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fab carb sync tool and use

Old 12-15-2009, 08:20 PM
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fab carb sync tool and use

I spent a lot of time messing around and was ready to order a Twinmax when i finally got things sorted out. I think it may helpful to those trying to sync carbs with a homemade tool like the one pictured on this site: http://www.powerchutes.com/manometer.asp

I used a tie down strap to hold the tank up as pictured by GregW on another thread and it worked great. https://www.superhawkforum.com/forum...ight=carb+sync

And I had previously ran a second vacuum line from the front carb and cut the vacuum line between the petcock and the rear carb and inserted a "T" (both lines need to be the same ID and length from the carbs to the point of connection of carb tool to keep vacuum readings accurate).
https://www.superhawkforum.com/forum...=carb+sync+mod


Carb sync tool: I didn't use a yard stick, but just a board about 3.5'x4" and about 8 ft of opaque tubing I had lying around. I used u-shaped electrical wire nails to affix the tubing to the board in the shape of a large "U", careful not to crimp tubing and to mark the center point.
Put 2 stroke oil into the tubing with a squeeze bottle with a pointy tip(mine was one I got from DynaBeads for balancing tires). I squeezed the oil to a level of approx 2/3 up the board. Don't fret about air gaps as I did(using mighty vac, inserting a thin wire, etc.) because it's a waste of time and energy. Just stand the board up against something and tie the tubing up with a small bungy and it'll drain slowly down on it own. It may help if its warm and you may have to blow it back and forth a couple times to get the inside of the tubing oil coated. After a few times it settles quickly on its own when stood upright. When it settles, use a small square and a thin black marker to make a few lines in the area of and at the oil level between the tubes(slide square under tubing and align with board edge to make straight lines). This will give you a more accurate quick look.

