Plug fouling issue.....

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nortncom

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My MKIII Commando is about to drive me nuts with its plug fouling problem. Against my better judgment, I changed quite a few parts on it at one time over the winter and I am now paying for it. Previously, it had a Boyer ignition, twin 6v German PVL coils, and a single Mikuni VM34 w/pancake filter. I have since converted to a Trispark y ignition, CNW dual-fire single coil, I kept the VM but swapped the pancake filter for a larger cylindrical UNI. The bike now feels quite under powered and fouls plugs rather quickly (like 20 miles quickly). I'm pretty sure I got the static timing correct - brought pistons up to TDC (verified with straw in cylinder) and bumped it rearward to 31*, then followed instructions per tri sparks manual. There is not an electrical issue between ignition and plugs because they are firing strong, as I verified this via trispark's test feature. I did not change the settings on the carb which are slide at 2.5 and airscrew 1.5, respectively. I would have thought using a more open filter element would have leaned the mixture, not made it more rich... The plugs I am running are NGK-R BPR7ES.

I'm not sure if any of this matters, but additional engine modifications are as follows: bored .020 over with hepolite pistons, Megacycle 560NR cam, Black Diamond valves, chromoly pushrods, and unbalanced head pipes with straight through pea shooters. Anyone have any ideas as to what might be causing this? I'm almost to the point of being afraid to ride it after having to push it over a mile home last night....
 
nortncom said:
My MKIII Commando is about to drive me nuts with its plug fouling problem. Against my better judgment, I changed quite a few parts on it at one time over the winter and I am now paying for it. Previously, it had a Boyer ignition, twin 6v German PVL coils, and a single Mikuni VM34 w/pancake filter. I have since converted to a Trispark y ignition, CNW dual-fire single coil, I kept the VM but swapped the pancake filter for a larger cylindrical UNI. The bike now feels quite under powered and fouls plugs rather quickly (like 20 miles quickly). I'm pretty sure I got the static timing correct - brought pistons up to TDC (verified with straw in cylinder) and bumped it rearward to 31*, then followed instructions per tri sparks manual. There is not an electrical issue between ignition and plugs because they are firing strong, as I verified this via trispark's test feature. I did not change the settings on the carb which are slide at 2.5 and airscrew 1.5, respectively. I would have thought using a more open filter element would have leaned the mixture, not made it more rich... The plugs I am running are NGK-R BPR7ES.

I'm not sure if any of this matters, but additional engine modifications are as follows: bored .020 over with hepolite pistons, Megacycle 560NR cam, Black Diamond valves, chromoly pushrods, and unbalanced head pipes with straight through pea shooters. Anyone have any ideas as to what might be causing this? I'm almost to the point of being afraid to ride it after having to push it over a mile home last night....
Click to expand...


It sounds like you have found out which filter flows better -open or not. jim
 
Touché Comnoz. I haven't even considered the fact the UNI may be more restrictive than the pancake filter.
 
Uni filters, like most foam filters don't flow very good, but they do filter better than most.
 
nortncom said:
I'm pretty sure I got the static timing correct - brought pistons up to TDC (verified with straw in cylinder) and bumped it rearward to 31*, then followed instructions per tri sparks manual.
Click to expand...

Did that also include doing the final timing check with a strobe?

The Tri-Spark instructions say to set the timing to "29" degrees BTDC, (not 31 as you would for a Boyer although I believe it should be 28 degrees BTDC as indicated by the photo of the Commando timing mark and scale in step 3 of the instructions).
 
If you still have the pancake filter put it on there with fresh plugs and see what happens. Based on the description of what you did to the bike that seems to be the only thing that would change the fuel delivery richer.
 
nortncom said:
I'm pretty sure I got the static timing correct - brought pistons up to TDC (verified with straw in cylinder) and bumped it rearward to 31*,
Click to expand...

There is also the minor matter that all timing work should be done by turning the engine FORWARD, in the usual direction of rotation.
Or all the backlashes can accumulate.
LABs comment about checking with a strobe may be very apt...
 
nortncom said:
My MKIII Commando is about to drive me nuts with its plug fouling problem. Against my better judgment, I changed quite a few parts on it at one time over the winter and I am now paying for it. Previously, it had a Boyer ignition, twin 6v German PVL coils, and a single Mikuni VM34 w/pancake filter. I have since converted to a Trispark y ignition, CNW dual-fire single coil, I kept the VM but swapped the pancake filter for a larger cylindrical UNI. The bike now feels quite under powered and fouls plugs rather quickly (like 20 miles quickly). I'm pretty sure I got the static timing correct - brought pistons up to TDC (verified with straw in cylinder) and bumped it rearward to 31*, then followed instructions per tri sparks manual. There is not an electrical issue between ignition and plugs because they are firing strong, as I verified this via trispark's test feature. I did not change the settings on the carb which are slide at 2.5 and airscrew 1.5, respectively. I would have thought using a more open filter element would have leaned the mixture, not made it more rich... The plugs I am running are NGK-R BPR7ES.

