Throttle not responding at random during riding! - Page 6 - Triumph Forum: Triumph Rat Motorcycle Forums
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post #51 of 118 (permalink) Old 12-10-2012, 11:48 PM
Grand Prix 250
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Check your spark plugs are the recommended "R" (resistor) type plugs. Sounds silly but it's important.

If everything else is OK....vents, fuel, filters, leads, igniter, pick up etc...........Check your valve clearances.
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post #52 of 118 (permalink) Old 12-11-2012, 03:23 AM
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Have you tried all the suggestions mentioned already?

Did you short out the side stand switch to see if it was interupting normal service? This is a common one and easy to test.

It does sound, from your description, like a soft-misfire I.e. on the fuel side of the equation. When you get an issue on the electrical side there is usually some jerking and/or back-firing to accompany the issue.

If you run for a minute or so with the issue in full swing and then turn the engine off and coast to the side you could remove a spark plug and see whether the engine is running weak I.e. the spark plug has gone from a nice crispy brown to a white colour.

If you suspect that fuel cannot get out of the tank due to a vacuum being formed just loosen the fuel cap. This will test the fuel tank breather pipe.

Have you adjusted or checked the fuel level in the float bowls? If they are really out of whack this might cause the issue when the bowls run out of gas.

Is there any chance that the engine heat is boiling the fuel in the carbs? This would give a weak mixture because of evaporation from the float bowls. Does the problem still occur in the cool of the night?

Have you eyeballed all nuts and bolts and all electrical connectors? You may need to pull them apart and make sure that they have not gone blue or green inside. Electrical connectors are the most unreliable thing on a motorcycle.

Is there an immobiliser/alarm on your bike. These can be a pain and the wiring for them can be a pain but they usually cause a complete shut down so I'd consider this last.

Good luck.
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post #53 of 118 (permalink) Old 12-11-2012, 05:57 AM
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Looking down your list you appear to have been doing some tank de rusting. I realise you've cleaned the fuel lines and filters but all it takes is a tiny flake of rust in the system to cause problems.
Make sure to inspect the carb diaphrams closely.
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post #54 of 118 (permalink) Old 12-11-2012, 07:04 AM
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Have you got your throttle cables set up corectly?
good luck.
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post #55 of 118 (permalink) Old 12-11-2012, 07:33 AM
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Originally Posted by RJ Triumph View Post
I have had a stalling/quitting bike for some time so I changed just about everything BUT the CDI box. The problems went away for a while but then came back recently. It happens more when the girlfriend is on the back but sometimes when Iím riding solo as well. Iím 200 LBS and girlfriend is 120.


Remove the seat and check for rubbing marks on its underside that correspond to the front top corners of the ignitor. If you see marks in that position start the bike and get it idling smoothly then press down firmly on the ignitor, just with your thumb in the middle of the ignitor. If the bike cuts out or falters the ignitor is faulty and needs to be replaced.

Once you fit a replacement ignitor make sure to pack up your seat to prevent it pressing on your new ignitor and killing it also.
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post #56 of 118 (permalink) Old 12-11-2012, 10:28 AM Thread Starter
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I do not have a garage so all repairs have to be done on the street except on the rare occasion that I can get the bike into my living room in my apartment building (which I did this summer for 2 months). Because of this difficulty I am relegated to doing only certain repairs at this current time. The easiest and first thing I’d like to do is to raise the seat. I will do this and to make sure nothing is touching the CDI and then ride her for a while and see how it goes.

I will visually check all of the fuel lines and again to see if anything stands out. I’m not sure what else I can do electrically speaking while she is parked on the street. It rains out the blue here and is hot and humid so it’s not all that conducive to doing any sort of work outdoors.

I will check all of the “easy” things suggested throughout this thread and report back as I do them and as I have a chance to ride her and see if it worked. I don’t think it would make sense to do too many alterations at one time as I won’t be able to narrow down the culprits and to see what the issue is.

I’ll start with the cheapest and easiest first and that seems to be raising the seat. So off the to the hardware store I go and I will report back.

Thanks to everyone very much! I’m not too optimistic about this being the cause but it is easy and cheap.. so I’ll go from here.

2005 T100 865 cc with 9500 miles
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post #57 of 118 (permalink) Old 12-11-2012, 11:54 AM
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I had a similar problem several months ago with my '07 Black. At higher rpms the bike would just stop as if it were starved for fuel.

Like the original poster I checked everything including chaging spark plugs. But the culprit was the rubber vacuum plug/cap on the left intake manifold was cracked and would suck in air at higher rpms when the vacuum was greatest. I changed the plug/cap and no more problem. Make sure the plug is tight fitting. I made the mistake of first buying cheap pluggs/caps from an auto parts store. No good there. I bought two from my dealer, put one on and was good to go. I took the bike out and rode it like I stole it. No more problem.

