feetupfun,
Thanks for the nice info. And I guess your specifications are loose enough that my settings would be in the ballpark. I neglected to mention that the reason I did initially start working on the TY was an oil leak from the clutch control arm and another leak under the magneto at the left crank seal. I ordered the factory parts and installed these, but the left crank seal being replaced was what changed the timing of the points and possibly the amount of air that was reaching the crank case. There was an oily residue under the magneto area, and that is why I suspected the main seal. But that was not the oil leak (gearbox) that had been p****** oil on my garage floor ever since I got the bike used. Anyway, with those two things fixed, I was (now) not getting spark enough to fire the engine.
I must have removed and replaced the fly wheel at least 6 times trying to get the points clean, cleaner, the gap set right and tearing the head, exhaust, tank, seat etc off the bike just to be able to take the TDC and BTDC measurements with a dial indicator.
I also was not completely sure if the double stator coils inside the mag should be on the left or right side of the crank because at one time I had these completely off the bike for inspection and I could not remember if I got them back on the right way or they were even the right parts to begin with. (used bike)
Then there was the condenser problem. I had ordered a new points and condenser from England and what showed up was the wrong condenser because of the way the felt wiper arm was welded to the side of the condenser body.
So with the advice of the local Yamaha mechanic I re-installed my old condenser and re-soldered the three wires to it that come from the points, the black lead out to the spark coil, and the lead from the ignition coil inside the magneto. I was also not sure of the schematic because of the shop manual being from a B model. The mechanic said he had never seen a condenser go bad. I thought that was a little strange, but I am not a mechanic. The parts guy priced me out of the realm of easy reach for the new parts and said he did not stock them any way, so I had to try something different.
With the ball park approach and a couple of temporary felt tip marker lines from when the TDC and BTDC positions were taken, I could tell that the timing was too far advanced. There was spark now, but the timing was so far advanced that all you would get was kickback.
Then I remembered what the mechanic said "less advance gives easier starts and maybe not peak HP, but more advance gives harder starts and more kickback"
So now I had the engine back together and between the BTDC and TDC ink marks on the flywheel there is about maybe 1.5 inches of distance. The ohm meter readings are VERY sensitive to any rotation of the magneto rotor (flywheel) so you have to go super slow from the BTDC mark CCW towards TDC with slow motion to look for when the readings go from 0.8 ohms to 1.7 ohms because the ohms reading will fluctuate on the digital ohm meter with the slightest wiggle of the flywheel.
So at a super slow CCW rotation you can eventually find the point at which the reading changes from .8 to 1.7 ohms on the black wire to ground and that is your opening position. Luckily, when that happened, I was between the .122" BTDC and zero TDC going by my crude marks on the flywheel. It was probably less than perfect and maybe closer to .080 to .100 of BTDC on the piston, but I was not in the mood to put the dial indicator back on to find out.
I could not use a timing light because the engine has to be running for that. A simple light bulb and a battery will not show a noticeable difference between .8 and 1.7 ohms, so that won't work and a buzzer will not change it's tune much for that small difference in resistance either as far as I know. ?? But the factory shop manual shows a "points checker" which I do not have, and that sent me back to the ohm meter. I think the best type of meter for this is an old school D'arsonval meter movement with a wheatstone bridge circuit that has a 1 ohm full scale setting.
I have one of those, but it is too big and fragile to really be of much use under a bike, so I put it back on the shelf.
So rather than trying to change the points gap again thru that tiny hole in the mag wheel ( it is shooting in the dark) I thought why not just kick it and see what it does.
I tightened down the adjusting screw and put the spark plug back in.
I also drained the float bowl and noticed some junk in the gas, but it could have been from the dust on the engine covers.
This time it ran but was running way too fast with no throttle applied.
I was really relieved to hear it run at all, so I waited till the next day to play with the fast idle problem. I had previously had the throttle cover/ kill switch opened up to inspect and clean up the kill switch and see if that made any difference to the .8 - 1.7 ohms on the other end of the black wire and I could never get a hard ground out of that kill switch, but I cleaned all the contacts inside and lubed up the throttle cable and cable housing while I was in there looking for something that could be causing the fast idle problem.
I remembered that I had put in a fresh left side crank seal and this could have changed the amount of air that was being ingested, so the carb settings were now looked at.
The manual says that the air bleed screw on the carb is the main thing that has to do with idle speed so I closed off most of the air bleed adjustment. This and a little tweak of the slide (down limit) screw seems to have cured the fast idle along with some lube of the throttle cable and careful re- assembly of the cable to twist grip fit.
So today it was idling well and I ran around the yard and grounds up and down some hills and put putted for about an hour. There were no leaks and it was fairly easy to re start, did not overheat even though it was about 90 degrees today and had plenty of low end grunt even with a 14 -56 combination on the chain drive.
p.s. When I first inspected the points I noticed that there was a white looking spot on both sides and some pitting. I suppose this could have been accelerated wear from the leak of the left crank seal. Some fuel/oil vapors from the crank side of the engine were leaking out under the magneto for sure. This was cleaned up with some 400 grit paper and some electrical contact cleaner.
So you are probably right about the points lasting for years - IF the crank seals are good.
I would be more tempted to get the timing spot on, but if it is running fine (excepting a few kick backs) and with the history of the .122 timing not working well at all, I think I might have to leave well enough alone for now.
