Help!! my engine kills plugs like a MF!!!

[sfab]

ive built a 61x-61x bigbore this winter with a set of 48mm dan lamey carbs and B-pipe. I thought it was nicely tuned (120L, 145H, 2.5N silver spring) but after about 2-3 tanks, the ski loose power at high RPM (1/2 throttle & +). ive checked the plugs and they were dark a bit but not wet. I just have to put new plugs and my engine is kicking like it was before. ive tried to go down to 137.5 for the high jet with a brand new set of plugs but it ran very poorly. it was almost as bad as when the plugs were fool... ive must have wasted a dozen of sparkplugs since ive modified the engine (about 12 tanks)... my high cicuit needle screw are completly close, i do notice a little drop in power if i open them a bit... is 145 to 137.5 is that big of a jump??

 

[Seb62T]

Which CDI are you using ??
Too much advance can cause plugs fooling. I had the problem with the stock CDI and a too optimist setup of the stator.

Regards,

Seb

 

[DAG]

also what plugs,, and whats you plug gap

 

[sfab]

NGK B8ES plugs with the gap that came right out the box.
i have a mild advance on my stator, same as it was before the bigbore and it worked great without fooling the plugs. What gap should i use?
thanks!

 

[crammit442]

What compression and fuel are you running?

 

[keefer]

Maybe the pilot jetting is too rich. Also I would ditch those 2.5 N/S and go to 2.0 and change the spring to get your pop off to around 21 psi. This might help clean it up by reducing the extra fuel dribble that can be associated with vibration unseating the big N/S.

 

[DAG]

dont really know to much but, but read awile back that the (R) plugs BR8ES seem to help with an issue like you stated. its a easy/cheap try anyhow

 

[sfab]

What compression and fuel are you running?

180psi with 94

 

[sfab]

dont really know to much but, but read awile back that the (R) plugs BR8ES seem to help with an issue like you stated. its a easy/cheap try anyhow

i will give it a try. at 3$ each, it get expensive fast when they dont last for more than 2 tanks....

 

[Mouthfulloflake]

can you not clean them and reinstall them?

also, what head are you running?
the ES plugs are for aftermarket heads.

 

[Matt_E]

i will give it a try. at 3$ each, it get expensive fast when they dont last for more than 2 tanks....

Won't do a thing. They are resistor plugs which are supposed to cut down on RF emissions - this has absolutely no effect inside the combustion chamber.