1976 XS 650 Crank, no start

[Willweepin]

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)?

It has not ran since I’ve owned it. I just scooped it up a few days ago from the original owner for 300 bucks with a clean title. It has been sitting since 1983. Typical ran when parked scenario. The original VM34 mikunis he had on there were toast. Everything sat full of gas for nearly 40 years

Compression seems great.

 

[gggGary]

doesn’t have a crazy amount of resistance

that's pretty normal. the points blocks on the cam kinda make it seem weaker than it is.
My goto is a bit of carb cleaner sprayed in the intake to see if it fires. narrows it down to a fueling issue.
The orifice in the bottom of the float bowls feed the choke circuit,

it's usually plugged on wake ups and she won't start if that's the case.
pic of the carbies? one throttle cable or two?

 

[GLJ]

It has not ran since I’ve owned it. I just scooped it up a few days ago from the original owner for 300 bucks with a clean title. It has been sitting since 1983. Typical ran when parked scenario. The original VM34 mikunis he had on there were toast. Everything sat full of gas for nearly 40 years

Compression seems great.

You definitely have compression. Does it look like the motor has been apart?

 

[Jan_P]

To sum it up
With starter fluid it talks to you Poff but not starting
There appears to be spark
Assuming ignition timing correct and I read it as new carburetors are there

The original VM34 mikunis he had on there were toast. Everything sat full of gas for nearly 40 years

What carburetors -- jetted how -- for what machine -- and are they serviced ?

 

[Willweepin]

To sum it up
With starter fluid it talks to you Poff but not starting
There appears to be spark
Assuming ignition timing correct and I read it as new carburetors are there



What carburetors -- jetted how -- for what machine -- and are they serviced ?

Starter fluid, Gas, no fuel, same "poff sound" which sounds like compression moving throughout the cylinders. It is enough back-pressure to blow the vacuum caps of the carb boots.

Right now the carbs on there are just some knock off vm34 clones that are brand new and "functioning" correctly.

When I pulled my plugs there is not a single spec of burnt fuel on either one. I can see they are both getting spark when I pull them and ground them out. It FEELS like timing is just way way off, but static timing adjustments say otherwise.


I appreciate everyone's help and patience in this thread, real kind of everyone to help a stranger trying to get this old girl back on the road.

 

[Willweepin]

that's pretty normal. the points blocks on the cam kinda make it seem weaker than it is.
My goto is a bit of carb cleaner sprayed in the intake to see if it fires. narrows it down to a fueling issue.
The orifice in the bottom of the float bowls feed the choke circuit,
View attachment 371459View attachment 371460
it's usually plugged on wake ups and she won't start if that's the case.
pic of the carbies? one throttle cable or two?

I've got brand new carbs on this bad boy, which I know they are just mildly "bench tuned" at this point, but I can not get this thing to fire at the right time I think. I can feel vacuum pulling through the carb and letting gas in, but both of my spark plugs look brand spanking new when pulled. I can also see them sparking when I hit the starter button.

Starter fluid nor gas haven't changed anything.

 

[Willweepin]

Is there any way to verify that I'm firing 180 degrees out of phase?

 

[Jan_P]

It is simpler flip the wires .experiment rather than think
please report back

 

[GLJ]

Take the spark plugs out and ground them. Hook timing light to left spark plug wire. Hold finger over left spark plug hole. Have someone crank it with the E-start, watch and see if light flashes when bike is trying to blow your finger off plug hole. Once you verify that the plugs are firing on the correct cylinders you can spin the motor and see if it's close being in time.

 

[gggGary]

verify the crank and cam are aligned
rotor spun to TDC mark (verify pistons at TDC with a carb cleaner straw)
one set of valves should be loose (at ML .003 and .006) the other both nearly closed.

note the lobes form a V, At TDC, one set straight up, one set down (cylinder on compression).

You have GOOD compression. 130PSI plus?

 

[Jim]

I'm not sure of your experience level with the old points setup, so maybe these'll help?

 

[Jim]

I'm not sure of your experience level with the old points setup, so maybe these'll help?

Re: the static timing (first) video. At about the 3 min mark he goes into setting the gap and doesn't go into much detail on that. You rotate the engine until the points cam is at it's highest point. It's opening the points as much as it can. That's the point where you set your gap. I feel like he could have demonstrated that a bit better.

 

[Willweepin]

It is simpler flip the wires .experiment rather than think
please report back

I've flipped the spark plugs, and no dice.

 

[Its been a long time]

Post #25. Personally, I have low confidence that "knock off VM34 clones" as stated by the OP are any use.

 

[Jan_P]

Post #25. Personally, I have low confidence that "knock off VM34 clones" as stated by the OP are any use.

Makes sense that it can be Carburetors
It is reported
Ignition timing is right
There is spark
It talks back on starter fluid the " Poff "
And it is not 180 degrees off.

I don't know carburetors but there is no inlet filter that can mean excess Air .( again Dont know Carbs )
But something there can be wrong

 

[Its been a long time]

Makes sense that it can be Carburetors
It is reported
Ignition timing is right
There is spark
It talks back on starter fluid the " Poff "
And it is not 180 degrees off.

I don't know carburetors but there is no inlet filter that can mean excess Air .( again Dont know Carbs )
But something there can be wrong

Yes, I would be looking for a known good set of carburetors to borrow for a couple of days.

 

[gggGary]

thing is you don't even need carbs to fire. They run for a few seconds on two shots of carb cleaner....

 

[Its been a long time]

thing is you don't even need carbs to fire. They run for a few seconds on two shots of carb cleaner....

That's right yes. After that you need known good carbs.

 

[Jan_P]

So we are back at ignition is that the conclusion ?
Timing off ?
Or partially shorted points ?

Strobe light while kicking ?
and the straw in the cylinder so there is correspondence between piston TDC and rotor markings
I have a rewound rotor with the timing marks at the wrong place after the shop did the Rewind

 

[Willweepin]

thing is you don't even need carbs to fire. They run for a few seconds on two shots of carb cleaner....

Exactly, that's why I'm not super worried about the carbs at this point. I'm going to try to take another wack at the timing today, and if I get frustrated I might take a break and work on the starter. It has not actually fired off a single time.