M model dual points (which one does what?)

[toddyboy]

Just wanted to verify something: My M model bike has TWO sets of points. The left side points have a red and black wire going to them. The right set of points, which are more recessed in the housing, have a black wire connected to them. 

My understanding has always been that the LEFT side points are the  "A" points and do the business to crack a spark that spins that exotic rotor thingy round in its chamber thus making the engine run. The RIGHT side points are the "B" points and kick in on the overrun to burn excess fuel.

I've always timed the bike using the LEFT side "A" points. I set the timing to 8.5 BTDC.

As for the "B" points, I just clean them up, set the gap and leave 'em alone. It was only today that I thought I'd check as I was curious when they make the plug spark (never done this before). I noticed that these points open at 12 degrees BTDC. It's just an observation cos there doesn't seem to be anything I can do about that even if I wanted to.

I was just asking because I wanted to be sure I'm using the correct set of points to set the timing. As I mentioned previously, I've always set the timing using the LEFT set of points that have the Red and Black wire connected to them

That is correct isn't it?

(Note: The bike starts well, pulls like a steam train and runs pretty good but I wuz just wondering ) 

[wayne]

I have a genuine RE5 parts catalogue. On page 26 the points are shown incorrectly. The book shows the right side labelled #3 and in the description says "POINT, contact (B)". That's not right, arse about.

The Right side points, the deeply recessed ones, are the A points and do the business of a normal set of points. The left side points are the B points and if connected, only fire the rotor every second face on overrun. You can tell which is which by simply looking into the the points housing and rotating the engine by pushing down on the kickstart lever (hey, if I can do it...). You'll see the deeply recessed one on the right opens twice as many times as the one on the left. IE the right side are your "driving" points, the A set.

I'm wondering if you've got the point setting procedure correct? When you go into the points housing, you're only doing one thing, setting the gaps on both sets of points. That's it.

To set the timing, you're not touching the points or point plates at all. You set the timing by rotating the entire point housing and that times both A and B points together.

EDIT: Fast forward 3 mins into this video to see Jess talk about ignition timing.



Subject for another time, the purpose of the B points is, sort of, to burn excess fuel but not what you think. With the B points disconnected, the A points burn off twice as much fuel on overrun as the B points did. The B points can only be considered as burning off excess fuel when compared to having NO IGNITION on overrun which was never used on production RE5's but has been used on some rotary engines. B points connected, you'll have a dirtier engine than with them disconnected.

[toddyboy]

Ok, if that's the case then I've set the timing using the B points, not the A points & I've set them to fire at 8.5 BTDC.

The A points (the right side ones which are recessed further into the housing) are opening at 12 degrees BTDC.

That would explain why the housing has to be turned pretty much all the way to the left to set the timing - because I'm timing the engine using the wrong set of points I guess!

Therefore, if I now do it correctly and advance the timing from its current setting by setting and set the the right side "A" points to open at 8.5 BTDC, then the actual B points (the left side ones) should open at 4 degrees BTDC.

The rotor is currently showing 120 psi compression (using a standard compression tester, not a 3 phase Suzuki one) The carb and all jets have been thoroughly cleaned and it's been correctly calibrated and to be honest, it's running pretty good at the moment but it still won't pass the "blip the throttle open in first gear" test. It still stutters like a mo fo when I do that, so it'll be interesting to see if this little tweak on the ignition timing makes any difference.

[wayne]

Sounds like you've got a good engine. Do it by the book would be my suggestion. Open up the points case and ignore everything else, set both A and B point gap the same (0.45mm +/- 0.05), grease the cams if required. It's a "heads up" to me if my case is rotated to some extreme, my gaps probably need attention.

Now do ignition timing. Ignore whether you're doing A or B, if you do it by the book you'll have set the point gap correctly and now all you're doing is the timing by rotating the casing. That'll set both points to where they should be.

I'd love to tell you it'll help your hesitation but the awful truth, in my experience, is it'll do zip to that. They are very forgiving of timing and you've got to be way out before they make a difference (I rode one set at TDC and the only obvious difference was it wouldn't go over 140 kph).

Those claims I've seen: "I fixed my hesitation by setting my timing......." Fantasy I'm afraid. Having themselves on.

