free off the AR unit.

John two of us have experienced the same problem as you and solved it by giving the chain a bit more slack, it may simply be fractionally too tight, so I would not dismiss this as a possible solution.

[Rob Harknett]

I would say consider the chain is a little too tight also it may not yet be clean. They takes ages to clean fitted, uses quite a lot of fluid to wash out muck while working the unit by hand.