kjodell10
XS650 Enthusiast
Will do.
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loose barbs in carb holder
- Thread starter kjodell10
- Start date
kjodell10
XS650 Enthusiast
I wanted to follow up, with thanks. Mike's barbless, '78-appropriate manifolds arrived; I marked from the tin holders and the old manifolds, centered and screwed each manifold to a hefty mahogany block on the drill press so I had a reasonable chance of drilling plumb and square; drilled (nothing like sinking a bit into brand-new part!), successfully- I had the ratty old manifold to cut up on the bandsaw, which gave me a better idea of where to hit the aluminum inside the rubber. I was concerned that epoxy might be forced into the barb when I pushed it through the hole in the manifold, so I made a couple of small cones with dowel and a pencil sharpener, pushed them into the open ends of the barbs and removed them with needle-nose pliers when the tubes had been positioned and excess epoxy removed. I'm just waiting for the Yamabond to mount everything; will wait a day so I can re-torque, per advice The gaskets came off easier than expected; there was no gunk between the old gasket and the head. The surfaces on the head are a little discolored, but appear otherwise free of stuff, and smooth to the touch.
Once again, thanks. This forum, and the SR version of it, have been invaluable, and people have been super generous with help, answering questions I wouldn't have thought to ask. Cheers!
If you don't feel like waiting, most auto parts stores carry this stuff. I've rebuilt/repaired hundreds of aircraft engines with it.... not to mention auto and bike engines. It's all I use.
kjodell10
XS650 Enthusiast
kjodell10
XS650 Enthusiast
I've been looking and can't find a specific torque setting for the machine screws holding the manifold to the flange. Anybody have this information? Thanks.
It's 6mm. All 6mm fasteners are torqued to 7ft-lbs
kjodell10
XS650 Enthusiast
kjodell10
XS650 Enthusiast
Yes, it's in the Yamaha service manual. Ignore column A. I honestly don't know why they put it there. A 6mm bolt/screw/fastener can have multiple head sizes and still be just a 6mm fastener that want's 7ft-lbs of torque. Pretty silly of 'em.
Remember this applies to un-lubed fasteners... sometimes referred to as "dry torque." Go about 15-20% less if you lube it.
Always look for a specific value for what you're torqueing. If it's not specified, then you go with the "standard" value.
Remember this applies to un-lubed fasteners... sometimes referred to as "dry torque." Go about 15-20% less if you lube it.
Always look for a specific value for what you're torqueing. If it's not specified, then you go with the "standard" value.
You'll actually find a range given for M6 fasteners in some places. It's 5 to 8 ft/lbs. I don't recommend using the max (8 ft/lbs or 96 in/lbs), especially on these old bikes. For many years I used 80 in/lbs but recently I've started backing off on that, down to the low 70's or about 6 ft/lbs. This is partly because I lube all my threads but also to reduce the stress on the threads, especially the ones into alloy. So far, this is working fine for me. The sump plate and right side cover have sealed up just fine using the lower value.
kjodell10
XS650 Enthusiast
kjodell10
XS650 Enthusiast
Thank you; I really appreciate the input. There's a certain degree of anxiety involved when you approach a vintage machine from a position of ignorance.
kjodell10
XS650 Enthusiast
I put everything back together yesterday- AND IT STARTED! It sounds great! I'd been eyeballing the synch process- access to the adjustment screw would appear to require tank removal and splicing in some fuel line to make it into a "remote" fuel source, but I'm wondering if synching is really necessary. How do you tell? After the investment of time and bucks I don't want to be half-assed, but neither do I want to spend more time and effort if it isn't needful.
Well, if the sync is really far off, you can usually tell by just cracking the throttle open a hair. You'll hear one cylinder speed up before the other. If close, the only way to really check it is with gauges of some sort (vacuum gauges or a manometer). This is another plus for having the vac nipples on the manifolds. It gives you some place to hook the gauges to.
You can usually access the sync screw using a 6" long 3/16" tip screwdriver from the side. Stanley makes a nice one .....
https://www.ebay.com/itm/253974358850?hash=item3b220d2b42:g:cGcAAOSwTiVb5vsg
I bench sync my carbs before install so they're usually very close. The sync screw requires very little adjustment to get them perfect, maybe 1/8 of a turn in either direction.
You can usually access the sync screw using a 6" long 3/16" tip screwdriver from the side. Stanley makes a nice one .....
https://www.ebay.com/itm/253974358850?hash=item3b220d2b42:g:cGcAAOSwTiVb5vsg
I bench sync my carbs before install so they're usually very close. The sync screw requires very little adjustment to get them perfect, maybe 1/8 of a turn in either direction.
Adding a short 1" or so section of tubing over the sync screw makes it easier to hold the screwdriver in place while adjusting.
How do you tell ? Good question.
I carefully eyeball sync the throttle plates while holding the carburetors up to the sky. A guy can see the sliver of light on each side and adjust them very close.
One "tell" of a well tuned engine is a combination of running on the road, I use plenty of throttle for those tests. And a well tuned engine will idle temporarily very slowly, maybe even 700 rpm, evenly in your driveway. Idle speeds below "practical riding" setting even which is approx 1100 rpm. It's real fun to fine tune and evaluate a warm, well tuned XS650 on its centerstand.
An easier and better way to bench sync is to back off the idle speed screw so it's not touching the cable arm. This closes the butterfly plates completely. It's much easier to see closed plates than to try and compare the size of the light slivers.
Unfortunately, Jim's hose trick won't allow access to the screw from the side with the long screwdriver and the tank still in place.
Unfortunately, Jim's hose trick won't allow access to the screw from the side with the long screwdriver and the tank still in place.
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Yeah, I unbolt the tank, slide it back a hair and block the back up with a piece of wood. Don't need to disconnect the tank and there's plenty of room to slide a stubby in there. More than one way to skin a
Left carb is the master because it has the idle speed screw. I'll set idle screw for a fine sliver on the left then match the right to it. This lets you work the right past the equal point then come back to it. If the left is closed you can only see if the right is further open, not if it's slightly further closed.
There are those that claim if you are really good you can see the light in the sliver turn blue as it nears completely shut.
IE it gets thin enough to start blocking red wave lengths of light. Guess I'm not really good. 
I seldom need more than 1/8 turn to synch with a gauges when it's running and that may be differences in how the engine's cylinders are drawing.
There are those that claim if you are really good you can see the light in the sliver turn blue as it nears completely shut.
IE it gets thin enough to start blocking red wave lengths of light. Guess I'm not really good. I seldom need more than 1/8 turn to synch with a gauges when it's running and that may be differences in how the engine's cylinders are drawing.
No, that's not true. If you continue to turn the sync screw after the right closes up, the left will start to open. Turn it back in the opposite direction and the left will close then the right will open. I shoot for the mid-point between when each plate starts to open.
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