Misfire Troubleshooting

o0norton0o · May 17, 2020

baz said:
Yes I see what you are saying
The smoke in the video looks like oil to me not richness
No doubt that the drain hole being blocked can cause this
It's only the issue of the oil causing a misfire is what I'm asking about, I'm keen to know because it's something I have never come across
I'm not doubting anything, just interested

Me too,... At one point in this thread I wanted to recommend that tornado make one change at a time, then try the bike, but I know how freaked out I get when something is obviously wrong with one of my vehicles. I go at the problem like a man possessed.

There's little doubt in my mind the drain hole caused the oiling of the cylinder/s. No way changing the carb would stop an oil leak, and there's no other explanation for the oil leak stopping all of a sudden, unless he re-torqued the head which stopped a head gasket leak.

As far as, "can an oil leak cause a misfire?" Maybe there is caked on oil on the stem of the exhaust valve causing it not to close completely, or the burnt oil is building up on the exhaust valve seat, so it's not seating. Both would be oil related misfires. I just went with the evidence I saw on the video and read tornado's discription for my diagnosis, where as a lot of norton owners think carburetors are the boogieman and often jump to the conclusion, "it's the carb". Just look at how many people recommend mikuni carbs every time someone with amals has any kind of problem... I have sleeved amals... I never had a problem after I learned how they work....

baz · May 17, 2020

o0norton0o said:
Me too,... At one point in this thread I wanted to recommend that tornado make one change at a time, then try the bike, but I know how freaked out I get when something is obviously wrong with one of my vehicles. I go at the problem like a man possessed.

There's little doubt in my mind the drain hole caused the oiling of the cylinder/s. No way changing the carb would stop an oil leak, and there's no other explanation for the oil leak stopping all of a sudden, unless he re-torqued the head which stopped a head gasket leak.

As far as, "can an oil leak cause a misfire?" Maybe there is caked on oil on the stem of the exhaust valve causing it not to close completely, or the burnt oil is building up on the exhaust valve seat, so it's not seating. Both would be oil related misfires. I just went with the evidence I saw on the video and read tornado's discription for my diagnosis, where as a lot of norton owners think carburetors are the boogieman and often jump to the conclusion, "it's the carb". Just look at how many people recommend mikuni carbs every time someone with amals has any kind of problem... I have sleeved amals... I never had a problem after I learned how they work....

I learned a long time ago to make only one change at a time
Saves a lot of tail chasing
Cheers

Tornado · May 17, 2020

As a former practioner of molecular sciences I know very well that changing one variable per experiment is the best way to determine causation. If the overiding concern is determining an exact cause, this would be how to proceed with motorcycle work. But there is more to consider here, like the balance of work needed vs getting to a satisfactory end point.
For example, I could have gone after just the coil terminal changes, maybe even one terminal at a time, test running engine at every single change. Then proceeded to ground line clean ups, more engine runs. Then oil drain clean. More engine runs. Then replace plugs. Engine run. Swap to single carb.
Instead I took the short cut. To make multiple changes to items most likely to be of impact, in one go. And it solved the problem and got me a very satisfying long ride before a new problem appeared.

Not to fret. We will do the follow up causation tests by swapping carbs onto my rolling single carb test bed, just as soon as I get a primary chain back on.

Craig · May 17, 2020

Can’t remember how long it been since I started my rolling resto of current Commando it is ongoing and was when I discovered this forum in ‘05 thanks to a young fella at work that was interested in my old bike .... he was searching the interweb to try and find out what a real original Commando should look like , at that point my bike would run and ride but was many different colours covered in oil , grease and grime , however it ran and got me to work each day rain or shine ..... lots of water under bridge since then .... one step at a time !

baz · May 17, 2020

Tornado said:
Primary off. Top inner cover bolt sitting in bottom of outer. Mangle washer. Also what upon closer examination, two halves of what appears to be chain roller. Found one link on chain with about 1/3 of roller missing. Must be at least one other somewhere on chain.
Cogs looking fine at this point.
New chain to be ordered & fitted.

Any idea what caused the bolt to fall out?

Tornado · May 17, 2020

baz said:
Any idea what caused the bolt to fall out?

