torque specs for TY250A

[Robert Lagana]

Does anyone have advice regarding torque specs for the TY-250A , 1974 bike?  currently reassembling after adding electronic ignition would like to know the torque for the flywheel nut. also would like to know after finding TDC what is the optimal advance or retard of the timing.  I will be using a strobe with advance degrees on it.  Thanks for any help.

[feetupfun]

The timing will depend on what the advance curve for that igniton looks like and what you are looking for.

I fitted an electronic ignition (not the same as yours) because I had just converted my TY175 to 210cc. With the 210cc, the motor response was a bit too fast for me at low RPM. The fixed timing (points ignition) was a compromise between low RPM and high RPM performance. With the electronic ignition with an advance curve, I could get just the right timing at low RPM to get rid of the snappiness and still not compromise the high RPM performance. By the time I was happy, the timing was a bit less advanced at low RPM, maybe 5mm less advanced on the OD of the flywheel compared to standard timing.

I would suggest you put yours in the middle of the slot and try it out. If you like experimenting (it sounds like you do) then try different stator plate positions and see which you like the best. A strobe will provide visual feedback for where the timing is, but it will just be moving by the same amount in degrees as you move the stator plate.

[Junglejeff]

On 5/28/2019 at 9:47 PM, feetupfun said:

The timing will depend on what the advance curve for that igniton looks like and what you are looking for.

I fitted an electronic ignition (not the same as yours) because I had just converted my TY175 to 210cc. With the 210cc, the motor response was a bit too fast for me at low RPM. The fixed timing (points ignition) was a compromise between low RPM and high RPM performance. With the electronic ignition with an advance curve, I could get just the right timing at low RPM to get rid of the snappiness and still not compromise the high RPM performance. By the time I was happy, the timing was a bit less advanced at low RPM, maybe 5mm less advanced on the OD of the flywheel compared to standard timing.

I would suggest you put yours in the middle of the slot and try it out. If you like experimenting (it sounds like you do) then try different stator plate positions and see which you like the best. A strobe will provide visual feedback for where the timing is, but it will just be moving by the same amount in degrees as you move the stator plate.

Thanks for the info.I am installing a electronic kit on my 250 and was wondering about the timing curve.

[feetupfun]

7 hours ago, Junglejeff said:

Thanks for the info.I am installing a electronic kit on my 250 and was wondering about the timing curve.

The one I put on a TY250D motor is a John Cane and I have not bothered putting a timing light on it. I just fitted it with the backing plate in the centre of the slots and the bike ran beautifully. The one I put on my hot rod TY175 is also a John Cane and I did look at the movement of the timing with a strobe but it was so long ago I don't remember details of how it moved. I do remember moving the backing plate to give me timing a bit later than standard at low RPM and that the timing did change as the RPM increased. I'll have a look in my bike log and see if I wrote something in there.

A friend fitted a Rex Gaunt ignition on his TY250A recently and I can say that his motor performs pretty similar to my TY250D motor at low to medium RPM but seems to have a bigger hit at medium to high RPM

[feetupfun]

8 hours ago, Junglejeff said:

Thanks for the info.I am installing a electronic kit on my 250 and was wondering about the timing curve.

I just read the bike log for my hotrod TY175 but no mention of the advance curve. The records are only about testing different combinations of head gasket thickness and the timing of the spark at low RPM.

[Junglejeff]

I just installed a kit on my 74 250 2 days ago.I put it center slot and bike ran well but it had bit more pull off bottom with points.I shot it with light and timing was pretty retarded.Ended up setting timing light aside and tune by how bike runs.Set at full advance and bike did not like it.It is now set slightly advanced of center position and bike pulls well off bottom and revs out better than it ever has.The trouble with the timing on stock is it is a compromise because lack of advance. The electronic advance gives you ability to make bike run better bottom to top.The old timing mark is not super usable for the electronic kit.It is a nice piece of kit and happy I have it.I actually find the motor works better for me than my modern GG 300 pro which is crazy.I am going to add a flywheel weight to my GG to see if I can make it more like the TY engine.I do notice the front end is easier to lift with the new kit plus added run out is a win win.

