Hot start problems

[bstratton]

I have looked through some of the previous threads on this subject. It seems there are a lot of potential causes - both fuel related and ignition. Took my R50 out for a ride this Saturday and ended up trailering it home. I Thought I'd put this in front of the seasoned owners on this forum.

Bike starts easily when cold. Since the rebuild, it has always been a bit of a problem to start when hot. I thought this was normal and I needed to spend a little time with her to figure out what she wanted. I am reasonably confident the fuel/ fuel mixture is OK. It doesn't act like it is flooding when warm. Once it starts it runs fine.

Saturday was something a little different. I noticed that coming off idle it would hesitate a little (this is after it was fully warmed up). Never did that before. After an hour ride or so it stalled at idle and would not start. Kinda tried a few times but after wearing myself out I gave up and borrowed my buddies bike and went home to get my trailer. Luckily only a mile or so.

I have not attempted to start it since. I will try today after work but would not be surprised if it starts right up....

Starting to suspect heat and ignition. I did not check spark when it failed on the side of the road. Had some time pressure. I did not replace my coil when I rebuilt the motor. Points and condenser are new. All electrics are original except points and condenser and high tension wires and caps. I just cleaned the magneto and generator. Static timing is dead on. Point gap is very close. Never timed it with a strobe.

Plugs look completely normal for around 250 miles.

[312Icarus]

Suspect coil. Poor hot starting is often a symptom of a tired coil.

If your’s is original, it warrants replacing anyway.

Icarus

[bstratton]

I took the chance with the original. at that point of the project I was likely about out of budget. Once I eliminate any other possibility I'll replace it.

Next obvious question: Re-wound European or repro?

[312Icarus]

Reprodcution is pretty reasonable and works well.

Icarus

[schrader7032]

Have you gone back to the bike and see if it will start? If it starts up easily again the next day when cold, it does sound like the classic coil issue. The coil starts out as a single strand wire wound around the core. Over time, the wire begins to break at a few locations. When cold, the coil is shrunk and enough of the breaks are actually touching again. But when the coil gets hot, the breaks are more apparent and instead of a single wire, you have several "smaller" strands that don't produce the quality spark needed.

[bstratton]

First chance I had since Saturday. I think this justifies the $160 for a new coil. Glad it is a simple problem and it will be nice to be able to start it easily when warm.

[Discogodfather]

I second the comments on the coil, had the same problem for years on a R60/2. At high temps in traffic on warmer days it would cut out cylinder #2 and loose about 100 rpm when idling at a light. If I turned it off for any reason at that point it would be a real pain to get started again. Waited until it cooled and it fired back up.

Best money I ever spent was on one of the newer Emerald Isle blue coils. My old coil was re-wrapped anyway and it always tested good- when it was not too hot. The old coils just seem to go to pot with that gel or epoxy or whatever it is, and it is either dryed and cracked or turns to mush. The cloth they re-wrapped with sometimes hides the reality on the inside.

[oldtimers.si]

hi,
yes you must change / replaced ignition coil with NEW and will be ok
the old have a lot of problems with different symptoms
inside wire is corrosion and then is bad ignition

regards,Mec

[bstratton]

Made a big difference.

First thing I noticed is the bike idled reliably when hot. Zero hesitation when coming off idle. Just as easy to start hot as cold. What a difference!

Thanks for all the input.

[Discogodfather]

Made a big difference.

First thing I noticed is the bike idled reliably when hot. Zero hesitation when coming off idle. Just as easy to start hot as cold. What a difference!

Thanks for all the input.

It was like magic for my R60/2 as well, don't know how many hours of false diagnosis I did on other electrical parts. Runs with better power at all rpm's too. Riding out in 97 degree weather today and it was a champ. I used to dread riding it in hot weather and always had my Hagerty towing number with me.