G9 Spark plug failure

[Andy Dewhurst]

I bought a G9 about a year ago after much searching. It started second kick after being stored for a year. It then stopped and has been problematic since causing much head scratching over the warmer months up to the end of last year, during which time I had the magnito refurbished, which I thought was the reason for the bike cutting out. I have now got to get it running ready for the summer or risk ridicule from my wife and friends.

On my last short outing the bike came to a halt with what sounded and felt like fuel starvation. It would start and idle but died when I opened the throttle. There was rust in the tank and the in-line filter was partially blocked. I cleaned these, then cleaned the plugs as these were oiled from many attemps at starting. I couldn't get the bike to run. I checked the carburetter, the jets and float bowl were clean. I then gave up for a while!

In the sunshine this weekend I had another look and a scratch of the head. There was a weak spark at the plugs, which sometimes arc to the barrel of the plug not the electrode.

What is the point of all this I here you ask. The plugs have only done about 30 miles and both have the same weak spark. Could there be a fault elsewhere on the bike that could cause the plugs to fail or is it just bad luck?

The plugs were new NGK B7ES as recommended on this forum, but the ones in the bike when I got it were NGK BPR6ES. Do you think I should get more of the same, and what is the difference? The ones that I fitted and got it running are new NGK BP6ES as I had these hanging about in the shed. Will the bike run OK on these?

Is there something else I should be checking?

By the way this is my first venture into classic bikes so it is all a bit new and slightly daunting!

Andy

[Cerberus]

Just to encourage, I'm a relative neophyte to old bikes, I bought an M16 which was initially working but then it took me about a year to sort out a whole series of minor faults, needing: new points, new auto advance springs, outer gearbox cover removal, reposition gear change stop plate, remove rocker cover and re-torque engine bolts, as well as a shed load of advice and assistance from the local section members. I found all this daunting, I still do, I've got so much to learn. However, it was all worth while, the bike is a joy to ride (just come back from a section run). ps I've also got a G9 which I bought from a club member which I rode whilst sorting the M16, a lovely bike to ride.Edited by - Cerberus on 01 May 2011 12:35:56 PM

[paul knapp]

Just for starters, the plugs you have now, B7ES, (or the BP6ES which is a slightly hotter platinum plug) are the correct ones in that particular brand for your G9. The plugs that the previous owner had in the engine were resistor plugs, denoted by the letter 'R' in the specs. and are not for use in those magneto fired engines.
Also, since the wrong type of plug had been inavertenately installed, best to check the H.T. leads to make sure they are not the carbon core type. Magnetos need only wire core leads.
Thats enough for starters!

Paul
G.M.

[Andy Dewhurst]

Thanks for the advice.

I had the mag refurbished by Tony Cooper. He re-wound it, replaced the brushes, points and fitted new pick-ups and new HT leads. It ran OK when I re-fitted the mag. (once I worked out that I had timed it to the wrong cylinder at first). I fitted the new plugs and new non-resistor caps at the same time.

The bike had been stored dry for a while by the previous owner. The tank wasn't too bad and I cleaned the surface rust out by shaking it about with nuts and bolts in it and swilled it out, as I had read somewhere, before I put any fuel in. I obviously didn't get it thoroughly clean, and that was when the in-line fuel filter blocked. I thought I had cured the fuel starvation problem, and the filter and float bowl look clean now.

I will make sure the 'R' plugs are filed under B to stop me fitting them by mistake in the future!

Andy