Carb Sync questions

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kampinguru
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Carb Sync questions

#1 Post by kampinguru » Tue Nov 14, 2017 10:14 am

I have replaced the throttle cable now and have a question about syncing the carbs. Should the carb slides be flush with the top of the intake port at WOT or how do I set them. They both bottom out but the right one moves before the left one. That part is easy to correct but I seem to recall from the racing days that you open the throttle all the way and the bottom of the slides should be flush with the top of the intake ports. Thanks very much.

MK
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Re: Carb Sync questions

#2 Post by MK » Wed Nov 15, 2017 2:15 pm

As nobody feels obliged to share their method:
The important area is certainly a low position where the needle position is important.

I though flush the upper position close to WOT (unscrew upper airbox and use a lamp & mirror to check visually)
For cable actuation that's ok, as they move pretty parallel (i.e. flush at WOT means also flush at low position)

The RD500 has a link coupling that doesn't move the lower/upper carb slides parallel.
It has a mark at the middle position that you ought to synchronize, but in my experience that's crap.
The important area is the very low range, so I put something like an 10mm allen key under the slide and actuate the throttle until it just gets free. Then keep the throttle constant and check the other side. Then do the same for left/right carbys.
Also saw a variant of that method with popsicles under the slide, that should start moving at the same time when slowly increasing throttle positions.
Bye
Martin

kampinguru
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Re: Carb Sync questions

#3 Post by kampinguru » Wed Nov 15, 2017 3:15 pm

Thanks Martin. I appreciate it.

hondaror
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Re: Carb Sync questions

#4 Post by hondaror » Wed Nov 15, 2017 9:15 pm

I'd look in to buying a carb Uni syn. It will be way more accurate as it deals with the vacuum associated with each carb and matches them while your engine is running.
Rory

kampinguru
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Re: Carb Sync questions

#5 Post by kampinguru » Thu Nov 16, 2017 1:06 pm

Thanks Rory. It looks like you would need two of them to do both carbs correct? Do they just go in the intake side of the carbs when you pull the airbox off?

hondaror
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Re: Carb Sync questions

#6 Post by hondaror » Fri Nov 17, 2017 5:21 am

One is enough. Yes on the intake. Read the first carb, and then the second. Make adjustments to even them up.
Rory

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T.RexRacing
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Re: Carb Sync questions

#7 Post by T.RexRacing » Fri Nov 17, 2017 9:31 am

I machined a set of fittings that fit into the crossover spigots that allow use of a mercury or dial gauges. I find it much easier and accurate.
There is only one difference between a madman and me. The madman thinks he is sane. I know I am mad.
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kampinguru
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Re: Carb Sync questions

#8 Post by kampinguru » Fri Nov 17, 2017 10:21 am

Hi Rory. Do you use the 4025 or the 4027 Uni Syn. There seems to be bad reviews about the 4027 motorcycle version. Seems it is pretty cheaply made in China and breaks easily.

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two-stroke-brit
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Re: Carb Sync questions

#9 Post by two-stroke-brit » Fri Nov 17, 2017 3:08 pm

T.RexRacing wrote:I machined a set of fittings that fit into the crossover spigots that allow use of a mercury or dial gauges. I find it much easier and accurate.
^^^^ and you can sync without disturbing the filter assembly.
can you post a pic of your set up .
thanks mark
350LC,Athena 392 big bore,stock porting,swiss cheese air box,stock reeds,spec11 pipes.(now TSA big bore pipes)
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hondaror
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Re: Carb Sync questions

#10 Post by hondaror » Fri Nov 17, 2017 9:00 pm

I can't tell you that right now, as I'm 900 kms north of home.
Rory

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T.RexRacing
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Re: Carb Sync questions

#11 Post by T.RexRacing » Fri Nov 17, 2017 10:39 pm

two-stroke-brit wrote:
T.RexRacing wrote:I machined a set of fittings that fit into the crossover spigots that allow use of a mercury or dial gauges. I find it much easier and accurate.
^^^^ and you can sync without disturbing the filter assembly.
can you post a pic of your set up .
thanks mark
Gimme a day or two. Kinda occupied and this site doesn't like me posting photos for some reason.
There is only one difference between a madman and me. The madman thinks he is sane. I know I am mad.
Salvador Dali

LC Cnd
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Re: Carb Sync questions

#12 Post by LC Cnd » Sun Dec 17, 2017 12:45 pm

Purchased a 4025 cause Rory advised this was the best way to go as apposed to the popicycle method of balancing carbs - I'm a believer. Be interested to see the photos and learn how it all works. Be a teachable moment for many I suspect - thx.

spook
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Re: Carb Sync questions

#13 Post by spook » Sun Jan 14, 2018 4:42 am

I have used the popsicle method for decades on my race bikes except for the Honda cb1100r that used to be my road bike.I still have the group of four vacuum gauges of which i can use two of them on the T rex racing system. Please Rory get those pictures up ASAp.

Many thanks in anticipation,
Russell in OZ.

hondaror
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Re: Carb Sync questions

#14 Post by hondaror » Sun Jan 14, 2018 5:55 am

I'm at school for another 4 weeks and then will likely be too busy when I return, for a little while, catching up after 12 weeks away, in the last 14. I'll need a bit of time.
Rory

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