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Throttle not responding at random during riding!

28K views 117 replies 31 participants last post by  roy rodriguez 
#1 ·
I have a triumph Bonneville t 100 2005 with 10,000 miles on her. I did a lot of repairs lately, changed the pickup coil, cleaned carbs and just about every other alteration that has been mentioned on this site for when the bike suddenly dies on the road in mid riding.

Without going into great detail (on the bike just turning off and dying part) the newest problem is while riding the throttle stops responding with the bike on. If I am cruising along at 70 MPH with a fixed position on the throttle, it is as if all of a sudden the bike just acts as if you stopped giving it gas and starts to slow down or sometimes jerks... if I rev the engine I get no response, the throttle seems to be dead or disconnected. Then as I’m coasting to pull over, just as mysteriously as this began, it comes “back to life” and starts to respond again. This happens several times mid ride and is very dangerous.

Please note when this occurs the bike is still running and has full power. It is just as if the throttle or the cable is disconnected or something.

I did take the throttle cables off when I cleaned the carbs but I thought I put everything back exactly as was and I checked all of the throttle cables and nothing looks out of the ordinary.

Any have any suggestions or have this happen before?

Cheers

RJ
 
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#41 · (Edited)
sounds similar to what happened to me a months ago after cleaning my bike

inadvertently dislodged the vent hose that connects to the fuel line between the two carbies. when I say dislodge, the hose is meant to be clipped in position where it terminates to atmosphere. mine was sticking out on an angle and during high speed must have been creating a vacuum in it, thus preventing a flow of fuel into the carbies and creating a surging or no response to throttle as you describe

this hose not to confused with the tank vent hose

I would also be making sure the inline filter between the carbs is clear as well
 
#46 ·
One thing I left off that I also did was cut the fuel vent hose (I think it is called a fuel vent hose) at an angle, that comes out of the bottom of the bike (as forchetto had recommended doing in some thread) I did this also about 2 months ago in response to try and fix the sudden bike dying/stalling. Obviously that wasn’t the problem and it didn’t fix my issue. But now I have this NEW throttle problem so maybe this cutting of the hose has contributed to this new problem?

I only mention this after reading Bonza’s post. I wonder if that has something to do with it?
 
#42 · (Edited)
This does sound like the problem I had with a 1200 Trophy. I would be riding along quite happily until, without warning, the throttle would cease to have any effect. After waiting for about 5 minutes or so it would start and carry on for another while and do the same again. It was worse in really hot weather.

It turned out that when the fuel tank was put back the last time before the problem, one of the fuel lines became kinked so the fuel wasn't getting through properly. The lines were fine, apart from being twisted. Once that was sorted I had no more problems with it.

Hope you get it sorted soon.

R

EDIT: The fact that the breather pipes were Ok meant that when I opened the tank there was no sound of hissing as if the tank was suffering from a vacuum.
 
#43 ·
long shot ...kick stand safety switch .if it goes bad and thinks its still down and your motoring along it will cut out the spark .... theres a thread on unpluging it from harness and jumping with a paper clip harness end 3 female jump the outter end ones , by passes the kick stand switch everything else safety switches thinks its ok ...make a better jumper wire and try ... no cost .no loss ...
 
#44 ·
try the crankcase breather hose to the air box..make sure its on the air box nipple ... mine pulled/came off when i rejetted carbs but looked like it was on ... leaned out the mix ..theres no clamp just pushes on and the vac. holds it .between 2 bulges in air box. would not go over 4000 rpm ..again a free check
 
#45 ·
Wow, truly overwhelmed with the awesome support and generosity of this forum. Sorry for the late response I just got back from work. I’ll 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 I’m riding solo as well. I’m 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 doesn’t 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... it’s dangerous but it didn’t happen that often and I tried so many fixes that didn’t 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 don’t 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 RPM’s 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. I’ll 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.

Cheers

RJ
 
#55 ·
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 I’m riding solo as well. I’m 200 LBS and girlfriend is 120.

Cheers

RJ
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.
 
#48 ·
#52 ·
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.
 
#56 ·
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.
 
#66 ·
If the ignitor is at fault the damage is already done and packing the seat will not eliminate the problem. Trying what I suggested is easy enough surely and it will tell you straight away if the ignitor is the problem. If the ignitor is the cause it will eventually die completely potentially leaving you on the side of the road with a dead bike.
 
#57 ·
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.
 
#59 ·
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

RJ
 
#60 ·
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
 
#61 ·
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...

If I remember correctly from a previous thread, his carbs were in a pretty sad state when he got the bike.
 
#68 ·
Can you see the throttle position at all when this happens? I mean, are the throttle plates moving when you twist the grip? if not, then maybe it's the grip itself? It sounds very mechanical linkage-like to me. especially since the battery connection is obviously good and fuel lines have been examined.
 
