Two problems. Crank/Cam lead and lag & Dwell Meter kills right Cylinder

[thuban]

As a reminder, 77 XS with stock point Igy. 1300 miles since build.

I built up the bike using the points that were in the bike. They could have been the original set for all I know. They looked good so I used them. I saved the new set from Mike's for later.

I'm still having the engine die at idle every so often. Kick it and it will spit, another kick and it starts right back up. Other than that, it runs great. No flat spots off idle or anywhere. No popping in the exhaust on closed throttle de-cell. Plug burn looks great. I had set the points on .012 instead of .014. At .014, the point plate did not have enough rotation to get the static light to indicate F during static timing. ( I never used my Dwell Meter on it.) I figured everything would wear in and the plate would slowly center as timing adjustments were needed.
So, I replaced the points with the new set. I checked everything. ( noticed something new to me and I'll get to that) I set the gap to .014. Nope, still not enough rotation to get the timing to fall in. Reset the gap to .012 and had just enough rotation to get the marks dead on, static, for right cylinder. Left cylinder also fell in. It started and ran good. But I decided to use my dwell meter to get the gap dead on. ( this would be 23 to 24.5 degrees on the 8 cylinder scale) I put the meter lead on the left cylinder and it read 15 degrees, way off. I touched the lead to the right cylinder set of points and it killed the cylinder, every time!

As I was static timing, I was rotating the crank CW far enough to take the slack out of the timing chain before I went back to CCW movement and watching the light and "F" mark. That is when I happened to notice that there was a 10 minute angle of movement ( my ratchet handle) at the crank before the point cam started to move. I never noticed this before. I don't know if it's normal or not? If the timing chain was out of adjustment, I might understand but that was the first thing I did. The plunger just moves in and out ever so slightly, so I believe that's good. I went back and checked it again. It's good.

I have no idea why there is so much lead and lag between the crank and timing chain / point cam movement, but it let me identify a "problem" I was living with because I don't know the XS engine well enough. I would be cruising steady and close the throttle to coast and let the engine brake. If I opened the throttle easy, no problem, It would just smoothly pick back up. But If I just opened it, I would get a "bump". I could feel a delay between the time the throttle was applied and the time the engine picked up. Don't know how else to explain it but I believe the delay in pick-up is caused by the lead and lag I just described. The book says to "Anchor the advance weights securely". I didn't do that. Could that explain the lead and lag? ( BTW, the advance checked good from the point plate side with the points out, without taking the advance cover off.) Timing light shows the advance is working.

So,
#1. Why is the dwell meter killing the right cylinder when I try to connect it? ( Bad coil? Condenser?)

#2. Why the lead and lag? Even if I failed to hold the advance weights closed when static timing, that shouldn't make a difference in throttle application to engine response?

I put 52 miles on it and it ran like normal but now I do have a popping in the exhaust at idle. ( May be that the dwell/point gaps are off or what?)

What am I seeing?

 

[5twins]

I may have a couple answers, probably not all though. First of all, you should use the dwell meter on the 4 cylinder setting. You'll still be looking for the same numbers - 22°-24.5°. Now you would think on a two cylinder machine you would divide the actual dwell value in half, but probably because of the dual points, you have to divide it by 4. The dwell value for these is 93°± 5°, or 88° to 98°. Divided by 4 gives you the 22°-24.5° you need to be looking for on the meter if it's set on the 4 cylinder scale. Also, the dwell meter reading is inversely related to the size of the gap. In other words, a smaller reading indicates a larger gap. I try to get the gap as close to 22° as I can. This gives me the largest still in spec gap. Since points normally close up as they wear, I figure this will give me the longest service before they are out of spec.

I'm not sure why the dwell meter is killing the engine when you try to connect it to the right set of points. Maybe the wire on that set is installed wrong?

Maybe the lag has to do with the advance unit turning from the retard to full advance position? It shouldn't be doing that when turning slowly by hand unless maybe it needs servicing (lubing). Well, more correctly, what might need servicing is the advance rod where it passes through the bushings in the ends of the cam. They have to be kept greased.

 

[member28833]

So good information 5twins !

 

[member28833]

I don't have a dwell meter to use and now wish I did

 

[5twins]

It's the best way to set points and really the only accurate way to set used points.

