89 VR Carb Sync Problems - HELP

[rmcclain]

Today I built one of the carb sync tools using the clear tubes, rubber stoppers, and transmission fluid as the liquid. The tubes are 18" long and I put about 4" of liquid in each. The unit looks just like the many posted on here before. After warming up the bike I connected the four tubes to the carbs, started the bike and all of the liquid was sucked into the #4 tube and was bouncing violently up and down and fluid was sucked into the carb. I finally got it settled down in tube #4 adjusting on both sides and some liquid was now in #3, however, bouncing up and down violently. The entire time no liquid in 1 and 2 tubes. I shut it down and added liquid back to the 4" starting point in each tube. Started it up and the same thing. I shut it down, thinking the carbs were way out of sync I set the three screws the same number of turns. Tried it again and the same thing. Shut it down and put it all back together. Never did get any liquid in 1 and 2 tubes. I tried adjusting the sync srews via the tach (plugs and hose back on) and could get the rpms to move up and down. Kept adjusting until the rpms were at the highest on all three screws then could not get it to idle down to 1000. I noticed the idle adjustment screw was not touching the plate. The only way I could get it to idle down was by adjusting the screw on #1 and 2 carbs. I assume my cable needs adjusted? Any thoughts on the liquid problem in the #4 tube and lack of fluid in the #1 and 2 tubes?

[Venturous Randy]

I am trying real hard to understand what you are doing. Are you sure you are adjusting the correct screws? It sounds like you are trying to adjust the fuel/air mixture screws when you are counting turns.

I suspect using transmission fluid would require a very small orifice in the line to slow the oscillations of vacuum surges. It does sound like your #4 has much more vacuum, which would require that carb throttle plate to be opened more.

RandyA

[rmcclain]

I am adjusting the correct screws. I have a shop manual and I have pictures from this site.

[MiCarl]

"Turns" is meaningless on the sync screws.

 

The reason you can't adjust the idle down is they are way out of sync and one of your butterflies is completely closed - holding the others open.

 

The 18" trans fluid manometer too short to sync with unless you're very close to begin with. I just worked this out for someone on the XJ bikes site. An 18" column of oil is only about 1 psi or 2" mercury. When I sync carburetors it's quite common for one to be out by 2" mercury or more.

 

From the symptoms you have after turning the sync screws you are likely to be out by at least 10" mercury. Your manometer probably needs to be at least 8-12 feet tall to straighten them out.

 

The guy I mentioned previously ended up using a vacuum gauge to get them close then used the manometer for the final tweak.

Edited August 3, 2009 by MiCarl

[Venturous Randy]

I suspect Carl hit this nail dead on the head.

If you have a vacuum gage with four hoses attached to the manifolds and plug the three you are not using, you should be able to get close enough to ultimately use the set up that you have. I wish I was closer as I would use my mercury gages and hope you did not suck the mercury out of them. I suspect you are so far off that you could take the breather off and hold open the slides and see how the throttle plates look. You may be able to visually get them closer than they are now.

RandyA

[Yammer Dan]

I suspect Carl hit this nail dead on the head.

If you have a vacuum gage with four hoses attached to the manifolds and plug the three you are not using, you should be able to get close enough to ultimately use the set up that you have. I wish I was closer as I would use my mercury gages and hope you did not suck the mercury out of them. I suspect you are so far off that you could take the breather off and hold open the slides and see how the throttle plates look. You may be able to visually get them closer than they are now.

RandyA

 

 

I would try what Randy just said. Open the top of the air box and see how far they are out. Adjust them by sight this way to get them as close as you can and go from there. Where are you in Ohio?

[Marcarl]

So far I agree with what been said, but maybe I'll say my two cents worth anyways, seeing as I can't do anything but type and sleep and read. Take off the air box, (there are two hoses attached to the bottom, one is in the center and goes to the middle of the the V in between the cylinders and has a wire clamp holding it in place, and the other is in the front left corner, also with a wire clamp). The one in the center comes with the airbox, the one in the corner stays in place. Loosen the 4 clamps that are above the carbs holding the airbox in place and then wiggle the airbox off. Now if you gently move the slider back in the carb you can see the butterfly at the bottom. Starting with #2 which is the back side carb on the left side, adjust the idle screw (not the idle mixture screw) so that the butterfly closes completely. You can check this by turning the screw in and out to see if the butterfly stops moving and is actually seated against the throat of the carb. If you can't get it to seat, as said before, you probably have one or two other butterflys holding it open, so then check #'s1,3,&4 to make sure they are open, so that they are not seated. I they are not seated, then #2 has to be seated. Once #2 is seated then you seat #1 and then # 3 and then #4, Now don't seat them tightly, adjust just so that they touch, no more. Now you can readjust the idle screw on #2 so that it starts to pick up the butterfly in #2, then start the engine and adjust to a proper idle. Let it warm up well, about 15 minutes, and then attach your carb tune and see what happens. If you suck the trannie fluid into the cylinders no harm will be done, except that it will smoke, but that will go away with time. The order for cyncing is #1 to #2, then #3 to #4 and then #4 to #2. Let us know how it works.

