TOPIC:

Hi All,

I've written a few times before about my attempt to resurrect my 'old' 1979 Kz1300 A-1.. I recently got it running after working on an ignition problem (pick coil for 3 & 4 was bad). It seemed to be running ok, so I've spent the last couple of weeks working on the brakes.

Anyway I just recently started to run it around the block and down the road a little and it appears that the engine is missing at low RPM but seems to get better from around 3000 up to around 5000 RPM. I haven't run it much past 5500 RPM's since getting it to run.

Further tests show that cylinders 1 & 2 appear 'wet' when I pull the plugs . In the picture you can see that from left to right plugs 1 & 2 are black and wet looking where 3 & 4 look fine. 5 & 6 (not pictured) look the same as 3 & 4. The spark looks the same on all 6.. Compression seems good at around 150-155 for each cylinder. The carburetors were recently rebuild professionally by Jack at oldschoolcarbs.com and appear ok.

So I'm at a loss as to what could be going wrong. Any ideas would be greatly appreciated.

Cylinder 1 & 2 share the same carb, but different coil combos, so it's likely still a carb issue.

Have the rebuilt carbs run OK at all prior to this issue?

Suggest check the float level (fuel level) on carb 1, could need adjustment or be sticking / flooding?

Richard.

Just a shot in the dark here. The plugs are shiny. I wonder if you have noticed if the coolant level has dropped suggesting a leaking head gasket maybe????
Do the plugs smell like engine oil? If it's engine oil, it could be from weak valve seals.
If the plugs smell like coolant, then I would pressure test the cooling system.
Sometimes you can get lucky and re-torque the cylinder head bolts and the leaking head gasket will seal up. Just throwing it out there for consideration.

RChaloner:

Yeah, I think you might be right that it is more likely a carb issue vs an ignition problem. I was reluctant to remove the carbs again but I may need to go ahead and check them out. Hopefully its something simple and I don't need them worked on again.

Kawboy:

I would think that the compression being good would take care of any oil or antifreeze leaks, but I really don't know for sure. I'll keep that in mind.

Well, I found the issue. The float needle value was stuck shut (or mostly shut). After pulling the bowl and float, i ended up just pushing on the needle value a couple of times and it started pushing out lots of fuel. I let if flush about 1/2 gallon of gas though it before putting the bowl back on. This is the second time this has happened to me on this set of newly rebuilt carburetors. I'll contact Jack at oldschoolcarbs.com and see if he can send me a new needle valve just in case it sticks again.


Thanks to RChaloner for the advice.

Glad you'e sussed it out.
If there's been a couple of occurances, suggest there may be deposits / varnish that's tending to cause the sticking when closing.

Hate to say it but.. may warrant removal of the carbs and inspection / detailed cleaning of the valve assemblies (albeit all very simple to do).