1969 Commando Restoration

I'm getting my 69 Commando back in roadworthy condition. Bought it disassembled in 1989, got it going, had some trouble with the tank and ethanol, replaced the tank with a steel one. (Stopped driving it as soon as I figured out ethanol with be a problem, so believe no gumming up the engine.) Put in a Pazon electronic ignition, rebuilt the carbs.

Fired it up over the weekend, timing seems right (set it carefully with a timing wheel), but getting nasty backfire from the right cylinder. Pulled the right exhaust, right exhaust valve looks to be operating properly.

Any suggestions on what to do now?

Have you strobe timed it?
Which Pazon system are you using?

Backfire could be a mixture problem. Could be a multitude of things: Worn jet needle or needle jet, incorrect float height, float needle not seating, pilot screw too rich, choke slide dropping. Nothing but wild guesses until you say exactly what you have addressed.

Thanks for the replies. My Pazon is the Sure-Fire Ignition. Haven't strobed it yet. Perhaps a dumb question, but would timing throw off one cylinder and not the other?

That's why I asked which Pazon. The Surefire is a "wasted spark" system. Both plugs fire simultaneously but only one cylinder is on compression, so the spark in the other cylinder is "wasted". Therefore setting the timing for only one cylinder should be suffiecient. However, it's remotely possible that the plate could have a manufacturing defect that throws one cylinder off. No matter how carefully you static timed it you really need to check the timing with a strobe and when you do it won't take but a few minutes to check both sides.
Sounds like it might be a carb problem. Fuel level should be .21" below top float bowl. Check with a utube made from a piece of hose and old drain plug. Clip may have come off needle. Mixture screw one and half turns out?

I spent a lot of time on the floats to make sure I had them right, have the new ones with the metal clip so it's easier to adjust, so likely not that. On the mixture, have them one and a half out, but seems to improve right cylinder quite a bit if I turn it all the way in, which is of course worrisome. The smart move might be to take at least the right one apart and reassemble. When I noticed the current problem, I took off both carbs and made sure there were not leaks on the way to the barrels, probably should have checked them out them while they were off, but still had hopes of some sort of Memorial Day ride.

Will need to acquire a timing light, old one died and don't use one on my other ongoing project, 87 Buick Grand National.

Again, thanks for the help.

Ethanol fuel and fibre glass tank would indicate highly probable blocked pilot jet to me...

Cleaning pilot jet
http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html
Best tool to clean jet is a #78 drill bit. Super glue a plastic tube from a WD 40 can as a handle.
http://www.micromark.com/no-78-drill-bi ... ,6661.html

Sounds like a plan, will give the carbs some attention. Thanks

Another good link on carbs.
http://www.tioc.org/amalbritbike.pdf

Thanks.

I disconnected and checked the coils, both show four ohms.

Making progress. Cleaned carbs, used correct small drill mounted on a small tube, per guidance.

Timing was helpful, thanks for the suggestion to check both cylinders, turns out despite being very careful and studying all available resources, I was way off setting the timing with the timing wheel, was in the low 20s, now set it to 31 degrees, backfiring stopped. Both cylinders are showing the same timing. Still running a little rough.

New problem is that the engine breather is spitting a lot of oil. This line cracked where it clamps to the top of the oil tank, next task is to replace this but I think that despite carefully measuring the oil going in, I think I've overfilled it. I got a cap/dipstick from a later Commando, but oil doesn't register on it. The clear tube on the side of the oil tank has been painted over, so no help there. Using dowel dipping into the oil tank, it seems to be at the level that would be shown if the clear tube were visible. Any suggestions?

Did you drain the engine sump before starting the bike. If the bike has been sitting a while it may have "wet sumped". Oil leaks past the pump into the engine sump, sometimes all it takes is a few days. If you then see the tank is low and add more oil to top it off you have too much in the system. If you start it the bike may smoke and puke oil out the breather. Always check your oil level after the engine has warmed up, like at the end of a ride.
Then before you start it again check the level again. If its low, odds are the missing oil is in the sump. Just drain the sump, put that oil in the tank and away you go.

Thanks. Had not topped it off, and had been messing with it enough that the oil hadn't settled. It seems likely that for some reason the spec on how much oil to put in after draining the bike (tank and engine sump) is either too much or oil is hiding someplace. Was sure I had drained completely (into pans and much onto the driveway, fairly awkward drain hole positions). Will need to study the oil tank more. What's the level below which it should not drop?

Best,

Tim

If you can see any part of the pickup screen, you are in trouble. Actually, just seeing a bit of it means it will be exposed when running; so, perhaps 2" above that, MINIMUM...

Hi.
Regards the backfire change the old spark plug lleads, they loose insulator and make great noise.
Abiut breather, you have put more than 2,8 liter into or have had a bad drain before.
Ciao
Piero