Triumph Bonnerville T140d 1980

Have you checked to see if there is a good healthy spark at the plugs...could also be a coil or ignition problem causing bad combustion on that cylinder, as for school i really cant remember names...it was 50 odd years ago.
Shame as if i still lived in st-Leonard's i would take a look for you.

 

If the battery is not 100% and not supplying a good 12v and full amps the ignition system is going to suffer and could cause the problem with combustion your having, try a good or new battery and see how it behaves, do you know whether the charging system is working correctly?

 

Nash.
And it could well be a valve letting oil past the guide. You should know if it is by starting the bike after a day or so. It will smoke from that cylinder. And carb balancing it would run hotter on the out carb. Get two 6mm drill bits I use tent pegs take of your rubbers and gently place them below the throttle slides then twitch the throttle till both twitch at the same time. Also run the bike till hottish and ticking over nicely. Take one plug out and run the other side at 1000 revs then the same with the other side. Then adjust the two carbs back to just over a thousand revs by adjusting each carb a pinch at a time. Hope this helps and the plugs really should be n5's.
Regards
Joe.

 

Joe he did say the bike was rebuilt from ground up so shouldn't be a guide if reasonably recent build...but could be a possibility i guess.

Nash, if you go with Joe's balancing and remove one plug make sure you keep that plug attached to the HT lead and the plug is earthed as a lot of electronic ignitions dont like if not earthed and it can kill the igniter.

I am still wondering how a plug can be burned out and carboned up.....if burned it would be down to weak mixture or knock, if carbon contamination it would be rich mixture, incomplete combustion, oil contamination form guide or ring seal.

 

Tricky-Dicky
Yes but I especially know all about some rebuild members of our world. But you are 100% about the plug especially if you have electronic ignition fitted. Thanks for that.
Ride Safe
Joe.

 

Sorry Joe but that didn't make much sense to me i'm afraid?

 

Tricky-Dicky.
I rode a bonnie to a supposedly reputable dealer. to get him to set the carbs and timing. Rode it half way home it blew up and never went again. It was all down to the dealers faulty work. But I had enough with that bike and sold it.
Regards
Joe.

 

I see your point now Joe, i was going on the the re-builder doing the job properly as you or i would...but you never know.

 

I agree with all above, mk11 can be pain set up right, there a free download on setting them up on the amal site. Just doing a full restoration on a T140D myself, previous owner switched to mk1 concentric due to cold stsrt problems, again problem issue with mk11 not set up right, I've switched back to a set of second hand mk11 that had to completly rebuild, been cheaper get a new set. Hope this helps.

 

Hi Nash,
I'm going to be of absolute no engineering help here. But I too own a T140E 1980 which has been off the road for good many years, a UK bike which has sat in collections for far too long. I was looking to get her back on the tarmac this summer and did a little looking around for a Triumph specialist that knows these models and give mine a once over. I've decided to give are couple a bell: Meriden Motorcycles located in Meriden, Coventry, 01676 523838. www.meridenmotorcycles.co.uk The other is down in Farnham, Surrey and probably a little too far for you? www.rocketbox.co.uk

 

Hi Nash and welcome to the forum, tell us a bit more about what you ride and how long etc, maybe throw in a picture, just hit the upload file button below where you type, easy peasy!