A strange one

Merz64cb77 · Post by **Merz64cb77** » Sat Jul 21, 2018 7:35 am

I’m no expert but I think it’s an electrical issue of some kind. Could it be a grounding issue?

Are you running NGK D10HS plugs?

malcolmgb · Post by **malcolmgb** » Sat Jul 21, 2018 4:08 pm

http://www.ngk-sparkplugs.jp/english/te ... index.html

mike in idaho · Post by **mike in idaho** » Sat Jul 21, 2018 4:57 pm

You may still have a fuel/air issue. It should be harder to start without the choke. Is the air filter new? Have you tried running it without the air filter?

PF1 · Post by **PF1** » Sun Jul 22, 2018 4:23 pm

When I was a young chap my C72 had this problem after reassembly, the cam was one tooth out.
Kept fouling plugs tag lag. I was sure I had assembled it correctly too doh!

modelman · Post by **modelman** » Sun Jul 29, 2018 1:56 am

PF1 wrote:When I was a young chap my C72 had this problem after reassembly, the cam was one tooth out.
Kept fouling plugs tag lag. I was sure I had assembled it correctly too doh!

I hear what you're saying & I did think you could be right, but thinking about it, since the points-cam is on the camshaft, one tooth out would make the lobe around 10 or so degrees out & my points & backplate are in the exact position, & i'm sure the timing is spot-on as it was timed using the test-lamp.
Put in a pair of new iridium plugs & it ran great!!

'Correct' plugs in & no-go, so I bought a plug-tester the other day & found that over half of the many plugs I have are dud, took the 2 'new' ones I bought for the 77 back to the shop & they replaced them, the bike runs well now with the correct plugs.
I remember just how quiet these were in the day, mine is a bit noisy at the top-end, the gaps are correct & there was no evidence of wear, but I did use the old chain & tension-wheel,
so maybe that's the reason.