Help with my VERY puzzling ignition problem

[350GUY]

these problems are exactly why none of my 15 bikes have points except 2. and thats going to change on both of them eventually .  but I hear where you're coming from. what's charging voltage at 2k?

Dang! 15 bikes! Are they all 2 stroke Yammies?

I second that! Your RD would thank you immensely. Once converted to CDI ignition, your engine will run cooler and smoother. CB points if not timed properly, quality of the points, wear of cam etc. are many factors that aid in timing not being optimum and with age they worsen, with symptoms of improper combustion and heat build up etc.....Also, if you have a spare carb, try swapping out the left carb to narrow down the issue.

[RD350NL]

Dave

Not to be rude but let my suggestion sink in. Points are outdated technology plus the mechanics/electrics are 50y+ already. They fail and are hard to get back to original condition without spending a fortune and you still end up with suboptimal performance and reliability.

I know its not what you want to hear but if you want to enjoy these bikes without too many worries it is the best option.

Been there done that, after many hours and replacing almost the entire system I chickened out and bought an electronic ignition. Best decision ever and I put it in all my bikes once the points ignition develops issues.

Its not only the points, the charging system is also 50+ y old and bound to fail next, then you can open the next topic wondering why its not charging.

[m in sc]

guys, he wants to stick with points. they do work well when set up right. that being said, the structure around it is old, wires do break down and IMHO the issues here become charging voltage and or wire (like in the harness) condition. My 67 C2tr and the LS2 are still on points and both run fine.

I will say the biggest issue w points these days is the quality of the replacements, the heels are almost always too long and need to be filed down so that the gap and timing can eb set within the range of the plate.

[Striker1423]

I bet you have a corroded wire that's resistance is too high.

[RDDave]

Have you read any of my posts? I have removed the ignition system from the bike's wiring harness and jumpered it directly to the battery and points.

How much is a new electronic ignition? It is sheer hypocrisy to say that someone must 'spend a fortune' to maintain an original ignition system when compared to the cost of a new system. Besides, I see more than a few posts here asking for help with their new system. They are NOT perfect. They are often better when right, but are not for me. Not until and unless they come down significantly in price. THAT is my biggest knock on them.

Back on topic; Yesterday, I did the following:

I swapped a different carb on the left.
I again switched the coils and their wires side to side.
Installed new plugs.
Swapped points side to side again.
Changed condensers again.
Wired the left coil directly to the battery removing even the relay. The battery has 12.4v.
Wired the coil directly to the points.
Completely disconnected the ignition from the bike's wiring.
I removed, cleaned, inspected and tested the stator assembly and cleaned and tested the rotor assembly. But haven't reinstalled the stator yet.

I think the left is hitting at idle because I feel good warm pressure out the exhaust, but it basically quits as soon as I twist the throttle. The flash from the timing light is a bit weird at throttle and has an occasional bright flash which corresponds to when the left cylinder hits. But it's just a hit now and then.

I am going to test and adjust the regulator today. As I have said; I have a lot of spare parts and parts bikes as well so I have lots of alternatives.

By going into the charging system this deep, I feel like I am getting into the weeds a bit. If the charging system was the fault, why does the right cylinder ALWAYS run fine while the left will not even with the parts from the right. That is the most confusing part of this for me.

Frankly, I have never had much trouble from the ignitions on my Yamahas. Most certainly NOTHING like this. And to be honest, if it weren't for the cost, I would consider a new electronic ignition. But for now, I really, really want to get to the source of this issue. This is not just about getting the bike running right.

I would have someone else look at this thing at this point to see if I am overlooking something, but there is no one anywhere around here to turn to. So, I am on here. Thank Goodness for this resource. I don't know what I would do without it.

Thank you for the helpful suggestions. And please keep them coming. Because I am nearing a complete impasse.

[1976RD400C]

Gas tank interfering with something on the left side when you put it back on? Crank bearings ok letting the points cam spin true and not wiggle?