I'm not sure if any of this matters, but additional engine modifications are as follows: bored .020 over with hepolite pistons, Megacycle 560NR cam, Black Diamond valves, chromoly pushrods, and unbalanced head pipes with straight through pea shooters. Anyone have any ideas as to what might be causing this? I'm almost to the point of being afraid to ride it after having to push it over a mile home last night....
Click to expand...

Any specific reason you're running resistor plugs? Also, have you timed the engine with a degree wheel to verify the guide marks in the primary cover? Simple test for the filter is to run the bike with the old one, if problem goes away you've found your answer.
 
Appreciate the all the responses. Tomorrow I'm going to refit the pancake filter and reset the static timing to 29* BTDC. I'll also buy a strobe to verify the timing. Furthermore, according to said modifications on engine, do the NGK BPR7ES plugs sound appropriate, or should a run a colder plug like an 8?
 
Is it fouling both plugs or just one? Oil-fouled or gas fouled? Gas will foul a plug with dry, black soot. Oil-fouling is wet.
 
nortncom said:
Appreciate the all the responses. Tomorrow I'm going to refit the pancake filter and reset the static timing to 29* BTDC. I'll also buy a strobe to verify the timing. Furthermore, according to said modifications on engine, do the NGK BPR7ES plugs sound appropriate, or should a run a colder plug like an 8?
Click to expand...

Why a pancake. Why not put the biggest air filter you can fit? Is there a space issue? Are you trying to save the old airbox?
http://www.knfilters.com/search/product ... od=RU-0690
http://www.knfilters.com/search/product ... od=RU-0990

If you are fouling then you may want a hotter plug, not a colder one.
 
Both plugs are dry fouled. Everything is black with exception of the top of the side electrode which is brownish.
 
acadian said:
Any specific reason you're running resistor plugs? Also, have you timed the engine with a degree wheel to verify the guide marks in the primary cover? Simple test for the filter is to run the bike with the old one, if problem goes away you've found your answer.
Click to expand...

A Trispark needs either resistor plugs or leads.
 
I may be wrong but I thought only one of the plug leads or plugs themselves had to be resister to work with the digital Tri spark?

So if Matt at CNW supplied you with his coil and Trispark, did he also give you his resister plug wires that you have now combined with your
own NGK resister plugs?

Can too much resister stuff cause this plug fouling?

I have the same set up as you, CNW coil, Tri Spark, Megacycle cam, resister plugs but standard plug leads to the coil

only difference is you have a single Mkuni versus my twin Premiers, but that should not be a reason for your fouling
 
1up3down said:
I may be wrong but I thought only one of the plug leads or plugs themselves had to be resister to work with the digital Tri spark?

So if Matt at CNW supplied you with his coil and Trispark, did he also give you his resister plug wires that you have now combined with your
own NGK resister plugs?

Can too much resister stuff cause this plug fouling?

I have the same set up as you, CNW coil, Tri Spark, Megacycle cam, resister plugs but standard plug leads to the coil

only difference is you have a single Mkuni versus my twin Premiers, but that should not be a reason for your fouling
Click to expand...

Yes, you only need resistor plugs or caps, not both. Too much resistance and a weak spark and you may get foul play...
 
That is a very good question about the ignition system being over suppressed. I'm not sure how to tell if the plug wires are suppressed or not; however, if Matt only sends out suppressed wires, then this could most definitely be part of my problem as well.
 
Plug 'wires' should have wire - copper or stainless steel - strands or woven. If not, the core provides a greater resistance for radio suppression.
Ta.
 
how's your charging system? If your rotor/stator isn't charging your battery, then 20 minutes of riding sounds about right before you battery's voltage is too low to throw a decent spark... Check all the charging stuff, rectifier, ziener diode, rotor/stator output...

Actually that's how I bought my bike from a friend over 40 years ago. It's stator was burned out and he would ride it somewhere, and it would die and wouldn't start... He would bring it home, charge the battery for his next ride and it would happen again... He finally sold it to me for $500.
 
I actually went through that last spring with a phantom electrical short I could not find; consequently, I said screw it, and rewired the whole bike from scratch. It now has a podtronics solid state regulator/rectifier. Not sure about the alternator/stator as it seems to be charging fine, it has three wires coming from it rather than two.
 
You have to strobe it. The static is only going to get it close enough to start it. Get rid of the resistor plugs. NGK BP7es will work. I would loose the foam filter as fast as you can. See what happens & let us know.
 
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