Hi,

Having truble starting my 172 with the kick start - think it must be compression related anyone know what it should be? I have bought a tester and will give it a whirl tonight.

The bike will statrt and run if you tow it but it takes some starting even then!

Open to suggestions

Cheers

Might want to look at changing the crankcase seals. Has the bike been stood for a long time?

Wayne....

It is hard to work out what the problem may be from the description you have given. Like wayne said. It could be the crankshaft seals. It could also be carb problems, points not adjusted right or even a sheared flywheel key which is putting the timing out. I would start with the easy stuff first ie take the carb out clean it properly, blow every hole you can see, make sure the idle jet is not clogged, put it all together, turn the mixture screw 1 and a half turns from fully closed and see how you go. If it still does not want to go I would check the other things I mentioned. Failing all that replace the seals and you should be right.

Thanks for your input ; the bike had new crankcase seals when I aquired it (as a nonrunner) I dont think the previous owner got it to run after fitting the seals. I cleaned the carb up at the weekend and replaced all of the gaskets, blew out every hole as you suggest so I pretty much dont think its carb trouble.

I will try whipping the flywheel off and check the points gap timing etc.

Compression at the cylinder head was about 180 - 190 psi.

What sort of a job is replacing the crancase seals again and would there be any visual indicators that they have gone?

I am working blind at the moment as I cant get any tech specs on the bike any ideas on sites that may have points gaps an the like.

where is the best palce to get bits such as seals?

Thanks

If it sat for a while you can get light rust on the cam for the points. When you do try to start it this quickly wears the heel of the points and puts your timing out. Try new points and stick a condensor and plug on at the same time. How healthy a spark do you get when you kick it over ?

Its been standing for a while before I got hold of it - the spark is a fat and blue, will try clean up and adjust before ripping into changing crankcase seals etc.

do you know of any sites that sell parts?

Thanks

Stick a little petrol down the plug hole, if it fires up, go back to the carb.

Stick a little petrol down the plug hole, if it fires up, go back to the carb.

Yep, an old but telling diagnostic! Carb or even carb rubber, they can perish and draw air.

Spanish Amals do tend to wear their slides at an alarming rate and thats another route for an excessively lean mixture.

Not so sure the Burlen Amals are much better from what I've been told.

I had a 172 once as a lad. It did have a habit of shearing woodruff keys to think of it, but a lot of that may have been due to youthful lack of mechanical prowess in those days!

Wayne...

Edited March 12, 200917 yr by wayne_weedon

Stick a little petrol down the plug hole, if it fires up, go back to the carb.

If that fails use more petrol, burn your bike, then buy a bultaco

Changed the seals, adjusted the timing and still no joy!

tipped some fueldown the barrel fired right up and kept running at high revs - no idle and gasping at small throttle opening leading to stalling. still couldnt kick the B****rd over even after it had run for a few minutes at 3/4 throttle.

Tipped more fuel in and fired up again! - Ive replaced and blown out the jets and still no joy. Any other ideas except torching it - it may come to that!

Cheers

Alan

Edited April 6, 200917 yr by Buggered172

You probably have a crankcase air leak by the sound of it.

Check the cylinder base gasket for leaks and the gasket between the carby and the inlet tube, unless it has a hose in which case check the hose for cracks.

You have probably checked but haven't said that fuel is getting into the float bowl.

Make sure there is no bung missing from the bottom of the crankcases (some bikes have a bung to let water out of a drowned motor)