[toddyboy]

Well, I timed the "A" points (the right side recessed ones) to open at 8 degrees BTDC. The left side "B" points (which are supposedly the ones that burn off excess fuel on the overrun) now open at 4 degrees BTDC. Haven't tested it on the road yet but will report on what I find.

Ok - so there WAS a difference. The tickover is more regular and it'll idle at 1200 rpm nicely. On the first 5 mile ride the power on full throttle was up. I gave it a real thrash and it felt like it had a few more horses in there. The ride below 4 thou was smoother and the low revs overrun less jerky. The hesitation had reduced to a "grumble" rather than a snatch. Stopped for a coffee and after several conversations with various people who were extremely interested in the bike I set off again. This time it had reverted a bit, but just a bit. Overall though an improvement.   

[wayne]

Good to hear but within your report is something I've said in many conversations and some recent emails.

When you're trying to sort an RE5, they can run so well up to the coffee shop and be a different bike on the way home. Or vice versa. It can make it very hard to discern what a particular tweak did or didn't do and can make it easy to jump to conclusions.

Glad that overall, it's running better. But please, just forget those B points when tuning. Gap them and forget them.

Also, if you're experiencing noticeable jerkiness on overrun, I do wonder if you're B points are working at all. It's very possible they're not due to a component failure (later model vacuum switch is suspect) or disconnection somewhere along the convoluted trail that makes them work. There's a simple electrical test in the manual that'll tell you.

[toddyboy]

There's definitely still jerkiness on overrun at low speeds. Its really the only irksome thing about the bike as far as I'm concerned and makes riding behind slow cars in town annoying. The overrun jerkiness dissipated (not completely) when I cleaned and re-set the points the other day, then it came back again after the bike had sat for thirty minutes during a coffee break at a cafe, but not quite as bad.

My bike has a black plastic vacuum switch that had a broken spigot when I got it. I fixed that and checked the diaphragm inside it when rebuilding the bike and all seemed ok, though ya never know it could be faulty electrical wise. I remember seeing in the manual that you have to mess about with the angle of the switch until it works? Never figuired out what that meant exactly. The diagram in the manual shows a different looking vacuum switch to the plastic one like I have on my bike. 

This secondary points issue is something I've never really bothered with until I found out the other day that I'd been setting the timing with the wrong set of points! Maybe I should just cap off the spigot on top of the manifold and be done with it.

In essence, all I'm attempting to do is get the bike to run smooth in low speed traffic. It's smooth as silk at low revs so long as you're just on the throttle. The second I let the throttle off it chugs. That's the only bugbear I have with it to be honest. I can live with a snatch or a shudder here and there as I open her up and for sure, once I really twist that throttle back and get on the twisties I have no complaints whatsoever.

[timpa136]

Aug 25, 2020 9:56:25 GMT -5 toddyboy said:

There's definitely still jerkiness on overrun at low speeds. Its really the only irksome thing about the bike as far as I'm concerned and makes riding behind slow cars in town annoying. The overrun jerkiness dissipated (not completely) when I cleaned and re-set the points the other day, then it came back again after the bike had sat for thirty minutes during a coffee break at a cafe, but not quite as bad.

My bike has a black plastic vacuum switch that had a broken spigot when I got it. I fixed that and checked the diaphragm inside it when rebuilding the bike and all seemed ok, though ya never know it could be faulty electrical wise. I remember seeing in the manual that you have to mess about with the angle of the switch until it works? Never figuired out what that meant exactly. The diagram in the manual shows a different looking vacuum switch to the plastic one like I have on my bike. 

This secondary points issue is something I've never really bothered with until I found out the other day that I'd been setting the timing with the wrong set of points! Maybe I should just cap off the spigot on top of the manifold and be done with it.

In essence, all I'm attempting to do is get the bike to run smooth in low speed traffic. It's smooth as silk at low revs so long as you're just on the throttle. The second I let the throttle off it chugs. That's the only bugbear I have with it to be honest. I can live with a snatch or a shudder here and there as I open her up and for sure, once I really twist that throttle back and get on the twisties I have no complaints whatsoever.

