First motorcycle and a cylinder not firing.

jpdevol

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There is a crossover tube between the carbs that is allowing the left petcock to feed both carbs. It would be unusual, but it would be possible to have a blockage at the inlet and not have a blockage at the crossover - both feed the float valve.
These aren't '76 carbs, but similar
BS38 fuel inlets.jpg
 

Jim

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Dunno.. we'd need some pics of the hose routing before even a guess.
As it stand though, we know the right carb has fuel in it. Work with that for the right cylinder problem.
 

jpdevol

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Did you happen to test the RH diaphragm by raising it and watching it fall while placing your thumb over the oval port on the intake carb bell? (CV diaphragm/slide test)

Are the choke plungers both lifting and does using the choke change anything?
 

Thursty

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Ill take the carbs off again tomorrow and take a closer look. As of now, fuel drains out of both carbs via the left petcock. The right petcock however, does not drain through the carbs, but does drain when the fuel line is disconnected. What do you guys think of the cam tensioner? Im not sure what to do next until i get it rectified. It's my understanding that it needs to be set before doing a valve adjustment, etc, etc.
 

Thursty

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Yes i did do a slide test on both carbs, and they both passed with flying colours. both enricher plungers lift. havent really given it a go while running tho, as i havent felt that the bike has needed it to keep running.
 

Jim

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Ill take the carbs off again tomorrow and take a closer look. As of now, fuel drains out of both carbs via the left petcock. The right petcock however, does not drain through the carbs, but does drain when the fuel line is disconnected. What do you guys think of the cam tensioner? Im not sure what to do next until i get it rectified. It's my understanding that it needs to be set before doing a valve adjustment, etc, etc.
Did you try and adjust the tensioner as I suggested? That didn't work?
No, you can set the valves with the chain too loose, too tight or anywhere in between. They don't know or care how tight the chain is as long as it's there.
 

jpdevol

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If you haven't already, spray contact cleaner through all carb passages - pilot, choke circuits,etc. to verify they're clear
Just my 2 cents - while the carbs are off and out of the road, I'd remove the cam chain tensioner housing assembly (6 bolts) and examine it for damage, wear and proper assembly (bent pushrod, spring, etc.) Might need a gasket.

https://www.xs650.com/threads/cam-chain-tensioners.1056/page-2
 
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Thursty

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I did try tightening it the way you suggested, however, i will give it another go tomorrow. Knowing that the valves dont care, helps. That means I can set the valves, points, and timing again while i potentially wait for parts (gasket) for the chain tensioner 'if' needed. Either way, I can move forward. If i feel necessary, Ill take a video showing all of the passageways cleared when cleaning. I'm not saying I haven't missed anything, however, i am confident that i did a good job and all passageways should be clear... obviously something is wrong tho. Im going to check the fuel inlet nipple/line on the right carb. Will keep you guys posted. Thanks.
 

jpdevol

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Knowing that the valves dont care, helps. That means I can set the valves, points, and timing again while i potentially wait for parts (gasket) for the chain tensioner 'if' needed
The chain does affect the timing, but nothing else. It's possible to make a crude gasket from a cereal box by placing a piece over the housing flange at rear of cyl. and tapping around with a hammer to make an impression then cut out. Replace when order arrives.
 
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Jan_P

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Here it is fellas. What do you think of that? Also, thanks for everyones help.

It does not look right at the right side pet cock can be right but it looks wrong
I have been working with piping and so and the handle of this petcock is pointing upwards on the video
I dont have that possibility on my 1980 it is always in the lower half between 3 and 9 o clock
look at #18 Mr 5Twins picture

with the on at 6 and a tube that opens from the air inlet underpressure
It is more or less a norm the handle in line with the flow when open and at 90 degrees when closed
Because it is easier to spot from watching ,,,sometimes at long distances at the shop floor

The flow can depend on the level in the tank halves I believe
If low on on side maybe it wont flow at all open that petcock

No carburetor expert but If I recall right there is a channel between the carburetors
So assume one tank half is empty and the other one is full without the channel between carbs the right side would stall.

