1962 A10 Flash, Starts, but won't Pickup

[CheeserBeezer]

As stated on many occasions, "Carburettor problems usually turn out to be electrical!". An observation that, unless they're blocked, carbs usually deteriorate over time. TerryB says he has checked the carb. Whilst others have "poo-pood" my suggestion of a magneto issue, I have come across this at a rally, where the points weren't springing back quickly enough due to stiffness. Unlikely, I know, but an easy check. I have also come across arcing at the slip ring as the revs increase. Don't forget that a magneto becomes more powerful as it spins faster and, therefore, arcs and shorts more readily. I'm not saying the problem is definitely the magneto. My money is still on a carb issue, but I wouldn't rule the magneto out of the equation because a) I've seen a mag cause this problem and b) TerryB reckons he's checked the carb. If the main jet is clean and the float bowl is filling at a reasonable rate, I would turn my attention to the mag.

[Terryb]

Fingers crossed I think the problem could be, that there was a needle seating washer missing from under the float needle seating assembly. Apparently all new Monobloc's have them. So what was happening that the lower float needle assembly was restricting the float movement. I will try it in the morning and let you know how it goes

[Terryb]

Well, tried the new carb with the fibre washer under the float needle assembly and no luck. Still will not run and pickup, I even tried a different fuel supply thinking that it may be fuel starvation from my tank and no luck. So I'm going to try a different carb and if that fails, then she goes back onto the table and I will start from scratch with the timing. I checked the spark on both cylinders and they look OK, I also checked the point gap.

[limeyrob]

Can you reach in the carb and move the slide up by hand?  Also what happens if you squirt some petrol in the intake?
Even if the timing is way off if it starts it should run even if it spits and misfires.
The other check is to put your hand over the intake briefly and see what happens.

[berger]

if a different carb doesn't do it buy my yonda , now where was i o yes pouring a black&tan now  i'v sampled that expensive gift of cognac , yummyumm

[BagONails]

Sometimes in cases like this it helps to go back to first principles and do all the checks involved to ensure suck, squeeze, bang and blow is all being supported in the correct way. Don't cut corners and tick everything off only when you are truly satisfied its OK. 

I wasn't sure after reading this whether you've had it running correctly before swapping the carb to the new one? Or whether the new carb was an attempt to fix an issue that was there before and is still there or maybe more than one problem?

If the bike has been standing there are many opportunities for things to cease working in their intended way, corrosion, drying out, all sorts of ageing and environmental impacts. Also think about everything you've disturbed while swapping parts? Maybe that old gasket that looked ok with a bit of grease on it may actually be letting air by? etc.etc.

Can be frustrating but kind of goes with the territory...

 

[CheeserBeezer]

If you think how much time you've spent on fuel issues you're probably up to 5 or 6 hours? It takes an hour or so to swap the mag. Do you have a spare mag or anybody locally who would lend you one? I'm happy to lend you one. At some point you have to, at least, eliminate the mag as the problem. If you swap the mag and there's no difference you have eliminated it.

[Terryb]

I needed to change out the old carb, due to its poor condition and not knowing if it was originally fitted by the previous owner. The bike hadn’t run since 1989 and I bought it last year and completed its Resto last November and started commissioning and after a half mile run, chicken out, it had suicidal brakes🥴 so yes she has run ok. Since then I’ve renewed both sets of shoes and installed an 8” brake at the front and I thought that when the roads dry out, I’ll resume the commissioning 🤞 So it looks like she’s going back into the sick bay 🥴

[Terryb]

Sorry CB didn’t see your post, the Mag has been refurbished, so I don’t suspect it, but thanks for the offer 👍

[Billybream]

I had a similar issue a few years back, after winter layup, usual maintenance tasks, carb clean etc, bike started up, but would not rev, tried every thing, then decided to remove the carb, and quickly discovered I had not located the needle correctly within its clip.

[Terryb]

Billybream thanks for that info, it’s something I’ve not checked and I remember changing the needle height 👍 all my carb checks have been concentrated on fuel supply, didn’t suspect the needle. Silly me 🫣

[Terryb]

Checked this morning and the needle is fitted correctly 

Sick bay here she comes 

[Rex]

If you've changed the carb then it's not that. Fuel supply seems OK so it's not that, and the mag has been rebuilt so (presumably) it's not that either.
Are you sure the timing hasn't slipped or is OOA somehow? ATD OK?
I have a certain US V-twin which needs full retard to start and full advance to rev. Get it wrong at your peril.

[CheeserBeezer]

Just because the mag has been done doesn't mean it is OK. We're dealing with old stuff and not everything is as straightforward as it should be. I restore magnetos and occasionally something goes wrong and I just have to suck it up and admit it. How much time have you spent chasing this problem now?

[Worty]

Just because the mag has been done doesn't mean it is OK. We're dealing with old stuff and not everything is as straightforward as it should be. I restore magnetos and occasionally something goes wrong and I just have to suck it up and admit it. How much time have you spent chasing this problem now?

After everything you've done, I'm with CB now.  I was supplied a maggie by CB some time ago, then had problems after about a year - bike not running properly/misfiring, etc.  CB sorted no quibbles.  The point is that the last thing I thought of was the maggie due to it coming from CB.  My assumption was that it should have lasted longer.  The only thing that put me back to pointing to the maggie was the nature of the erratic running, and a bit of logic.  I would imagine it's quite possible for the bike to fire up but not rev out due to problems with the maggie or ATD.  If your carb is functioning properly, I can't see what else would give this problem apart from valve clearance issues.