Triumphrat

coelacanth · 01-30-2008

Hey. I need your help big time.

My 07 bonnie started to act really strange. She was running fine and strong until one evening when she started to have a huge hesitation around mid rpm after riding about 5 min.

When I go really slow, she is ok and idles just fine. as soon as I start to open the throttle even a bit more than 1/4 or so, she starts hesitating like running out of gas or something. I really cant describe this well, but she loses power suddenly for very short amount of time and come back to normal, then do it again and again. But again, she idles fine and doesn't stall.

Another thing is that this problem gets worse as she warms up. She starts up and rides fine for 5 min, then start this hesitation / hiccup thing.

Any idea what's wrong, and what might be causing this? She was running just fine until a couple days ago.

her setup is

TORs, UNI filter, 120 main, 40 pilot, 2.5 out, 1 shim, typical outside temperature is 45-50 degrees f.

I'm getting really nervous about this. I know I should take her to my dealer, but I'm also hoping you guys can give me some opinions and thoughts.

TB-T100 · 01-30-2008

If she behaves like she's starving for fuel, that may just be it. Something similar happened to mine. The problem turned out to be the fueltank vent hose. If you do a search you will find that lots have had trouble with it. What sometimes happens is that (particularily in wet / dirty road-conditions) the vent hose gets plugged at the bottom. It goes from the tank and down under the bike. What I did, was to squirt a bit of WD-40 down the hose (from under the tank-cap) and the plug came out.

Or it could be something else.

ChuckT120 · 01-30-2008

I had a similar problem. It turned out to be a bunch of very fine brown powder that all but plugged the sock filter, the valve, and the hidden filter in the fuel T.

oldroadie · 01-30-2008

It will be easy to diagnose a fuel vent problem, just loosen your gas cap and see if that mitigates the symptoms. Then you can follow the vent line to sort out the blockage. You might check your vacuum caps at the carbs to make sure you haven't lost one, that'll give a similar symptom.

wolfgang · 01-30-2008

Make sure the fuel petcock is on and actually moving with the outer part. They are screwed together and if the screw is loose the outside piece can be in position and the actual valve could still be closed. I heard from someone who left the petcock off that their bike ran similar to how you describe. Names have been changed to protect the guilty.

19554 · 01-30-2008

Check your uni-filter has not become totally dry.
I had the same problem, not on a bonnie, but on a CCM Supermoto.
I had to re-oil the unifilter every 2000miles or so or she would hesitate every time you opened her up, may not be the same problem but worth a look!

mikeinva · 01-30-2008

I would start by checking the fuel supply as others have told you . you might allso check float level ,make sure the choke is coming off.It could be a ignition box that messes up after it gets hot but i would take it to the dealer before getting one because they are big $$.maybe you should look at spark plugs to .could allso be a coil going bad .The bike hasnt been wet lately has it? check vac hoses and vac plugs for cracks to.
there are so many things it could be its hard to say

coelacanth · 01-31-2008

Hi all. Thanks much for your advice. I had non-motorcycle related health issue and couldn't get back nor work on my bonnie sooner.

So took UNI filter out, and it was dry side I'd say. I'm not sure it was completely dried out, but I thoroughly reapplied the oil, massaged, wiped off with kitchen towel, and did this one more time. I've let it sit overnight last night so it should be in an ideal condition.

I'll see if this fixes the problem.

I remember when I opened carbs for the first time for jetting, I noticed tiny amount of that red-ish paints from the top of tank. I've done several rejetting job after that, but have not noticed anymore paint chips. I quickly inspected inside of the tank and the hose right after the petcock, but they seemed ok. I have not checked the filters around the tank / petcock yet, though.

If UNI filter reoiling doesn't fix this, I might have to bring her to my dealer. I really really hope that this will be a warranty issue if it's not Uni filter. I'll report you back when I test ride with uni filter reinstalled. The weather is not behaving well lately in SanFran and my own problems are preventing me from working on bonnie.

It seems I'll have health problem when she has one...

Thanks again for your help.

coelacanth · 01-31-2008

a question to those who found out the clogged fuel was the cause. did you work with your dealer under warranty? Or you took care of it yourself or paid to do the repair?

I have to work on my bike in a shared garage building, and my neighbors won't feel too comfortable smelling too mach fuel fume around the garage.

oldroadie · 01-31-2008

If you found paint chips in the float bowls you may well have bits in the filter that's hidden in the carb's fuel inlet "T". That, too, can cause a sputtering problem that's hard to find because the filter is difficult to access.