Triumphrat

TBAbob · 08-21-2005

My '01 Legend has been driving me nuts for the past few weeks. Sometimes it will start missing and bucking badly during a ride and then start running fine. Lately, it has been starting and running for 10-15 minutes and then dying almost completely unless I give it full throttle and stay in first or second gear. Running on part of 1 cylinder!! Happened again yesterday within a mile of the shop and I limped it back, bucking all the way. This morning I noticed that fuel is dripping out of the airbox joint by the filter!!

Originally thought that it was the coils. Replaced them with the Nologys. New plugs and battery installed. Thought about vapor lock and checked the vent line. The stinking check valve at the end of the vent line was totally blocked. I cut that off and the vent is open. Didn't help the problem however. Yesterday, I even unscrewed the gas cap while it was limping home and it made no difference. Sigh!

If the bike sits for and hour or so, it starts just fine but will die later.

Really don't think it's a fuel problem as there was enough unburned fuel in the cylinders to be sucked back into the air box and still be leaking out 12 hours later. Jeez!

Any thoughts out there??? I'm running out of ideas and may actually have to go to my dealer. Oh the shame of it!

Cogito ergo equito

Bob

Slinky · 08-21-2005

Have you checked the ignition pickup? These have been known to fail. Also it is worth checking that the air gap is correct.

j98sprint · 08-21-2005

That was my thought too.

j98

BigVinny · 08-21-2005

I had the ignition pickup (hall probe coil I think) fail on an old 91 Trophy. your problem sounds just like it.

Coughing and spluttering, rough running and got to keep the revs right up or it will die and its a***** to restart if that happens. Mine failed suddenly about 2 miles from a Triumph dealer. I didnt know what it was but the dealer spotted it straight away.

They are a cheap $10 component. Replacement is the only solution for a duff pickup.

jimmyj900 · 08-21-2005

Quote:

Really don't think it's a fuel problem as there was enough unburned fuel in the cylinders to be sucked back into the air box and still be leaking out 12 hours later. Jeez!

You've got a problem there.

Fuel isn't going to come back out of the cylinders and somehow drip out the airbox -- the cylinders are below the level of the carbs and unless a cylinder completely fills with gas that can't happen. (Of course, if a cylinder is filling you'll have a hydro lock which is pretty identifiable after it's too late.)

You need to do some checking and see where that fuel is coming from. It might be just a cracked fuel line, but if it's dripping from the inlet of the carbs you've probably got a leaky needle valve or leaky float.

Check the float bowls for crud. If you have dirt in the system that can cause the needle valves to leak and block either the fuel tank or carb filter and cause poor running.

Another possibility is the blocked check valve on the tank vent line. If that's blocked, fuel tank heating and fuel expansion can force extra fuel into the carbs under some conditions. Check your sparkplugs for fouling. If they're wet and blackened, either wire brush them and give them a blast of brake cleaner or replace them.

I don't favor the ignition pickup as the culprit since you'll usually lose all three cylinders -- not just one or two.

Jim

JWoodsie · 08-21-2005

I had a problem similar, it would miss when cold on first start up. It turned out the petcock was fullof crud. Some of this found its way into the Carbies, causing it to flood. I even got a hydaulic lock one time.
Check the petcock, remove it and clean it out. Then check the little filter down near the carbs, its actually on the inlet to the carbies, inside the line, its a little bronze looking thingie.Clean that too, drain your float bowls. Mine hasnt missed a beat since.
Its worth cleaning out the fuel tank annually. Cuppa500 had the same problem also. Mine was dripping fuel on the ground occaisionally. Out of the vent tubes.

Hope this helps , cheers .....Jim

TBAbob · 08-21-2005

Thanks guys, you've given me some things to at.

I didn't think too much about the ignition pickup. I know there's one on the bike but, like Jimmyj900, I'd think it would be 100% or 0%. However, as a wrench twister I know that ANYTHING is possible. LOL! Where the heck is the pick up located on the bike??

Plugs are brand new. I just installed a new Pingel fuel tap about two months ago. Flushed the tank at that point. Drained the right side carb bowl earlier today and the fuel was perfectly clean. I already found the bloody check valve on the tank vent line! It was blocked and it is now in a new home: my trash can! Unfortunately, that wasn't the problem.

I'll pull the tank and the fuel line off tomorrow. Didn't know that there was a metal sponge filter right at the carbs. That's a possibility.

The fuel leaking from the air box threw me for a loop. It may be wicking down the outside but it sure seems to be leaking all along the bottom of the air box joint! I was thinking that, with no ignition taking place, the unburned fuel was somehow being sucked back. Kinda like a backfire thru the carbs. Hell, I don't know! Maybe it's haunted! Sigh!

Cogito ergo equito

Bob

jimmyj900 · 08-21-2005

Quote:

I didn't think too much about the ignition pickup...Where the heck is the pick up located on the bike??

The ignition pickup generates seven pulses each time the crankshaft rotates. Six of them are firing pulses and one is a timing/reference pulse so the igniter box knows which sparkplug to fire and when. (That seventh pulse is why new Triumphs don't fire instantly when you hit the button: it takes a full rotation before the igniter knows where it is.)

If the pickup is intermittant or has a weak signal, it's going to take a full rev for the igniter to figure out it's location so it's either going to shut down completely or behave as if you've just hit the redline -- which could be the behavior you described.

BTW: The sensor is on the right end of the crankshaft under the front right cover.

Anyhow, the symptom of having to open the trottle too far sounds more like an excessive fuel condition to me, but it's possible it's the pickup. It's also possible that bucking from a bad pickup knocked some crud loose from the tank or float bowls and is causing a fuel problem. (Sorry!)

Quote:

I'll pull the tank and the fuel line off tomorrow. Didn't know that there was a metal sponge filter right at the carbs. That's a possibility.

On my bike there's a small plastic "duckbill" filter inserted in the "T" connector for the fuel line. Pull off the fuel line and you'll see it in the the connector.

Quote:

The fuel leaking from the air box threw me for a loop. It may be wicking down the outside but it sure seems to be leaking all along the bottom of the air box joint!

There are only a few places fuel can get out of the carbs and into the airbox: the air jets, needle jet and transfer ports. The air jets are located below the mouth of the carb and are below the level of the main jet, so they'll drip excess fuel first. Most folks think the air jets are overflows or vents and refer to them as such.

Fuel on the inside of the filter box has to come from one of the above places so if the fuel isn't leaking down the outside of the box, you've either got a bad/dirty float needle or one of the floats is leaking and isn't giving enough "up" force when the float bowl is full.

Jim

MickMaguire · 08-22-2005

My 2 cents is that this is most likely to be float valve problems caused by rust/crud in the float bowls.