Greetings!

I am just starting this thread to document and share as my friend Bill and I get his RT1 up to snuff. i'll get a a photo uploaded soon.
last year i dug it out of his shop to get it rehabbed and maybe turned into an ice-race bike for the 2019 winter. never really materialized, but he kinda got the bug and adopted it as his project to rebuild it, so he could have a dirt ride (i got a 2003 KTM that fall and needed a riding partner)

with a few hours of futzing around on it, we got it firing and running, but it wasn't great by any means. I rode it around the neighborhood a bit, but without any 2 stroke experience for basis of comparison, i couldnt make any assessments. he said i had be careful or it would wheelie and flip me over. couldnt even get the wheel off the ground, and i tried.

anyways, fast forward, he rebuilt the bike because that's what we do for fun. tore it all apart, new seals, rebuilt the oil injection system, new points with set gap, new airbox to carb snorkel, new air filter, rebuilt carb w a kit, new fuel/oil hoses, lined the gas tank with POR-15, new tires, new paint, new control cables, some other stuff which i will share once we get back to the project. after putting it all back together, it's been difficult to start and keep running. weird intermittent symptoms. we suspect ignition. kick kick kick kick kick kick no fire. swap the plug wire to the spare plug... fires.. run it down the street... dies.... push it back.... kick kick kick kick kick nothing.... just one example of a head scratcher moment.

we pulled the flywheel off and were looking at the mag and those windings, and the simplicity of the system is having us scratch our heads. electrical is my forte, but all my experience is with later 4-stroke, stator-type bikes that run on DC for the most part.

he was really considering putting a $400 electronic ignition on the bike to just "fix it", but obviously thats very expensive and in my opinion, very unnecessary.

we kinda shelved the project as nicer weather rolled around, but as the temperature begins to drop again up here, we're looking at our small collection of project bikes and the proverbial gears are turning. we will jump back into this soon, and when we get re-oriented to where we left off, i will likely be back with some questions.

thanks for reading. look forward to sharing this hopefully short journey to get the bike ripping!

The old points magneto is pretty reliable. Condenser is most likely to cause strange issues in my experience.

One thing you said is "gapped the points". On your bike you set the timing by adjusting the point gap. Then you can check to see if the max gap is within the specified range... but you don't adjust the gap as an adjustment.

thanks, and good to confirm that mag system ought to be ok. it was sparking somewhat reliably (at times LOL)

re:gapping points - interesting. i'm 2 stroke uninitiated. Bill has done almost all of the wrench turning on this one. i do remember him saying that they are new points. i did assist him, though, when we were setting the timing (or so we thought). it was similar to my experience with 70's 4 stroke honda CBs and such, except without the convenience of an "FT" mark on the flywheel...

so using the factory service manual, we had a dial gauge set up, zero'd out when the piston was TDC. i'm pulling the spec from my memory, but we had to set the piston to it's fire mark, like 4.2mm BTDC, and then rotate a points plate so the points were just opening. using a multimeter or a test light, i remember it being a PITA to figure out where to meter for continuity breakage, because the 2 sides of the points were still in contact via the magneto coil. i disconnected and reconnected some wires in my head scratching and "wait this can't be right" mode of troubleshooting, but i am like 90% confident that the way i left it was the way i found it. i remember the manual's language being slightly "wait, let me reread that again", in addition to there not being a complete wiring diagram, only separate ones for the lighting circuit and ignition circuit.


it seems like my understanding of 2 stroke ignition timing isn't up to snuff. the max points gap indicates spark timing?

Love the RT1's & regret selling my cylinder which fitted RT2 & RT3. Anyway--my memory says 2.9 BTDC for all the 360's. 4.2 btdc & you'll break a leg--& the kick start gears. Base plate is fixed so just set it at 2.9 & release the points screw then let them settle together & tighten. In theory they should crack open at that point, but of course things move so it's a trial & error game until tightening lets them open 'then'. NOW--one thing i totally forgot 'is' one model 'i had'--had an advance mechanism built into the flywheel. If that's the case, which you'll see as the arm is visible in the slots, then forget what i said & will need to lock the arm open against spring pressure & still go for 2.9 btdc. As MarkT said above, the mags are pretty reliable.