Make sure engine is warmed up well. Unplug the vacuum lines. I just used a plug on the front carb line and a “T” for the rear. Pull the plug from the front vac line and remove the rear carb line from the “T” so that both lines are bare end tubing, the same length and ID. Use the cap to cap the “T” on the vac line going to the petcock.
Now you have two open tubes, one to each carb.
Next, I laid the board down next to the front wheel with a bucket under to tilt it towards me, hooked up the lines and started the engine. The oil rushed up one of the tubes so fast I couldn’t adjust fast enough and had to shut engine down so as not to suck oil into carb; then there were air spaces everywhere. Remove tubes and stood board up with the tubes tied high to let the oil drain again. I did this a bunch of times til I read something about using restrictors to keep vacuum gauges from fluttering or bouncing and thought that this may help with slowing down the oil rushing up the tube too fast. I found a piece of tubing that would snugly fit inside the sync tool tubing and cut two 2.5 inch pieces. Before inserting it, I took the spray tube from a WD40 can(the new one with the gray spout because it is a bit larger ID/OD than the reg spray cans); then cut two 2.5 inch pieces and inserted them into the other 2 cut pieces. So now you have two restrictors. Next, I forced a pointy ice pick type tool into the holes on both ends of each WD40 tubing piece to assure congruent openings and blew through them to make sure air could pass easily. Push these restrictors into the tubing allowing half to protrude. Now you should be able to push the restrictors into the vacuum lines coming from the carbs, leaving the same gap on each(no need to force them all the way in). Now you’re ready to start the engine(make sure the line going to the petcock is plugged).
With had the tank tilted up as high as possible, you can reach in above the upper frame rail with a 7mm or 9/32 open end wrench to adjust the sync bolt. Start the engine, adjust the idle to 1200 rpm, then start adjusting. If the oil starts to move, adjust slowly til it stops at which time you’ll probably have turned the bolt too much. Try to get the oil to stabilize even if it one tube is higher than the other. There is a miniscule amount of adjustment bolt turn between still/even and oil movement. It’s unbelievable. Mine started to idle slow and stalled. So I turned the key off and turned the idle **** up a hair. Then disconnected the tubes and stood the board up with tubing tied up so it could drain level again. It drains faster now. Plugged the front carb line and reconnected the vac line between the rear carb and the petcock. Then started the engine and make sure the idle is at 1200rpms. Shut down and reconnect tool and see if the oil in the tubing stays level. If it does you’re done, although I would repeat to make sure, mainly because I like to stutter a lot, ha ha ha ha. You see.
I had to remove, set idle, and reconnect tool a few times before it would stabilize. If there is any popping, clunking, backfiring, stumbling, or roughness you should call your physician immediately.
Hopefully, this description will make the carb sync much easier for anyone who makes their own sync tool and is attempting this for the first time. Have fun
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Old 12-16-2009, 05:26 AM
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Nice writeup nathan. I'll use it when I get around to doing a sync. I discovered the homemade tool a few years ago with my old VX800. it works like a charm, and numbers on the yardstick ar irrelavent. what's important is that the fluid is the same on both sides.
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Old 12-16-2009, 05:42 AM
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Originally Posted by NCDave View Post
Nice writeup nathan. I'll use it when I get around to doing a sync. I discovered the homemade tool a few years ago with my old VX800. it works like a charm, and numbers on the yardstick ar irrelavent. what's important is that the fluid is the same on both sides.
thnx Dave. a little long and cumbersome, but better too much info. hopefully will save others time and uncertainty in terms of their first attempt.
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Old 12-16-2009, 11:09 AM
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A really easy way to eliminate the air gaps in the oil is to swing the carb synch tool over your head (like a lariat). The centrifugal force will act on the oil, drawing it to the bottom in just a couple of quick swings.
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Old 12-16-2009, 11:21 AM
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Originally Posted by Brother J View Post
A really easy way to eliminate the air gaps in the oil is to swing the carb synch tool over your head (like a lariat). The centrifugal force will act on the oil, drawing it to the bottom in just a couple of quick swings.
yeah and maybe you could use this move on dancing with the stars too lol. First post. welcome aboard Bro. do you have a SH or........ Give us a little background info so we have something to use against you.
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Old 05-02-2010, 02:16 PM
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If you just stick the tube into the container of fluid you have chosen, you can just siphon the fluid up. Quick and easy with no bubbles.
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Old 05-22-2010, 03:51 PM
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Originally Posted by Brother J View Post
A really easy way to eliminate the air gaps in the oil is to swing the carb synch tool over your head (like a lariat). The centrifugal force will act on the oil, drawing it to the bottom in just a couple of quick swings.
definitely works. We were syncing carbs the other day(Steve29s bike again)and had to do the carb dance several times to eliminate air gaps. The problem that was giving us fits ended up to be related to too little oil in the the tubing. Anyway, we kept trying to sync, and despite the fact that i had the red WD 40 tubing installed inside the ends of the fish tank tubing, the oil was moving too fast to respond to. We kept trying and finally decided to add more oil because half of it was gone, either sucked into the carbs or pushed out the ends to relieve air gaps. So I added some trans fluid and it slowed the movement of the oil to the previous level noted in the #1 post, i.e., easily manageable

The other thing we noted was that we were holding the sync adjuster forward to counter the pressure from the snake tool we were using to sync the carbs(to turn the adjuster bolt). This turned out to be affecting the idle, so we had to figure out how to hold the snake tool so that it wasn't pushing on the throttle spring. This got us in the ball park, then we used an open end 7mm wrench to get it exact, which is the equivalent of a hair.

One more thing I should note. We disconnected and capped off the vacuum that goes to the rear carb. This causes the bike to run out of fuel after it idles a bit, so we reconnected everything and ran the bike again to get the fuel back in the carbs. We wouldn't have had to do this if we would have had the tubing filled to a higher level. I have a 3' board with the tubing attached and the oil level is about 2" below the top of the board. Cheap-*** sync tool works great if you have all the variables covered, so that's why i added this info to the thread. Hopefully, this will prevent others from suffering similar problems.

the other thing i should mention is that when we got it right it was idling smoothly at 800 rpms.
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Old 05-24-2010, 07:48 AM
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Originally Posted by nath981 View Post
One more thing I should note. We disconnected and capped off the vacuum that goes to the rear carb. This causes the bike to run out of fuel after it idles a bit,
If you pinch off the line with the bike running first, it will trap vac press to the fuel valve and stay running.
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Old 05-25-2010, 04:04 AM
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Originally Posted by alwayshonda View Post
If you pinch off the line with the bike running first, it will trap vac press to the fuel valve and stay running.
How the hell did you figure that out? I'll try this when I sync mine shortly. Thanks.