[m in sc]

there's a lot to read thru to be honest, i didnt catch you had bypassed the points to coul wire.
You never gave what the charging voltage is  either. its fairly well documented that w low voltage,  one cyl will drop before the other.  its common tbh. the cdis work well and they replace the charging system completely.  so its 2 birds w one stone. its a hard pill money wise to swallow, thats for sure. but, it is what it is. that being said, points absolutely should work just fine when everything else is in good order.  check the health of the charging system 1st. then go from there.

[RD350NL]

If you really want to stick with points you will have to work through this systematically.

Meaning: Make a proper diagnoses before swapping parts.

1. Did it run right before? Y/N
If yes: What changed that caused this behaviour? Perhaps you did some work to the bike and damaged something in the process. If it appeared all of a sudden while the bike always ran fine it's probably due to wear or a faulty part.

2. Check basics first: Compression (you say is OK), check spark: (you are not sure), check air/fuel delivery (you say it's OK), check charging system (you didnt check yet)

If you can eliminate the standard suspects you end up with the culprit.

Unfortunately, as mentioned before, diagnosing these old ignitions can be a real pain. There are many things that can cause your symptons.

- bad spark plugs
- bad spark plug wires
- bad spark plug caps
- bad coils
- bad condensator
- bad points
- bad point vilts
- uneven cam on camshaft/unbalance, but this doesnt happen all of a sudden
- flywheel damage
- rectifier/regulator faulty
- generator faulty
- battery faulty
- bad wiring in/to all of the above
- bad timing

You claim its always the left cylinder and the problem doesnt move to the other cylinder despite swapping points, coils, etc. This makes me believe it's either an ignition wiring problem to the left cylinder or a mechanical problem (cam on crankshaft uneven). As mentioned before, the latter will not happen all of a sudden.

Check your wiring from the point all the way to the ignition coil on the left cyliner, wiggle it a bit while measuring and see if you lose continuity.

[RDryan]

Gas tank interfering with something on the left side when you put it back on? Crank bearings ok letting the points cam spin true and not wiggle?

I have nothing to add here except that when I first started tuning  my RD as I was learning and a steep curve at that I believe looking back on it I know I couldn't trust the stock ignition in regards to the points staying put. I repeatedly checked the gap and it was off after running the bike. Thought the new points were installed and fastened correctly. Who knows but maybe it had something to do with what you suggest,crank not running true. That and other things pointed out like no one of higher knowledge to help locally + making good money at the time, I took the hit and got the Vape and a Vito's crank. All that said I lucked out with the help of all of you on this site...Vape install for dummies like me, couldn't of done it without this board because I still had issues. And well after the Vape install I still had to revise/clean up the wire harness, a simple short behind the headlight bucket prompted that as well as the flasher relay burning out. However I get the OP's intent and really he's right. It's just hard when you are on your own.

Interesting thread, I'm staying tuned to learn even though I may never touch upon this issue knock on wood.

[SoCal250]

there's a lot to read thru to be honest, i didnt catch you had bypassed the points to coul wire.
You never gave what the charging voltage is  either. its fairly well documented that w low voltage,  one cyl will drop before the other.  its common tbh. the cdis work well and they replace the charging system completely.  so its 2 birds w one stone. its a hard pill money wise to swallow, thats for sure. but, it is what it is. that being said, points absolutely should work just fine when everything else is in good order.  check the health of the charging system 1st. then go from there.

This ^
Also, if you have a spare good battery, swap it out. Or see if running it while on a charger changes anything.

[RDDave]

Well, well, well................

First off....I  would like to thank almost all who offered the help that I asked for...........THANK YOU!

Second....it wasn't the ignition at all. Which in one way reinforces what I have said all along; the stock ignition for a near stock RD is fine for a driver. In the hands of someone who knows what they are doing, the stock points ignition was good in 1975 and is fine in 2025, just like carburetors on 70s era engines.

Now..................the issue was a sucked reed.