 

[Tillerman6]

On 5/28/2019 at 2:09 PM, Robert Lagana said:

Does anyone have advice regarding torque specs for the TY-250A , 1974 bike?  currently reassembling after adding electronic ignition would like to know the tosrque for the flywheel nut. also would like to know after finding TDC what is the optimal advance or retard of the timing.  I will be using a strobe with advance degrees on it.  Thanks for any help.

the flywheel nut (magneto) gets 4.0- to  4.5 kg-m or 28.9-32.5foot pounds  of torque, but you need a special tool to hold on to the flywheel. 

the timing is normally set with a dial indicator riding on top of the piston with the head removed.  the spec is 3.1 +/- 0.15mm BTDC and the engine rotates CCW as viewed from the left side. At that position, if you had points, the points should just open right then.

But with your electronic ignition and if you have a degree wheel and a timing light, and your conn rod is 125mm long, then you should get the equivalent timing at 22.74 degrees BTDC on the wheel.  This is only a ballpark figure and assumes a maximum amount of advance at that point.  Depending on the rpm, your electronic ignition will regulate the amount of advance. At the very low rpm's you would want less than 22.74 degrees to make the bike easier to start and reduce the chances of a kickback. I hop this makes sense to you.  I keep getting notified that you are still looking for this information, but this is my last attempt to reach you without feedback.

Good luck!

 

 

Edited June 2, 2020 by Tillerman6
clarificaion and consolidation

[Tillerman6]

22 minutes ago, Tillerman6 said:

the flywheel nut (magneto) gets 4.0- to  4.5 kg-m or 28.9-32.5foot pounds  of torque, but you need a special tool to hold on to the flywheel. 

 

there are 25.4 mm to an inch.

 

the timing is set with a dial indicator riding on top of the piston with the head removed.  the spec is 3.1 +/- 0.15mm BTDC and the engine rotates CCW as viewed from the left side.

 

Who made your electronic ignition kit and how do you like it?

I found a piston position/degrees calculator online  but you need to know the length of the rod to use it.

That should be doable

http://www.torqsoft.net/piston-position.html#ex2

[b40rt]

Just something to consider, on fitting electronic ignition on a Rotax in place of original points set up, the petrol screw (Dellorto carb) went from about 1.5 out to about 0.5 out before it ran nicely off the bottom.

[Tillerman6]

8 hours ago, Tillerman6 said:

I found a piston position/degrees calculator online  but you need to know the length of the rod to use it.

That should be doable

http://www.torqsoft.net/piston-position.html#

The rod length for the 74 250A is 125 mm and using the calculator above, the angle you seek is 22.74 degrees on the wheel.  That is the starting point anyway.  So is your kit from electrex? how do you like it?

 

[jon v8]

Electrex World ignition can be difficult to set or check with a strobe, some strobe lamps get confused with them,my Snap On one did when I was sorting out my sons D14/4 Bantam. The boss of EW told me that strobing could be difficult with his system. It was a couple of years back now,but I seem to remember there are two firing events per rotation,so there is a spark as well near BDC. The strobe would jump between the two events,making it difficult to see what was happening.

I'd be inclined to set it as per the EW instructions and see how it runs.

[feetupfun]

8 hours ago, jon v8 said:

Electrex World ignition can be difficult to set or check with a strobe, some strobe lamps get confused with them,my Snap On one did when I was sorting out my sons D14/4 Bantam. The boss of EW told me that strobing could be difficult with his system. It was a couple of years back now,but I seem to remember there are two firing events per rotation,so there is a spark as well near BDC. The strobe would jump between the two events,making it difficult to see what was happening.

I'd be inclined to set it as per the EW instructions and see how it runs.

I found the same thing using a HT lead-triggered strobe on one of my DT175H motors with standard Yamaha electronic ignition.

[Junglejeff]

On 5/30/2020 at 12:15 PM, jon v8 said:

Electrex World ignition can be difficult to set or check with a strobe, some strobe lamps get confused with them,my Snap On one did when I was sorting out my sons D14/4 Bantam. The boss of EW told me that strobing could be difficult with his system. It was a couple of years back now,but I seem to remember there are two firing events per rotation,so there is a spark as well near BDC. The strobe would jump between the two events,making it difficult to see what was happening.

I'd be inclined to set it as per the EW instructions and see how it runs.

That explains why my stobe was acting so wierd.Ran bike without cover so I could pull flywheel quick to test adjustments. Was reasonably easy to find sweet spot.