[Goofyfoot2001]

Ok, I realized I had an extra carb so I wanted to figure out why my idle was so high after synching my carbs. Well, it makes sense if you watch the video. Also, I tested for air leaks and found none using propane and WD40. The propane thing is kinda scary yo.

Video is here http://youtu.be/Zc59BThqRa4

And so now, it's like, crappers, so in order to get the carbs to synch I have high idle, so how do I get them synched? Going to replace some spark plug wires and see if I that helps. Maybe I'm not burning enough in the front cylinder.

 

[Knifemaker]

First, I'd like to thank you for the video. Always wanted to see what that screw did.....

Next, I'll say this, and I know there will be folks here that will say I'm wrong, but I was always told that in this bike, because it uses CV carbs, the only thing you really need to "sync" on the carbs is to make sure both butterfly valves open at the same time when you crack the throttle. ("Butterfly Valve" is the term you were looking for in the video BTW)

I asked an actual mechinic at a Kaw dealer this and he said the same thing.
I remember "synching" carbs on a Triumph twin by pulling the air boots off and holding a mirror up to see if both valves opened at the same time...(helps to pull the diaphragms out)

Your vacuum diffrence might be do to a clog, a defect in the carb itself, or something else....

 

[Goofyfoot2001]

Something else

Well, short of ripping the carbs off, I have no clue. I'll wait for cold weather before I get into that stuff. It rides pretty well now except for the slight vibration at 3500 up. I put some rubber in between the foot peg and the bike and that helps. It would make sense what you say about the valves opening at the same time and hopefully at the same rate.

I can't believe carb boots cost $25 bucks a piece! Man.

 

[wmsonta]

In the video, the idle adjuster isn't touching because the throttles are closed tight.

Back off the lower throttle cable until you have about 3/16-1/4 " play. Start over.

got to go .

 

[Goofyfoot2001]

Back off Lower throttle adjuster

It doesn't touch because of the synch screw pushing everything away from it. The throttle cable wouldn't do anything cause it's all the way loose (in the video there is no throttle cable so it's definitely loose.)

 

[wmsonta]

ok, you are saying when the carbs are in sync, the throttle plates are too far open. You opened one before the idle got too high.

So, barring vacuum leaks the front throttle plate is sticking too far open. In order to sync, you then open the rear.

Unusual problem, but I think I understand.

If in your shoes, with no vacuum leaks, I would pull the carbs. I would look for mechanical obstruction to closing in the front carb. Gummy buildup, piece of dirt, throttle plate improperly adjusted on the throttle shaft, etc.

edit- before doing any of this, you may want to compression check both cylinders. Either cylinder poor could cause this.

 

[Knifemaker]

Yes what he said^ ...... But are you saying the same "gap" exsists on the carbs that are on the bike?

Again I submit that synching the carbs is a somewhat useless endevor... As it only deals with zero throttle idle. If both butterflies open at the exact moment you begin to twist the throttle, that's all that really matters as engine demand will effect the rise and fall of the carb diaphragms.

Is there anyone that disputes this?

 

[WilliamTech]

ok, you are saying when the carbs are in sync, the throttle plates are too far open. You opened one before the idle got too high.

So, barring vacuum leaks the front throttle plate is sticking too far open. In order to sync, you then open the rear.

Unusual problem, but I think I understand.

If in your shoes, with no vacuum leaks, I would pull the carbs. I would look for mechanical obstruction to closing in the front carb. Gummy buildup, piece of dirt. throttle plate improperly adjusted on the throttle shaft, etc.

edit- before doing any of this, you may want to compression check both cylinders. Either cylinder poor could cause this.

I also was thinking along these lines, but due to inexperience with carbs, I let the experts speak there wisdom & experience.

:smiley_th

 

[blazblu82]

I gotta ask, how bad is the vibration when you feel it? Is it bad enough to shake mirrors? If so, I would be concerned your balancer dampeners are going out.

Here's a quick test you can do w/o the bike moving down the road. Put your bike on center stand on a smooth concrete floor, turn it on and let it warm up (skip this if already warm), then start cranking the throttle to where you feel the vibes and watch to see if the bike moves around the floor. If it moves a lot, then again I'd be concerned about your balancer dampeners.

Before I had the balancers replaced, my 750 had bad vibes in the pegs and mirrors at around the same RPM's.

I could be wrong, but the sync adjustment shouldn't affect the carbs beyond off idle / slow cruise. Beyond that, both should be getting enough air to where the sync doesn't matter anymore. Again, could be wrong on that analysis.

 

[wmsonta]

I could be wrong, but the sync adjustment shouldn't affect the carbs off idle / slow cruise. Beyond that, both should be getting enough air to where the sync doesn't matter anymore. Again, could be wrong on that analysis

The sync will affect the entire pilot circuit. The first 25% of the throttle, 90+% of all your riding. I now run 60-65 mph @ 1/4 inch of throttle.

These people are right, no discernible difference in WFO. Do not have mpg yet, I expect little change. Dunno.

The intermediate circuit does not 'see' vacuum until the end of the pilot circuit.

 

[blazblu82]

The sync will affect the entire pilot circuit. The first 25% of the throttle, 90+% of all your riding. I now run 60-65 mph @ 1/4 inch of throttle.

These people are right, no discernible difference in WFO. Do not have mpg yet, I expect little change. Dunno.

The intermediate circuit does not 'see' vacuum until the end of the pilot circuit.

I meant to say beyond idle / slow cruise.

 

[Goofyfoot2001]

The whole point was to reduce vibration

So it was the front carb that had the least pressure FYI which is why I turned the adjuster bolt out for the rear carb. They did get even until you gave it gas then the front shot over the rear and you were out of room to adjust idle.

The vibration is a buzz on my feet and maybe a little on my butt. I did the center stand thing and it didn't move at all. When it buzzes, it also rattles something, maybe in the headlight bucket, not sure. It's just really annoying and can't be right.

I may just have to wait until the season is over to rip out everything. I think I heard some tapping so prolly have some valve stuff going on. I will do the compression test however! Once I figure out how to do it :doh:

 

[Jakzen]

Sounds kinda like you might have a vacuum leak somewhere on the rear cylinder. As far as the vibration, a buzzing sound may be something as simple as a wire connector floating around, a loose bolt or screw, etc... I'd also check the motor mounts. Not something I've really seen much on in the forum, but it's a rubber part and you know you can't always trust them rubbers...

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[blazblu82]

Sounds kinda like you might have a vacuum leak somewhere on the rear cylinder. As far as the vibration, a buzzing sound may be something as simple as a wire connector floating around, a loose bolt or screw, etc... I'd also check the motor mounts. Not something I've really seen much on in the forum, but it's a rubber part and you know you can't always trust them rubbers...

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This. There are springs on the throttle cables which can vibrate against the cylinder head. Also, the radiator cap has a spring which can vibrate. Loose heat shields and other areas of the bike can produce a buzzing sound, too. Mine had one in the right-front turn signal housing which was caused by a loose reflector.

 

[Goofyfoot2001]

It's not a buzzing sound it's a buzzing feeling I got