You said the plastic vacuum switch, that is a problem. It is not adjustable per the early shop manual. The switch is the reason Suzuki recommended to dis able the decell points.The switch is Not OK. 

[toddyboy]

Fair enough. In that case I'll disconnect the thin tube from the manifold that connects to the switch, cap off the manifold spigot and see if that makes any difference.

The only thing with doing that though is, if the switch is U/S anyway, disconnecting it isn't going to change anything - is it? 

Q: Does that small spigot on top of the manifold blow or suck?

[timpa136]

disconnecting it isn't going to change anything - is it?

The switch you have was inconsistent back in 1975 so it would not operate any better these years later. I would suggest trace back the wire and connector from the single lobe points in the housing to under the tank and disconnect and tape up the end. Plug the vacuum hose to prevent a leak is suggested.

[wayne]

The earlier vacuum switch is a metal bell housing like the bell housing on top of the carb. This switch is much more robust than the rubbish plastic one. You should be able to pick one up second hand.

If your only bugbear with the bike is jerkiness on overrun, then you should get your B points working. They smooth it out considerably below 3000 rpm. That's what they do and give you a small amount of extra engine braking. Forget this "burn off excess fuel". While they do that, it's not what the whole B point system is actually about.

I don't routinely recommend the reconnection of the B points, but due to your specific requirements, I suggest you get them working. They make the bike so much nicer around suburban streets specifically because they reduce that jerkiness.

Here's a clear demonstration of the what the B points do. Make sure you have the sound on. The bike in this video is fitted with a toggle switch which can enable and disable the B points on the fly:

[toddyboy]

Ok, I took off the small vacuum tube and plugged the spigot. I left everything else in place (switch, tube, wiring etc.) Bear in mind that the bike had been running as good as it had ever done before I did this.

I wasn't expecting any improvements and I didn't get any, rather the reverse. It ran ok for about 4 miles till it had warmed up. I opened her up and ran it up to the redline a couple of times. It then started holding back, then it just downright wouldn't rev past 4 thou, then it started chugging, misfiring and eventually cut out on me in the middle of the road. It's never done that before, ever.

I pulled over in a layby and quickly removed the plug I'd fitted over the spigot on top of the inlet manifold and replaced the thin tube that feeds the switch - no difference. I barely got the bike home. It tried to die on me twice when I attempted to get it past 4 thou and I limped back by keeping it below 3.5 thou rpm. WTF! All I did was remove the thin vacuum tube, plug the manifold spigot and when it started playing up out on the road I then removed that plug and replaced the small tube again, which put it back to exactly the same state as when it was running fine two days ago, only now its erratic as hell.

Back in my garage I pulled the plug out. It was black and sooty. I replaced the plug (R1 plug with adapter) and took her out again - no difference. It felt like either fuel starvation or the advance retard mechanism wasn't functioning, i.e. rideable at low revs but open her up and she wouldn't go. 

I then opened up the points housing and checked the advance retard mechanism and it DID look like the weights were sticking on thier spindles a bit. I've since freed them up by squirting a little Plus gas on the pivots and they seem to be moving freely now.

Fingers crossed, it'll be ok now.

Q: theres a little bit of lateral play on the points cam. I can push it in and pull it out approx 1.5mm. Is that correct or should there be no play at all? It's always been there since I've had the bike so it's not a new thing. 

[wayne]

Checked one of my bikes that. There is lateral play in the camshaft, probably a bit more than yours. Runs perfectly, only 26,000 miles.

Re your problem, very hard to say what's going on when one is not part of the work, so many variables. Re advance, easy to check with a strobe light. As noted I rode one timed at TDC and it wouldn't go over about 5,000 rpm under load so your problem, to me, doesn't sound like lack of advance if your stalling at 4000 rpm and with timing set at ~8 BTDC.

I can tell you categorically that disabling or enabling the B system will have nothing to do with your symptoms. If you saw that video and read my notes, you'll know I can switch them on and off on the fly. Doesn't affect normal running in any way. Enabling the B points just disables the A points on overrun above 1,700 rpm. That's all they do to the "normal" bike systems.

Contact Roger or Stuart. Nothing like their expertise and they'll be able to actually see the bike.