Was last in there for the GB rebuild two Jan's ago and had the inner off. I used fresh tabbed washers....yet this is what didn't hold the missing bolt and the two remaining were just loose (likely b/c the entire gasket had departed and wasn't any trace of it once I got it home/dismantle....though could clearly see some protruding before I left). So I will not trust the tabbed washers without added locktite...likely will use the strong red stuff. These bolts are sturdy and should have not problems when it comes to remove them, heated if needed.

Tornado · May 17, 2020

OK, slightly off- topic but didn't want to start a fresh thread. I've dismantled the clutch cage, center & bearing. Cage splines look pretty nice, only showing witness marks and no actual detectable by feel notching:

The center is another matter, quite deep notching:

Clutch action wasn't too bad, maybe a little grabby recently. Time to toss the center? It's a spendy item ($120 USD at AN; $95 from CNW (and $51 USD to ship here!?!?) as the new improved hardened type). Better to keep original a few more years and save up for a belt drive?

Chain sprockets looking fine also other than witness marks:

gortnipper · May 17, 2020

Time to toss it. CNW.

blaisestation · May 17, 2020

Yes that clutch inner is shagged .
Time for a new one.

Tornado · May 18, 2020

Got a message out to CNW to see if there is an alternative. Shipping option to Priority International USPS. Usually id have items from US sent to a mailbox receiving service just a quick drive across the border to collect in person. Not an option with borders closed.

baz · May 18, 2020

Regarding your bolts falling out are you certain the chain case is shimmed properly on the center stud?
The gasket between the motor and case can vary in thickness
The clutch centre is bad but it's still useable, the worst it will do is cause some drag if you can't afford to get one yet
And note that some belt drive kits use a standard clutch centre anyway ,not sure if all belt drive kits do?
There's nothing wrong with the stock primary chain drive on a commando
The only reason I personally went to a belt drive on mine was to save weight

Onder · May 18, 2020

I quit using the tabs on the little primary bolts. You gain a thread or two and red locktite seems to work.
Touch wood of course.
Despite the cost it is nice to be able to just buy that centre !

maylar · May 18, 2020

You have it this far apart, you really really should check the mainshaft for being bent. I would assume that the fallen bolt got jammed between sprocket and chain and caused the primary chain to break. This is a very serious matter.

With the chaincase off you can put a magnetic base dial gauge on the steel cradle and measure runout of the shaft. Please do that.

Tornado · May 18, 2020

maylar said:
You have it this far apart, you really really should check the mainshaft for being bent. I would assume that the fallen bolt got jammed between sprocket and chain and caused the primary chain to break. This is a very serious matter.

With the chaincase off you can put a magnetic base dial gauge on the steel cradle and measure runout of the shaft. Please do that.

I do have a dial gauge. How best to rotate engine with all the bits out of primary?

maylar · May 18, 2020

I'm talking about the gearbox mainshaft. The kickstarter will rotate it.

Fast Eddie · May 18, 2020

Or put it in gear and rotate the rear wheel, you can do that nice and slowly whilst watching the gauge.

acadian · May 18, 2020

Onder said:
I quit using the tabs on the little primary bolts. You gain a thread or two and red locktite seems to work.
Touch wood of course.
Despite the cost it is nice to be able to just buy that centre !

Or replace with studs

cliffa · May 18, 2020

Onder said:
I quit using the tabs on the little primary bolts. You gain a thread or two and red locktite seems to work.
Touch wood of course.

Do a dry run first, as you do need to turn the engine over by hand to make sure that the bolts aren't now touching the crank.

Cheers,

cliffa.

Tornado · May 18, 2020

Ok, new CNW center coming up. Matt stated shipping calc on webpage frightens off many a new customer as it is way to heavy handed

Got it done for $20 usd as 1st class post. Thats $30 less the calculator gave. Chain on way from Chainman Jason and other ancillaries coming from AN.

The down time will give me opportunity to chase out those rear iso's and renew, putting in the Hemmings vernier adjuster. Should easier job without primary interference for lowering cradle.

concours · May 19, 2020

New clutch hub & Barnett plates. Alloy host wont harm it.

Misfire Troubleshooting

Similar threads