The new plugs did help with performance.
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post #58 of 118 (permalink) Old 12-11-2012, 12:16 PM
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Originally Posted by RJ Triumph View Post
Wow, truly overwhelmed with the awesome support and generosity of this forum. Sorry for the late response I just got back from work. Iíll try and sort all of these suggestions and questions out here:

Over the last 2 months I have replaced and changed a few things. I live in hot humid south Florida. I have had a stalling/quitting bike for some time so I changed just about everything BUT the CDI box. The problems went away for a while but then came back recently. It happens more when the girlfriend is on the back but sometimes when Iím riding solo as well. Iím 200 LBS and girlfriend is 120.

For the problem of the bike just dying, turning off mid-ride (as described above) I will try the last thing I have not done yet, which is putting some rubber gaskets or washers under the rubber bumpers under the seat to raise it off the CDI ( I had previously cut a hole out of the underside plastic of the seat for the CDI box and thought that would be sufficient in case the seat was putting pressure on it but since that did not work, I will now go the extra step and try lifting the seat as well.) This doesnít bother me as much as the new problem because the bike always started back up even mid ride on the highway while cruising at 70 mph... itís dangerous but it didnít happen that often and I tried so many fixes that didnít work so I thought I would just have to live with it.

BUT the NEW problem and even more concerning one is the one I started this thread with. It is the non-response of the throttle while riding. Sometimes as some here have mentioned, the bike jerks haphazardly, and other times it is just completely non responsive. I donít know why or how long it does it for and it seems to be completely at random as far as I can tell. I twist the throttle a few times maybe for 30 seconds (As the bike is slowly decelerating and running) as I coast over to the side of the road and then just as mysteriously as it stopped responding, twisting of the throttle works again and off I go.. Very dangerous and odd. Please note with this problem the bike does NOT turn off. The RPMís are around 1000 as when idling.

Here are some of the recent things I have done to the bike if this adds any color to the problem to help.

Sealed and Relined gas tank
Cleaned petcock and all parts
Cleaned fuel filters
Changed spring for kick stand
Changed carb screws for other hex stainless steel ones
Changed front and rear brake pads
On both brakes I bled and changed fluid
Changed oil
Oil filter
Changed Gasket around pick-up-coil cover
New pick-up-coil
Cleaned carburetor float bowls and pilot jet and main jet and float bowl drain screw
Re-oiled and lubed all bolts and screws
Cleaned manifold and air box rubbers
Cleaned air filter
Cleaned battery
Sand papered gas tank fuel valve neck to get rid of pain chipping
Sealed and relined gas tank with caswells to get rid of rust
Replaced spark plug boots with nology ones
New spark plugs
Took off SAIS with conversion kit

Does that help with suggestions?

Thanks again for everyone who has helped. Iíll try just about anything at this point..

I can try some things as soon as tomorrow. All I want is a reliable bike and have never had one... very frustrating.


For me, your comment that I have marked in red seals it. Its more than likely that the CDI is at fault, and reading on, both problems could be linked with the CDI being the culprit. Personally, my next action would be to replace the CDI (with a borrowed one if possible) and test ride.
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post #59 of 118 (permalink) Old 12-11-2012, 02:08 PM Thread Starter
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Yes, this is what I’m leaning towards yet I didn’t think that it was possible to have the throttle just be completely non responsive and then just come back to life at random times. In the past i was used to the bike just stalling and quitting once in a while that I attributed to the Pickup coil and a host of other things that I just fixed and replaced. I’m also aware that the CDI could be the culprit for the bike suddenly dying as well. But the NEW problem was with the throttle and I didn’t think a malfunctioning or broken CDI could be the cause for that, could it??

I just got back from the hardware store and installed 2 metal washers under each of the 8 rubber bumpers on the underside of the seat. That will give it a nice lift. I’m riding solo for the next few weeks as the Girl friend is away for work so I’ll have to see if that helps at all. I can try weighing down the back with some heavy objects although since she is 120 LBS I don think it will be an accurate representation of someone riding on the back.

Ill test it out all day today and this week and report back. In the meantime, I will also look through every single generous reply in this thread and see what I can do to test all of the suggestions. The easiest and cheapest will come first and then if the problems still exist I will keep trying other suggestions as well.

The throttle non response is just so weird, has me very confused...

Thanks guys


2005 T100 865 cc with 9500 miles
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post #60 of 118 (permalink) Old 12-11-2012, 05:07 PM
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why did you disconect the throttle cables all you need to do was remove carb set from the left and flip them over to get at the bowels [ now facing up ] .leaving the cables as they were , plastic drain pan catches any gas draining from the vents or in the bowels ..clean -flip up right - pull and clean slides - reinstall .....slide in -push foward into the rubbers -move air box foward and clamp everything- conect the electrics -gas hose-vent hose clearance -done
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