4.2mm BTDC doesn't sound right (I think it's around 2.9mm) but the process of just getting the points to open with piston there is correct.

One important thing is the advance mechanism in the flywheel needs to be locked at full advance when setting the timing... I'm not that great on the details on the larger bore bikes but pretty sure RT1 had the advance mechanism.

Some models have slotted stator plates but you should not rotate the stator to adjust timing. Keep that at the factory location which is usually the screws about centered in the slots.

What you do is adjust the point gap so that the points just open at the correct time.

Then you can check the maximum points opening to make sure it is within the range given in the manual. Something like 0.012" to 0.016". If the maximum gap is not in the correct range, then someone could have rotated the stator plate to one extreme or the other, you forgot to wedge the advance open, or the points are worn out and need replacing. If you never touch the stator rotation, it's the points.

(Hint: often you can tell where the stator was tightened at the factory by the marks the screws leave on the stator plate... as long as someone hasn't messed with it too much.)

There are a couple more reasons you don't rotate the stator plate... One is that the relationship between the magnets in the flywheel and the charge coils at the time the points open is somewhat critical. System is designed so primary voltage generated by spinning magnets in is at or just before peak when points open. This gets you the best spark... it's actually possible on some magnetos to get the magnet to stator coil far enough out of "time" that you lose spark completely

Another is when you have the head off with your dial indicator all set up and are watching the piston go down to the right amount BTDC, it's actually fairly easy to either forget to wedge the advance mechanism open or to turn the flywheel CCW instead of CW... if you make mistakes like that it might be impossible to adjust the point gap to set the timing... If you accidentally rotated flywheel CCW you'd be ATDC (way retarded) and it would be impossible without rotating the stator.

So leave the stator where it was from the factory or pretty much centered in the slots if you don't know.

yes, cool. im sure your spec is right @ 2.9...
it does in fact have the advancer mechanism, which made it at least a 3 handed job. i recall this now.

great information, will be very happy to have it all as reference material once we get back to it.
i don't believe we rotated the stator plate, and i presume that adjustments were in fact made on the points arm.

are you using an ohmmeter clipped to either side of the points to verify contact opening?

I believe the way you described setting the timing is the correct way. I've had good luck simply using a feeler gauge with a super thin gauge of .001 or .002 and my naked eye to see precisely when the points begin to open. You have the points and timing set correctly on the RT1 when you are at that point and see 3.4 mm BTDC on your dial gauge. No need to disconnect any wires that way. Also, Yamaha built an extra black wire into the wire loom leaving the magneto for checking timing with a meter. That wire is probably poking out of the loom around a third of the way up the loom from the magneto. The end has a female connector and is usually partially taped over in the loom with just the connector visible. It'll be there unless someone hacked it off. It is on all of my RTs and the so!e purpose was diagnosing when points open. Check it out. But the feeler gauge and sharp eye method works too.

Here's a crummy drawing showing the AC voltage sine wave generated in the stator coil by the spinning magnets. "PO" means "points open". Which is designed to happen just before or at peak voltage. If you start rotating the stator plate and messing with points you can have the points open when the voltage is low or dropping and the spark will suffer... and obviously if points open when voltage is zero you'd have no spark.




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One more tip is when you have the head off and the piston at the correct distance BTDC, there should be a little tab under one of the stator coil screws and a faint chisel mark in one of the flywheel windows.

The tabs are often bent up but you can tweak it back to line up with the mark on the flywheel and use it as a "quick and dirty" way to verify timing. Dial indicator with head off is always best.

If using an ohmmeter, I find an Analog meter (swinging needle) with an Rx1 scale works best. Points closed should be 0 ohms and points open are like 1 to 2 ohms. I don't use the jumper wire (just my habit), I disconnect the black stator wire at the ignition coil and connect one meter lead to it and the other meter lead to ground.

Just another FYI....my manual calls for 3.4 mm BTDC for the RT1. That's what I've got mine set at. I believe it was MarkT that posted a Yamaha service bulletin in another post that stated it you experience surging and bucking try reducing to 2.9 mm.