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Tillerman6

Trying to set the points correctly

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So today I had the left side cover off and wondered if the points needed any attention- It had been a couple of months since I attempted to set them up, and I re-read the instructions in my 75 shop manual again just to refresh my memory.

But laying on the garage floor trying to peek into a small hole in the flywheel is not much fun, nor is trying to guess at the timing.

Probably the worst part is that the slot in the points plate is wider than the securing screw by about 1mm.  This allows the breaker plate to move in both a left-right direction and also up and down which ruins any repeatability of the settings.  

Reason for this is that the wiper on the points arm is very sensitive to changes in it's position relative to the cam.  So while you are trying to move the points left-or right to adjust the timing as it relates to the flywheel position, you will almost certainly move the slot in the plate up or down ever so slightly relative to the clamping screw.  I think just tightening the screw can also move the points plate assembly a few tenths of a millimeter which is more than enough to change the timing and the maximum opening measurement of the points.

So does anyone know if there is supposed to be a special washer or bushing around the clamping screw?  With my present setup, there is no way to limit the Z axis motion of the points plate if an adjustment is needed (and it will be).

I was lucky enough to find a spot where the engine would start and run (albeit with more backfiring than I would like) but without removing the gas tank, the head, the flywheel and the tiny woodruff key, and fitting special parts, I am not looking forward to the next time when the points need attention.  

Note- I do not know if my points assembly is OEM or something off a lawn mower.  Your points may be relatively easy to adjust with no fuss at all, but without a visual picture and some measurements it may not be possible to tell If my bike has the "right stuff".

After my fiddling with the points position this time I noticed an improvement in the throttle response and maybe a little more power, but this is just a guess and I am considering upgrading to an electronic ignition from B & J racing for lack of a better solution.  

Any help or responses are much appreciated as always!

 

 

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There should be a washer under the clamp screw.

Here are some tricks to help you:

When changing the points setting, clamp the points just firmly enough so they don't move, but loose enough that you can just move them by twisting a flat, mid-width screwdriver blade.

It helps to use a screwdriver that is not attracted to magnets because those flywheel magnets are pretty strong.

Make a timing mark on your flywheel rim at the spot where the points should open. You should not have had to take the head or the tank off to set the timing. To find where to put this timing mark, make a mark on the flywheel rim (with the piston at top dead centre) beside one of the holes for the cover screws. From the TDC mark, measure 24mm counter-clockwise around the steel band on the flywheel and make another mark. That's the timing mark.

You can find top dead centre on a TY250 with the tank and head in place by putting something down through the plug hole and using it to feel what the piston is doing. Move the flywheel until you can feel that the piston is at the top and that's top dead centre. The 24 mm measured on the flywheel reproduces the piston being whatever the standard timing distance is in mm BTDC.

Yes electronic ignition is a popular way to get a bike running well if you are not confident setting points.

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Hi Guys, I used to have an old two stroke motorcycle with a 225 single cylinder twin exhaust engine.   It had a 6 inch lever on the side of the points backing plate, that could be used to vary the timing.   The engine would run with this lever either vertically up, all the way to about 90deg horizontal.   So Ignition timing was not so critical.  Admittedly there was one best position, that you could find when driving down the road, but that was +- 10 degrees before you could notice anything.   The starting position was best set a little retarded, if you didn't want a kick-back. . . .  So Guys, it's not so critical that you get it to less than 1 degree.   Having the points surfaces polished smooth is much more necessary.

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Just to add to the advice given, the standard ignition on all Yamaha TY's with points is very good quality and extremely reliable when set up properly. For the little effort it is to make it work properly I don't think the cost of electronic ignition is worth it. Yes, the 175's may benefit from the extra power available at the top end, but 250's make enough power for the bulk of riders. Personal choice and only my opinion. Only once in the last 15 years of using Ty250's have I had a problem with the ignition, my fault for using a dirty old set of points that I didn't bother to check when I built an engine out of 3 boxes of bits, using only a couple of new gaskets and circlips. The moving point was tight on the pivot and tightened up when the engine got warm. Cleaned out and greased, its not missed a beat since.

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Not only points gap and timing must be correct, also distance A in picture must be correct. If points for some reason not is correctly made for the engine/flywheel you may end up with a weak spark or no spark at all. Make sure points are within original manufacturers spec.

Abriss.jpg

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When I ordered the points for this bike, I think they had to substitute part numbers to get anything.  So I will be doing my best to match up old to new.   And thanks for the nice diagram, although I do have good spark, just not exactly at the right instant in time. 

I will be tinkering again today- see what happens.  - I want to make a special washer to limit the Z axis travel of the breaker plate assembly around the securing screw.  That should minimize the sloppy fit it has now.  ( the slot in the plate is for a larger screw)  - hope I don't drop anything and have to pull off the flywheel again! 

 

 

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I would seriously go the electronic ignition option if you can. I’ve got it on my TY175 and it is definitely punchier and - probably more importantly for me - another less thing to worry about. Just seems a lot snappier/more responsive.

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Yes, an electronic ignition is the solution. Less worries for many years,specially as I think lot of modern replacement breakers are out of spec. Perhaps good for other engines but not for old trials bikes.

