Diagnosing a weird issue

[jimbyjimb]

It's amazing how much power these old bikes have when they're running on all 4!
I've seen that the 78-79's are a bit more powerful than the 80-81's.
Kinda of wish I had done some research into that before I picked up my SG project.
However, it has been nice to have a readily available parts bike sitting right next to me when ever I needed a part, it's right there!

I would LOVE a 78. I have never even seen a 78 for sale here. I think people tend to like that year a bit, plus 1980 is a super common year.

[Fix]

Sure as ****, the throttle cable snapped in the throttle housing and got caught. Looks like I'm ordering a new cable. Might as well do the clutch while I'm at it. Not sure how old that one is.

[Fix]

http://www.motorcycle-superstore.com...100-Parts.aspx

Will that work on a 1978?

[bikerphil]

All the XS11's, all years, use the same replacement throttle cable. The cable will fit both Standards and Specials. The one in the above link should be fine.

Edit: Here is another source for the cable, also shows that it fits all XS11 models...

https://www.denniskirk.com/parts-unl....prd/C4530.sku

[Fix]

Thanks Phil!

[Shacknasty]

Short-shifting and running at low rpms should be avoided. Let yer motor sing!

[Fix]

Hmm, seems the issue's back. I can't find any wires broken, but it's cutting out randomly. The way to recover is to pull in the clutch, let the revs drop, and then let out the clutch. Kind of a 70mph push start almost.

It seems like it's gotta be the same issue, the loss of power feels exactly the same.

One thing I've noticed, with the timing cover off and the bike running, should I see the advance moving at all? It's not moving, at least that I can see.

[motoman]

Hmm, seems the issue's back. I can't find any wires broken, but it's cutting out randomly. The way to recover is to pull in the clutch, let the revs drop, and then let out the clutch. Kind of a 70mph push start almost.

It seems like it's gotta be the same issue, the loss of power feels exactly the same.

One thing I've noticed, with the timing cover off and the bike running, should I see the advance moving at all? It's not moving, at least that I can see.

Remove the vacuum advance can and make sure the advance assembly is floopy loose rotating it. It rotates on ball bearings similar set-up as a lazy susan.

[Fix]

Ok, I'm kind of slow. What part is the vacuum advance can? The plastic part that the wires attach to will move if I move it with my fingers. It feels spring loaded and pops back to position.

[motoman]

Ok, I'm kind of slow. What part is the vacuum advance can? The plastic part that the wires attach to will move if I move it with my fingers. It feels spring loaded and pops back to position.

Remove the left side timing cover(one that says YAMAHA on it), push the vacuum hose off the connection, remove the retainer clip that holds the vacuum can shaft in place, remove the phillips screw that holds vacuum can in place, lift it up and at same time rotate it a bit so the vacuum hook-up tube clears the case. Now with your hand rotate the advance assembly on the side of motor. It Should be 'floppy' loose rotating back and forth. Doing that you can also see the movement and abuse the wires take over the years. Those are the ones you see talked about on here that will break internally. Also, make sure that vacuum hose is plugged on the nipple on the SECOND carb, not the carb boot itself. The nipple it plugs onto is up close to carb body itself. Report back your findings......

[Bonz]

YES, what Motoman says is on the right path. Take off the pulsar cover/timing cover/whatever you want to call it cover, and lubricate the base plate or whatever it is that the timing unit rotates on. Mine did the same thing, the engine would just bog flat, would not pull out of the rpm it was at, unless I'd pull the clutch in, downshift it then go back up to the gear I had just been in.

When I had it apart, it was SO nice and clean in there, and it sure seemed like it was rotating easily. UNTIL I LUBED THE BASE PLATE, and then it did rotate ever so slightly easier to my hand. As well, you should be able to easily suck on the vacuum line and watch the thing rotate as well.

So, don't jack with the pick up wires until you use some silicon spray on that base plate and work it around a bit by hand. If it doesn't come around, then go check the pick up wires.

I promise this will help.

[Fix]

The vacuum hose was fine and correct. Removed the can as instructed. The advance assembly feels almost chunky. It is anything but floppy.

[Bonz]

Floppy may be a bit overstated, but chunky it should not be!

If it feels chunky when you rotate it by hand, do what I shared above and lube it with some silicon spray while rotating it back and forth. That will loosen it up, then you can check one more thing off the list of what you have done, if it somehow still isn't working right. What do you have to lose?

I really feel that is where the answer lies.

[Fix]

Howard,

When you say to hit it with silicon, I assume you're talking about taking it off and hitting the inside where it's actually contacting?

[Bonz]

I did it a couple years ago so my terminology might not be spot-on. However I simply put a shot(s) of silicon spray on the mechanism where it rotated. The timing mechanism rotates with the vacuum, and it was at the base of where the mechanism rotates that I sprayed the lube.

I looked at it and said "Hmmm... nice and shiny in here under the timing cover, but any lubrication this initially had from the factory probably isn't working any longer"... Then I said "if something is a bit sticky, what looks like a good spot for a shot of lube based on how this thing functions?"

Then put the lube there, and it loosened up a little bit (it was pretty free moving already, so I was also thinking it didn't need any lube based on my initial gut reaction), and the problem has not returned. What I thought was good and loose, was not good and loose apparently.

Don't go crazy with the silicon in there, as it doesn't need to get all over everything, but put a judicious squirt where it looks like it could use some lube based on how it rotates, and that is what I did.