Pod filter and larger jets = carbon fouling plugs?

Hey guys,
I'm finally back to working on my Maxim. I'm still carbon fouling spark plugs like crazy (new plugs dead after a half hour of riding around the neighborhood). I've still got the Pod filters and I'm wondering if those plus the larger jets that the PO put in would cause me to want a hotter plug. Does that make sense? I've cleaned the carbs out twice and I've got the air/fuel mixture screws set in to where the bike throttles up great (no dead spots, no hesitation, no popping and no backfiring). What else should I be looking for so I don't have to buy new plugs everytime I want to ride the bike?
Thanks in advance,
You guys are always incredibly helpful and I really appreciate it.
-Wayne

 

If the plugs are black, wet looking and smell like fresh gas I'd say your likely over jetted though too other things can mislead you into thinking your over jetted. Process of elimination, drop one size or so off the pilots and see how it likes that, keep tabs on oil and fuel consumption etc. I mention pilots first because you mentioned this is happening while driving around the neighborhood. BTW what pods are you using? Some of the small foam types can be restrictive enough to act like a choke...

 

I'm certain that the pods are screwing me up. I've heard they can be problematic. I'm not sure the brand. They're not foam though, they're like a mesh plastic-y material. They don't seem to restrict air flow at all. I'll see about getting smaller jets in the next few days. Thanks for the advice.
-Wayne

 

Pod filters will only change the mixture very slightly unless they are clogged but then any filters will cause problems if clogged. I only had to go up one jet size with pod filters. However you still need to adjust the jets to the correct size no matter what kind of filters you have and a small change makes a big difference. Like SteveG says only go one size (that's one size bigger than stock) and try it. If in doubt remove the filters and put in stock jets to get it back to a known baseline condition then go from there and change just one thing at a time and see what difference it makes each time.

 

You might also check to see if the jet needles have been shimmed up.

 

Check float levels first.

Then, whileyour in there, let us know the size of the jets in there so we know how far from stock they are. And, as stated, whether any shims are on the needles.



Also, compression check numbers if you have them.


Does it use any oil?

 

If the bike had a Jet Kit installed ... it's likely that the base of the Diaphragm Piston was drilled to allow the Needle to rise with the Piston more rapidly.

You might have to solder the extra hole shut and get back to having the Diaphragm Piston rise slower than it will with two holed of larger than stock diameter.

 

Ok this weekend I'm going to take the carbs off and take some pictures of everything so you guys can have all the info you need to give me a place to start. Thanks so much and I'll get back to you guys in the next couple of days.
-Wayne

 

Ok, no pictures yet...
I've taken the carbs off though, and here's what I've got.

The Main Jets (from 1-4) are 118, 120, 120, 118.

The Pilot jets are all 40.

Is this out of whack?

Remembering that I have mesh pod filters that don't seem to offer much air resistance.

 

Stock mains are 110. Stock pilots 40.

 

Here a good thread on jet sizes/re-jetting:

http://www.xjbikes.com/Forums/viewtopic/t=7324.html

It's odd that two jets were different sizes, and points in the direction that someone was trying to compensate from some "other issues" by using bigger jets on only two of the carbs....

 

Ok. So I'm 5 sizes up from stock on the main jets and at stock on the pilot jets.
According to the thread Chacal sent me to...I should be 2 or 3 sizes up from stock on the mains and 1 size up on the pilot jets?

So I guess it's not a bad idea to go buy a few sizes smaller main jets (smaller jets = less gas mix getting to the spark plugs = maybe no gas fouling plugs?) right?

 

It looks like your 4 up on the outside and five up in the middle two.

Four sizes up shouldn't be too far off for your configuration.

Do all four plugs foul up or just the middle two.


Going by your original post it sounds like your bike runs perfectly apart from fouling plugs so I wouldn't go changing too far from what you have got.

Different sze jets in the centre two is not uncommon but when rejetting for more air it is easier to keep them the same across the board.

Have you checked the float levels yet? I'm guessing that this is the main problem causing the fouling.

If float are within spec then go down to 116 mains in all and see how it goes.

 

The size of the main jets won't make any difference except at wide open throttle. If you never drive at WOT and don't do a lot of drag racing then changing them won't make any difference. I'm guessing that most of your driving around the neighborhood is at part throttle so you should look at the tapered needles which controls the mixture in the mid range from slow to high speed. If your plugs are fouling only at slow speeds with the throttle nearly closed someone probably drilled out the pilot jets or your floats are set too high or the needle valves leaking.

 

When you say tapered needle. Are we talking about the needle under the float? The one that the float should close when the fuel level gets too high?
Whats the best way to check if they're leaking?

 

We refer to the jet needle (blue in the diagram). It may have been raised (shimmed) or modified to make the mixture richer.

 

Kind of what I was thinking when he first posted...likely his problem is in the low speed circuit somewhere provided it is fuel that's fouling the plugs. Something I thought about too is would his bike have the rubber plugs sealing the pilot circuit like some others? Seems he hasn't mentioned seeing them...

 

Those are the needles that in a previous post, I talked to Rick about. They had small hexnuts raising them up a 1/4 inch or so. Rick said something to the effect of "PO something something Mickey Mouse something something else" Everything seems to be fine with them now (they pass the clunk test fine)
The pilot screws didn't have the rubber caps on them when I got the bike...so I've tweaked them as per Rick's instructions to the point where the bike was running beautifully. No popping so stumbling good response....then I fouled the plugs again.
I like the idea that I've just got the floats set too high.
Every drain plug is destroyed, so I guess I have no real option but to drill them out.
-Wayne

 

Not to be a "Grinch" this time of the year ... I hoping that you are fouling the plugs in a "Fuel Related" issue ... but, a classic reason that Plugs get fouled when the bike is running good is: ... Valve Seals.

When the Valve Seals are leaking ... the Intake Valve has a small quantity of Oil on its Stem not wiped by the Seal ... this Oil enters the Combustion Chamber when the Valve opens to allow the Mixture to enter the Cylinder during the Intake Stroke.

The Oil gets cleaned-off the Valve Stem by the incoming Fuel Mixture and does not burn-off completely during the Power Stroke.

Almost like you are running 2-Stroke Mix ... enough of it not getting burned-off winds-up collecting everywhere in the Combustion Chamber, especially the Spark Plug ... which, over time and the continued accumulation of unburned "Fuel" ... fouls and effects the performance by missing and causing rough running until the New Plug fouls; too.

If you are seeing Oil ... "Disappear" from the Oil Level Window ... without seeing a leak ... Valve Seals are the Usual Suspects!