Short plug life (G9)

Colin Kent. · Post by **Colin Kent.** » Sun Oct 28, 2001 4:11 am

Greetings Sages,

Can anyone please suggest why my G9 has suddenly started "eating" spark plugs ( B8ES), since a recent magneto rewind ?
I have had to replace 6 plugs in the last 100 miles of admittedly short runs.
All suggestions will be appreciated.

Colin Kent

Dave · Post by **Dave** » Wed Oct 31, 2001 7:45 pm

Colin,
Are they B8ES NGK Plugs or another make? Also are they fouled/contaminated in any way when you remove them? If you clean a plug that fails does it then work OK or if you re-fit a previously 'failed' plug when the engine is cold does it then appear to work OK? answers to tese questions may help to pin-point the problem.
Dave.

Colin Kent. · Post by **Colin Kent.** » Thu Nov 01, 2001 1:10 am

Greetings Dave,
Thanks for your response.
Plugs are NGK B8ES.
When removed they are wet, slightly oily, but generally clean and free from hard black or other deposits.
When re-fitted after cleaning, drying and gap check
(using 0.023 in.) they will not produce a start.
Fitting a new plug results in an immediate start and
faultless running.
Regards, Colin Kent

TommoT · Post by **TommoT** » Thu Nov 01, 2001 10:12 pm

If the mag rewind is the only alteration to engine set-up the answer to your troubles must lie here! Maybe with a fresh mag, providing a healthy spark the carb set-up is no longer ideal. It may have suited the weaker spark and ignition timing before the rewind. Your symptoms match exactly the ones displayed by my G80 after a rebuild. I tried everything in the ignition department, rejetted the carb, lowered the needle etc.. Not until I changed the airslide, went from a #3 to a #3½ (Monoblock 389) did I get the mixture right. The bike was transformed, has run on the same plug since!

Good luck!

Tom M. (TM)
Denmark

RogerNorman · Post by **RogerNorman** » Fri Nov 02, 2001 7:58 pm

I would be inclined to say that you are running the wrong plug. I run my G9 on B7ES and have done for years. From memory the B8ES is a softer plug

Colin Kent. · Post by **Colin Kent.** » Fri Nov 02, 2001 9:13 pm

Greetings Roger,
Thanks for this. I changed to the B8ES plug to overcome a "whiskering" problem encountered during running in after a bottom end rebuild. The change cured the "whisker" problem, and since the engine now has nearly 500 miles up since the rebuild, I will try reverting to the B7 grade.
Colin Kent

Colin Kent. · Post by **Colin Kent.** » Fri Nov 02, 2001 9:24 pm

Greetings Tom,
Thanks for this. I have been concerned for some time that the mixture is too rich. A previous one notch change of the needle setting resulted in immediate "blueing" of the RH exhaust pipe, which suggested to me that the mix was then too weak, so I reverted to the present setting.
I will try the needle adjustment again.
I do not understand your suggested need to change the carb. slide.
Thanks again for your interest.
Colin Kent