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Louie
Louie, Technician
Category: Motorcycle
Satisfied Customers: 11444
Experience:  25+ yrs. experience
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I have a 1966 Yamaha YM1, fully rebuilt, which isn't

Customer Question

I have a 1966 Yamaha YM1, fully rebuilt, which isn't starting. The 6V lithium battery is fully charged at 6.5V and when I test the spark plugs (the old fashion way of grounding, kicking, and watching for a spark) they seem fine. Any ideas?
Submitted: 1 year ago.
Category: Motorcycle
Expert:  Louie replied 1 year ago.

Hi and welcome to JustAnswer,

Thank you for the question and your patience. Should you still need assistance for information purposes only...

Initially, proposed preliminary tries would be to:

  • • ensure no residual 2-T oil at the bottom of the crankcase;
  • • cover carb mouth with the palm of your hand when attempting to start to determine suction and fuel;
  • • strongly consider a compression or perhaps better yet, a leakdown test.


Please post back results / observations of the above once tried.

Customer: replied 1 year ago.
The bike's compression seems to be fine. I've covered the carb mouth and feel suction. I've also opened the carbs to make sure everything is clean and in place. Still no luck.
Expert:  Louie replied 1 year ago.

A review:

  • • fuel - "...carbs...clean and in place...";
  • • but is there fuel in the bowl? And "...covered the carb mouth...suction..." did your palm got wet with fuel when attempting to start?;
  • • compression - "...seems to be fine..." Bear with me, any PSI reading please?
Customer: replied 1 year ago.
1. Yes, there is fuel in the bowl.2. No, I didn't feel gas on my hand when covering the carbs with my palm.3. I do not have the tool to do a PSI reading. I'll purchase one ASAP and let you know the results.4. One other thing to note, I sprayed a small amount of starter fluid into the carbs and it would still not turn, not even for a moment.
Customer: replied 1 year ago.
I'm also getting a shop manual tomorrow. I want to change the sparks and battery. Note that the battery is holding a 6.5 volt reading on a multimeter (6v lithium battery).
Customer: replied 1 year ago.
But I'm unsure if the battery is messed up.
Expert:  Louie replied 1 year ago.

The "...didn't feel gas on my hand when covering the carbs with my palm..." is very significant as it would indicate that fuel is not sprayed/delivered to the combustion chamber even if it is present in the carb bowl; likely clogged idle /slow jet.

With "...sprayed a small amount of starter fluid into the carbs and it would still not turn...", can you please re-try and attempt to start again but still cover the carb mouth with your palm.

Then check if the sparkplug got with with fuel. If not, please try wetting the sparkplug tip with fuel, screw back in and re-attempt to start again covering the carb mouth with your palm.

Customer: replied 1 year ago.
Okay, thanks for the fast reply. I'll try it out tomorrow.
Expert:  Louie replied 1 year ago.

Yes please; an update tomorrow or when able.

Cheers.

Customer: replied 1 year ago.
I wasn't able to diagnosis it so I took it into a shop.
Expert:  Louie replied 1 year ago.

I understand and appreciate the update.

Good luck with the Yamaha.