Thread: Need help from any mechanically minded biker

Originally Posted by kingwilly

Originally Posted by FailSafe

Honda C90 Super Cub- world's best selling motorbike (by a mile) and reliable as a hammer.

super ?

does it look like this one ?

Nah......here's the fickle bitch.

My mistake- it was "Greatest Ever"- check this out:

Yes, I saw it.
The main reason it was voted number one (actually, the Honda C100 50cc), was that it changed peoples attitudes to motorbikes. Before Honda came out with their advertising campaign of "You meet the nicest people on a Honda", motorbikes were frowned upon in polite society. Motorbikes were associated with gangs and yobbos etc.

Honda didn't bring out the C70 and C90 until 1968.

I used to despatch ride one in London. Un killable. Had nearly 80k on it before a lorry backed over it. Not ridable but still started.

Before you dig deep into carb-problems check where the exhaust fits into the barrel...many cases of backfiring means air being drawn in here. A worn exhaust gasket (piss-cheap to replace) or loosened exhaust manifold studs/nuts will cause this...lay down there with ya socket+extension and check those nuts.

Not from wiki or the Internet ..

Little backfires can come from lean mixtures, the big bang comes form accumulated petrol in the muffler, too rich.

There are several ways to check head gasket leaks. My fav is to spray oil where the head meets the block and look for blue/gray smoke out the back.

Almost all motorcycles fire twice as often as autos. An auto's distributor's capacitor charges as it rests and fires on the power stroke (one in four). Since motorcycles haven't distributors their ignition is directly on the end of the crankshaft. As such they fire twice for each four-cycle rotation, i.e. one firing is worthless/wasted. This second token firing happens about the cycle where the piston is all the way up just off the exhaust stroke. If the valve timing is restarted an exhaust valve could be not quite closed. Any residual fuel left over would cause an explosion out the rear.

There are many short and simple procedures to diagnose your bike. Just about all of them are here on your thread. IF all the simple trials don't yield results it just could be valve timing or slack in your cam chain.

Hope this helps