Fortunately, once we figured out that the volume of oil affects speed of travel in the tubing, syncing is much more manageable.
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Old 05-25-2010, 05:53 AM
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Originally Posted by nath981 View Post
How the hell did you figure that out? I'll try this when I sync mine shortly. Thanks.

Fortunately, once we figured out that the volume of oil affects speed of travel in the tubing, syncing is much more manageable.
or install a vac T in the rear line,, add a short piece of hose and then cap it when not in use..

Add the vac fitting in the front, short piece of tube, cap when not in use.

Now yo have both ready to go, no gas tank removal, no running out of gas while tuning...

When your done tuning, tuck both lines behind the frame spar,,, go ride.
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Old 05-25-2010, 06:11 AM
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Originally Posted by E.Marquez View Post
or install a vac T in the rear line,, add a short piece of hose and then cap it when not in use..

Add the vac fitting in the front, short piece of tube, cap when not in use.

Now yo have both ready to go, no gas tank removal, no running out of gas while tuning...

When your done tuning, tuck both lines behind the frame spar,,, go ride.
Already have all this. Raise the front of the tank(strap method)for easy access to sync screw. The problem was that if I couldn't get it synced within a couple of minutes, it would run out of fuel, which is alledgedly alleviated if you clip off the vac line after engine running.
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Old 05-25-2010, 10:53 AM
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Originally Posted by nath981 View Post
Already have all this. Raise the front of the tank(strap method)for easy access to sync screw. The problem was that if I couldn't get it synced within a couple of minutes, it would run out of fuel, which is alledgedly alleviated if you clip off the vac line after engine running.
I did like E.Marquez did. Never had to remove the line to the fuel valve. That way it won't run out of fuel either. If you are worried that this would affect the accuracy (didn't seem to), then just pinch the line like I was saying earlier. It's just like holding your finger on a straw to trap the fluid. Time to go enjoy this weather!!
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Old 05-25-2010, 10:11 PM
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Originally Posted by nath981 View Post
Already have all this. .
Think you may have missed something then...
If you did it like I described (think I described) then the vac line to the fuel tap is still conencted... And you really do not need to mess with raising the tank to gain access to the scyn screw. 1/4 drive driver handle, 4" extension, universal joint and socket is all you need.

Start and warm up motor, hook up gage's, balance them off one cylinder, hook up second cyl, check sync, adjust screw as needed, removing driver each time and gently opening and closing throttle between adjustments ..

Other then motor warm up.... it's a 5 min job.... and once done with sync.. you pull the gage tubes, cap to vac lines and your on the road..
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Old 05-26-2010, 04:23 AM
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Originally Posted by E.Marquez View Post
Think you may have missed something then...
If you did it like I described (think I described) then the vac line to the fuel tap is still conencted... And you really do not need to mess with raising the tank to gain access to the scyn screw. 1/4 drive driver handle, 4" extension, universal joint and socket is all you need.

Start and warm up motor, hook up gage's, balance them off one cylinder, hook up second cyl, check sync, adjust screw as needed, removing driver each time and gently opening and closing throttle between adjustments ..

Other then motor warm up.... it's a 5 min job.... and once done with sync.. you pull the gage tubes, cap to vac lines and your on the road..
the problem i had was related to using a snake-type extender and discovered it was putting pressure on the adjuster spring(rear carb); then I tried to hold it forward with my thumb to counter this and ended up putting pressure the other way. So now I lift the tank using the ratchet strap to hold it up at a 45 deg angle and watch that the throttle spring is not being moved either way. Then, when it's close, i use a 7mm open-end to tweak out the final adjustment.

The way i've been doing it now is to disconnect the rear carb hose from the vac line, then cap off the vac line(to the tank). Next uncap the front carb hose and attach both carbs to the home made sync tool(tubing with oil).

