Forum

[Mike-T]

I have an Indian 350 bullet and spark plugs are not lasting very long. Some last a couple of months, others have lasted days or weeks. One only lasted 10 mins. The first symptom is a lack of power/sluggish acceleration. Then difficult starting for a day or two. Then will not start at all. I have used different brands of plugs and tried heat ranges either side of standard. When the pugs are failing they still look a good colour, but when i test them against the head the spark is very weak. Popping in a new plug instantly restores normal operation and a big fat spark when tested. The ignition timing has been regularly checked (points). I have checked the carb tuning and looked for exhaust leaks. The coil is only a couple of years old. So far i can find nothing. What would be causing repeated spark plug failure?

[another Allan]

For plugs of different brands and heat ranges all to fail suggests to me that it is more likely to be the coil. A coil can start to fail in many ways, but one way is to lose the ability to propduce a spark as it heats-up in use. A brand new plug may help until it gathers a little of the products of combustion, then the coil is not up to it gain.
I would try a new (or a known-to-be-good used) coil.

[another Allan]

'propduce' = produce. Oh for an edit facility!

[John M]

Are you treating the symptom rather than the cause? If there is a weakness or fault in the ignition system then it may be that you only get a good spark with a really clean plug. I would check and clean all the connections on the ignition system and consider new points and condenser if it's still on points.

[Alan R]

Hi guys-------- MIKE-T ...First, what make and grade are the plugs ?? ( Are you sure they're not reproduction ones ??)......Second, what make is this 2-year old coil ( If it's an Indian LUCAS one then SCRAP IT and fit the German PVL unit as supplied by our hosts...Third, How old is the capacitor ( Condenser )??..I would fit a new one and DUMP the old one (it's only £5 approx)..........Some fresh HT cable, clips and Plug Cap would help........Make sure your battery terminals are clean and well-clamped.......Check the two connectors on the Ammeter for cleanliness and continuity......What fuel is in the tank ??----------When did this first start ??

[Norm]

My Crossbred did this to me, did my head for 12 months an an unknown number of plugs, I finally worked out that it would fail if the bike was under load starting to go up a hill and opening the throttle and it would just die. I finally decided that fuel was wetting the plug as the throttle opened, I lowered the needle one notch and that was the end of my plug problem. Sounds bizare I know but that is what it was. I tried so many different plugs plus Iridium, all did the same. I was buying plugs in a six pack if I wanted to go on a decent ride

[Mike-T]

A few more details as suggested by Alan-R. The coil is a lucas as supplied by our hosts. The plugs i have used have been NGK and champion and the original 22yr old indian one (the one dependable one that will always get me home). The champions all died very quickly. The NGK's have been variable, some lasting months, one only ten minutes. Even when i have good period with one plug the bike performance can be variable, one day the bike is lacking in power and i think the plug is failing, then the next day it's running really well. This can repeat until it just won't start and off i go with a new plug. I have just been out to the garage and tested the coil and i am getting 0.3 primary and 7100 secondary which is about right. The condenser is about 2 years old as well (6V to 12V conversion done 2 years ago). problems started about 9 months ago when i got through about 4 plugs in one week' prior to that one plug lasted for about 5 years. Then i've had a good patch and this week i'm now on my third plug! I can run with or without a battery (boyer powerbox) but doesn't seem to make a difference. The petrol (standard unleaded) is always fresh as i use the bike daily for commuting. I need it for work tomorrow but i'll have a closer look at all the connections at the weekend.

[Norm]

Mike, the fuel we are getting these days will kill plugs so my bet is a fuel problem

[apparently lucky eddie]

Fuel is almost certainly a contributory factor. I NEVER use cheapo supermarket petrol - its cheap for a reason. ie. its cheap 'n' nasty petrol. A couple of days ago I had to put some Esso in my Triumph, within a couple of miles she was missing under load. Get home, drain the tank into the lawnmower and refill with high octane Texaco, and problem gone instantly. So far as I can see, at least here in Devon, Texaco is the only "super green" that is pure and contains no ethanol.

[Jonesy]

Hi,Mike-T.Try using a BOSCH W78 plug.I use one in my 08 500 clasic.Iam using a9:1 piston and have had no problems,touch wood.