I _{know I read it somewhere but I did not find it: I am installing new points and condenser on my TY B, I normaly set them to 3.1mm BTDC as per my Yamaha service manual ( A model ) but I remember that many don't set them at that BTDC. What is your input on that ?}

_{Thank you}

 

_Guy

Up to 3.25 will give more torque just above idle.

 

Nearer 2.5 will give smoother idle and less chance of stalling at low revs

Humm !!!  Decision  decision... Thank you

Have a word with John Lee Motorcycles (I hope I have got the right dealer). I think they prepared exceptionally well running but very standard 250 Yamaha engines for Russel Carr and others in the mid to late 1970s.

 

The dealer could have been Lee Brothers of Sowerby Bridge as they are a lot closer to Skipton where RC came from.

 

Sorry I can't remember which one - quite a time ago.

Edited May 24, 201511 yr by dadof2

Guy with the B and later model motors you can run them with an earlier spark than the A model without fear of stalling, unless the B or later model flywheel has been extensively lightened

I don't know about the rest of the world, but here in Canada, the B model was sold in 1975 and the weight added to the flywheel is twice as thick and larger than than A model. I run a weightless A flywheel on my B , and I went for 3.4mm advance. the bike start and run well ( in the backyard ) but I did not have the chance to try it properly. If I went wrong, don't be affraid to point it out, I would be happy to read your input.

 

Guy

I find that all the TY250 motors stall quite easily in some riding conditions if there is no weight band on the flywheel. If there is only dirt with good traction, I had no problem with running a flywheel with no band. If there is slippery or loose riding, I found a reasonable risk of stalling.

After experimenting with no weight band on B and D model motors, I now use a weight band that is approx half the width of the BCDE model band and run standard spark timing on my B and D model motors. I run the standard flywheel with standard weight and standard spark timing on my A model motor.

B C D E models here came with weight bands about twice the size of the A model weight band.

By personal preference, I ride everywhere without touching the clutch which is maybe why I like a bit of flywheel weight.

David, I will keep your advice in mind. I should be able to make a good test ride this week end, so I will be alert to stalling. I have an unmodified  A model apart my heavy B model flywheel so if the bike have a " stalling tendency " , I will go back to a standart weight A model flyweel and see if the rider isn't the cause of the bike behavior. I also try to ride without the clutch.

 

Guy

David, I will keep your advice in mind. I should be able to make a good test ride this week end, so I will be alert to stalling. I have an unmodified  A model apart my heavy B model flywheel so if the bike have a " stalling tendency " , I will go back to a standart weight A model flyweel and see if the rider isn't the cause of the bike behavior. I also try to ride without the clutch.

 

Guy

 

 I run a stock A model flywheel on my stock C model engine. I like the way it runs (peppy) and it requires some extremely erratic behavior on my part to make it stall.

from my understanding, the heavy flywheels are better for low rev slogging

 

Yes, but the heavier the the flyweel the slower the response on and off throttle, and you have to consider the position of the weight: the further out the more effect it as on the motor. With the heavy TY B flyweel, the throttle response is slow and it seem's to take forever to get down to idle speed. I think I have a picture off the A and B flywheel, I will try to find it and post it.

 

Guy