 

[thuban]

5T said, I may have a couple answers...:
It seems like, with a new timing chain, the point plate should have fallen in the middle of the adjustment band, all things being equal. It never did. (The old T-chain may have been worn but I replaced link for link, so)
My dwell meter shows 4,6,and 8 scale. You don't have to switch it. Gap is .012 to .016. : I run out of plate adjustment on right cylinder at .014. I can get it to fall in on the timing mark at .012. I think I have too little dwell ( points too wide) messing with it, on the right cylinder, giving me a weak spark and the meter lead sucks what little juice there is, away from the plug killing the cylinder.

As far as the lead and lag, I'm stumped. The pins driving the point shaft may have a bit of play, but not enough to mention. If the cam shaft is turning, the point shaft has to turn. If the crank is turned, the cam/point shaft, has to follow. There may be a small lead and lag. That is why you make sure to turn the crank CW far enough to be able to take out the lag going back CCW when timing. That leaves me with a sloppy timing chain, which would cause the lead and lag. If the tensioner is adjusted correctly, and I can feel the pin working in and out just a bit, It's not bound up and I have to assume the tensioner is working, then I don't get it.

 

[GLJ]

As I was static timing, I was rotating the crank CW far enough to take the slack out of the timing chain before I went back to CCW movement and watching the light and "F" mark. That is when I happened to notice that there was a 10 minute angle of movement ( my ratchet handle) at the crank before the point cam started to move. I never noticed this before. I don't know if it's normal or not? If the timing chain was out of adjustment, I might understand but that was the first thing I did. The plunger just moves in and out ever so slightly, so I believe that's good. I went back and checked it again. It's good.

I think what you are seeing is normal. The chain adjuster just uses a spring to tension the chain. When the motor is running the slack is normally on the adjuster side of the engine. The reason the plunger moves in and out is from the valve springs pushing the cam CCW when a valve is closing. When you rotate the crank CW you are putting the slack on the opposite (front) side of the engine. Then when you go back CCW the crank has to turn a bit to take up the slack you caused on the front side. What you are seeing is the amount the chain has stretched. Normally it's not recommended to turn a engine backwards. If the cam chain has stretched too much it's possible to cause the chain to jump on the crank sprocket.
Is what you are seeing to much? I do not know. I will mention I just checked my XS2 and there is no movement of the crank before the cam moves doing what you did. The cam chain only has 600 miles.

 

[GLJ]

I should mention I'm running a Boyer ignition system so there is no mechanical advance on my engine.

 

[thuban]

GLJ, said, "The reason the plunger moves in and out is from the valve springs pushing the cam CCW when a valve is closing" Hummmm, I never considered that in relation to the tension rod pulsing in and out. I can see that puts strain on the chain at certain times. But there is no way to get this much movement unless it's built in. I'm betting it's not or the lead and lag of the throttle would be unsat for riding. I'm gona have to pull the covers off and check to see what the advance mech is doing when I rock the engine back and forth.
Mean while, I'm getting a handle on the point gaps. ("If you cannot not bring the firing point retarded enough with the points gap set at the .012" to .016" specification, due to a worn cam or a cheap after-market point set, ( Mike's) go back to step (7) and set the gap to .010" (10 thou.). At that gap you will probably be able to get the firing point to where it has to be, and the bike will still run just fine.") It does run fine, but that don't mean it's right. I'm measuring old point contact lengths now to see if there is a difference.
I don't know if dropping a wear strip off a guide would cause the lead and lag, even with the tension adjusted? I don't think that is the case. Engine is too quiet when running. Thanks for the input, GLJ!

PS. Mike's point cams SUCK! There rough as hell and the one I got and sent back had the pin slot milled to shallow. They took it back but had the e-mails flying back and forth to get it done.

 

[thuban]

Oh man, do I feel better! The lead and lag is the Advance unit "breathing." Other words, if your moving the crank the weights have to go all the way closed or all the way open before you see movement on the left side at the point cam. Like you said, GLJ, It's normal but it had me fooled, which is not that hard! "Bar Keep, gimmie a whisky and one for my bud, GLJ!" ( "GLJ, if you don't feel it, I'll have you another!")

 

[GLJ]

Oh man, do I feel better! The lead and lag is the Advance unit "breathing." Other words, if your moving the crank the weights have to go all the way closed or all the way open before you see movement on the left side at the point cam. Like you said, GLJ, It's normal but it had me fooled, which is not that hard! "Bar Keep, gimmie a whisky and one for my bud, GLJ!" ( "GLJ, if you don't feel it, I'll have you another!")

