Triumphrat

UJMrider · 08-01-2005

Just wondering if what I experienced yesterday was likely the result of paint chips clogging up the gas lines.

Here's what happened: I rode back from Steamboat yesterday afternoon (because of prior commitments I couldn't stay the whole weekend), and because I was trying to beat the darkness back, I was pushing it, speed wise, the whole way. As a result my normal range of 160+ miles to reserve was somewhat shortened. Riding back along C-470 (beltway-type freeway that goes around Denver), the bike started to choke and cough at 142 miles. Figuring that it was just going onto reserve, I reached down and flipped the petcock onto the reserve position.

Fine and dandy, the bike perked back up, but then just a few seconds later, it started stumbling again, running rough and acting like it wasn't getting fuel. That continued for a few seconds but didn't improve, the stumbing got worse, so I rolled to the shoulder. There was a gas station at the next exit, about 1 1/2 miles ahead, and fortunately for me, this stretch of the highway has a long, gentle downward slope. So I clutched in and the engine immediately died. I kept rolling and tried to restart the engine a couple of times, but it just spun without catching. I shifted to neutral and switched off the ignition so it wouldn't drain the battery. Kept rolling probably another 3/4 of a mile or so, and by this time I was getting worried, because while I knew there was a gas station at the exit, the road between the bottom of the exit ramp and the gas station was a steep uphill grade, and I didn't relish pushing that 500+ lb bike!

Finally, thinking that maybe whatever was apparently clogging the gas line may have dislodged, I switched the ignition back on and tried the starter, and the bike fired up, much to my relief. I rode up to the gas station, filled the tank and switched back to the "on" position on the petcock, and rode home with no incident.

Does this sound like the "paint chips clogging the reserve fuel line" problem some people have mentioned? I do have noticeable flaking of paint on my tank, and I try to be very careful with it when I refuel.

Just one question, why is it only the reserve position that this happens to? I would think if something was clogging the fuel lines it would be the same whether it was main or reserve. Or is in that the paint, being heavier than gas, falls to the bottom of the tank and the intake for the main position is higher than the reserve?

Also, what's a good solution for the paint chipping? My bike's out of warranty, so I'm pretty much on my own to repair the cap. Is there a kind of lacquer I can put on there to stop the paint peeling?

PS: I met some Triumphrat.net folks at the rally and had a good time talking with them, and of course ogling the bikes!

[ This message was edited by: UJMrider on 2005-08-01 01:25 ]

JWoodsie · 08-01-2005

Mate I have washed my tank, and fuel tap out twice in the last two years
. Looks like Im gunna have to do it annually. Drain the tank, take the tap off and dimantle it completely, clean it and dry it, lube it up with some vaseline.and reassemble. Give the tank a bit of a wash out with some methylated spirits.

NOTE: Take all precautions with any flammable substance. Keep well away from any source of ignition, naked flames, pilot lights etc.

Put it all back together. I would add an inline fuel filter. Clean fuel in, start er up...dispose of the dirty fuel & metho thoughtfully.Please.

DISCLAIMER: I do not take any responsibilty for any fool who blows themself up doing this....you have been warned.....I cannot stress enough how dangerous fuel and other hydrocarbons are.

:hammer:

JWoodsie · 08-01-2005

Oh and I forgot to mention it blocks your reserve as it is the lowest part of the fuel tank.

jimmyj900 · 08-01-2005

Quote:

...the bike started to choke and cough at 142 miles. Figuring that it was just going onto reserve, I reached down and flipped the petcock onto the reserve position. ... the bike perked back up, but then just a few seconds later, it started stumbling again, running rough and acting like it wasn't getting fuel. That continued for a few seconds but didn't improve, the stumbing got worse, so I rolled to the shoulder. ... thinking that maybe whatever was apparently clogging the gas line may have dislodged, I switched the ignition back on and tried the starter, and the bike fired up, much to my relief.

Clogging from paint chips is a possibility, but vacuum buildup in the tank is a much higer probablity based on the conditions you've defined.

The stock Classics fuel cap has a spring loaded vacuum valve that maintains a partial vacuum in the tank and that's usually not a problem. With sustained high-speed operation and a low fuel level, however, it can become a problem even though it's "normal operation" for the design.

There are a couple of things going on under these conditions. As the fuel level drops, the air space in the tank increases which results in a partial vacuum developing in the tank. At the same time the fuel pressure (vertical weight of the fuel) also decreases. This combination of vacuum and low fuel pressure results in a drastically reduced fuel supply to the carbs.

By all means check your tank for crud: that's worth doing every couple of years just to check the condition of the fuel system.

If it's vacuum buildup in the tank then there are a couple of options. Removing the poppet valve spring in the fuel filler cap will reduce the vacuum buildup, but replacing the cap with an aftermarket "Monza" cap is the best solution.

My fuel system is flowing a bit more than 1/2 gallon per minute with that cap.

Also, the best way I've found to remove paint from inside the filler neck is to press duct tape into the area and then pull out the duct tape with any loose paint attached.

Jim

UJMrider · 08-01-2005

Thanks, guys.

Jim: Your comments about the fuel cap have me thinking hard about a vacuum issue. Here's why:

I have actually had this problem once before, way back in April right after I first got the bike. Symptoms were the same, i.e. rode until the main fuel supply was exhausted, switched to reserve, then had the stumbling/rough running until I could get the tank filled (though the last time it was not as bad and the engine kept running as long as I kept the revs above 4000.)

Did not have the problem afterwards until Sunday, but, there was another significant change: Right after the April incident, I switched to a Bellacorse locking fuel cap for a Bonneville. Now the Bellacorse cap fits the threads, but it either doesn't "lock down" as much as the stock Tbird cap does, or it has an open vent. The reason I know this is because I started having a real problem with filling up the tank and then after I'd ride off, if I made a hard stop or a sharp turn, fuel would run out from under the cap.

This got so annoying to me that last week I took the Bellacorse cap off and put the stock cap back on - which is when I had this problem again!

So if it happens again, I'll try loosening the cap to see if that allows the engine to run freely.

jimmyj900 · 08-01-2005

Quote:

I switched to a Bellacorse locking fuel cap...but it either doesn't "lock down" as much as the stock Tbird cap does, or it has an open vent. ... started having a real problem with filling up the tank and then after I'd ride off, if I made a hard stop or a sharp turn, fuel would run out from under the cap.

That's odd... I don't have that problem on my bike with the Bellacorse cap. I'd suspect that the cork/composition gasket is deforming to the point it doesn't seal -- since I noted that the same seal on mine kind of "slid" off the top of the filler neck when I tightened it the first time.

It took a little diddling the second time around, but it finally went on straight. I remember thinking at the time that finding a better quality gasket would be a good idea...

Jim

JWoodsie · 08-01-2005

Hmm interesting. Ive had no problems with the stock cap, and I do a lot of sustained high speed stuff. Maybe try the seal off your stock cap UJM if it will fit.
I forgot to mention, both times I cleaned my tank and tap out,I got a good half a handful of dirty rusty looking ***** from around the fuel tap.
I replace the fuel filter annually.