Running bad then good

[jjz28]

Well I know my carb has enough suction cause it started it without the cover and it moved the advance the full range. Also, I can move turn the 2 pickup coils at idle and it will idle up. Will it still idle up when you turn it by hand if the pickup wire is broke. If anyone knows please let me know, I have this apart right now working on it. Thanks.

[GLoweVA]

Also check the 2 bolts that hold the #2 carb boot to the head.
Once I had a hell of a time trying to sync my SG. One cylinder had no vacuum, turned out I had a vac leak because the bolt had backed out and the cylinder was sucking past the gasket/joint rather than thru the carb.

[jjz28]

George, it still runs really good. I can pull 100 quickly but I know it aint right. And I should notice a difference without the advance hooked up shouldn't I. Its almost like when it was right it was real zingy like a crotch rocket and now its more fluttery. Almost like too much fuel but not near as bad. Fluttery I don't mean up and down I mean quickly all the time but still revs very good just not as cleanly or crisp as when its right.

[GLoweVA]

Well I know my carb has enough suction cause it started it without the cover and it moved the advance the full range. Also, I can move turn the 2 pickup coils at idle and it will idle up. Will it still idle up when you turn it by hand if the pickup wire is broke. If anyone knows please let me know, I have this apart right now working on it. Thanks.

Okay, so the advance is advancing like it should.
The rev up at idle while you manually rotate the pickups is normal, thou it may still only be running on 2 instead of 4. At idle with no load, it's hard to see, but the head pipe spray test will show that 2 aren't firing.

Another check you can do is, with the bike off, unplug the TCI and put an ohm meter on the pick up coil wires there and you should see about 720ohm, then manually move the pick up coils thru the full advance and back a few time slowly and see if the meter moves at all. This may be difficult with a digital meter, that's why I say go slow so the meter and see a change in ohmage.

[GLoweVA]

George, it still runs really good. I can pull 100 quickly but I know it aint right. And I should notice a difference without the advance hooked up shouldn't I. Its almost like when it was right it was real zingy like a crotch rocket and now its more fluttery. Almost like too much fuel but not near as bad. Fluttery I don't mean up and down I mean quickly all the time but still revs very good just not as cleanly or crisp as when its right.

Okay, we may just be chasing a performance issue vice a 'running on all 4' issue.
Maybe a sync is what you really need.
Do you have access to any type of vacuum gauge?
Heck you can even make a tube type and use some heavy fluid like oil.
All you really need then is some clear tubing.

[GLoweVA]

Too much fuel you say..... That's about the same thing as saying 'not enough air' .... How about that air filter? haven't got the new one in yet?
Try running the bike for a short run without the filter. (Just don't ride thru any dust storms okay)

[jjz28]

I know It not running on 2 cylinders cause I have had that happen before. Unless maybe 1 or 2 aren't firing as strongly. Its just barely noticeable. I just don't understand why unconnecting the advance makes no difference while riding. It does idle up though when I move it. Also the suction coming out of the #2 nipple pulses. Is it supposed to be quick pulses or a steady pull. I will try the water and see what happens. I know all 4 are running but maybe not as strongly.

[jjz28]

Too much fuel you say..... That's about the same thing as saying 'not enough air' .... How about that air filter? haven't got the new one in yet?
Try running the bike for a short run without the filter. (Just don't ride thru any dust storms okay)

Man, I will feel like an idiot if that is the case. I am going to go try it. Let you know.

[jjz28]

Well, that wasn't it. I took off my plugs one by one and you can definitely tell a change with all of them. I just don't understand why I cant tell a difference without the vacuum advance hooked up. When I first got the bike I hooked it to the wrong nipple and it would barely move. If I hadn't hit that sweet spot the other day, I would never had known anything was wrong. It just ran so good. I thought it was the petcocks but even then it didn't run as good as it did that day. I think it used to run like that last year. I have the slip on Harley type mufflers and it growls, especially when it hits 3500 but when its running right, theres not as much grow. That is why I call it a flutter. Someone who has never ridden my bike would probably think there was nothing wrong with it. The only other thing I can think of is one of my needle (fuel) vavles that the float sets on isn't as springy. The spring is a lot weaker but they still sit at the same height and it closes off.

