Triumph Bonneville 2001 Start And Idle Problems

TraiaRider · Jul 5, 2025 at 8:13 PM

I have a Triumph Bonneville 2001 and have had crud in my carbs problems.
It ran only with choke/enrichener enabled but pretty good then.

I tried running Red Line SL-1 additive
to clear out crud in the carburator and it was succesful at first. I didn't have to run with choke/enrichener engaged. After a short period of time it developed a leak that got worse and worse. Still it ran OK allthough gas was collecting on the top of the engine.

One morning it was suddenly hard to start and I drove only for a km and it stopped and wouldn't start anymore. I figured the leak was running haywire with the vacuum and so set about to dissasemble the carburators. I belive the leak was in one end of the T-junction for the inlet of petrol. Changed the o-rings and applied a new gasket for the floatbowl. Cleaned the carburator and parts in a sonic sound cleaner. I could then see through the idle jet, no problem. I also applied the Dynojet tuning kit with a new needle and with what they call DJ110 main jet. The idle jet is still the original one.

I followed the instructions and set the idle screws to 3 turns out. (They were set at 4 turns out before cleaning procedure, I checked)

I assembled the carburators and mounted them on the bike. No more gas leakage. The leak was fixed. However it was very hard to start and when started it idled at high rpms. The engine dies intermittently. Does not give good response when I blip the throttle. Dies on to much gas. I can milk it a little bit.

I tried to fiddle with the idle knob but when turned counter clockwise a fair bit the engine would die.

The bike has TOR exhaust, the baffle in the airbox is out. It has the bellshaped mouth and high flowing airfilter for the airbox. 3 out of 4 vacuum caps are new and all of them are good so no problem there. It got a new fuel hose and new inline gas filter. Battery is new and was hooked up to charger during the carb cleaning procedure.

Can this be helped by adjusting the idle screws? if so should I go in our out?

The bike is undrivable at the moment.

please help

Robbi18 · Jul 7, 2025 at 1:48 PM

Since it’s idling high and dying on throttle blips, your pilot circuit might still be clogged or the idle screws need tweaking. Try turning them in to 2.5 turns (from your current 3) to lean it slightly if it improves, you’re on the right track. If not, double-check the idle jet again sonic cleaning doesn’t always clear stubborn gunk. Also, verify the float heights and needle seating since you swapped jets. Hang in there it’s close.

TraiaRider · Jul 7, 2025 at 4:11 PM

I tried 2.75, 3.5, 4 and 4.5 turns out on the idle mixture screws and it felt like 4 was the best.

It started quickly but idles very low and stuttery now on every setting. Dies intermittently.

I push in the enrichener and pulled just a little wee bit on throttle and keeping the throttle here it runs ok for like a minute and then just stalls.
I try it repeatedly and get the same behaviour all the way up till the engine gets warm and it continues after.

More twist on the throttle and it dies immediately.

Really weird.

I also discovered that the original main jet was a 115 wich is the same as dynojet 110.

I'll do what you ask and will clean out the idle circuit again. I will revert back to stock needle with what it ran well previously.

Not sure how to check float height?

What do you mean by needle seating? That I didnt forget the collar?

I am on the right track you think and its not electrical?

TraiaRider · Jul 8, 2025 at 1:05 PM

I have now ascertained that the canals in the main circuit and idle circuit are free flowing.

The jets and idle mixture screws are swimming in a jar of carb clean untill tomorrow when I will inspect them for flow.

Needleseats are undamaged.

I guess then I will assemble the carburator, leak test it and check petrol level in float bowl