What to do next ...

I'm working on a 1978 KZ650 SR. I've spent time repairing intermittent ignition troubles, stopping short of wiregeorge's coil re-powering mod. I have spark on all 4 cylinders, I spent yesterday setting the fuel service level on the carbs I recently rebuilt. I've installed new points, timed the engine statically and with a light, checked the ignition advance mechanism for proper operation, both by visual inspection and with a light. Everything appears to be operating as expected.
I put the bike on the road for a bit today and it appears to have power coming from all 4 cylinders. I get some very minor hesitation as I roll on the throttle and I get a little 'burbling' when I decelerate. Much better than I was getting before I set the service fuel level. After I turned the bike off, I checked the exhaust pipes and all 4 were hot. I pulled the spark plugs to examine their condition. It used to be, prior to working on the carbs and ignition, that all 4 plugs would be sooty. Now 3 are and 1, #3, is actually pretty clean. Could it be that my ignition efforts to date have fixed #3 well enough or is something else going on?

I'm now at a point where I need to decide what to do next, or, in other words, where do I spend money next. Compression tester? Valve lash checking and setting? Coil re-powering? What would YOU do next?

Thanks

Summary to date -- Spark on all 4 cylinders; 4 exhaust pipes were hot; spark plugs 1,2 and 4 are sooty, #3 is actually pretty clean; what to do next; Compression tester? Valve lash checking and setting? Coil re-powering? What would YOU do next?

If not already done, would ---

Measure voltage across battery terminals.

Measure voltage between battery positive terminal and engine head (helps assure good ground connection where negative cable from battery attached to engine or frame.

Measure voltage at coils to determine voltage drop between battery before reaching coils.

Wanting to assure sufficient voltage available at coils to provide sufficient spark at plugs.

Next -- do compression test. (I believe some auto parts stores such as AutoZone regularly loan tools to customers, so may be able to borrow a compression gauge).

Also check valve clearances. (Need feeler gauges). If too tight, the actual adjustment by changing shims is more difficult, involving removal of cam shafts, etc., so hope the existing clearances are within specs.

It is necessary to assure correct valve clearances regardless of good compression figures, because a too tight clearance may cause loss of compression when engine attains normal operating temperature.

Good Luck!

markc3wa wrote:

I'm now at a point where I need to decide what to do next, or, in other words, where do I spend money next. Compression tester? Valve lash checking and setting? Coil re-powering? What would YOU do next?

Thanks

I think those are what you should do first, but better late than not at all.

OK I'll do the valve lash check next .. thanks!