Bogged down, now it won't start

Had the bike running and took it to work. Ran really rough after work, so I synced and color tuned and synced again. It fired up then stalled, and now it won't start. Took the carbs off and gave them a quick clean. Had it running for a bit on choke, but it stalled after a bit. Now it turns over, but won't start. Checked to see if there is spark, and it has spark but it doesn't look all that strong. I have the battery on the charger now. Any thoughts on what I should be looking for?

 

Spark looks weak on our XJs because it's a TDI system. When you refit the battery put multimeter set to 20 volts probes on battery and press starter button. You can also try a car battery and Jump leads. voltage must not drop below 10 volts when you try and start the engine. The TCI needs 10 volts to operate the transistors which switch off the current causing high voltage which creates the spark. If voltage is low the engine can crank but there is no spark as the starter motor is drawing current and the engine compression is putting greater load on the electrical system. When plugs are out to check for spark there is no compression on that cylinder.

Did it splutter to a stop or cut out suddenly? If you get it started put the multimeter on it again and check the voltage to see if the alternator is charging the battery. Post the voltages you get.

 

I'll check that tomorrow. It did sputter and slowly stop.

 

Splutter sounds like fuel starvation rather than ignition. Put fuel tap on prime. Slacken float bowl screws each bowl has one to see if fuel leaks out. A blocked fuel tank cap causes a partial vacuum above the fuel and prevents fuel getting to the carburettors. Do you have an in-line fuel filter?

 

Check oil level, check the air filter as it can get contaminated with oil if the fuel is leaking into the crankcase via the hose on the gear shift cover.

 

When balancing carburettors did you use the bikes fuel tank? Try starting it on an auxiliary tank if you have one.

 

Out of fuel?

 

Make sure the gas tank vent is bout blocked

 

No inline filter. I'll check the fuel bowls when I get home. New seal on the gas cap as well.

 

Changed the oil yesterday again. Air filter is clean.

 

I used the bikes tank, so I'll try my auxiliary tank as well. When I had the carbs out, I checked the fuel levels in case I moved one of the floats. All were at the proper level.

 

Did you disassemble the gas cap fully and clean? A new seal by itself doesn't mean the vent is clear.

 

Yes I did last year. The bike ran fine last year, and up until now.

 

Mabe vent is blocked again?

 

12.75 battery alone. 10.90 when turning the bike over. Bike turns over but won't stay running.

 

Had it going for a bit, 12.75-13v

 

Started with auxiliary tank

 

Is it running normally or cutting out when you are using the auxilliary tank? Assuming it runs normally with the auxilliary tank then there is a problem with the fuel tank, petcock or fuel tank cap. If you try starting it with the tank on the bike open the fuel cap to see what happens. It must be fuel starvation that is the problem.

 

If it runs with aux tank there may be an issue with your petcock.

 

Ran for a bit then bogged down again. Checked the two spark plugs and one was wet, the other was dry. I'll try with the cap open.

 

Yes something wrong and the vaccum cannot draw enough fuel for the carburettors. Is it the diaphram in the petcock that causes this if it is old?

 

Rebuilt that last year. Also changed out the wave washer. I had bent the old one last year and it worked fine, but wanted to eliminate that

 

I took the gas cap off to check, and a little ball bearing came out. Where does that go?

 

That ball is part of the vent system.

 

13 minutes 20 seconds approx you see the ball bearing. Is the fuel cap the same as your machine?

 

That's new also

 

Started and running with the cap open

 

I had the same problem when I was young on an MZ lol. I did not know how to fix it, but my father did. Your fuel cap vent must be blocked.

 

Great, how do I fix that?

 

http://www.xj4ever.com/gas cap.pdf

 

Site can't be reached

 

Had it running. Did a sync, colortune, and sync again with the gas cap closed. I did take a q-tip with some carb cleaner and cleaned whatever holes I could see. Everything seems to be fine now, or maybe not. Bike sat for about half an hour and now won't start again. WTF!

 

Must have cleaned the holes for the vent, so it should be fixed.

 

Won't start again

 

Strange not even with the cap open?

 

Nope

 

I think I'll do a compression test tomorrow to see where it's at.

 

If you are cranking the engine a lot remember if the voltage drops the engine can still crank but the voltage is too low to operate the TCI. Crank it with the multimeter on the battery again to make sure you still have a minimum of 10 volts to operate the transistors in the TCI. You can try a car battery with jump leads if you want as the bike will not be affected. Keep car engine off though. Do your compression test too but valves don't go out of spec quickly.

 

One of the guys from work said it was smoking when I brought it last time. Might be nothing though.

 

Don't think the smoking is anything to be concerned about those engines are tough. Could be condensation if started from cold or combustion smoke if the engine is missing on the ignition stroke.

 

12.75 battery, 13.20 bike is running. One exhaust is smoking when I rev the engine. Left side plugs were wet when I did the compression test. Must be running rich somehow.

 

Plugs can be wet with excess fuel when engine was not starting. Get it to operating temperature and see how it is. Do the colour tune again

 

Tried to colortune again, and gas was coming out of the plug, and the adjustment screw was only 3/4 turn out from bottom. Taking the carbs off again to see if the Jets are in the right spots.

 

Everything is in the correct spots.

 

What do you mean gas is coming out of the plug? Vapour l assume? Is the bike running at all?

 

It was running. I went to colortune again and gas was dripping out of the hole when the engine was running. I tapped the bowls to see if the float got stuck, but no change.

 

Dripping out of the spark plug hole. Colortune was as tight as I could get it in the spark plug hole.

 

If you have fuel being forced out of the spark plug hole l would remove the left engine cover and the plugs and turn the crankshaft a few revolutions anticlockwise with a 19mm spanner. I am surprised that is even possible because normally unburnt air fuel mixture should go out into the exhaust system. Have you checked your valve clearances recently?

 

I'll try that. I had color tuned the right side and was starting the left side when that happened. I had done the valves last year.

 

I don't doubt what you are stating but l have never heard of fuel getting out of a spark plug hole unless the crankcase is full of oil and fuel mixture which cannot be the case as you rebuilt the petcock and you put new oil in the bike. It would need to get above the pistons too. Have you checked your float valves? Could they not be sealing property? But if this was causing the carburettors to flood the engine the overflow pipes would have fuel coming out of them. And your floats are the correct height.