Topic: CB750K2 problem with cylinder Number 1

[olasek18_18@o2.pl]

Hi, I have a problem with cylinder number 1.
All other cylinders get hot, while number 1 is still cool, it only starts to heat up when the engine revs up.
I have the compression at all cylinders...
  I think number 1 cylinder is not idling,
the spark plug is not flooded, the spark is strong.
Compression on all cylinders is ok.
Carburettors cleaned, jets clea,  approx.
Ignition timing and valve is ok.

Any suggestions?

Regards

[olasek18_18@o2.pl]

I bet the idle jets in the carburetor # 1, but I cleaned all the carb duts and gave a new jet and it did not solve the problem ...

[ekpent]

Did you try a different spark plug yet just to make sure there is not a weird problem with that one. I would look at the float in that carb next to make sure its working properly and not hung up ' You can also pop the bowl off or drain the bowl to get an idea as to how much gas is in there be it too much or not enough.

[olasek18_18@o2.pl]

Yes, I tried to change a different spark plug.
Fuel level right, I set the height of the floats 26mm on each carburetor, I also swapped the floats and needle valves to make sure

[evinrude7]

The float could be binding

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[Stev-o]

Have you ridden the bike so the engine gets up to operating temp?

When I start my 550 after it's been sitting awhile, it seems to run on 3 cyl but then runs great once warmed up.

[olasek18_18@o2.pl]

wouldn't he then overflow the fuel? It seems to me that the fuel valves are holding

[olasek18_18@o2.pl]

wouldn't he then overflow the fuel? It seems to me that the fuel valves are holding

Yes,while driving, it is almost approx but on low rpm engine work back to 3 cyliders

[ekpent]

wouldn't he then overflow the fuel? It seems to me that the fuel valves are holding

I was think more the opposite that it wasn't getting enough fuel. Is the spark plug still white and clean if it was new when you put it in and showing no signs of a burn.

[BenelliSEI]

Pull the idle jet out and blow some air in the idle passage...... is it really clear all the way?

[evinrude7]

wouldn't he then overflow the fuel? It seems to me that the fuel valves are holding

Could be stuck...up high.

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[HondaMan]

This was EXACTLY how my own 750K2 lost it's coil. Mine was the 2-3 coil, though, not the 1-4 coil. The #3 cylinder simply would not run belw about 2000 RPM, so when i would take off from a stop it was always a "launch" lurch, and then it was slightly erratic - and it wouldn't idle without help, dropping out the #3 cylinder.

Try this, if the wires are long enough: swap the #1 and #4 spark wires and see if the #4 cylinder then acts like your #1 does now. If so, you just need a new coil. The insulation in the OEM coils was only designed to last 10 years, so it is a marvel so many of them still work today.

[Tracksnblades1]

And if the all above doesn’t work, remove the pod filter from carb #1 and try hand choking it.
Place a finger or two or more slowly over the inlet of carb one and see if it will pick it up..
It’s cheap and doesn’t cost much or time either…

[olasek18_18@o2.pl]

This was EXACTLY how my own 750K2 lost it's coil. Mine was the 2-3 coil, though, not the 1-4 coil. The #3 cylinder simply would not run belw about 2000 RPM, so when i would take off from a stop it was always a "launch" lurch, and then it was slightly erratic - and it wouldn't idle without help, dropping out the #3 cylinder.

Try this, if the wires are long enough: swap the #1 and #4 spark wires and see if the #4 cylinder then acts like your #1 does now. If so, you just need a new coil. The insulation in the OEM coils was only designed to last 10 years, so it is a marvel so many of them still work today.

I was think its coil but not! I have 4 hondas and replace the coils from other bike...