Bike dies after 2 mins

Hey guys,

Would appreciated some pointers on where to troubleshoot this issue.

Recently rebuilt the carbs and bike was running well. Need to re-shim my values as got some ticking but besides that it was running great. Took it for a several long rides with no issue, running better than it ever has. Was going to start the re-shim process but I had an issue with the front brake so I got it on the lift in the garage and rebuilt the front caliper.

Now here comes the rub, front brake is now great (thanks Len) but soon as I took it for a ride after about 1-2 mins it just died, like it was flooded. Won't start after that until I leave it for about 10 mins, then same issue, runs for 1-2 mins and dies. I did an oil change and still have the same issue and it happens riding and in the garage, although possibly takes a little longer to die when not riding but no more than 3 mins.

Cheers
Rich
xj650, 1981

 

I had kinda the same issue.
Bike was great then it would just die and after 10minutes or so I could start it as if nothing was wrong.
The dieing part was sporadic though. Might happen on the freeway or might happen popping up to shop.
So a bit different in that respect also.

In the end... It ended up being the regulator passing over voltage to the tci and cooking it and I figure when it cooled down it started working again.
I replaced that twice also.

Hopefully not your problem but keep it in mind when going through the possibilities.

 

Oh. First normal thing that comes to mind is a crimped fuel hose.

I should have started with that.

 

Gas cap vent. Loosen the cap and see if that solves the problem...

 

Thanks, so I seem to have "fixed" it but I don't know how which is not so good. I think I've narrowed it down to a fuel issue. Here's what I did on the lift in the garage.
Ran the petcock on PRI and it didn't die at all, although during this time there was one spluttering moment and it back-fired once.
I opened the gas-cap but I didn't hear any rush of air so doesn't seem like there's any vaccum issue.
I then ran it on reserve for another 3 mins (cos my gas was low and I was out in the garage).

Once that was good I decided to risk it and rode to the local EXXON about 2 miles down the road and filled up. From there I rode around for about 10 mins in reserve and then switched to normal/main and road for another 10mins.
All seems well now.
--
I'm thinking one of these things:
- petcock was stuck in some weird way although when I had the issue before I had moved it to PRI and still had the same issue.
- some debris in the tank was blocking the line and finally freed up
- bad gas
- the TCI issue you mentioned and it's just a matter of time before it happens again

I guess time will tell - is there any way to test the TCI without it actually being in a bad state?

 

You cant check the TCI at all really.. it either works or doesnt. and if it doesn't, you swap it out.

However, sounds like the TCI issue cds1984 had was happening when his regulator was failing & passing too much voltage.. This is easy to check... Just hook your multimeter up directly to the battery and check voltage... Before starting you should see 12.6-12.9v for a healthy battery. When running at idle, you should see 13.5-13.9v. When you rev the engine to 3000rpm or more (if the regulator is in good order) you wont see the voltage go above 14.5v. If you see voltage of 15v or more, the regulator is failing & could cook your TCI box or other components.

 

Thanks - no more issues so far but will check the TCI at the weekend.

 

...and I spoke too soon... bike was fine for a bout 2 days then I left it in the garage for a week as I was out of town and came back to the same issue and it's leaking gas out the left side and pouring gas into the airbox...

See this video: https://drive.google.com/file/d/1eOdNUDWFA4BYJw_oIfzBB62mSvSwc7as/view?usp=drive_link

Seems like spark issue maybe if gas is not getting ignited?? Any thoughts on how to troubleshoot? Maybe it is a TCI issue but I can't really test it running now.

 

Yeah it's your petcock sounds like it's overloading your carb while sitting and it has an issue where it's stopping up. you need to take the petcock apart and clean it out and clean the screen out you probably need to drain the tank and take the petcock off of the tank and clean the screen out properly and you'll have to clean all the passageways inside the petcock sometimes those will get gunked up. I had a Supra that would run great for about 2 or 3 minutes and then it slowly start running worse and worse until about 10 minutes later it wouldn't run at all you let it sit for 30 minutes and then it would run great again it turned out to be rust clogging an inline screen filter in the fuel line

 

I bypassed the fuel tank in that video. Using an auxilary gas tank that I've used in the garage for a long time with no issues and I have an in line fuel filter so I don't think it's a petcock issue. Seems to me like gas is not getting ignited on one or more cylinders but not sure where to go from here...

 

Fuel, spark, compression, that's all you need for ignition. If it's sparking then it's a fuel issue. You never know what you are liable to find inside a carburetor. Yesterday I found a large clump of jb weld blocking a pilot jet. Someone had used jb weld to repair things in the fuel system. And it ended up inside the carburetor. A little too much fuel and it won't run, too shallow of a fuel level and it won't run. If fuel is leaking out of the left carb then it is certainly at least an overloading carb bowl, this can be due to pinholes or all sorts of stuff. Anytime a motorcycle won't start, the very first test should be to shut off the fuel, pull the plugs and make sure that they are dry and that there is no continuity between the electrode and ground. Sometimes they can look okay but actually be fouled because of buildup on the back side between the electrode and the strap, while doing this check the plug gap. Then in the dark if possible, check and make sure that all four plug wires are sparking with a blue spark. This will tell you everything you need to know. If it Sparks, and you have compression, and there's no water blowing out of the cylinders, then it is definitely a fuel issue. The best way to start one of these motorcycles is not spraying starting fluid, it is not pouring fuel in the cylinders, it is to put fuel in a spray bottle, prop the throttle shaft open, reach inside an individually lift the slide of each carburetor as you spray one or two sprays inside the carburetor no more, and then release the throttle shaft so that it can close. If you do this and you have spark and compression on at least 3 cylinders then the bike will start immediately. Always. It is very easy to flood these engines. To know whether it's flooded badly you can remove the oil cap and smell it and that will tell you the story most of the time

