What's the opinion about this problem. My 2001 40000km Bonneville has a bad hesitation and jerking when accelerating from any RPM under 3000RPM. The lower the revs the worse it is and seems to be getting worse.
Over 3000RPM so far ok.
Assuming the bike is not new to you and previously ran ok then the jets are not the problem but dirt might be. I would unscrew one carb base to inspect the float bowl for debris or water. There is a chance you will find some red dust (rust) from your tank that squeezed through the petcock filter and the inline one hidden in the fuel line (both always worth cleaning too). The jets can be blown through with an aerosol of carb cleaner without need for further disassembly.
However, on the balance of probabilities, the symptoms you describe sound like a dying coil. Your hesitation is probably a misfire. Shedloads of posts about resistance values etc.
My 205 T100 had near identical issues and a new coil fixed it but I also had a decade of crud in the carbs!
Gill electrics are known problem areas. Before purchasing anything run carb cleaner through the system, check for cracked wires and leads. What do your plugs says? could be igniter, Hall sensor ( crank pos. sensor) coils, valves ( rarely) air leak from boots or vacuum take off. Is in on one or both cylinders? There are better aftermarket coils with the same Ohm resistance. It's a lost spark on a 360.
I will jump in here and hedge a bet on the pickup coil. It doesn't quite sound to me like the pickup coil is faulty in its more usual way, but its worth checking that out before going to a more expensive item. Problem is, both pickup coil and ignition coil can give similar symptoms. I note that the bike is an 01 model, and its also worth pointing out that Triumph changed the air gap on these and a few later year models from 1mm to 0.8mm because of starting and rough running problems similar to these. If the OP has owned the bike since 2004 and not touched that area since, it may not have been done. He also does not state whether the problem occurs right from cold or whether it only happens when the engine is warm. Straight from cold would point to the ignition coil, whereas the pickup coil will ususally get problematic as it heats up.
What gears? I hope you are no higher than 3rd gear when trying to accelerate under 3K rpm. I never run my '03 790 under 3K rpm unless I am in 4th gear and then only momentarily.
It's when in 1st and 2nd when taking off or going around a corner. Thinking back it started off as one little occasional jerk which I did not worry about but now it's constant and will jerk three times until the RPM gets over 3000.
It's there right from cold. I will read up in the manual on how check the air gap.
Just to let you know i had a very similar problem and after replacing coils etc I lifted the carb tops to find that the left top had oxidation around part of the groove that the rubber membrane sits in, this obviously let in a tiny amount of air upsetting that carb, after cleaning the bike was ok, I think that as the 2 inner screws that fix the top down sit under the frame a screwdriver is difficult to sit in the screws correctly and the previous owner hadn't done them up fully allowing the damp to creep in and foul the seal, might not be the case with your problem but it may be worth a look if all else fails, good luck!
I had similar symptoms when the bike ran too lean from a misguided (on my part) carburetor rejetting and shim removal. I'm not saying it's your jetting if you haven't changed it, but it could point to air getting in where it shouldn't, as Ednersand mentioned.
It's been a while but I finally got around to attending to my issue, I took the bike for a good hard ride last nigt and started playing with the choke setting to eliminate fuel or electrical and the hesitation problem definately went away when I had the choke pulled out a little.
So I have started pulling the carby tops, slides, the float bowls and the jets out. I can see there is a fair amount of wear on the slides so theses will have to be replaced for sure.
Is triumph the best place to get the new slides.
Have not got the bowls off and jets out yet to inspect them.
The diaphragms look ok, no damage, the bike has only done 42000 kms.
It's been a while but I finally got around to attending to my issue, I took the bike for a good hard ride last nigt and started playing with the choke setting to eliminate fuel or electrical and the hesitation problem definately went away when I had the choke pulled out a little.
I can see there is a fair amount of wear on the slides so theses will have to be replaced for sure.
Before you think about replacing the slides, go over the rest of the instruments. It's not uncommon to have wear on the slide ears. It's unlikely that is the issue. You wouldn't get them new from Triumph anyway.
An update, with carbs on the bike I removed the mains and the pilot jets, gave them a good clean and blow out, then sprayed some carby clean in the carby bodies and blew them out the best I could.
130 mains and 42 pilots.
Put back together, checked all the electrical connnection, warmed up the motor, set the mixture screws at one and a half out, idle speed at 1100rpm.
While it is better still gives one or two bad hesitations when accelerating away from 1500 to 2200 rpm. Definately feels like there is not enough fuel at that throttle position.
Might try a good fuel additive to see if that will clean out the carbys, if not I guess I will have to take the carbs off the bike and give a real good clean.
Any other suggestions.
It seemed the plug leads test ok, so I purchased a bottle Motul carby clean fuel additive, put the full bottle in the tank with a almost full tank, warmed up the motor and went for a 50km ride, no problems. Went for another good ride tonight,no hesitations at all.
It seems to be ok.
I guess I will give it another ride tomorrow, I will be pleased if it is fixed.
So since running the fuel cleaner additive through the fuel system the bike seem to run with no hesitation but I have not had another ride since then. This week end will give me a chance to put it to the test.
I try to give all my bikes a shot of fuel injector cleaner annually. Keeps them from "gunking up". Only takes a couple of ounces per bike if you do it regularly. I just keep a bottle on the shelf and add a few ounces with the first fill up in the spring. ...J.D.
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