#70 ·
RJ,
I had the SAME EXACT problem. We finally figured it out after 3 months in the shop and multiple guesswork repairs. It was a loose bullet connecter on the small wire that branches off of the positive battery cable that runs to the instrument gauges.

Trace the positive battery cable from the battery until you find the small wire that branches off. Follow that small wire until you find the bullet connecter. Simply cut it off and hardwire this connection together. Might fix your problem. Definitely corrected mine.
 
#72 ·
Nobody has suggested this, so, the next time you experience the problem pull right off the road and see if you can actuate the carburetors by reaching in and opening the throttle at the carbs. If you can open them up and nothing happens or something happens you've got a buttload of new information to work with.
 
#73 ·
Thanks for your suggestion. As I thought, since my girlfriend has not been here to ride on the back seat, the problem has not come up yet. I’m not convinced it is gone yet because this sabbatical has occurred numerous times in the past. I will of course post to this thread if and when it occurs again. The ONLY thing I have done differently so far was to put 2 metal washers under each of the 8 bumpers under the seat to raise it some more. And of course my girlfriend has not been here to ride on the back of bike as well. The real test will be when she returns and is on the back of the bike again in 3 weeks.

Thanks RJ
 
#80 ·
I have not forgotten to update you guys. I was waiting for my girlfriend to come back to see if the problem still arose when someone was on the back of the bike. The good news is that the cutting out and more importantly, the throttle twisting, and then not responding at all “kind of” stopped as well.

I’m not 100% convinced that either of the problems have gone away because I only got to ride about 20 miles with her on the back thus far but with solo riding it has not happened and I have ridden a couple of hundred miles.

All I did was go to local hardware store and by 8 metal washers. I took off each of the rubber bumpers on the underside of the seat and installed 2 washer, to give the seat more lift, under each of the rubber bumpers and then re-installed the bumpers.. this seems to have done the trick so far....

BUT, what I think I found that might have been causing the throttle problem came up yesterday. I was riding along when all of a sudden the engine started revving and racing, without me twisting the throttle. Almost the exact opposite of the original problem or no power or results when twisting the throttle.

I pulled over on the street and looked at the cables to see if anything mechanical seemed “off” or observable and when I quickly revved the engine the revs came back down to normal. It was as if someone was twisting the throttle even though I wasn’t. I saw what the problem was but have no idea how to fix it.

At the end of the throttle cable, on the LHS of the bike, there is a tiny cylindrical piece that hangs off the end (in my case a little corroded) that is attached to the very end throttle cable. I think it is supposed to be housed inside of that little piece that looks like it was made for it, but mine for whatever reason is outside of the little case and just free floating. I never noticed it before and I am not sure what the functionality or purpose is? This little cylinder is getting caught in the metal piece (next to it where I think it is supposed to be housed?) when I twist the throttle this little piece gets caught/stuck on that other metal piece where it looks as if it should be housed, and therefore gets caught up holding the throttle in the open position. It is only when I rev the engine again that it falls out and the cable is released back down.

Anyone have a clue what this is supposed to look like and how it is supposed to function? I’m not sure if this is this was the cause of the original problem, twisting of the throttle and randomly no response, but it sure is the cause of the new problem of twisting the throttle and not having the engine stop revving after...

Thanks all,
RJ
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#81 ·
Theres you problem.......thats one of the throttle cables. It should be inside the throttle cable cam next to it. If yours is the same as mine, there is one cable to open the throttle, one to close it. I recommend slackening off the cables at the handlebar end (you will probably need to remove the throttle twistgrip and handlebar assembly from the bars), refit the cable at the carb end, then re-assemble everything and adjust the slack in the cables to the recommended. That was probably the problem all along. It looks like it is occasionally getting snagged, jamming the throttle open or closed.......it's dangerous like that fella, I would sort it before you ride it again.
 
#85 ·
Yes, I suspect it has been the culprit of the throttle issues I have been having. Although the other issue, when the bike just quits randomly, I am hoping was due to the seat not being raised off the CDI. (Ill find out soon enough and report back)

Do I need to unassembled everything? That would be a royal pain in the ass. i was thinking I could just thread it back into the housing / throttle cable cam, somehow...

What do you think?

Thanks

RJ
 
#82 · (Edited)
This isn't a Triumph, this is one off a car, but the principle is the same.....this is what it looks like when the cable is where it is supposed to be. Although on yours the cable runs vertically. The nipple goes in the hole, and then the cable runs round the cam. It may be fiddly to fit as there isn't a lot of room in there.....carefull not to put a kink in the cable.
 

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