What is the Trick to Reinstalling Stock BS34 Carbs to 1980 XS650

JonW

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I bought my bike without the carbs installed and purchased a set of rebuilt carbs, ready to be installed. So far, I have learned, that there is no room to fit the carb assembly in its bolted/screwed-together configuration. I took the manifolds off and fitted them to the carbs and even took the carb tops off, but still no joy. Before I go any further, what is the preferred method?

TIA and my Clymer manual and searching did not reveal the results I am looking for, and I apologize for asking an obvious question about what has surely been asked in the past.
 
Remove the timing chain acorn nut. Have airboxes removed.......Mount the manifold on the motor.............. From the left hand side of the frame the carbs can be slid in. There i a bit of gentle turning, twisting, head and mouth movement, to get the right angle for them to get into position.

When in position i use a large crew driver as a lever, off the batterybox, Frame to lever, (gently but firm), the carb into the manifold. I also use a smear of lithium grease around the inside of the manifold.............just a smear, enough to help the carb slid in without any excess
 
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On a stock frame, IIRC, I put 'em in from the left, angled with the front pointing up (maybe 40*) insert the bottom into the intakes and rotate them up and in. Tried that?
 
I attach the manifolds to the carbs. Remove the airboxes. Remove the plate on the top of the carbs that connects the carbs together. Slide them in from the left side. Bolt the carbs and manifolds to the cylinder head and replace the airboxes. Replace the connecting plate on the top of the two carbs.
 
IIRC it is a firm fit. Ensure that the clamps are loose (LOOSE), and a firm push/roll forward does it. Mind you, ensure the bike cannot roll forward off side stand or center. because those rubber manifolds can be that snug.
 
Remove the timing chain acorn nut. Have airboxes removed.......Mount the manifold on the motor.............. From the left hand side of the frame the carbs can be slid in. There i a bit of gentle turning, twisting, head and mouth movement, to get the right angle for them to get into poition.

When in position i use a large crew driver as a lever, off the batterybox, to lever, (gently but firm), the carb into the manifold. I also use a smear of lithium grease around the inside of the manifold.............just a smear, enough to help the carb slid in without any excess
This ^^^

Taking the acorn nut off the timing chain tensioner provides just the right amount of room to get the lower carb bracket to fit past...makes a big difference.
 
Very important the manifolds have flex in them. If they are old and hard its near impossible to get the carbs in them without braking the lip in the boots. This can create air leaks around the manifolds.

I like to attach the manifold first, I find it easier to wriggle the carbs into position, then the boots, than attach and tighten the manifolds to the motor after
 
Very important the manifolds have flex in them. If they are old and hard its near impossible to get the carbs in them without braking the lip in the boots. This can create air leaks around the manifolds.

I like to attach the manifold first, I find it easier to wriggle the carbs into position, then the boots, than attach and tighten the manifolds to the motor after

I did mount the manifolds to the carbs and did find it wasn't easy but I made it happen. I typically use WD40 for lubricating rubber upon assembly. I will remove the chain tensioner "acorn" cover and give it a go.

Thank you to everyone, for all the replies/help!
 
I did mount the manifolds to the carbs and did find it wasn't easy but I made it happen. I typically use WD40 for lubricating rubber upon assembly. I will remove the chain tensioner "acorn" cover and give it a go.

Thank you to everyone, for all the replies/help!

In addition to the key step of removing the timing chain adjuster "acorn", putting just a little slippery stuff (WD40, petroleum jelly, KY...etc....) on the carb-mounting boot interface is very helpful - and also, a good-sized, but flat, crowbar can be used to gently encourage the carbs to seat into the boots by prying - GENTLY - against the vertical frame members in where the airbox will eventually go.

I emphasize again - gently.

Carburettors are not robust and there are lots of little external details that, if bent, will make getting the bike to run properly damned near impossible. The fact is that there is precious little room in the area of the airboxes, carbs, etc. on all XS650s - and so any operation in that area can be fraught with frustration and use of the "extended vocabulary".

Go slowly, lubricate things and be methodical and gentle.

Pete
 
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In addition to the key step of removing the timing chain adjuster "acorn", putting just a little slippery stuff (WD40, petroleum jelly, KY...etc....) on the carb-mounting boot interface is very helpful - and also, a good-sized, but flat, crowbar can be used to gently encourage the carbs to seat into the boots by prying - GENTLY - against the vertical frame members in where the airbox will eventually go.

I emphasize again - gently.

