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Discussion Starter #1
Anyone have any issues synchronizing their stock carbs? I've been trying to synch them and found that the horizontal cylinder doesn't produce the vacuum that the vertical one does (or vice-versa). So I took the air box off and looked at the sliders while revving the engine. I found that the slider for the horizontal cylinder opens up significantly faster & easier than the vertical one. I cleaned the carbs, rebuilt them, changed the seals and still found the same problem. Should I replace the spring on the slider on either one of the carbs?
 

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they're called slides, not sliders.

you need to examine the carb diaphragm on the slide thats not rising, likely torn or something not assembled correctly.
 

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they're called slides, not sliders.

you need to examine the carb diaphragm on the slide thats not rising, likely torn or something not assembled correctly.
I had the same problem. Spent lots of cash for two nice vacuum gauges and I couldn't get them to sync. I acutually did a better job by removing the airfilter and syncing the throttles visually. Just made sure they were both closed while turning adjustment screw. Took it to the dealer for other maintenance issues later that week and they verified I did a great job!

Some how using gauges can be inaccurate because of too many factors with older bikes according to the tech. Leaking, old, cracked vacuum hoses and worn carb parts will cause uneven gauge readings.
 

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i'd want to examine to eliminate any problem limiting slide action prior to adjusting to compensate. i say give diaphrams/slides/springs a looksee first.

OP, what kind of synch device are you using anyway?
 

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Discussion Starter #5
Finally have a chance to look at the responses. I just rebuilt them and they looked fine - as far as the diaphragms are concerned, and the springs too. I visually checked them and wiped them down with a soft cloth/solvent to remove any residue that was on them.

I was trying with a hand held venturi. Not the greatest, so I bought a couple of fittings to connect to a monometer I made. Haven't check it yet since I've been traveling lately. That'll be the next thing I do.
 

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Interestingly, I also noticed that the slide on one of the carbs on my 900SL was a bit "sluggish" compared to the other when I manually opened the slides & let them return by themselves. Since the diaphrams & slides were in perfect condition, I carefully stretched the spring on the "sluggish" slide so that both slides returned to the close position at the same rate.

Admittedly, I first should have checked to see if the slides moved in unison while the engine was running & creating vacuum pressure.
 

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Interestingly, I also noticed that the slide on one of the carbs on my 900SL was a bit "sluggish" compared to the other when I manually opened the slides & let them return by themselves. Since the diaphrams & slides were in perfect condition, I carefully stretched the spring on the "sluggish" slide so that both slides returned to the close position at the same rate.

Admittedly, I first should have checked to see if the slides moved in unison while the engine was running & creating vacuum pressure.
That is basically whay I did. Visually checking the sync and cleaning all the "residue" from the diaphrams and springs. I think the vacuum gauge method is only for when you don't want to take the airbox out! :)
 

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Discussion Starter #8
Didn't think to check the slides to each to each other as I was rebuilding the carbs. I'll have to do that and tweak the spring on the sluggish one. Thanks
 

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Didn't think to check the slides to each to each other as I was rebuilding the carbs. I'll have to do that and tweak the spring on the sluggish one. Thanks
Bruno,

I would suggest that you first check the action of the carb slides by blipping the throttle with the engine running. By removing the air filter, you can observe the action of the slides in the carb bores. If you blip the throttle & the slides move smoothly in tandem, that should indicate there is no problem.

If one of the slides seems sluggish to return, simply remove the black plastic caps & the diaphrams to access the springs.

BTW, be sure to re-check the carb synch. Best of luck.
 
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