XJ650 lean against the odds?!

Recently I noticed my plugs getting white, so I decided to freshen up everything in the air intake system. I repaired the holes in the diaphragms, sealed up the airbox, readjusted the rubbers, only to discover that the plugs are getting whiter!

For the first time this morning I fouled a plug! I am suspicious of the electrics, could this be a sign my coils are on the way out? or another electrical item?

I have made no modifications, just sealed of all the air leaks, I was expecting to have to lean them out, not richen them!?

any hints would be helpful,
cheers, Mr Blackstock

 

Did you clean adjust sync your carbs recently?
Did you check your valve clearances?

 

You Fouling a Plug may have absolutely no connection to the work you did eliminating Air Leaks.

You might be getting some Oil introduced to the Cylinder from a failing Valve Stem Seals, trouble related to Piston Rings and the possibility that some Oil is being introduced to the Cylinder from a Head Gasket problem.

If this is something new:
Check your Oil Level for Consumption.

Do a Compression Test.

Ride the Bike with someone following you and watching your Exhaust Pipes for smoke and puffs as you drive along.

Fixing a Pinhole or repairing a tear in a Diaphragm Rubber might be a cause if the Repair caused the Diaphragm to become inflexible and not allow the Piston to descend.

 

I should have added how the bike was running. Before I sealed up all the leaks, the bike would rev all the way to redline, with a great kick in the pants of speed at around 6000rpm.

since doing the seal up, the bike has lost its kick, and has a hard time revving past 5500rpm.

I have not adjusted the carbs at all, and I have not checked the valves, will do that tonight, but these changes have occured in just the past month, so i figure it should not be the valves, not all four at once.

Also, all plugs look the same, glazed black on one side of the electrode, white on the other.

I am confused!

 

Are you absolutely sure that the Diaphragms were SEATED in their Locating Grooves when the Covers were replaces over them?

A misplaced Diaphragm Lip will slow you down.

 

Yes, the diaphragms are seated properly. I just do not understand the issue, I have the idle screw virtually not doing anything. I am considering drilling a lot of holes into the airbox, to simulate the previous leaky condition, then fill the holes with self taping screws to get the mixture back to normal.

I suspect the mechanic I paid two years ago to adjust the carbies and get things real good, ignored the gaping gaps, and tuned the carbs to match the air rich mixture. but if this is the case, me sealing all those holes should have made the mixture rich.....

I'm a gonna warm up the old drill....

 

You'll fee pretty silly having drilled holes in the Box, only to have it be something we've not yet discovered.

One thing you might want to try is seeing how well the Diaphragm Pistons are rising and falling within their Bores.

You might need a simple Aluma oxidation removal in those Carb Bores.
Some people find that their Diaphragms are actually seized when they check the Bores for friction-free movement.

The Nozzles in your Carbs (Emulsion Tubes) could be clogged and not letting AIR break-up the Main Jet's Fuel supply.
That Fuel will enter the Combustion Chamber in a stream or in droplet form and fail to have an effeciently atomized state making you think more Air is needed.

When a Bike suddenly acts differently from the way it did when it was running great not too long ago, ...
(Two years ago is too long to not suspect the Carbs)

Because:
In more than 95% of the time, ...
"It's the Carbs."

Drilling holes in the Airbox isn't going to improve your situation.
The Bottom Line is:
It's just going to make the situation worse.