white plugs as usual

I need some advice. I cannot seem to bring color to my plugs after riding at high speeds for any length of time. I have chopped at 65 mph many times as well as checked the plugs every 30 miles or so. I upjetted the pilots and was able to blacken the plugs at idle but they burn clean everytime making for an underpowered bike upon take-off and one that I worry will overheat at speed. This bike wants to run very lean. Should I upjet my main jets or add shims? If shims are the way to go, how and where are the installed?


Thanks in advance.

 

The easiest thing to do is Step-up the Main Jets.
That might be all you have to do. You'll know when you do testing.

If you get an acceptable coloration after bumping-up to a hotter Main Jet ...
And, ... the Performance is acceptable to you. That might be enough Mods to alleviate needing to have the Diaphragm Needles shimmed.

This is not to say you won't benefit from lifting the Needles.

 

I'll give it a whirl. Thanks Rick.

 

What was done to the bike? If it still has the stock exhaust and the stock airbox you might want to check into other things. Also what RPM were you doing the plug chop. High speed does not mean 65 MPH on the bike it usually means from about 7,000 to redline on the bike. Also where are you looking?? the white insulator on the plug should not be black, it should be a tan color. The rest of the plug can have a darker tone to it. You might have a pluged emusification tube. Its the brass tube that has all of the holes in it where the needle goes into. Make sure that is not plugged up, if it is then you are not getting the gas that you should. If the bike is stock then it should run fine unless the carb ports are clogged. If you have made changes like exhaust or K&N filters or Uni Filters than you will have to rejet. However the bikes from the 80's were known for coming in lean from the factory and the magazine guys would usually put a .020 shim under the needles to richen up the midrange and get rid of the stumble that plagued some of these bikes.

Sean

 

Thanks Rick, Sean,

Everything is stock. I have, in the past, achieved some color on my plugs when doing stationary plug chops at 7k rpm but generally speaking, I am rich at idle (black) and lean at all other times unless I am missing something conceptually. Theoretically though, I should never have ceramics that are CLEAN WHITE, correct? I mean they look brand new after riding! I've never had any luck maintaining that "chocolate" color that everyone else seems to be able to achieve with a few turns of their pilot screws. Carbs are clean. Has anyone had a similar situation with an 85?


I'm going to order some hotter jets and see if that helps (come spring). The stock jets are #107. Cycle recycle has 110-134 for Hitachis. Does anyone have any suggestions for a good starting (and hopefully finishing) place? I was thinking #110 or #112?



Thanks in advance.

p.s., I'm coming North to visit the fam at xmas. I wish I had a trailer and vehicle to tow my bike with so I could spend xmas with you Rick! We could roast marshmallows over my perfectly tuned engine and harmonize with the exhaust notes.

Marshall

 

If the bike is stock, there's something wrong. It shouldn't be running that lean. Are you sure the carbs are clean and you're getting the right amount of fuel? Also, did you color tune the plugs and set the idle jets at the correct level? A good place to start is about 2.5 turns out from gently seated. If you don't know, the idle jets are very small brass screws at the front of each carb, recessed within a round well. Maybe sure these are set up correctly. Also, try a trick that RickOMatic has suggested in the past and that's worked really well for me.
Take out the diaphram assembly and throttle slide beneath each carb and sand the inside of each carb body. The surface gets rough over time and a good polish will let that round slide drop as rick says, "like a bag of cement out a second story window." But it requires gradual steps of different fine sand paper and emory cloth. Ask Rick what the exact procedure is.
Anyway, before you go putting in hotter jets make sure everything is working properly. Otherwise you could just cause yourself a whole new set of problems.
Let us know how it goes.

 

I have found an interesting site with information about NGK sparks plugs. On page 5/5 of the first chapter there is a spark plug temperature chart with the corresponding spark colors. At the optimum temperature range between 450 to 850 degrees Celsius the color of the spark plug also looks a little pale to me but according to NGK it's the right color. I hope this information will be of any use for futher diagnose. NGK E-LEARNING

 

The NGK Learning Page is good solid information.
But, the color of the Plug they call optimal would be LEAN in a XJ-Bike.

Fuel Injected Systems with Lambda Sensor loops provide feedback information that changes the Pulse Width activating the Injectors.
It allows the Engine Combustion Mixtures to be constantly regulated for the Engine's best performance under all conditions.

There's no computer adjusting the Mixture on your Bike.
Therefore, the Mixture needs to be set such that BURN is regulated to be RICH enough for all conditions.

 

There is on mine!

 

What new problems might I encounter after upjetting?

Thanks.

 

It might be too rich but that is always better than too lean and you can work on it. I agree though that there is probably another issue like maybe throttle shaft seals? How many miles on the bike and have you checked/adjusted the valves?

 

18,000 miles on the bike. I agree about being too rich rather than too lean. I have not adjusted the valves. How do the valve adjustments affect fuel delivery? What are the shaft seals?

Any input is helpful,
thanks.