hard start- doesn't idle (sometimes)

[nutsandbolts]

Hey all,

78 gs 750, stock setup, won't idle and hard to start but last ride was perfect start and idle.
Here's what new; shims to spec, coils and plugs, condensers, points, intake o-rings, carb to air box boots, carb clean and complete new factory o-rings, new air & fuel hose from carbs to petcock. Timing is set to spec.

This idle issue comes and goes. One day all is fine, next ride (few days later) and problems.
Any ideas to chase? Thanks in advance.

[Larry D]

Thoroughly check all the electrics. Sounds like a connectivity problem to me.

[Kerry]

I had intermittent idle issues from a faulty petcock. Might be worth checking...

[salty_monk]

Hard start is a classic simple of too tight valves.... Check the valve clearances.

[nutsandbolts]

thanks for the petcock note- I'll look into that.
If I put all the shims to within spec in a previous adjustment and it ran fine afterwards, what would be acting up in the valve train to make periodic hard starting?
Thanks for the feedback.

[Nessism]

You might want to check for voltage at the coils. Less than 10 volts or so is signs you might want to consider the coil relay mod.

[nutsandbolts]

Thanks. I have done the coli relay mod.
I also have checked and cleaned all my electrical connections about 3 months ago. I haven't used dielectric grease on the electrical connections but that shouldn't have impacted cleaned connections in less than 3 months you'd think.

I noticed this morning my petcock has been leaking while sitting on the side stand. I think this might be the problem to chase.

[nutsandbolts]

FWIW, fired up okay this morning, though number one exhaust header is cold this morning and plug is wet. Didn't want to idle again until I turned up the throttle stop.

I'm a bit stumped since new coils/ caps are in there. Not sure why number one is dead. I guess I'll try new a new plug and see what happens. Plugs are only 3 months old.

[nutsandbolts]

Well, #1, 2 & 4 plugs have all stopped working over different time frames. Seems unrelated to anything. A new plug fixes the problem though. Any ides as what would cause plug failure?

[MisterCinders]

Bad plug wires? Ignition timing off?

[Big T]

Bad plug caps?

[nutsandbolts]

I've changed all the caps and clipped back the wire an inch before mounting the new caps. Wires and coils are showing some age.
I checked the timing and its right on. Has new condensers & points.

I think it may narrow down to the coils and wires. I don't think the fuel mixture could be randomly wrecking these plugs could it? They don't look fouled, just mild sootiness after they are pulled and that could be from running the bike until I find out the plug is dead.
Thx for the comments.

[bobthebiker88]

Im pretty sure there is a spec listed in ohms for the primary/secondary windings in the coils, break out the meter and check em out.

[Coady]

I've had these symptoms in the past from a combination of a weak/dying battery and oil coming up past worn cylinders and rings. It would be alright if I rode daily but if I let her sit more than 2 or 3 days then I'd usually foul a plug or 2 at startup.

Doesn't sound like they're oil fouled though so maybe check the resting voltage of the battery and the spark on each plug (by pulling them all and earthing them one at a time to the cylinder head, while turning the motor with the starter). That's if you havn't already.

I'd also check the resistance across the coils - plug cap to cap from memory it should be between 20,000 - 30,000 ohms for stock coils and 5k ohm plug caps. If its a lot higher or an irregular or no reading then there may still be a weak connection at the plug caps/wires. Search the forums for more details on this test. Once again I guess you may have already been here if you've done the coil relay mod number.