I have a 72 OSSA MAR. I just got it and it ran pretty good. I knew I was going to slosh the gas tank but thought I could run it a bit before the slosh came in the mail, etc. In short, I ran it one weekend and the throttle was sticking pretty bad so I knew it was time. I sloshed the tank with Caswell epoxy coating and while the slosh was setting up (total bike sat was two weeks) I cleaned the carb which had lots of fiberglass goo but is now spotless. Also the plug had a thin fiberglass film baked on. Now new plug, clean carb and it won't even cough. Before it at least tried to start first kick.

Do you think that goo is causing some problem with the rings or what. I had a 4 stroke (Norton Commando) that had sticking throttle problems from a fiberglass gas tank when I got it and it ran fine after I sloshed the tank. Is there something about 2 strokes that could be causing it not to fire at all. It has spark and the carb is as clean as a whistle. Do you think it would start if I took it to a friend that has a power starter just to get it running and adjusted?

Thanks for any help on this, Jim

Don't forget to check the basics.... Air Fuel Spark all at the right time...... You may have bumped something when you had it apart.

primary compression?..seals?

I agree with NZRalphy, OSSAs from this period could suddenly have their motoplat ignition fail.

It's a fair bet the problem is due to ethanol in your fuel, it could attack alsorts, seals, fuel pipe etc on a 1972 bike

Cheers

But it was just running two weeks ago even with a cruddy tank. I see spark. It won't even hiccup with starter fluid. I did nothing but slosh the tank, clean the carb really good, and change the plug.

So after you kick it alot(ten+). Is the plug wet or dry?

I`ve seen it happen multiple times after a carb clean something goes bad.

Usually something adjusted 180 wrong. But it appears that you have many things going bad.

Edited November 2, 201114 yr by lineaway

But it was just running two weeks ago even with a cruddy tank. I see spark. It won't even hiccup with starter fluid. I did nothing but slosh the tank, clean the carb really good, and change the plug.

I know this sounds dumb, but put the old plug back, it that is all you did. New does not mean good, just a thought!

True - my brother once went out to his brand new just delivered by the dealer Yamaha and it would not start. No spark, a change of plug sorted it.

CHECK CARB AGAIN IS IT FULL OF PETROL ?

where are the wires from the stator? originally under sump have they been moved?

If a bike runs well and then you make some changes to it (or remove/install parts) and it won't run, it's a good idea to reverse engineer what you did to see if the problems lies there. Look for wires loose (or broken) under the tank. You'll want to pull the connectors and make sure the wire is not broken inside, where it would not be observed by just looking at it. Trace the wires back to the stator like Nigel suggests and look carefully at the insulation, which may have cracked in the last 40 years of use.

Jon

Thanks for the ideas guys. Plug is wet and plug has a spark. I went through the carb one more time and everything is clear. Carb is full of fuel. I've tried choke, no choke, starter fluid, etc and still can't even get a cough.

Edited November 13, 201114 yr by yellow_cad

Is it a strong spark... have you ried closing the gap down... have you dried/heated the plug with a blowtorch..can you risk a bump start..it might just be flooded now. just keep telling it resistance is futile!!!!!!!!!!!

Sparkplugs can sometimes fail under compression and that includes new ones !!

Sparkplugs can sometimes fail under compression and that includes new ones !!

I checked the plug both ways: out against the cylinder head and also under compression with an inline light that lights with a spark (has a male at one end and female at the other and made for this test). I'm not sure of a good way to tell if the spark is strong enough. I see it but I am not totally sure what it should look like when of the correct strength.