Popping back through the carbs

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This summer i went to help a local Noc member with a 'freshly restored' non starting mk2a 850 with exactly the same symtoms as the OP. He insisted that he had checked the timing etc I rapidly found that he had timed it on the wrong rotor mark, he still insisted that it was correct so i let him carry on.... After watching him trying for another fruitless 15mins or so i then said 'shall we do it my way now?' I retime of the boyer rotor and 10 mins later she fired up.
Although i could start the bike, the owner couldn't, his technique was just too slow, He then said that he had knee ligament damage/problems....
I politely suggested that he invest in an electric start kit as i could see this bike giving him some real grief.
What is the standing voltage of the battery?
How did you use a dial indicator 'to set the valves'
TDC should be found using a piston stop or dial gauge and a degree wheel. Just using a dial gauge is inaccurate.
Describe exactly how you set the ignition timing.
Report back what you find
 
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Fast Eddie said:
What does ‘fart’ mean ?? (you might think me pedantic, but I’m not, the more accurate your description of the symptoms, the better help folk will be able to give you).

A big engine like this will always make a noise through the carbs when kicking it over, air being sucked in or pushed out (like a fart), especially with no air filter fitted.

Is it actually firing, or not? Ie does the fart sound different with the ign on / off ?
Click to expand...
I would interpret that as the "PFAT" soft blowback, rather than a sharp "pop" through the carbs.
 
Butch at TriStar Cycles owned the local Triumph shop in the 70's. He can't figure it out either. The battery is good, and we boosted it while kicking. The valves are set, the timing is spot on, the valves are set, we have spark, compression, and new fuel. The only thing that I can think of is low floats in the carbs, but I set them to the specs Amal says to set them at. I just don't know what to do next, other than put a Boyer or Trispark on it.
 
Never heard of Butch, but we're all allowed to miss something now and then. Did you leave it with him for a repair or bring it by for 20 minutes of dinking around? If he took it in for a repair, and gave it back with a shrug and a bill, find a new wrench. If you guys just fussed around with it, take it back to him and leave it for an actual repair, including the rev ceiling issue. That ain't right.

If you're committed to DIY, why not triple check all the mechanicals with your dial and wheel: TDC, ignition timing, valve timing, valve lash, (perhaps even the valve lift to check a dreaded flat cam/wrecked lifter scenario), clean out your #19 pilot jets, fresh gas, etc? Eat your Wheaties, put on your biggest boots, give a spray of that ether and...

Sounds faster and cheaper than a new ignition system -- that very well may not be the problem after all, if you're getting spark now, and will probably have to be done anyway since you say it never ran right. It sure is nice when it's just a failed component, but sometimes it's just us.
 
Schwany said:
I use an AK47 approach to troubleshooting. lol

Nortons are kind of sensitive to inaccurate timing.

This won't help but is a fun example:

Have you ever timed a carbureted V8 180 degrees out cuz you were in a hurry and not paying enough attention to what you are doing? If you have, you know it will backfire up through the carburetor and not start.
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Yep. FWIW I bought a basket case '69 Commando waaay back in the 70's and it wouldn't start either, only pop when I kicked it over....it turned out that to PO had reversed the ignition points wires at the coils, fired right up when I corrected that.
 
t ingermanson said:
Never heard of Butch, but we're all allowed to miss something now and then. Did you leave it with him for a repair or bring it by for 20 minutes of dinking around? If he took it in for a repair, and gave it back with a shrug and a bill, find a new wrench. If you guys just fussed around with it, take it back to him and leave it for an actual repair, including the rev ceiling issue. That ain't right.

If you're committed to DIY, why not triple check all the mechanicals with your dial and wheel: TDC, ignition timing, valve timing, valve lash, (perhaps even the valve lift to check a dreaded flat cam/wrecked lifter scenario), clean out your #19 pilot jets, fresh gas, etc? Eat your Wheaties, put on your biggest boots, give a spray of that ether and...

Sounds faster and cheaper than a new ignition system -- that very well may not be the problem after all, if you're getting spark now, and will probably have to be done anyway since you say it never ran right. It sure is nice when it's just a failed component, but sometimes it's just us.
Click to expand...
 
I should have said that Butch is still working on Britt Bikes after 50 years in the business. He built Triumph's for beach drag racing. He tuned his brother's bike and won a championship.
 
Only time in recent years I had a backfire was on a WD16H when I forgot to retard the manual ignition.
Using a dial indicator to find TDC is not best way to do it.
 
Could be the Pazon is totally wonky, but try this.... retard your timing about 5 degrees from what you have it set at now. If it does the same, try 3 or 5 degrees more.
In short, just back the timing off a bit at a time to see if it will start & run. If it does run, fettle the carbs in close & then time by ear for the fuel you are using & then back off a degree or 2 to be on safe side. ( reflects a favorite saying...."Toast it until it smokes... and then 20 seconds less".... wink.
Other checks... measure lift on valves to see if cam is flat. Also a timing wheel can be used to check opening and closing timing of the valves. (specs are in manual)
If this bike has been a POS for a long time, possibly a poor cam, and not just regarding wear but design or manufacturing screw up.
If the above doesn't help, I would pop for a Boyer.
Best of luck
 
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