Carburettors are not robust and there are lots of little external details that, if bent, will make getting the bike to run properly damned near impossible. The fact is that there is precious little room in the area of the airboxes, carbs, etc. on all XS650s - and so any operation in that area can be fraught with frustration and use of the "extended vocabulary". Go slowly, lubricate things and be methodical and gentle.

Pete
Great minds think alike :thumbsup:
 
Guess I'm the the odd man out. (imagine that!)
Intakes off or maybe held loosely by an inner bolt on each side, put the carbs in place, finish installing the intake manifolds to the motor. Next it really helps to get the manifolds good n warm with a hair dryer. I also typically and CAREFULLY round off the sharp outer corner on the carb mouth just a little (front and back), eases the slide in, so does silglide. There's a trick involving reaching one arm around the front of the motor so you can pull the carbs into the boots from both sides but that's more of a 4 cylinder thing.
 
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There's a trick involving reaching one arm around the front of the motor so you can pull the carbs into the boots from both sides but that's more of a 4 cylinder thing.
My SOP on 4-Cyl's includes
52LA97_AS01 (2).jpeg
X 2 and:cussing:
 
My install/removal technique involves lube and rocking the carb set up and down as I push it in or pull it out. For removal, I spray the boots with some light lube then rock the carbs up and down a little bit so it can penetrate and get in there. Then, I rock them up and down a lot while pulling, and they pop right out. For install, I apply some rubber friendly grease to the insides of the boots and on the carb spigots, start the carb set into the boots, then rock it up and down while pushing. They usually "walk" right into the boots pretty easily, no need for pry bars and the such.

For getting the carb sets in and out, I remove the cam chain adjuster acorn nut and the throttle cable bracket on the carb set, then work the carb set in or out the right side. This past summer, I did quite a lot of carb swapping so maybe all the practice just made it easier, lol. I pulled one set of BS34s out and removed or installed 4 different sets of BS38s using this method. I'll add that both intake manifolds are in place. They need to be because you can't get a torque wrench on their inside bolts with the carbs in place.
 
I also typically and CAREFULLY round off the sharp outer corner on the carb mouth just a little (front and back), eases the slide in, so does silglide.

Couldn't remember having to do this, my carbs were tapered from the factory. Had squiz at a few different B34 carb sets, the ones i looked at, (non factory black ones), didn't have the taper on them My 83 B34's, (factory black), has the taper from the factory, definatly a worth while thing to do.

IMG_7867 reize 2000 copyright.jpg
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For install, I apply some rubber friendly grease to the insides of the boots and on the carb spigots, start the carb set into the boots, then rock it up and down while pushing. They usually "walk" right into the boots pretty easily, no need for pry bars and the such.

For getting the carb sets in and out, I remove the cam chain adjuster acorn nut and the throttle cable bracket on the carb set.........I'll add that both intake manifolds are in place. They need to be because you can't get a torque wrench on their inside bolts with the carbs in place.

I successfully installed the carbs today! I removed the acorn nut and reinstalled the manifolds to the head per your guidance. I actually came in from the left side, no problem...also with carb tops off. Lubed the manifolds and after a minute or two, I had them in. It isn't hard and it isn't easy! The carb tops and both top brackets are in place and the throttle cable is attached. I still need to attach the bottom bracket but need two screws in order to replace the two on the right side that I had to destroy in order to remove. And yes, I have JIS screwdrivers but those things were in there like they had been doused with Loctite or something!
 

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You may have fuel leakage issues if the "T" fitting between the carbs isn't tight. Normally, you fully assemble the BS34s off the bike. With the top and bottom brackets installed loose, you clamp the carbs together so the "T" is tight, then tighten the top and bottom bracket screws while the clamp is still in place .....

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Check your "T" fitting. Can you easily rotate it by hand?
 
You may have fuel leakage issues if the "T" fitting between the carbs isn't tight. Normally, you fully assemble the BS34s off the bike. With the top and bottom brackets installed loose, you clamp the carbs together so the "T" is tight, then tighten the top and bottom bracket screws while the clamp is still in place .....

Check your "T" fitting. Can you easily rotate it by hand?

The carbs came to me fully assembled, and the "T" fitting was tight. I just checked and it is still tight. Thanks for the heads up.
 
Agree with all the above. For lube I actually smear a bit of gasoline on the rubber boots and quickly position the carbs and rock them into place. Pretty easy once you’ve done it a couple of times.
 
Good news....I was able to confirm that the bike does run and, was firing on both cylinders. It sounded good!! It was a spur-of-the-moment thing, with enough juice to get it to fire. I will have to make a video of it running in a new thread in the next week or so.
 
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