But I would check the petcock how it is supposed to look like
 

Thursty

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It does not look right at the right side pet cock can be right but it looks wrong
I have been working with piping and so and the handle of this petcock is pointing upwards on the video
I dont have that possibility on my 1980 it is always in the lower half between 3 and 9 o clock
look at #18 Mr 5Twins picture

with the on at 6 and a tube that opens from the air inlet underpressure
It is more or less a norm the handle in line with the flow when open and at 90 degrees when closed
Because it is easier to spot from watching ,,,sometimes at long distances at the shop floor

The flow can depend on the level in the tank halves I believe
If low on on side maybe it wont flow at all open that petcock

No carburetor expert but If I recall right there is a channel between the carburetors
So assume one tank half is empty and the other one is full without the channel between carbs the right side would stall.

But I would check the petcock how it is supposed to look like
Thanks Jan, ill give it another look. However, I will say, im 95% sure that mine runs between 6 and 12 oclock, with the valve being closed when pointed perpendicular to the direction of fuel. The other side is set up the same, and it works flawlessly. The inscriptions on the petcock, uhm,... plate? show that the off position is pointed at either 9 or 3, depending on which side of the tank the petcock is set up for. Again, I will also note, that with the fuel line detached, as shown in the video, the problem side literally pisses out fuel when in the 'on' or 'res' position, and stops in the off position. Again, ill investigate further based off of your advice. Today is a rain day (as stated before, im a bricklayer by trade), so ill be working on the bike as much as possible. Going to head out and start by removing the carb, and inspecting the cam chain housing.
 

5twins

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I don't see much point in removing the whole tensioner housing, there's not much to see in there. But, you can (and probably should) remove the adjuster screw, plunger, and spring assembly from it, it just screws out. What you'll be looking for is the damper washer, a copper washer placed on the plunger rod to quiet the operation of the unit. Many times they are missing and then the tensioner can make noise, sounding like loose valves .....

Cam Chain Tensioner.jpg


If missing, this will also allow the end of the plunger to come out past the end of the adjuster screw during operation. If you loosen the adjuster so it's flush with the plunger, you will have the chain set too loose.

I find the "book" method for setting the cam chain tension very confusing and easy to screw up. The first time I tried it many years ago, I ended up with the chain way, way too loose. Every time I rotated the engine, the rod would pop out past the adjuster, so I loosened it to make it flush. Another engine revolution would have the same thing happening so I'd loosen the adjuster more, etc., etc. My setting ended up being way too loose. I started the engine and it rattled like the valves were loose. There had to be a better way, and there is - you check and set the tension while the engine sits there idling. I borrowed and adapted this from the cam chain adjustment instructions for Yamaha's big singles .....

SR500CamChainAdjust.jpg


The actual instructions can't be applied. You can't set the motor on the "T" mark. There is no spot during a 650 engine revolution where all the valves are closed and there is no tension on all the rocker arms. It's the note at the bottom that's important. We can do this on our 650, and it's a pretty much foolproof method for checking and setting the chain tension. You want to see a small amount of in-out movement on the plunger, maybe 1 to 2mm. If it moves more, the chain is too loose, if it moves less or not at all, the chain is too tight.

Easiest way to do the adjustment is to tighten the adjuster until the rod almost stops or stops moving, then loosen it back up until you get your 1 to 2mm of in-out movement. Don't worry too much whether the rod is flush with the end of the adjuster screw, that can vary due to worn (or missing) parts.
 

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A lot has happened this morning. I cleaned the carbs again, focusing on the passageways that i felt would be associated with fuel from the right petcock not being able to reach the float bowl (pretty much just the fuel line nipple). After hooking things back up again, for some reason, it worked. fuel filled both lines, reaching the carbs. I also inspected the cam chain tensioner while the carbs were off, and they looked good. pushrod didn't have any bends in it, and seemed to function properly. I reinstalled it, and set the tension by starting in a loose position. tightening the adjuster until flush on the T marking on the stator (i think thats what its called?). Then i reset my valves (which i realized i did wrong, by getting metric and imperial mixed up), cleaned my feeler gauges, set my points, and then set timing. All seemed good.

I then tried starting the engine, but didnt want to go. THEN, i realized, my throttle cable was binding up somewhere and the throttle was stuck 3/4 open. Unhooked the cable, and put a fresh set of old (haha) plugs in it, and it fired up shortly after. It seemed to want to fire up better with the enricher turned on. once the bike was running, it didnt seem to run very good with throttle applied. it actually ran better at an idle, but still needed a touch of the throttle every so often to keep it going. Does that make sense? However, both cylinders seemed to be firing the same, and performing together (from what i could tell with it running kind of rough)!!! Do you think that it running too rich could cause this? the plugs did look rich after running it for a short period of time...

