[GregW]

My right cylinder is running rich and miss firing. Checked timing and carbs. Checked spark. All look good. Checked compression - 140 psi in left but only 90 in right. Adjusted valve clearance according to the manual. No change. I think I need to do a valve job on the old girl (1967).

I've been looking for posts on the subject but can't find any. Any suggestions would be welcome.

Also, do I need to buy a chain break and rivet tool? Any tips for keeping the chain from falling into crank case? Can I get this done without removing engine from frame? Any advice on where to buy parts if needed? Any other tips?

Thanks

 

[66Sprint]

Yes, you need to remove the engine from the frame to extract the head....... You will need chain tool for the cam chain...... Why do you think it's valves rather than the rings?...(IT NEEDS RINGS.... 163 PSI is the minimum spec before re-ringing, and you don't even have that on the better cylinder.....180 PSI is normal for a 450, as high as 213 fresh)

 

[GregW]

Good point. I didn't know what the spec was. It turns out I checked the compression without opening the throttle all the way <duh>. I get 150 PSI in both. Not 165 min as you note.

Here's the problem:

It runs well when cold but after it's warm not so good. When I start out from stop, the engine bogs and will stall when I open throttle. If I feather it I can get the rpms up and then get going (or if I wait till it gets cold). The plugs are black and fouled indicating it's running rich (I think).

I took carbs apart and cleaned. Float level is good. Spark is good. Timing is dead on. Charging is good. Plugs and points are new. Maybe this is all due to poor compression and I need to do valve job and replace rings. Any ideas would be appreciated.

Thanks

 

[66Sprint]

Again, Why are you insisting on a valve job?....When the head is off to replace the rings, etc,....Run the acetone test....Then IF the valves aren't sealing do a valve job understanding that the valve shafts (stems) will have to be shortened by whatever amount the valve seat was cut deeper.....Valve clearance is minimal (.0012") on these engines, so even a good lap-in can require stem grinding......

 

[GregW]

I'm not bent on a valve job or replacing piston rings. I'm not really sure why the bike runs poorly after is warms up. If compression is the culprit, I take the heads off. However, if compression isn't true reason for the engine bogging down then I'd prefer to avoid taking the engine apart. I'm no engine expert so I'm trying to move slowly. Maybe the carbs are the problem. Not really sure which is why I'm asking in the forum. Any thoughts on why it acts weird when it warms up?

 

[66Sprint]

Low compression could be the culprit..... You are below minimum spec, and the problem gets/will get worse as it gets hotter...... Part of that "black" on your plugs might be burnt oil that is getting past the "too loose" rings ("rich" fuel deposits tend to be "fluffy", while burnt oil tends to be smoother and "baked-on")........Could be carbs and/or timing too, but you won't know that for sure until you fix the engine itself.......