[jjz28]

Ok, so I went and took a video. I think it looks as if the vacuum advance is working properly? If it is, why can I not tell a difference if I unhook it and ride. If I twist it by hand it will idle up though (not the whole thing, just the pickup coils). So what do you guys think?

[GLoweVA]

Watched the video and that's exactly what mine looks like at idle and reving.
SO I think that your vac advance is good.
I was looking thru the manual and there's a check to see if the mechanical advance is functioning, but it requires a timing light to see it.
Basically, you disconnect the vac line, rev the bike to 5,200rpm and it should be at 31deg. (36 for the standard)
You can test the vac advance too, but like I said it looks good to me.
That test is at 150mmHg (5.9 inHg) vacuum the plate should rotate it's max travel. (about 15deg)

Have you ever taken a look behind the pickup coils and seen what condition the mechanical advance is? It may be rusty/dirty/sticky.

Another thought is that you may have some obstruction in one of your pipe/muffler. Maybe some rust broke free from a header and is clogging up one of your baffles.

[jjz28]

So, George, there is a mechanical advance behind those pickup coils? I know nothing about this part of the bike. I do know that the little timing plate is warped a little. So, if I take that off to check behind is there anything that will fly apart on me? If its maybe the bolt bent instead of the little plate, could that do it? I'll also check those slip on mufflers. Thanks.

[DGXSER]

Hey Jeff, yes, the mechanical advance lives behind the plate the pickup coils are mounted on. So when you see the pick up coils move, that's the mech advance in action. Also, the mechanical advance works off of centrifugal force. Meaning, that as RPMs go up, those weights get thrown out and move the assembly changing the timing. Kind of like spinning a nut on the end of a string.

Now the vac advance is also attached to the same plate and moves it just the same. In fact you can see in your video the arm off the vacuum advance. So, it will be hard to see specifically if the vacuum is moving the timing or the weights. I would think that is why they tell you to remove the vac advance for timing the engine. Additionally, vacuum is not strictly RPM driven it is also load driven. I am not 100% certain if it is as drastic at the vacuum nipple for the advance as it is at the carb slides, but here are a couple videos TC put together some time ago that demonstrate the change in vacuum at the slides with and without load on the engine.

Carb Slides NO Load

Carb Slides WITH Load

[IanDMacDonald]

You say your timing plate is warped, but is it really? Is there a possibility that your mechanical advance fell out of its slot, and it gives the impression that the timing plate wobbles.

[TopCatGr58]

Hey Ian,

I think "we" may be confusing the "plates". The outer timing plate which has the degrees and timing marks etched into it just sits and spins on the end of the shaft. The actual PU coil plate that houses the pu coils and that the vac. adv. is also attached to is the one that of course rotates a bit with the advance of timing...but it's nice and flat. It's his outer timing mark plate that has gotten a little bent, and so it wobbles just because it's not exactly flat, but aside from that it doesn't affect anything else.

Now, Jeff, the Vac. Adv. does not contribute to "performance" feeling unlike on a car. Our vac. adv. kicks in mostly under varying loads...usually low which causes more vac. to occur because the throttle butterfly is close to closed=leaner...and so increased timing helps in fuel economy only. When you crack the throttle open, vac. drops...the vac. adv. unit RELEASES the vac. adv. so that the timing plate rotates back/retards to the more powerful level of timing adv. ~35 degrees max....vs. the ~50 degrees it was at when just cruising. This is why you didn't notice any performance feel difference with the vac. adv. disconnected.

Before you go tearing into/behind the pu coil plate...you should get a timing light and just check to see IF the timing plate is advancing to the ~35 degrees mark at the ~5k rpm point. If so...then it's working properly. And you can watch it as you slowly increase and decrease the rpm and see if the timing smoothly increases or decreases to and from the ~35 degree mark, or if it sort of jumps from lets say...10 degrees quickly to 35 or such which then might indicate that it's hanging up or intermittently sticking. IF so..then it would warrant the tear down and cleaning/regreasing/lubing of the parts. Regrettably, you can squirt lube behind the plate without taking it off.

T.C.