I like to lift the tank because it's easy with the ratchet strap and i can see what I'm doing better. But your way is a bit different and obviously works well for you. I don't understand how you do one carb first, but I don't use a gage, so maybe that's why.
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Old 09-28-2010, 11:21 AM
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ok, what fitting here? am I missing something?





Attach a piece of vacuum tubing to the fitting and use that to screw the fitting into the engine. I use the 8mm wrench to guide it into the hole as follows:


is that large copper colored pipe inside the vac tube a "fitting"???? and where is this getting screwed into the allen hole that is clearly occupied?
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Old 09-28-2010, 12:01 PM
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The allen head is there to block the hole for normal operation... And yes, you could use that soft copper pipe as a makeshift fitting, since it will most likely be airtight... But the smart option is to purchase the parts from Honda for the cost of a decent beer and install the correct nipple and then a cap for when you are done... The artno# are in a thread around here somewhere...
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Old 09-28-2010, 12:15 PM
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Old 09-28-2010, 12:56 PM
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it's a part, what exactly is it and where does it go in that hole? does it come oem on our bikes?
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Old 09-28-2010, 01:18 PM
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That part is a nipple for a vaccum hose... There is one fitted to the other carb for operating the petcock... You remove the allen head and put this in there... Once you are done, you replace the allen head, or put on a cap on the nipple, leaving it there for next time you need it...

BTW... If you use the partno# that you got in the link, and search on Ron Ayers parts fische you will easily answer the questions you just posed... Ie does it come OEM on the VTR... What is it, where does it go... It's a totaly wonderful concept... Information, just there for the taking...

Sorry about the sarcasm... You get that as a freebie... hawk just posted the partno# i mentioned the post before, so I thought it would be pretty obvious what it was...
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Old 09-28-2010, 01:18 PM
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It's #7 on this diagram:
http://fiche.ronayers.com/Index.cfm/...LINDER_HEAD_FR

It goes in the hole that has a solid plug in the front cylinder head (the same spot that the vacuum port for the petcock is located on the rear head) and yes it is OEM but only on Ca model bikes.
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Old 09-28-2010, 01:20 PM
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damn too slow again..... and light on the sarcasm, need to take better notes.....lol
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Old 09-28-2010, 01:22 PM
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BTW... This is the cap I mentioned... If you like me prefer not to curse at it every time you need to swap the nipple for the allen head or reverse...

http://www.ronayers.com/Search/N/687...-000/Source/HO
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Old 09-28-2010, 01:25 PM
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Originally Posted by Tweety View Post
That part is a nipple for a vaccum hose... There is one fitted to the other carb for operating the petcock... You remove the allen head and put this in there... Once you are done, you replace the allen head, or put on a cap on the nipple, leaving it there for next time you need it...

BTW... If you use the partno# that you got in the link, and search on Ron Ayers parts fische you will easily answer the questions you just posed... Ie does it come OEM on the VTR... What is it, where does it go... It's a totaly wonderful concept... Information, just there for the taking...

Sorry about the sarcasm... You get that as a freebie... hawk just posted the partno# i mentioned the post before, so I thought it would be pretty obvious what it was...
haha no worries, but I did initially cross reference the part on there and it was mostly cbrs and vfr's up to 1997. I'll pick one of those nipples up and then do the sync.
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Old 09-28-2010, 01:26 PM
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ps thanks for clearing that up
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Old 09-28-2010, 01:33 PM
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Originally Posted by nothing View Post
haha no worries, but I did initially cross reference the part on there and it was mostly cbrs and vfr's up to 1997. I'll pick one of those nipples up and then do the sync.
Yeah... For some reason the VTR's doesn't make it to the top 100 for that part...

I think it's stupid to cross refernce each year separate... If you do top this or that give the models, then click them and get the years... Could it be that hard Ron Ayers?
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Old 07-16-2018, 02:20 PM
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Just got all my parts, synced carbs when I got them back on. Made a tool about 10 years ago, differential gear oil in clear tubing. Used it for years syncing ZRX in line 4 carbs. Worked well for the VTR also.




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