1976 XS 650 Crank, no start

[Willweepin]

Hello Everyone,

I like to try to dig through the forums before I creating yet another crank no start thread. I couldn’t find anything with my specific issue, and I’m hoping to get some advice.

This 1976 XS650 is kicking my ass.

I’ve checked timing chain, timing, points, spark, coils, everything I can think of and I’m still not getting this thing to even try to fire.

It’s cranking oddly and there is a rather loud clunking sound. It also doesn’t seem to want to spin over after 2 or 3 revolutions and then disengages. There’s also some pretty heavy back pressure through the carbs. (I know they’re setup pretty jank like, I’m waiting on proper boots) but I figured it would TRY to start.

Any advice on what to check out to get this thing to even poorly run would be much appreciated.

Here’s a video link to show what’s going on.

 

[Jan_P]

This will be a challenge
assuming that is correct

I’ve checked timing chain, timing, points, spark, coils, everything I can think of and I’m still not getting this thing to even try to fire.

If you have a spark My first guess it is to weak The e starter is using all power and the weak spark is not able to fire
Is the battery OK ?
I use the kick starter last 40 years be careful so it is not kicking back
It is not stock carbs as far as I can see and no air filters so the mixture can be off to lean ( Extra air )

Unless full choke and no choke helps Are the plugs wet or dry ?
I would probably try starter fluid

Edit no exhaust either that also can make it difficult

 

[Willweepin]

This will be a challenge
assuming that is correct



If you have a spark My first guess it is to weak The e starter is using all power and the weak spark is not able to fire
Is the battery OK ?
I use the kick starter last 40 years be careful so it is not kicking back
It is not stock carbs as far as I can see and no air filters so the mixture can be off to lean ( Extra air )

Unless full choke and no choke helps Are the plugs wet or dry ?
I would probably try starter fluid

Edit no exhaust either that also can make it difficult

Hey Jan, Thanks for the response.

Battery is a brand new AGM, I am getting spark, I've got new boots on it, and the coils are good. Choke doesn't affect it at all. I know the carb setup is a little jank, but it won't even get remotely close to kicking over even with starting fluid.

Plugs are very very slightly wet, when continually trying to crank it, but nothing that screams out of the ordinary.

I had just taken the exhaust off prior to taking the video, just to make I could physically see the valve moving with the amount of crazy backpressure I got.

All my previous attempts with the same setup had the exhaust.

Edit: I am getting strong vacuum on the carbs while cranking, but there was enough back pressure to blow a vacuum cap I had on the boot.

 

[Willweepin]

This will be a challenge
assuming that is correct



If you have a spark My first guess it is to weak The e starter is using all power and the weak spark is not able to fire
Is the battery OK ?
I use the kick starter last 40 years be careful so it is not kicking back
It is not stock carbs as far as I can see and no air filters so the mixture can be off to lean ( Extra air )

Unless full choke and no choke helps Are the plugs wet or dry ?
I would probably try starter fluid

Edit no exhaust either that also can make it difficult

I feel like I'm losing my mind over this thing. I've owned some vintage CB750's over my life, including one of the hondamatics, and none of them have ever given me an issue like this.

It seems like the timing is just WAY off, but I'm honestly not sure how to verify that past things I've already done.

 

[Jim]

Try swapping the plug leads. If your timing is 360° off, it'll look correct, but it's firing the wrong plug.

 

[Jim]

Your starter kicking out after a few spins is likely caused by a weak spring clip. It's a known issue... do a search here on the forum and you'll find lots of info on it.

 

[Wingedwheel]

Are your intake boots on upside down?

 

[Willweepin]

Are your intake boots on upside down?

Yes they are, the bike sat for about 40 years before I got a hold of it (with a full tank of gas), and I had these boots that matched kind of closely. New Proper boots should be in tomorrow.

 

[Willweepin]

Try swapping the plug leads. If your timing is 360° off, it'll look correct, but it's firing the wrong plug.

That's a genius idea. I'll go give it a shot and report back.

 

[Willweepin]

Your starter kicking out after a few spins is likely caused by a weak spring clip. It's a known issue... do a search here on the forum and you'll find lots of info on it.

Thanks for the info! I might have it in the massive box of parts that came with this thing.

 

[Willweepin]

That's a genius idea. I'll go give it a shot and report back.

No dice, but I think the starter issue might be holding it back a minute.

Also I feel like I'm going crazy, but isn't this chain tensioner supposed to have a locking nut on it.

 

[gggGary]

2nd on swap the coil wires at the condenser wire junction., actually the usual problem is advance rod pins will allow the points cam to be 180 degrees off, very easy to do!

 

[gggGary]

No dice, but I think the starter issue might be holding it back a minute.

Also I feel like I'm going crazy, but isn't this chain tensioner supposed to have a locking nut on it.

No the lock nut came later 79ish?
Often times they'll start with the kicker when the e-start won't do it.
Go ahead and retard the timing some, you can always adjust once it's running.
Is the advance rod turning freely? It can get stuck in the advanced position. you can tell at the RH cam cover, the springs should retract the weights.

 

[Its been a long time]

I am getting strong vacuum on the carbs while cranking, but there was enough back pressure to blow a vacuum cap I had on the boot.

It's a rare condition, but my 650 had a blocked right side exhaust header that gave that symptom.

What happens is the headers are dual skinned. If the bike is stood outside for years, the space between inner and outer header tube fills with water. That freezes in winter and collapses the inner tube. My right side header was blocked so badly you could barely blow air through it.

It's a rare condition to find but given your comment it's the next thing I would check.

 

[Jan_P]

If you take out a spark plug
Hold it against the Cylinder head and there are spark
put it back in

And the wires are not flipped per above

Ignition is set correct please inspect at the points so there is some sparking there
that is a spot where it often goes wrong ..One point grounding

And you use starter fluid

And use kick starter

Some Poff should be heard maybe even poff poff poff

 

[Willweepin]

It's a rare condition, but my 650 had a blocked right side exhaust header that gave that symptom.

What happens is the headers are dual skinned. If the bike is stood outside for years, the space between inner and outer header tube fills with water. That freezes in winter and collapses the inner tube. My right side header was blocked so badly you could barely blow air through it.

It's a rare condition to find but given your comment it's the next thing I would check.

That's exactly why I pulled the exhaust off, I was kind of going down the rabbit hole. My exhaust is clear and back on now.

Edit: The bike has aftermarket headers on it, that are fairly open as well.

 

[Willweepin]

If you take out a spark plug
Hold it against the Cylinder head and there are spark
put it back in

And the wires are not flipped per above

Ignition is set correct please inspect at the points so there is some sparking there
that is a spot where it often goes wrong ..One point grounding

And you use starter fluid

And use kick starter

Some Poff should be heard maybe even poff poff poff

I'm definitely getting that poff sound, and there is a very small amount of sparks right when the points start to open when setting static timing.

 

[Willweepin]

No the lock nut came later 79ish?
Often times they'll start with the kicker when the e-start won't do it.
Go ahead and retard the timing some, you can always adjust once it's running.
Is the advance rod turning freely? It can get stuck in the advanced position. you can tell at the RH cam cover, the springs should retract the weights.

I'll go take a look, I honestly haven't checked.

 

[Willweepin]

I'll go take a look, I honestly haven't checked.

Seems okay, doesn’t have a crazy amount of resistance

 

[mike in idaho]

Has it ever run, since you've owned it? What kind of compression does it have? Points cam/ advance rod assembled correctly(not 180 degrees out)?