How it had the affect on the timing light that it did is beyond me, but there it is.

I had exhausted ALL efforts to have any impact on the ignition of the left cylinder. EVERYTHING checked good. EVERYTHING. I will spare you the list. Nobody reads it anyway.

So, I was going to tear down that left side in desperation and when I pulled the reed block, out fell a reed set. Someone had changed to fiber reeds probably a long ago and one had failed and had partially blocked the intake tract.

Live and learn. I feel a little sheepish.

So, one more question if you'll allow me; I have plenty of the stock metal reeds and have one in that left cylinder which runs good NOW. Should I just put the metal reeds in both sides.......or is there enough advantage to going with the pricey fiber V Force or fiber replacement reeds. This engine is stock except for Bassani chambers. How much (if any) difference will either of the fiber reeds make and bottom line; are they worth the hundred or so dollars for this basically stock bike?

Thanks once again for the assistance.

.

[SoCal250]

Congrats   Odd root cause, but OK   Glad you got it sorted out!

Regarding your question on reeds, I would replace them all at the same time unless you know that brand of the ones in there now. Of course, replacing just one will bring up the question; "when will the others fail?" Also, by replacing just one you may end up with a performance difference between the new one and the older 3 pieces, especially if it's not the same brand and type.  An upgrade over stock metal OE would be OE Yamaha YZ "55Y" reeds with one petal trimmed off. Or you could do TDR fiber reeds.

EDIT: In my notes I found the following comments that I saved from 2T guru Ed Erlenbach:

Stock/Unmodified Reedcage
Even on stock bikes I recommend replacing the factory steel reeds with fiber reeds. With the money you spend when you have to rebuild one of these engines to me worrying if one of those steel petals is going to break off and ruin my engine just isn't even worth it.
So there's "basically" three options:
-Some guys like using YZ125 petals part # 55Y-13613-00-00 because the reedcage they come off of is a 6 petal cage, they come as three individual petal joined at the bottom, so you buy 4 of these and cut one petal off of each reed.
- I like to use YZ85 reed petals part # 4ES-13613-00-00 they are a single petal so you buy 4, they bolt right on but you do have to trim the front edges to narrow them just a bit at the front easy peasy.
-Here in the US, TDR makes a racing petal for the RD's, they are a single petal reed that bolt right on but are a little thicker than stock YZ85 or YZ125 petals so they bias topend performance a bit.
(There are of course other brands and materials but these are 3 great options)

[m in sc]

thats weird. let time i had a reed issue it ran well up top but showed its ass down low. thats super weird but glad you found it. I'd second the yz reeds. i'll be honest,  I was never a fan of  old school fiberglass reeds and would rather run stockers given the choice. but the yz reeds are a solid option as well.

[RDDave]

Weird is the word. I have never has a reed break and act that way either. And it impacted the way the timing light acted. Weird again.

So let me ask this again; how much (if any) noticeable difference in my near stock bike would a hundred dollar's worth of fiber reeds make? I have to change the other one back to metal at this point anyway (or both with a change to new fibers) so this is a 'bang for the buck' question.

And just as an FYI; I have personally NEVER broken a metal reed in any of the bikes I have owned and nearly all have had the original metal reeds. So, one breaking like this fiber one did is not a real concern to me. Should it be?

[Striker1423]

Well, it doesn't sound implausible that if the reed breaks the seal for any reason, that the fuel/oil/air mix simply slows or stops moving for that split second. That would change the amount of fuel that goes kaboom in the boombox, and thus change the burn rate. Burn rate changes, timing appears off, because the engine is running out of sync? Though, the light reads the spark signal, so that leads you back to some other ignition fault. Meh.

Fiberglass reeds, being lighter change the opening, dwell, and closing speed of the reed petal as compared to stock ones. The theory being, the faster you get the fuel in, and reed shut, the more efficient the port timing is. Does it make a difference? Only if you are asking for performance along with most other engine mods.

But, I don't really see the point since I can't reed, metal/fiberglass.