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Discussion Starter #1
Hi everyone!
Pls, I need some advice to find a problem (sorry possible for mistakes, I'm not English native speaker):

What we have;
Triumph Bonneville T100 Carb 2004. Bring it from Japan.

After short ride for 10-15 km when i stopped I have a strange problems with unstable RPM's
Here is 2 videos:

cold start after night parking (temperature on the street is +20C)
No Choke opened. After opening engine dies at the moment:

Right after a short ride:


When I ride and have RPMs higher than 2000 - everything is good. But when I stops - it happens again.

What already been done:
New air filther
New CDI (triumph twin power Stage 1)
New Sensor
New Spark plugs
Carbs cleaning and synchronization

Any ideas what can i do to ride normally? (no stops is not a option :smile2: )
 

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Check the coil - you can measure the resistance on the both primary and secondary coils - the old Bonnie’s are well know for bad coils.


Sent from my iPhone using Tapatalk
 

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Taking a wild swing here, but how is the rubber bits on the carbs, and on the ports above also? Likely you'd have noticed any leaking from the carbs, but maybe remove the carb tops to see if the rubber diaphragms are installed correctly?

Good Luck - Check back with progress.
 

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Did the carb cleaning do any good at all? Sounds like carbs might need more cleaning or vacuum leak as @LapinAgile suspects. Pull the spark plugs and compare them, they should look the same. If one doesn't look as good as the other check that carb.
 

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Discussion Starter #5
Carb were cleaned twice, but the problem still there. All rubbers are in a good condition. Sparks looks the same and they are in good condition too (they are new) Air leakage possible, but I can't understand how can I find it? Do you have advice it this maybe?
 

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Discussion Starter #6
Thanks for word about the coil. Possibly this is the last part in electrical system that wasn't changed. I'll try to check it in a couple of days and give an answer how it works
 

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Considering the year and the sh177y fuel now days maybe needles and seats need cleaning or renewing
 

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Sounds like maybe a hole in the carb slide diaphram. They loose shape over time and get pin holes. pop the slide out and stretch the slide rubber to check for holes. Sounds like its running on one cylinder.
Chris.
 

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I would look at changing the coil for a "Nology" unit if you can get one where you are.
Why? One cylinder is cutting out like someone is playing with a light switch = electrical = coil
 

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Either hot or cold, the video clips look like a misfire to me, which would be most likely electrical. In the clips I can hear one of the cylinders failing to fire every so often, which will result in the rpm dropping momentarily. Has the air injection been removed? I ask because (although my bike is an EFI ) when I had my bike brand new it had exactly the same problem at idle. I found the cause to be arcing between the right hand plug cap and the air injection tube, they are extremely close together. The air injection was removed a couple of days after and the problem went away.


Of course its a shot in the dark and may not be the cause of your problem but if the SAI tubes are still in place its something else to check out.
 

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Discussion Starter #11
Thanx for this advice! I'm still trying to find any air leakage but don't understand how to do in better. Checking all the cables and tubes don't give a result. But seems that the problem should be somewhere here
 

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Discussion Starter #13
Bike stays for a half a year in garage, but after that is starts and goes normally for about 200 kilometers, then CDI unit died and I've change it to Triumph Twin Power and at the same time problem appears
 

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I'm still thinking pilot circuit problem, needs cleaning again, air leak or bad needle and seat (leaking) as @steventhechef suggested. Usually plug wires, coils will show up more under load or at hi RPM than at idle. All ignition parts, except igniter can be tested with an ohm meter.
 

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My 2006 is having a very similar problem. Sputters under 2K and one sided popping on decel. Also thought it was a fuel problem, but it wasn't. Waiting for a new Nology coil to arrive now. As already said... likely your ignition coil causing the misfire.
 

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In my case it's just process of elimination. I eliminated the carbs, same as you have. OEM coils are common to break down and mine is 12 yrs/38K miles used. Still waiting for my new coil, but will let you know tomorrow if it fixed my misfire or not.
 

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For suspected problems, oversimplified rule of thumb: running rough on both cylinders = fuel / vacuum
one cylinder not firing = coils / wires
shuts off all at once and re-fires again and goes dead again = ignitor

coil can give a good reading and not fire when under load ignitors will faill intermittently before going completely dead sometimes.
 

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Thanks for info'! I for now this problem is not solved? How do you understand that it's about coil?
Because it's misfiring on one cylinder, then turning back on - like kid playing with light switch.

If carb / air leak, then it would be constant problem
If Ignition pick-up or ignition computer it would be both cylinders cutting out or randomly switching from side to side

The ignition coil may test OK cold, but when it gets hot, problems show up.
 
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