 

:
I have to figure this replying out .
My 82 xj400 dies after 10 min. It sits for 30 min and restarts. There is no miss fire, it just dies. It gets fuel, but the plugs are black. I checked with a spark tester, and it does have spark but it won't start, nothing. I removed the fuel hose, and it flowed.
First I thought that the TCI was bad, then I thought I had carb problems.
Now I'm not so sure. I don't have a spare TCI, but I have a regulator. I will try that .
I'm old, and we had a saying. "If you have a Triumph. Don't ride it any farther than you are willing to push it". I'm starting to feel the same way about my Yamahas (6)

 

If the plugs are black they are likely fouled. Do they look wet? A spark tester won't tell you if the plug is fouled, it only shows you if the coil is throwing high voltage to the plug

 

The plugs are black, but not fouled.
I installed new plugs, with no difference.
I just went out and tried it. The bike started instantly, and ran perfect.
Right before it dies, maybe 30 sec ,the bike won't idle anymore. I have an aftermarket manual petcock. As soon as I pull the fuel line it flows.
I know the carbs need to be cleaned, and I blew a little air in the fuel inlet in case the needles were stuck ....no difference.
Maybe it is fuel related.
When the bike quits next time, I will try starting fluid.

 

Thats the craziest thing I've ever seen. How could gas be coming out into the airbox under pressure like that? Hard to see with the camera shake, but it wasn't just leaking, it looked like a firehose. Is it coming out of the crankcase vent tube? It looked kind of milky white like water contaminated oil. All the carbs combined couldn't hold that much gas. What does the crankcase oil look like?

 

Yeah it's actually just normal gas after it comes out. It's aerated i guess which is why it looks foamy and yes it's coming out the crankcase vent-tube into the airbox under-pressure.

 

Gas in the crankcase says bad floats or float valve(s) somewhere. Fuel is continuing to flow in to the carbs and making its way in to the cylinder(s) then dripping down in to the crankcase. First thing is to figure out what's letting fuel flow freely and getting that fixed. Then you'll definitely need to change oil again which is all contaminated now.

Check floats to make sure they actually float, make sure the float valves properly seat and seal. Replace if necessary. Check float height adjustment. It's got to be something preventing the carbs from stopping the flow of fuel.

 

Lots of things and sounds going on in that vid. Wow, I don't think I have even seen that much fuel coming out of the carbs and "shooting" into the air box. Maybe some overflow but not a jet like stream. I think I am picking up an air leak on vid. Make sure you have that vacuum line that used to feed the OEM petcock blocked off. Try to take pressure off the gas tank before you start the bike and see if that makes any différance.

You said something about pulling on the fuel line makes fuel flow? Has to be a pinch or a blockage in that fuel line. Check your breather line from the crank as well, make sure that is open. Engine is just one big air pump that runs on gas. As the motor runs, it creates back and for pressure in the crankcase. The breather line from under the carbs left side needs to be clear.

When the floats are working as they should, even with the petcock open, they should not overflow or leak. As @co.dirtbiker mentioned above, them floats need to be checked. You said you think the carbs are dirty anyway. Make sure you go to the "church of clean" link and do them carbs right. I would stop all other troubleshooting and take care of them carbs first. You could be chasing lots of "what if" things, and it might just be dirty carbs and float issues.

 

Thanks guys, just to be clear I recently rebuilt the carb and it ran amazingly well for over a month so I don't think it's a carb issue per-se. I'll find some time this weekend to do more diagnosis based on the above. Mucho gracias on the help...

 

How is the inside of the tank? New fuel lines were install at that time?

 

The thing about carbs... if there is contamination...of any kind... one ride can be just peachy.. and the next attempt is a no start. [Sometimes] it really can boil down to just a few specs of dust effing everything up.. Lucky for you, it's a total breeze to pull carbs on a UJM!

 

ok, so I drained the float bowls and it starts up great and runs fine again for a few mins and does the same thing. idk if maybe it's the TCI / regulator issue -- i guess it could be something getting stuck in the float bowls but I'm hesitant to pull the carbs again cos they were just rebuilt and it was a PITA getting them back on. Any way to narrow this issue down guys?

 

Stick a clear tube in the bowl outlets and check the float levels by opening the drain on each.

It definitely sounds like your floats aren't stopping the fuel and it is just overflowing into the engine.
So oil would we shot also.

See wet setting, I did a search but I can't find it.

In the service manual it is how you check the float level while the carbs are in although most people do it with the carbs out, to adjust the floats.

 

There is no way a TCI or regulator would have any effect on fuel overflowing. You can forget about that being related.

Sorry to say you're going to have to pull the carbs. Something isn't right with the float system.

 

Definitely a carb problem. You let it sit and carb overflowed? If carbs are level or slightly angled toward engine on kick stand, there is gas in the oil. I always shut my gas valve off. If it has vacum operated petcock make sure no gas comes out of line when engine is off.