Motorcycle wont idle when warm

[toreckman]

43 minutes ago, bmart said:

Looks nice! I wish that someone would volunteer to do mine. It has been icky since I bought the bike. 

 I hear you, it is a lot of work. I'll be glad to be finished.

[toreckman]

Final stage completed today I took my time slowly rotating the tank to make sure it got completely coated. That took over an hour. 

 

I will leave it for a week to cure. The new gaskets came during the week too.

[toreckman]

On 2/5/2023 at 2:11 AM, Grum said:

Your fan coming on at around 80degC sounds too low! Fan thermoswitch should switch on from 98-102degC. Is your coolant level ok?

Good spot. I just checked the overflow tank.... bone dry.

 

I will do a coolant flush, then fill with new coolant. Hopefully there is no leaks.🤞

[toreckman]

Quick update.  After doing more maintenance & modifications, the bike stays on now without any issues. I don't think I will need to get the injectors cleaned.

[SushiFiend]

Wow, I have a 2001 model with EXACTLY the same symptoms. It had been left standing in my garage for a couple of years without running while I had been working abroad and I made the mistake of riding it without changing the fuel. It was fine for the first ride to the MOT station for an annual inspection but now does the same thing you describe. Runs okay when cold, but as soon as the temperatutre gauge hits 65 degrees C, the engine dies and won't stay running without blipping the throttle constantly. Even raising the idle speed with the adjustment screw doesn't solve the issue. Initially I suspected the fast idle wax unit, but I've taken it out of the bike, opened it and tested it and the little part inside does expand by a few mm when I drop it into a mag of boiling water. So I now think that part if fine and I'm going to move on to checking my tank and injectors...

[SushiFiend]

Checked the tank using my borescope and while I can see tiny bits of rust, it's very clean on the whole for nearly 25-year-old bike and I'm not worried about it. I did try to remove the fuel pump to check the filter, but I couldn't get it through the opening as it looked like I was going to break some plastic part. But because the tank looks so clean, I don't think it's the problem. The pump has no problem sending fuel out of the fuel line at the rate given in my Haynes manual for the bike.

 

I've also removed the throttle bodies to get access to the injectors, and have removed them. Using a 12V computer hard drive PSU with a barrel plug, I've tested each injector for basic functionality. The centre section of the barrel slips over opne of thre injector connector pins, and then the outer jacket is very close to the other injector connector pin.I then used a paperclip to short the outside of the barrel plug to the other pin, and doing so each injector clicked very clearly. That doesn't test whether the injectors are blocked, so I've ordered an injector tester that contains adapters so that I can spray injector cleaner or brake cleaner through each one and check the nozzle pattern. The good rainforest people are hopefully delivering it to me tomorrow.

 

 

 

 

 

 

Borescope video - https://youtu.be/kLwLA0Jzwyk

Injector tester - https://www.amazon.co.uk/dp/B0DQPSFTK5

[SushiFiend]

Finally figured it out. Somehow, two of the spark plugs were not sparking. I hadn't done a spark test until now - instead I'd measured the resistance of them and they all came back at around 4.7kOhms from terminal to tip, and infinite resistance between the two electrodes and also the terminal and the threads. Which is what I would expect from a good plug.

 

But finally while fiddling about I pulled out the spark plug lead from the two rear cylinders while the engine was struggling to idle, and there was no change in the sound or the engine RPMs. That instantly set alarm bells off in my mind, and so I pulled all four plugs out (thenkfully all fairly easy to get to) and tested them by connecting the in turn to a known working coil. and grounding the plug against the frame. Two of them sparked normally, and two don't. The bad plugs do spark when I pull them away from the frame of the engine by up to an inch. Then the spark jumps from the threads of the plug to the frame.  So I can only surmise that there's some sort of internal breakdown that only comes into play with very high voltages, and that a multimeter isn't a reliable way to test plugs. I'm pretty flaberghasted to be honest. The whole bike has less than 7000 miles on the clock and the plugs LOOK absolutely fine and with the correct electrode gap of 0.8 to 0.9mm. Well I've learned my lesson but I'm very pleased to have finally solved the proiblem!

[bmart]

So it is the plugs themselves of their wires? I can't tell from your note. 

[squirrelman]

check  the headers for heat after its run 30 seconds to find non-firing cylinders.