Low rpm hesitation and bucking - Triumph Forum: Triumph Rat Motorcycle Forums
Hinckley Classic Triples 885cc Classic Styled T3's: Legend, Thunderbird, Thunderbird Sport & Adventurer.

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post #1 of 12 (permalink) Old 06-16-2017, 09:14 PM Thread Starter
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Main Motorcycle: 2001 Triumph Legend TT
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Low rpm hesitation and bucking

Haven't had my Legend too long but at low speeds it hesitates unless I gun it...especially noticed in 1st and 2nd gear...I don't think I notice in the other gears because I'm usually accelerating right through them to higher rpm's but it's very difficult to just cruise at low speeds...I'm constantly feathering the clutch in and out...any ideas?

I'm thinking fuel filter...is it in the tank? Possibly a good carb cleaning...

Wondered if anyone else has experienced this same issue. This bike has barely been ridden the past couple of years.
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post #2 of 12 (permalink) Old 06-16-2017, 09:58 PM
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Possibly a good carb cleaning...

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post #3 of 12 (permalink) Old 06-16-2017, 10:27 PM
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Quote:
Originally Posted by Atrain1973 View Post
Haven't had my Legend too long but at low speeds it hesitates unless I gun it...especially noticed in 1st and 2nd gear...I don't think I notice in the other gears because I'm usually accelerating right through them to higher rpm's but it's very difficult to just cruise at low speeds...I'm constantly feathering the clutch in and out...any ideas?

I'm thinking fuel filter...is it in the tank? Possibly a good carb cleaning...

Wondered if anyone else has experienced this same issue. This bike has barely been ridden the past couple of years.
You are on the right track. Here is what I would do......

1) replace in line fuel filter. Mine is located in the fuel line below the petcock to the carbs. Clear plastic, and cheap......buy a few, and change once a year.

2) Add Sea Foam to the tank, and see if you can smooth your low RPM response. 90% sure you have a fuel issue w/ the bike being run so infrequently. How fresh is the fuel in the tank?

3) Even if the Sea Foam clears your issue, I would pull the carbs and give them a thorough cleaning. They are probably vanished, and this will give you additional peace of mind.

4) Re install and balance the carbs.
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post #4 of 12 (permalink) Old 06-17-2017, 01:01 AM Thread Starter
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Thanks for the replies!
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post #5 of 12 (permalink) Old 06-17-2017, 02:56 AM
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Same thing happened to me. Classic symptom of coil breakdown. Hesitation and bucking at lower revs and boom off she flies...... I'd check this first, simpler than pulling carbs.
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post #6 of 12 (permalink) Old 06-17-2017, 08:39 AM
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If you have a stroboscopic timing light it's easy to check the coils. If they spark inconsistently then they are suspect. If your coils say "Nology" on them they probably are not the issue.

If the gas in the tank was allowed to sit for a long time then the carbs are suspect, unless they were drained for storage.

The factory did not use an in line filter. They often cause problems if added. there is a screen in the fitting where the fuel line connects to the carbs and screens in the valve on the tank. IF you must use an inline filter, I'd remove the "duckbill" screen and be sure you use a filter intended for gravity feed systems.
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John
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post #7 of 12 (permalink) Old 06-17-2017, 09:47 AM
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Quote:
Originally Posted by Burren Boyo. View Post
Same thing happened to me. Classic symptom of coil breakdown. Hesitation and bucking at lower revs and boom off she flies...... I'd check this first, simpler than pulling carbs.
Agreed. I had the same symptoms, and a new set of Nology coils fixed her up.
Try Fast eddy Sports.
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post #8 of 12 (permalink) Old 06-17-2017, 10:46 PM
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I'd like to second WSC's suggestion not to add an inline filter. Its unnecessary if the bike is setup properly and just adds drag to the fuel system.

There should be a duck-bill in the carbs as he mentions. You pull off the fuel like and if you look real close you will see a lip to slip a finger nail under and pop it out.

If its dirty, then you need to have a look in the tank. Make sure its not rusty.

Drain the tank and pull the fuel tap off and there are filters on those pipes too, you may want to clean those as well.

If you haven't changed the plugs, now's a good time to have a look at those as well - they can be a pain. If the stock wrench doesn't seem to fit, try a smaller socket. There are smaller size hex NGK and well as Champion that some folks have used.

If you want a more cost effective solution than 3 new Nology coils (over $200), you can look into the TT600 Coil Stick Mod. With used coils from eBay, grommets, connectors, wire, shrink wrap and about 2 hours time you're done for under $100.

Don't let the thought of cleaning the carbs scare you. I've now up to round 5 on them, because I had some leaks and didn't do as good a job as I should have initially. It only takes about 2 hours to get them out, torn down/cleaned and back together now. Longer is better if you can soak them, but I find I can do a pretty good job with a couple spray cans of carb cleaner and some brass brush needles.

Scott
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post #9 of 12 (permalink) Old 06-18-2017, 11:20 AM
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I get a little different take on your problem than the others. If the engine runs good under full throttle (when you are drawing the maximum fuel flow) I cannot see a fuel filter problem. Yes coils could be a problem, but before you spend all that money try this. Either turn out the pilot screws a bit or raise the height of the needles. This will richen the fuel mixture on transition. Just a different view. ...J.D.
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post #10 of 12 (permalink) Old 06-18-2017, 01:55 PM
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Agreed, filter issues will manifest themselves under heavy load, like full throttle and/or high speeds.

The pilot jets, which handle transition from idle to mid-throttle, where the needles take over, have tiny passages for both air and fuel and are easily plugged up. I'd go there first. Turning the idle mixture screws out a half turn might help diagnose it as any improvement points to lean mixture. However, if turning them out doesn't also increase your idle speed then they were probably right in the first place, and not the root cause.

If it runs right at half throttle then the needles are probably not the root cause, either.

John
Laconia Bike Week 2017 See you next year!
2004 Thunderbird Sport
1999 Legend TT
1975 T150V, 1968 BSA Thunderbolt
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