Flames out me arse

Ok, still trying to get this bike to run right.
What are possible causes of flames coming out the left exhaust when it's backfiring? Right exhaust seems fine.
Single Mikuni, old Boyer. Exhaust joints tight.

thanks guys!

have you checked your valve clearances (esp exhaust) & 2x your timing

As the good old Aussie expression goes ' Youd Whinge if your arse was on fire ' ., Check Plugs . Picture ?

Guess how we get trained to make effective blood curdling Rebel Yells down here...


Fuel and air and ignition sources needed. If exhaust valve not sealing on the compression stroke that'd pop a flaming fart out nicely. Its also possible you just ain't put the old Norton HEAVE HO on the exhaust ring bolt so sucking O2 in on the unbrunt mixture left overs. If not joy there its traditional to switch sides of paired items to see if symptoms follow or not. Likely just a holed piston is all.

A single carb cannot be tuned to suit two pots properly as there may be too many differencies between them like valve timing, comp ratio, inlet/ exhausttrack etc. In a perfect world everything would be exactly the same. BSA used to have angled plates to go between carb and head to direct more flow to the weak pot to compensate any difference.
Other source may be a weak ignition on one pot - thus you tune your carb to make that pot run and get a less then optimal mixture for the other....

mikegray660 said:

have you checked your valve clearances (esp exhaust) & 2x your timing

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Was going to check valves as possibility, got it planned for the weekend. Thanks!

Also forgot to mention it has a single dual output coil.
Anything else I should be looking for?

Hey Donny, Do you have a compression tester, and feeler guages.
we could try that.
It almost sounds like the Cam timing might have slipped,.. sheared a keyway perhaps.
Let me know, going passed your place tomorrow.
AC.

AussieCombat said:

Hey Donny, Do you have a compression tester, and feeler guages.
we could try that.
It almost sounds like the Cam timing might have slipped,.. sheared a keyway perhaps.
Let me know, going passed your place tomorrow.
AC.

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Hi AC!

Haven't got a comp. tester. If you're coming this way, it would be a big help. Have you got an inductive strobe? Last time I checked the timing I took it around to K&M's and they checked for a couple beers. It's running so back now that I can't ride it down there.

HYMPH >
TIRADE

READING SPARK PLUGS is compulsary for Anglophile Motorcyclists of redoubtable parantage .

SETTING Valve Cleances should be able to be done in the dark , blindfolded . AS SHOULD the Contact Breakers .

Write this out 100 Times , Then Practise till you ENYOY doing it , its MANDATORY skills for Maintanance . 8)

If shes a bit weal in the elictrikary ( points closed ) the unburnt Feul can go pop , particularly with a balance pipe Ex .
PLUGS will tell you if shes a trifle damp in there .

ONE WOULDNT ORDINARILLY Ride It , IN THAT CONDITION . Was a phingo on Ref to Reading Plugs here the other day .

Points and tappets are suitable for well trained 12 Yr Olds to Acomplish . Dont be scared of it . It wont Bite .

STUDY the little mechanism so as you understand them :idea: . Yahwhol , Comrade . :lol: :wink:

9.40 pm, ring you in the morn.
I've got a trailer.

like said check timing and valves clearances - closed /to tight valve can cause - other stuff suggested maybe, but only 1 cylinder makes me suspect this first

Oh now Matt, not everyone has cycle grime in their background like you, me for instance.
OK its as rare as guys with 3 balls that a twin engine is so screwy a single carb can't feed both jugs to hardly notice plug chop difference let alone fire hazard on one side. Same goes for the single coil, pretty much eliminates spark time or intensity issues to matter. Also cam profile is symetrical so if one side ok then other should be too. This leaves possible wart on top of one cam lobe or some crap fouling exhaust seat or maybe like pre-Peel something like a Amal slide piece was inhaled to bend/chip the seat or valve lip. Rocker may be over adjusted down too. Sucks not to just get on w/o the racket fire, so let us know what you and helper uncover.

hobot said:

Oh now Matt, not everyone has cycle grime in their background like you, me for instance.
.

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i think there is a lot more grime (cephalic perhaps) than cycle grime in common between you and matt -

If your bike was previously running ok I would suspect ignition or carb issues. I have seen bad ign wiring cause same trouble. Check wires at: ign trigger,coils and or black box.
Dox

I'm trying to catch on both the grimes and the grins Matt and many have under their skin. Someone mentioned switching everything that come in two's to see what happens through didn't mention its never a bad id to have fresh set of plugs in, as I've solved a misfire connection problem w/o knowing it because the misfire fouled the plug, ugh. Its always worth a peek and poking after dark too.

Considering single carb and dual output coil, I'd be looking at something unique to the left cylinder. Valve adustment (exhaust side too tight), or maybe the intake manifold not sealing on one side.

Aussie Combat came around yesterday and we adjusted the valves. They were all a bit loose, we were able to fit the next thou gauge in each.
Afterwards we fired her up and still had popping out the exaust, this time mostly out the r/h pipe. AC went back to the shed to grab tools to adjust the Boyer plate and I adjusted the idle and let her sit at 1000rpm while we waited. Idled fine. AC adjusted the plate about a "poofteenth" and then I revved it.... no problems.
We went out for a quick 15 minute ride and I opened her up a couple times, still no problems.
Was it the valves? Just had torun a few minutes to clear out all the carbon built up from weeks of short, low rpm running during diagnostics?
Was it the miniscule adjustment in the Boyer plate? I remember them needing a bit more movement to make much difference.
Could it just be that I had cleaned out the not very dirty carb last week?
Ah well, I'll take her for another spin today and see what happens.
Still not sure if the original charging issue is solved, perhaps that was just an anomaly that will not be seen again. Before our quick ride the batter was only sitting at about 10.5v, after the ride is was back up to around 11.4v.

All in all, I'm still a bit nervous but we'll just have to wait and see. And it was bloody good to spend some time in the shed with a fellow Nortonite, haven't done that in years!