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Brief guide for setting points timing on TY

Posted: Sat Aug 10, 2019 3:43 pm
by David Lahey
I've been asked for help with setting the ignition timing on TY that has the standard points ignition, using a light bulb. We had some trouble with the messaging so I'm posting it up here.

You will need to gather a light bulb which matches the voltage of the battery you are going to use, wires to connect it all up and two alligator clips to hook it up to the bike. When I use a light bulb for this I use a 12 volt lawnmower battery and a 12V taillight bulb. A few years ago I bought a timing buzzer and use that for the job now. It is easier because I don't have to take the battery out of the lawnmower and also because I don't have the bulb shining in my eyes while I do the other things. Anyway here is the bulb process:

Using a bulb and battery to detect opening and closing of the points:
Identify the wire that runs from the points to the HT coil. Disconnect that wire somewhere between the two. On your TY250 there will probably be a joiner near the front of the airbox. Make a single circuit to light your bulb and which includes the ignition points. To do this connect your light bulb circuit to the bike frame (earth) and the wire that comes from the stator. The bulb brightness should change a little bit when the points open and close.

Setting the points so they open at the right piston position:
The points are supposed to open just before the piston gets to the top. I use a mark on the rim of the flywheel to indicate when the points should start to open. To decide where to put the mark, you need to make a mark on the flywheel rim for when the piston is at the top. You can use something inserted down through the plug hole for this. Once you have the piston exactly at the top, make a mark on the flywheel rim where it lines up with something on the engine casing, like a screw hole.
Then measure anticlockwise around the flywheel rim 22mm and make a second mark. That is your timing mark so when the timing mark lines up with the part of the engine casing you chose before, that is where the points are supposed to open as you rotate the flywheel anti-clockwise.
Adjust the points to get them opening at the right place. On some bikes you move the stator backing plate to get the timing right but on TYs there are no slots for the screws. The gap you get between the points contacts when they are fully open is not critical but should be between 0.2mm and 0.6mm. There is an ideal gap which I think is 0.4mm but you will only get both the timing and the gap right with a brand new cam in the flywheel and new genuine points. It is the timing that is the most important, not the gap.
To make it easy to change the setting on the points, adjust the clamp screw just tight enough so you can still move the points using a screwdriver in the slot but tight enough to that the points won’t move as you move the flywheel. Once you have the setting right, then tighten the clamp screw fully and check the timing again. I always pull the flywheel off and clean the points and lube the cam before I set the timing.
Any questions? I may have missed something

Re: Brief guide for setting points timing on TY

Posted: Sat Aug 10, 2019 9:46 pm
by Twinshock200
Nice one David, thanks for the detail, much appreciated.

Re: Brief guide for setting points timing on TY

Posted: Sun Aug 11, 2019 5:57 am
by tat ty
Thanks David.

Alastair

Re: Brief guide for setting points timing on TY

Posted: Sun Aug 11, 2019 8:22 pm
by Tiggs
Thanks David.

Re: Brief guide for setting points timing on TY

Posted: Tue Aug 13, 2019 9:27 pm
by Greg Harding
Hi Everyone,
David Lahey wrote:The points are supposed to open just before the piston gets to the top. I use a mark on the rim of the flywheel to indicate when the points should start to open. To decide where to put the mark, you need to make a mark on the flywheel rim for when the piston is at the top. You can use something inserted down through the plug hole for this. Once you have the piston exactly at the top, make a mark on the flywheel rim where it lines up with something on the engine casing, like a screw hole.

Love your work David, here is the :yamaha something to put down the plug hole. Thanks PA, I now have a set.
1565657079841.jpg
1565657079841.jpg (132.1 KiB) Viewed 4592 times

If you are wondering what came inside the :Honda: metal box, M3 x 0.5 camchain adjuster screw with tape on it so I don't loose it. Oh and the :kawasaki pouch contains heavy duty stuff!

Re: Brief guide for setting points timing on TY

Posted: Wed Aug 14, 2019 9:29 am
by Jools
What no fag-papers?
(Sign of the times eh?)

Re: Brief guide for setting points timing on TY

Posted: Wed Aug 14, 2019 6:39 pm
by David Lahey
Jools wrote:What no fag-papers?
(Sign of the times eh?)

I figure you are probably joking but in case not, fag paper is OK for bikes where you can get at the points easily but TYs are pretty much impossible to get the paper in because you have to rotate the access hole away from the points to get the points open to get the paper in

Re: Brief guide for setting points timing on TY

Posted: Thu Aug 15, 2019 9:43 am
by Jools
Yep, joking of course D!
Thx for the excellent guide.