 

[thuban]

That's one problem solved. ( between rain showers) Now it's back to the point gap and why my point plate won't fall into the middle adjustment range when the point gap is set to .014. ( and I think I know why the dwell meter is killing the right cylinder. Weak spark due to point gap; also causing popping in the exhaust at idle.The honda had the dwell/point gap wrong and hooking up the dwell meter killed two cylinders, naturally, before I set the right dwell, then all was good. I have another new point set from K&S and am checking the length of the contact points. Does it make a difference? I don't know but something is not right.)
Cost me $40 bucks for a OEM point cam but it's worth it to have it for a spare, or to retro-fit the 81 engine.
Edit: Oh, forgot to mention, the lead lag in the throttle must be the slack in the drive chain? I check it regularly and never let it get to rubbing the rub block on the shift shaft but...may be what I'm feeling. ( Can't help it. I'm damn picky when it comes to mechanical crap. Must be the A/C back ground?)

 

[thuban]

OK, I measured several heights of point contacts. Average swings between .030 difference. That's twice the point setting, of middle of the road .014. gap. That could well run you out of point plate adjustment when rotating the point plate CCW to get the marks to fall in. So I guess the manufactures figure, "What's the big deal?" " The points are adjustable." Yeah, but there is only so much wiggle room of the plate adjustment slot. ( But Thu, black boxes are easy to get and use.) Uh huh, that's why Tiesco is stealing Dilithium Crystals from the U.S.S. Enterprise!

 

[TwoManyXS1Bs]

5twins clued me in on the "different" points...

http://www.xs650.com/threads/different-set-of-points.51146/

 

[thuban]

Outstanding, 2 many! Thanks. All my spare points and point plates are later ones.

 

[thuban]

5Twins said "Maybe the lag has to do with the advance unit turning from the retard to full advance position? It shouldn't be doing that when turning slowly by hand unless maybe it needs servicing (lubing). Well, more correctly, what might need servicing is the advance rod where it passes through the bushings in the ends of the cam. They have to be kept greased. "
Hit dog hollers first, 5T! Thanks muchly! I'll check the lube on the advance unit and rod. I have to readjust everything and maybe I can get the dwell to fall in on the right cylinder with out killing it.

 

[5twins]

The advance rod is one of the most sadly neglected parts on this bike. I can't fault people really because nowhere in any of the manuals is the need to service it mentioned. But it does need servicing, not often but still it needs it. Most have not been re-greased since they left the factory. The only mention of the rod is in the engine rebuild section of the shop manual. It tells you to use a grease containing moly.

There are 2 bushing in each end of the cam that the advance rod turns in. The inner one is a plain, solid bushing but the outer one has grooves in it's I.D. .....

Those grooves are there to hold grease and keep the advance rod lubed. Pack them full .....

This will last you quite some time, 5 or 6 years at least, maybe longer. Just be aware, like I said, that it does need doing occasionally. The grease the factory put in back in the '70s is long gone, lol.

 

[5twins]

Mike's used to sell good points, from the original Yamaha supplier, Daiichi, but I don't know what they sell now. It wouldn't surprise me if they sell the China ones now. If you watch eBay, you'll often run across these original Daiichi brand points for a good price, no more than the MikesXS offering and often less.

 

[thuban]

5T, I'll be watching. Yep, China stamped on the points. Yep, I filled the grooves with Moly B when I built it up. I checked it and re-lubed. I did get the timing to fall in. The right cylinder points were not giving the coil time to saturate. It had very weak spark and the lead from the dwell meter was killing it. No problem now! Dwell set on 22 on 4 cyl scale. It was the best middle of the road I could get. Starts good and runs good. I need to check the burn at the plugs.

 

[5twins]

22 on the 4 cyl. scale is ideal in my eyes, the perfect setting. Where the dwell meter really comes into it's own is for setting used points. The points develop pits as they wear and the spark jumps between those pits. There's no way to measure between the pits with a feeler gauge, the gap is actually bigger than what the feeler gauge indicates. But the dwell meter measures the gap electronically. Pits or no pits, it doesn't matter. A dwell meter is the only accurate way to set used points.