Triumph T120 Tiger Spark Troubles


| 1/3/2018 12:00:00 AM


Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Q: I have restored my 1971 Triumph TR6R T120 Tiger from top to bottom. The engine and electrics were professionally done, while I stuck to the other things. I’ve had the bike out half a dozen times and all seemed fine. Recently, while riding my Tiger, which now has 168 miles on it after the rebuild, my engine decided to run on one cylinder. I limped home. The coils are original Lucas 17M12. I checked for spark at the plugs first, the wires secondly, and got spark on the left side (as I sit on the bike) but not the right side. The bike has a new Pazon ignition in it. I then switched the wires to the opposite, and also did the same with the plugs and the coils. I got the same results on the right side — no spark. I took an ohm reading on both of the coils and got 4.7 on the primary side, and 5.36 and 5.3 on the secondary sides. I also changed gas. Upon start-up after all of this, the bike ran fine for about 30 seconds and then the right cylinder stopped running again. Am I on the right track to assume that I need to replace the coils? Both sparks are orange/light yellow when they fire. Are the coil ohm readings correct/within specifications, or does it indicate that they need to be replaced? The book says 3 ohms minimum and 3-4 ohms maximum for primary resistance, but nothing about the secondary resistance. Maybe I’ve answered my own question, but I’d like to hear from an expert if I am on the right track. — Burt Horner/via email

Blaster logo

A: The biggest problem I can see is you are running two 12-volt coils in series in a wasted spark ignition system that calls for two 6-volt coils in series. Since the Pazon charges and fires both coils every time, you are giving it too much of a load to deal with. Switch to two 6-volt coils in series or get one dual output coil of 3 ohm primary resistance and I think your problems will disappear. Update: I got an email back from Burt, and after changing to 6-volt coils and chasing down a grounding problem, he’s on the road again.



DAVIDP
1/13/2018 12:33:58 AM

I'm glad he got that sorted. Two 6V coils are always recommended. Beware of dual-lead coils with the OIF models. Mounted under the seat they need a heat sink. I had one Harley coil go low resistance on me. I can only assume that it got hot. Fried my Boyer. It helps to put a 5A fuse in the power lead to the black box just in case.




The sound and the fury: celebrate the machines that changed the world!

Motorcycle Classics JulAug 16Motorcycle Classics is America's premier magazine for collectors and enthusiasts, dreamers and restorers, newcomers and life long motorheads who love the sound and the beauty of classic bikes. Every issue  delivers exciting and evocative articles and photographs of the most brilliant, unusual and popular motorcycles ever made!

Save Even More Money with our RALLY-RATE plan!

Pay now with a credit card and take advantage of our RALLY-RATE automatic renewal savings plan. You save an additional $4.95 and get 6 issues of Motorcycle Classics for only $24.95 (USA only).

Or, Bill Me Later and I'll pay just $29.95 for a one year subscription!




Facebook Pinterest Instagram YouTube Twitter

Free Product Information Classifieds