XT600 lazy in the mornings

[connal]

Hi, I've been banging my head against the wall for a couple of weeks trying to sort out why my 1997 XT600 has become so reluctant to start in the mornings. It's not particularly cold here in Portugal but I struggle to start it. Once it goes and runs for a while it will start all day long with no problem. This is what I know so far:

- The battery seems good - resting it sits at 12.9V, under starting load it drops to 11.5V and when it is charging with engine running it shows 14.4V.

- The voltage under starting load drops to 10.6V across the starter motor.

- Resistance across the spark plug cap is 11.5ohms, not the 10 specified in the manual.

- Resistance on the primary coil is 4.9, not the max of 4.6 specced in the manual.

- Resistance on the secondary is within spec.

- The spark plug is new. If anything it is a touch darker than the pictures I have seen of how an ideal plug should look.

- The spark on the plug is weak and erratic when I hold it against the cylinder head and push start.

- I get a strong smell of petrol when I have been trying to start it for a while.

If anyone can identify where I should be looking I would be very grateful. I am a beginner at this and do not know where else to look. I have stripped the carb and checked the float height and needle valve. I have looked for continuity issues on the electrical circuit and found none. The bike does leak fuel from the carb if I forget to turn the petcock off but I haven't figured out how to fix this yet. I figured this might be the source of the problem but that wouldn't explain the weak spark.

I'm sure the solution lies in replacing some aged parts - I just don't know which ones I should be looking at first. If it is possible from the info above I would really appreciate some advice on whether I should be working on the fuel system or the electronics.

Thank you in advance for your help.

[Tango]

Welcome to TMBF mate. .........

I'd start by looking at the plug and coil.......but it could be that the carb is a bit gunked up after all this time.....so, a carb strip and thorough clean could help too.....

[Stu]

I would look at replacing the plugs and sorting the leaking/sticking float valve

thats if the fuel is leaking out the overflow? if its leaking elsewhere it could be draining the carb dry

do these have a fuel pump?

[TimR]

Does it leak fuel internally or externally .

If its leaking internally ( fuel coming out of air filter inlet ) then it can cause internal engine damage by hydrolock which can bend valves and break Piston rings causing low compression .

If externally not to much of an issue generally.

Common cause will be float height incorrect set or float damaged or dirt causing the needle to stay open or damaged diaphragm.or damaged gasket

Bad cells in battery can still show a good voltage but underload will weaken the electrical power required for a good spark .

Are the measurements taken allowing for the +&- percentages of the range

[connal]

Thanks for the welcome and the really helpful replies. Averaging them out it seems fuel supply could still be the issue so I think I'll wrench the carb out again to deal with the overflow. The carb is gravity fed (these are very basic bikes) and the overflow pipe simply dumps the fuel on the ground. Replacement parts like a needle valve are cheaper to replace than any of the electrical components so it makes sense to first eliminate the possibility of the carb being the problem. I'm fairly new to working on bikes so I'm afraid I don't understand the bit about taking measurements which allow for the + and - percentages of the range. Thanks again guys.

[TimR]

Thanks for the welcome and the really helpful replies. Averaging them out it seems fuel supply could still be the issue so I think I'll wrench the carb out again to deal with the overflow. The carb is gravity fed (these are very basic bikes) and the overflow pipe simply dumps the fuel on the ground. Replacement parts like a needle valve are cheaper to replace than any of the electrical components so it makes sense to first eliminate the possibility of the carb being the problem. I'm fairly new to working on bikes so I'm afraid I don't understand the bit about taking measurements which allow for the + and - percentages of the range. Thanks again guys.

In the manual it gives you the specified measurement .. so say 100 ohms but generally it will give a tolerance of say + or - 5% so your reading could between 95 and 105 ohms and still be acceptable

[connal]

Great. Thanks TimR. I understand it now.

[Guest]

You checked connections on the coil?

[connal]

Yes I cleaned the contacts and checked the resistance. The only possibly dodgy thing I could see was that it measured 4.9 ohms across the primary coil whereas according to the manual it is supposed to be between 3.4 and 4.6. I don't know if this is enough to make a difference. Do you think an over-filled carb bowl, which happens when I forget to turn the petcock off, could be causing the engine to flood when I try to start it?