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Discussion Starter #1
I'm trying to decide if i should just pay $45 and get a tool off of eBay or if i should just pay someone some $ to do it for me/show me...I figure somebody here lives in Brooklyn and wouldn't mind helping me tune my 500T, right? I could be wrong...
 

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ok, i get the hint...i'll just buy the tool.
The old Haynes and clymer manuals used to have diagrams for carb synching tools you could make out of vacume line and baby food jars. Total investment of $10 tops if you wanted to get fancy.

Do a search on the web and you'll find plans out there somewhere. My clymer for a cb750 has plans to make on in the back.

If I am not mistaken your cb500T has CV (constant velocity carbs). There really isn't much to synch on these carbs since the slides operate off engine vacuum and not a cable. IF you are expirencing unequal slide movement it is probably something else wrong.
 

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Discussion Starter #4
hmmm i didn't know that...so, as long as the cable is adjusted right, than there's really nothing to adjust right?
 

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hmmm i didn't know that...so, as long as the cable is adjusted right, than there's really nothing to adjust right?
yes and no. The carb butterfly valves determine carb velocity and vacuum pressure which is what moves the slides up and down. You would still need to check if the butterflies are moving in sync otherwise one carb may be expirencing a different vacuum reading than the other at the same throttle position. And there is still the idle circuit to adjust (the air or fuel bleed screw) to insure a proper idle.

With traditional carbs you use vacuum pressure to measure the mechanical adjustments and fine tune the setup. With a CV carb measuring vacuum is still diagnostic but the adjustments you make are different and the system is more forgiving. Because of their nature you are less likely to feel the difference of an out of sync cv carb because the carb automatically adjusts to the engine's needs (via vacuum). More often than not any problems are the result of air bleeds somewhere else in the system (like cracks in the rubber intakes for example).



Edited by - geeto67 on Oct 16 2006 2:27:29 PM
 

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Discussion Starter #6
good to know. i think i'll still synch them to be sure. hard to tell b/c this is my first road bike and i've got nothing to compare it to or know anybody else who rides a 500T or 450 to ride mine and give me suggestions.
 

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good to know. i think i'll still synch them to be sure. hard to tell b/c this is my first road bike and i've got nothing to compare it to or know anybody else who rides a 500T or 450 to ride mine and give me suggestions.
On the butt dyno, the biggest change you will see from sync-ing the carbs will be that your clutch noise will be less at idle. Your powerband may also be smoother if your carbs were really out of sync. It doesn't hurt to sync the carbs, but it is not a band aid fix for anything - if you have bigger problems sort them out first or your efforts will be for naught. SOme of the most common problems I hear people trying to fix with sync-ing the carbs are:

1) cam chain tensioner - this gets noiser if it is about to fail or out of adjustment. Sync-ing the carbs will reduce some of the engine noise but if your tensioner is on the way out nothing will keep it from going.

2) noisy clutch - air cooled hondas have a noisy clutch at idle, it is just how they are. Sync-ing the carbs cuts this noise a lot but it never really goes away. If the clutch is overly noisy you may want to check the botls holding the springs aren't backing out.

3) uneven powerband - if you are noticing the bike has hesitations in the powerband it is more likely a carb or intake problem. Same if you have surges. When synching the carbs if the carbs trade places in terms of the vacuum they draw as the rpms climb, then your problem is not the carbs being out of sync but more likely an air leak on one carb vs the other.

4) CV carbs - constant velocity carbs have slow throttle response. It is their nature. people think that sync-ing the carbs will improve their throttle response, and it will to some degree, but it won't work miracles. If you are wacking open the throttle and have time to contemplate the universe before your bike gets up and goes, you have other problems. Also if you are used to a cable bike and switch to a bike of equal power but uses CV carbs - that throttle lag is normal and sync-ing will not fix it.
 

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Discussion Starter #8
thanks i really appreciate the info. like i said this is my first time really messing with carbs. i'll post the results of the carb sync after i get it.
 

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Discussion Starter #9
so, i got the vacuum dial gauge tester thingy...hooked up to carbs, warmed up bike and noticed that 1 side had more pressure than the other. what's strange is that i couldn't get the pressure to change via adjusting the idle limiter or the throttle stop screw. what's even more strange is that the carb with the higher pressure is the side that pops a little when it's cold. any thoughts?
 

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Higher vacuum (lower pressure) or lower vacuum (Higher pressure)?

Doesn't really matter but if there is a big difference between the cylinders you've got another problem. As someone else mentioned check the carb boots for cracks. Also how is your valve adjustment? These bikes have a fiddly valvetrain and the valves are run tight. If your valve adjustment is closed up then that valve or valves cannot close all the way and leak out combustion pressure causing all kinds of issues including low vacuum at idle.

What is your compression like? You should ask over at the CB450 yahoo group or forum.
 

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Discussion Starter #11
the valves are properly adjusted so that's not the problem..it's hard to get a reading on the gauges at idle as i have the shorty mufflers and the gauges flutter, easier to read when the bike is above 2,000rpms but isn't the point getting the carbs synched at idle?..i guess my problem could be an intake boot or compression in 1 or both cylinders.
 

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Discussion Starter #12
the valves are properly adjusted so that's not the problem..it's hard to get a reading on the gauges at idle as i have the shorty mufflers and the gauges flutter, easier to read when the bike is above 2,000rpms but isn't the point getting the carbs synched at idle?..i guess my problem could be an intake boot or compression in 1 or both cylinders.
 

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If they're fluttering a lot that's another problem. With stock cams it shouldn't be that bad. Could be leaky valves. I wouldn't waste time diagnosing it until you check the compression.
 

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If they're fluttering a lot that's another problem. With stock cams it shouldn't be that bad. Could be leaky valves. I wouldn't waste time diagnosing it until you check the compression.
 
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