TOPIC:

Stock GPz550 engine fouls plugs every which way upon start up.

Was considering running a hotter plug to see if that will cure it before going on to other causes.

Has anyone had luck running a D7EA instead of a D8EA NGK or ... suggestions welcome.

chopper1963 wrote: Stock GPz550 engine fouls plugs every which way upon start up.

Was considering running a hotter plug to see if that will cure it before going on to other causes.

Has anyone had luck running a D7EA instead of a D8EA NGK or ... suggestions welcome.

... suggestions welcome.

Would suggest before using hotter plugs :
Assure clean, clear and unobstructed air filters.
Assure choke is fully off when running.
Assure that plugs are not "R" plugs.
Verify that plug wires are solid metal core and not old, hard and cracked. If condition is in doubt, replace with new Dyna solid metal core plug wires from Z1 Enterprises. Could test for spark leakage by spraying water mist over the plug wires while the engine is running at night in the dark.
Assure valve clearances are within specs.
Perform compression test.
Perform poor man's leak down test to check specifically for blow-by and/or valve leakage.
Perform clear tube tests to assure fuel levels are within specs.

Good Fortune!

In addition to what Patton alrady said...

If you are in a super cold climate you may want to consider hotter plugs, maybe, but if you are in a normal to warm climate, fouling will be carbs or ignition or engine condition.
In my years of tuning 550's, fouling plugs was never a plug issue. .. always something else.

Is it oil fouling or fuel fouling?

The general order of checking, especially if the bike is new to you, would be:
Compression test.
Valve clearance.
Ignition operation.
Ignition timing.
Fuel flow... (The petcock shuts off properly.)
Carb fuel level.
Jetting (make sure a jet didn't fall out).

If any rejetting was done recently, that would be the prime suspect.
If not, and this is a symptom that comes out of the blue on an engine that ran properly for years, then ignition would move to the top of the list.
If you 're exhaust is blowing a lot of blue smoke, then the engine needs some work.

You may want to try switching to ND spark plugs in the same NGK D8EA heat range. I had problems with fouling of NGK plugs in my KZ650, but when I switched to ND plugs in the same heat range the problem totally disappeared. Ed

Agree ND plugs comment. NGK never are the same once fouled however well you try to clean them.

So often a poor spark causes the issue. The simple test is to check the voltage at the battery, and then see how much reaches the coil. 12.5 to 12.75 v at the battery may get recued to well under 11v at the coils.. Checking you need over 11v to get a decent spark, and really better than 11.5v to get a good spark.


Often just cleaning all the electrical contacts can help restore the power.

Thanks.

But cleaning which electrical contacts? Seems like it has great spark.

The connections in the ignition circuit. The wiring diagram in the fsm can be really helpful, otherwise, you can start at the coils and work your way back to the battery. How do you know the spark is good?

650ed wrote: You may want to try switching to ND spark plugs in the same NGK D8EA heat range. I had problems with fouling of NGK plugs in my KZ650, but when I switched to ND plugs in the same heat range the problem totally disappeared. Ed

I read an article in 14 about NGK vs ND plugs. In the 70's Honda's ran ND plugs stock but when KHI tried them they didn't work as well as the NGK's. It was explained the Honda coils produced a "longer spark" where as the Kaw's didn't. They came out with the "Hot U' plugs for the other bikes. When my bike was fouling plugs due to bad valve guide seals I tried hotter NGK, Split Fire, Hot U's and even Champion plugs. I ended up using NGK BP8ES plugs for their longer reach. They worked better than the rest without fouling as bad so soon. When I put in new valves and seals I went back to the NGK B8ES plugs.
Different manufacturers heat ranges are slightly different so even though by the book they can be correct but in use they can be too cold or too hot.
I'm sticking with the KGK B8ES plugs as called for per the manual.
Steve

I believe B8ES was only specified by KHI early on in 650 manuals. Updated versions for the same bikes changed to B7ES. Which is slightly hotter. If you read up on current spec sheets from plug manufacturers they say with modern fuels in classic engines to go one grade hotter than specified by manufacturer literature.
So that would be B6ES.
I run ND plugs in all my bikes because I find them far superior in every respect, not to mention all the fake NGK's on ebay which are absolute shite. Interestingly though, I find no difference in performance using either ND24's (8 Equiv) or ND22's (7 Equiv) . They just seem to be a lot more tolerant of cleaning than NGK's.

Plug fouling on start up is usually caused by an excess of fuel or oil and not the wrong plug heat range.
Check that the carbs are not flooding, the fuel float levels are not too high or that the valve stem seals are not shot.
Depending on mileage badly worn bores/oil rings can also be the cause, amongst others.
Is this an issue that has suddenly presented itself or something that has got gradually worse ?
Is the bike new to you and has been stood for a while or one that has been owned for some time and has been in regular use ?

Warren3200gt wrote: I believe B8ES was only specified by KHI early on in 650 manuals. Updated versions for the same bikes changed to B7ES. Which is slightly hotter. ............

You are correct. The first KZ650 manual "KZ650 MOTORCYCLE SHOP MANUAL - Part No. 99931-539-01" "First Issue: April 20, 1976" specified NGK B8ES or ND W24ES plugs. That manual covered the 1977 KZ650-B1. These plugs may have worked for Kawasaki on the test track where they were flogging the daylights out of the bike, but they were too cold even for aggressive street use.

The next KZ650 manual was "KZ650 MOTORCYCLE SERVICE MANUAL - Part No. 99924-1001-01" "Revised 1: April 11, 1977". That manual covered the 1977 KZ650-B1 and the 1977 KZ650-C1. It had several corrections in it including changing the recommended spark plugs to the NGK B7ES or ND W22ES-U or Champion N-4-MC plugs. Each of these plugs is one heat range hotter than those specified in the first edition of the KZ650 manual. I can tell you from personal experience that they work much better than the cold plugs even for aggressive for street use. Ed