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4 hours ago, rr62 said:

I would seriously go the electronic ignition option if you can. I’ve got it on my TY175 and it is definitely punchier and - probably more importantly for me - another less thing to worry about. Just seems a lot snappier/more responsive.

Can you tell me what brand of electronic ignition you installed on your Ty 175?  There are now at least two makers of these and all are quite expensive.

 

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On 6/1/2021 at 12:38 AM, feetupfun said:

There should be a washer under the clamp screw.

Here are some tricks to help you:

When changing the points setting, clamp the points just firmly enough so they don't move, but loose enough that you can just move them by twisting a flat, mid-width screwdriver blade.

It helps to use a screwdriver that is not attracted to magnets because those flywheel magnets are pretty strong.

Make a timing mark on your flywheel rim at the spot where the points should open. You should not have had to take the head or the tank off to set the timing. To find where to put this timing mark, make a mark on the flywheel rim (with the piston at top dead centre) beside one of the holes for the cover screws. From the TDC mark, measure 24mm counter-clockwise around the steel band on the flywheel and make another mark. That's the timing mark.

You can find top dead centre on a TY250 with the tank and head in place by putting something down through the plug hole and using it to feel what the piston is doing. Move the flywheel until you can feel that the piston is at the top and that's top dead centre. The 24 mm measured on the flywheel reproduces the piston being whatever the standard timing distance is in mm BTDC.

Yes electronic ignition is a popular way to get a bike running well if you are not confident setting points.

I noticed from reading old mail that you have or had two TY 250's with electronic ignition from Trials and Trails UK.  You seemed to like the operation of these and thought it was an upgrade or advantage to have these kits onboard. And from looking at prices online recently, it appears that the spark only version from Trials and Trails is not too terribly expensive.  But also from reading other mail it seems that people are not getting a response from T & T for whatever reason.  Could be Covid related?  So I am a little apprehensive about ordering from them right now.  Should I be?

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The time you are spending researching and pontificating over which way to go with this situation, you could easily strip down,set up and enjoy reliable service from what you already have. Its not that hard,and decent quality service parts like points and condensors are easily available at very little cost.Even if you bought 2 or 3 of everything you would have enough parts to keep it running for another 20 years of trail or trials use...

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11 hours ago, Tillerman6 said:

I noticed from reading old mail that you have or had two TY 250's with electronic ignition from Trials and Trails UK.  You seemed to like the operation of these and thought it was an upgrade or advantage to have these kits onboard. And from looking at prices online recently, it appears that the spark only version from Trials and Trails is not too terribly expensive.  But also from reading other mail it seems that people are not getting a response from T & T for whatever reason.  Could be Covid related?  So I am a little apprehensive about ordering from them right now.  Should I be?

I have no idea. You could try phoning them to find out.

Just because I bought something many years ago doesn't mean I would buy the same thing again. Things change. If I wanted to buy a TY ignition today it would be from Rex's Speed Shop.

Those ignitions from John Cane many years ago are still going perfectly, as are my TYs that have standard Yamaha ignition systems.

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19 hours ago, jon v8 said:

The time you are spending researching and pontificating over which way to go with this situation, you could easily strip down,set up and enjoy reliable service from what you already have. Its not that hard,and decent quality service parts like points and condensors are easily available at very little cost.Even if you bought 2 or 3 of everything you would have enough parts to keep it running for another 20 years of trail or trials use...

I am running my old factory points set for now. New ones on the way.   I had problems from making substitutions and not using a washer under the screw head- my fault totally.  But I failed to mention that I am 72 and have managed to sprain my right ankle walking around in my front yard.  This is not fun when the bike kicks back during the startup.   So I guess I'm looking for perfection and that is probably not going to happen.  

 

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2 hours ago, Tillerman6 said:

I am running my old factory points set for now. New ones on the way.   I had problems from making substitutions and not using a washer under the screw head- my fault totally.  But I failed to mention that I am 72 and have managed to sprain my right ankle walking around in my front yard.  This is not fun when the bike kicks back during the startup.   So I guess I'm looking for perfection and that is probably not going to happen.  

 

If its kicking back the timing is too advanced. They are not the easiest bike to start because the kickstart shaft is so high up. I'm only 56 but my right knee is not too good, fitting a decompressor into the cylinder head has helped me starting mine mine a great deal.

Decomp.jpg

Edited by jon v8

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1 hour ago, jon v8 said:

If its kicking back the timing is too advanced. They are not the easiest bike to start because the kickstart shaft is so high up. I'm only 56 but my right knee is not too good, fitting a decompressor into the cylinder head has helped me starting mine mine a great deal.

Decomp.jpg

Jon v8- I could do that with what I have in the shop. I guess there is a cable up to the handlebars?  And where did you find this part?  - Luckily I now own a new 14mm x 1.25 tap so it should be pretty easy to fit if everything else is available.  Thanks very much for the idea anyway!    BTW- with the timing as it is right now it will just kick back maybe once before it decides to start up, so since the new shouldered washer was installed, the timing is much closer to being right.  

Other factors affecting startup- Temperature, a very short (maybe 60 degrees of actual engagement of the starter shaft for each stroke of the kickstarter lever and the old carb seems to leave the plug wet even when I run it dry on daily shutdown.   

Today I just received my new OKO carb from Mid-Atlantic Trials!

 

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