Track Tac

Plug ?

D

Dirtkartin

New member
I have a 304wx tilly on non ethanol premium octane on a modified gx200 with a NGK bpr6es . MY current problem is that I frequently flood out spark plugs, sometimes as much as two a night. I was told by my carb builder that a tilly isn't meant to sit and idle. Well obviously you have to idle during a race if there is a caution and they try to reset the order.(Some times taking a minute or more sitting still.) I have tuned the high and low as instructed, and it runs like a scolded dog when going wide open.

I have been told by two experts, one being Russell from nrracing and one is the family mechanic that I trust with anything, that I might stand a better chance with going with a cooler plug. Everything I can find on the internet states the opposite, that I need the extra heat (hotter plug) to clean off the plug to prevent fouling. As I do trust the 2 experts and am going to try a cooler plug, I was wondering what the reasoning was behind running a cooler plug, and why my findings from a google search are condescending.
 
not too discount your info, I doubt a cooler plug will help at idle.
You may need to raise the clutch stall so you can idle at a higher rpm.
also have you been adjusting the needles for such times as waiting too line up?
you may have to learn to turn the low in at those times and then open up as you roll of for the restart.
possibly open the gap .010
 
I, on the other hand, would never recommend raising the clutch stall RPM to cure an idling problem. You might try raising the idle RPM. Closing the low-speed needle is a good idea. It can be a little tricky to do, (getting it back to its best racing position) but with practice I'm sure you can figure it out.

As far as a colder plug is concerned, I don't understand the thinking as far as fouling is concerned, but, depending on the compression ratio, it might be a good idea for better performance. Choosing the right heat range plug is important, but I don't think it's a critical consideration for the problem you're having.

How much colder can you go? The plug the factory recommends, when the engine is used as intended, (industrial power source) wouldn't (as I'm sure you know) be appropriate for racing.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
We ran br4 iridium core plugs in a similar build gx200. Not that the plug ever made or lost us much in trials. I believe the key to the puzzle is in the Tilly. They can be a little tricky to find a good idle and great acceleration. Your clutch stall should be set at peak torque. Which will be plenty high enough to idle fine. An easy start point would be to measure the opening between the throttle bore and butterfly at idle. That will give you a decent reference for how much fuel your metering at idle.
 
If you are fouling a plug, going to a colder plug will only make it worse.
If you are not real high on compression I would suggest going to a hotter plug which will burn off deposits.
 
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