Also, just thinking of what you guys had mentioned before about ignition. It would probably be a good idea to just get new coils, spark plug wires, and even a wiring harness wouldnt it?

Also i took videos along the way, so i can post them if you guys would like. but im not sure that they are necessary as the sound quality is bad anyways.
 

Thursty

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I don't see much point in removing the whole tensioner housing, there's not much to see in there. But, you can (and probably should) remove the adjuster screw, plunger, and spring assembly from it, it just screws out. What you'll be looking for is the damper washer, a copper washer placed on the plunger rod to quiet the operation of the unit. Many times they are missing and then the tensioner can make noise, sounding like loose valves .....

View attachment 226143

If missing, this will also allow the end of the plunger to come out past the end of the adjuster screw during operation. If you loosen the adjuster so it's flush with the plunger, you will have the chain set too loose.

I find the "book" method for setting the cam chain tension very confusing and easy to screw up. The first time I tried it many years ago, I ended up with the chain way, way too loose. Every time I rotated the engine, the rod would pop out past the adjuster, so I loosened it to make it flush. Another engine revolution would have the same thing happening so I'd loosen the adjuster more, etc., etc. My setting ended up being way too loose. I started the engine and it rattled like the valves were loose. There had to be a better way, and there is - you check and set the tension while the engine sits there idling. I borrowed and adapted this from the cam chain adjustment instructions for Yamaha's big singles .....

View attachment 226144

The actual instructions can't be applied. You can't set the motor on the "T" mark. There is no spot during a 650 engine revolution where all the valves are closed and there is no tension on all the rocker arms. It's the note at the bottom that's important. We can do this on our 650, and it's a pretty much foolproof method for checking and setting the chain tension. You want to see a small amount of in-out movement on the plunger, maybe 1 to 2mm. If it moves more, the chain is too loose, if it moves less or not at all, the chain is too tight.

Easiest way to do the adjustment is to tighten the adjuster until the rod almost stops or stops moving, then loosen it back up until you get your 1 to 2mm of in-out movement. Don't worry too much whether the rod is flush with the end of the adjuster screw, that can vary due to worn (or missing) parts.
Also, thanks for this. I had the same experience and observations that you mentioned in your second paragraph. I will use your method while the bike is running and try to dial it in. I would like to get it running better first tho... You mentioned earlier that u used the same up4200 pods that i have. I switched out the hiflow ones for the 4200s. What would be a good benchmark main jet to start with given that the standard main size for my bike is 122.5?
 

Raymond

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I think it's progress Thursty. At least both cylinders are doing the same. Maybe just needs some adjustment, like putting the idle up a little, but don't overdo that, mine needs a tiny touch of throttle until it's good and warmed up, then it settles to a nice idle.

The plugs would look rich if you've been running it with the choke/enrichener on.

See how it goes after it's been running a few minutes - should start to respond to throttle better.
 

Thursty

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I think it's progress Thursty. At least both cylinders are doing the same. Maybe just needs some adjustment, like putting the idle up a little, but don't overdo that, mine needs a tiny touch of throttle until it's good and warmed up, then it settles to a nice idle.

The plugs would look rich if you've been running it with the choke/enrichener on.

See how it goes after it's been running a few minutes - should start to respond to throttle better.
As soon as i got it going, i actually turned the enrichener off, and tried to keep it going just by feathering the throttle. again, it seemed to run better at lower rpms, but after a bit, would need a touch of the throttle to 'keep' it going. i will go back to it however and try to keep it going a little longer. maybe with a video if this rain can slow down a bit...
 

jpdevol

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Progress!

So both pipes are getting hot now? How is the "clanging" noise now? What pilot jet size is in there?
 

Thursty

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Progress!

So both pipes are getting hot now? How is the "clanging" noise now? What pilot jet size is in there?
Yes, both seem to be running the same (as far as i can tell with it only running for 1-2 mins before shutting down), clanging is still there, however, want to try 5twins method of tightening the cam tension before investigating things deeper. pilot is 27.5 supposedly, according to rebuild kit.
 

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If you hold a steel rod or screwdriver against the engine various points and the ear you will be able to better localize the clanging
The rough running at upstart is nothing unnormal .. can take 2 tanks or 3 before things settle
But the clanging would be good to get rid of.
 
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