Commando kick back.

Hello. I'm a new member and I'm sure one of you out there can give me some good information concerning my problem. I recently purchased a 1972 Commando Roadster from a guy in Georgia. He assured me it was in fine fettle; not a show bike but a good runner. Spouted off a list of items that had been completed recently by a "mechanic" buddy of his who had gotten the bike ready to sell, and ready for the road. To cut to the chase; I had a tough time getting the bike start and run, and the bike has a violent "kick back" EVERY time the engine would catch and try to start. It will not start at all now and no matter how fast or slow I kick it, the kick back is painfull! Literally. Compression is good, dual Amals, and original points set up. Any suggestions will be greatly appreciated.
Thanks. :?

'72 kick back

Chuck,

Sounds like the timing is too far advanced. If your Commando still has points ignition, the auto advance unit might be stuck in an advance position. The original '72 auto advance unit was prone to this and was supposed to be replaced by the '73 version.

Kickback

I agree that it is almost certainly timing. It WILL give you a smart kick if it's too far advanced. The other thing to check is, if you are running a Boyer ignition, that the battery is fully charged. Timing becomes erratic on the Boyer when the battery is low and it defaults to full advance.

kickback

Assuming the battery is charged OK (you check the spark by screwing it out, connecting the cap and kicking the engine with the plug resting against metal, you should see a blue spark) - try this before you start taking things apart:

1) Flood the carbs until you see petrol coming out of the vent hole on the tickler. If you suspect that the bike has not been running for a while - drain the petrol through the taps and fill up with new. (Then you will know that the tank vent is OK too).

2) Push the choke halfway in (ie pull the lever towards you...)

3) With the ignition off - kick it three-four times.

4) Switch the ignition on and kick it the best you can with no throttle opening.

5) The next thing I would do if it does not start is to take out the air filter and repeat the process. Then have a look at timing and carburettor settings.

Good luck - regards Thore Bergsaker, 72 750 Roadster

Yeah
That's what I like to read. Consice trouble shooting techniques. The kind of knowledge it would take a newbee like me all afternoon, a gallon of sweat, and a trip to the cardialogist to learn. Thanks...

Commando Kickback.

I want to thank those of you who took the time to reply to my question. I really appreciate it. Since I posted my question I have discovered a new possibility to explain my problem; the layshaft bearing. After pouring over Captain Norton's Notes and some other sources, I have had to accept that my troubles may lie within my gearbox. I'm upset about this, but there is a positive side to it. The guy from Georgia who sold me the bike in December, and has told me that "operator error" is causing all of the bikes problems, will have to come up with a good explanation for a busted gearbox. That would be interesting. Thanks again.
Chuck

Kick back on your '72 Commando

Chuck,

The advise given was you have an ignition problem. The kickback you read about related to the layshaft bearing is very different. The issue with the bearing is it seizes which when the engine speed increases causes the kick start arm to drop then return bumping your leg. It has the power of the kick start return spring only.

Kick back from ignition has the power of the engine's compression. It still sounds like you have an ignition issue. Did you install the Boyer the previous owner sent? Are you sure the timing is correct. Follow the initial static setting described in the instruction with the Boyer, get the engine warmed up then fine tune with a strobe setting max advance at 28 degrees BTDC or at 5000 rpms.

If you lost acid from the battery, what is it's condition. Lower voltage as mentioned will cause misfiring in the Boyer.

You really can't blame the previous owner for a layshaft bearing as the original was typically a poor quality ball bearing. The upgrade is an FAG manufactured roller bearing. However if you haven't gotten the engine running you won't have experienced this problem which is not related to engine starting.

Even the most experienced motorcyclist may have problems starting a combat 750 engine. The ritual for me is gas on, tickle both carbs for 3-5 seconds (floading the fuel bowls), choke on, ignition on and very firm swing of the kickstart. Don't jab at the starter, rather a smooth swing transferring all your weight as you follow through.

David,
I see your point on the layshaft bearing. As of yet, I haven't been able to install the Boyer but I'm going to try to get the job done within a couple of weeks. Too little time and too much cold! I have'nt bothered to check the timing as I knew I would be replacing the points with an electronic unit.
The battery appeared to be brand new and once topped off took, and held, a good charge.
I don't want to come across as a jerk regarding my comments on the bikes' prior owner. I understand that with a 30 year old British bike there can be no gaurantees, however, he did assure me that the bike was in excellent mechanical condition and ready for the road. I apologize for being redundent.
You have given me excellent information and advice, and I thank you for taking the time. I would appreciate it if you could answer another question I have; As stated, my bike is a 1972 Roadster, engine and frame # 204XXX. Does it have a Combat engine? I have read some information claiming that ALL '72's came standard with the Combat engine. However, I could not locate the definitive "C" on the top of the head after removal of the head steady. Your thoughts?
Chuck

combat confirmation

I can understand the frustration and have heard and seen some real nightmares from e-bay. The comment that all '72s were combats is probably not entirely true, but I suspect most roadsters and interstates had that option. My readings indicate not all combat heads had the "C". If it is stamped it's right in the center under the head steady. If you have the original Amal carbs and they are stamped R932/19 and L932/20 you likely have a combat. The standard models had 930 carbs. Look at the space between the lowest head fin and the upper cylinder fin. That space will be noticably less that the other fins only on the combat (.040" milled off the head). Another issue is the head may have been replaced over the last 32 years with other than a combat. The standard models didn't come with the disc brake.

I bought a combat roadster in '73 with 300 miles, so really new (201123 built Sep '71). Six years ago I bought my current combat roadster built Dec '71 (201xxx). You can see it on the club website under Mt Hamilton ride pictures. www.nortonclub.com