[rmcclain]

Marcarl, good information, however, my shop manual shows carb #1 as the back carb on left side. I hope to try all of this today or tomorrow. I have had the air box off several times so no problem there and I understand what you are telling me so I will give it a go. Thanks to all of you who have replied. This is a great site for getting me out of my own trouble.

[Marcarl]

Marcarl, good information, however, my shop manual shows carb #1 as the back carb on left side. I hope to try all of this today or tomorrow. I have had the air box off several times so no problem there and I understand what you are telling me so I will give it a go. Thanks to all of you who have replied. This is a great site for getting me out of my own trouble.

#1 one is front left, #2 is behind it, # 3 is front right, that leaves #4 being the one behind that. Don't read the book tooo much, some translations didn't work so well.

Just to verify for yourself, take a look at your carbs, check out the linkage(s). You'll notice that the throttle cable leads to the left rear carb, regardless of it's supposed number, that makes it the primary carb to which all other carbs are synced. Now you'll also notice that the carb in front of it is linked to it by an adjustable 'shaft' linkage. So now you can see how to make those two work on conjunction with each other and the front one is adjustable to the back one. Now if you go to the right side and twist the throttle you be able to notice that there is a link moving between the left bank and the right bank and that this link primarially goes to the front carb, also you'll notice how they have cleverly managed to somewhat duplicate that shaft linkage from the other side, it's not quite the same but pretty close. Now the trick is to make the right bank equal to each other, so you adjust the back carb to the front carb. AT this point now we have 2 adjusted banks, the left bank works by itself and so also for the right bank, but they may not be the same to each other. So now is the time to make the front right one equal to the primary, which is the left rear, as we said before, and seeing as there is a link going directly back to that carb without interferring any other carb, by adjusting the front right carb to the rear left carb, you will be able to sync them together and seeing as the rear right is tied to the front right and will stay the same as the front right, when you adjust the front right to match the left rear primary, all will now be perfect.

I hope you like reading, because this is helping me in not getting too bored. Anymore questions, the doctor is still in.

[Squeeze]

#1 one is front left, #2 is behind it, # 3 is front right, that leaves #4 being the one behind that.

....

 

 

I'm sorry Carl, but ...

 

#1 is left rear

#2 is left front

#3 is right rear

#4 is right front Cylinder

 

Also, Throttle Cable is fixed on #2, you adjust #1 to #2, then #3 to #4, then the right to left Bank.

[a1bummer]

Yup, what he said. On page 3-8 in the service manual.

[Venturous Randy]

I think Carl is looking at it from a carb adjustment perspective, not a timing perspective.

RandyA

[rmcclain]

Here is the latest. I set the rpms at 1000. I removed the air box. I discovered that two of the slides did not slide so I got them moving with some carb cleaner and WD40. I then shimmed them back out of the way with thin pieces of cardboard so I could see the butterflies clearly. The throttle cable is attached to the left front carb (whatever number it is). I backed out the screw on the left side until the left back carb would not open when I started to open the left front carb. I then adjusted the screw in until both butterflies started to open at the same time. On the right side the front carb opens first so I did the same adjustment on the right rear screw and got both of the butterflies opening at the same time. I then did the same adjustment on the left front screw and got the two banks opening at the same time. This is really a nice way of doing it since you can see all four butterflies working. I put it all back together and also cleaned the spark plugs since it has been smoking quite a bit from the transmission fluid sucked into the engine. I started the bike and let it warm up. I cannot get it to idle down below 2200 rpms and there is about 1/8" space from the idle adjustment screw and the linkage. I can get the linkage to touch the idle screw if I force the throttle handle but cannot if I let the throttle handle work on its own. Any suggestions?

[rmcclain]

This morning I thought I would try it again so I removed the airbox and backed out the three adjustment screws until they were all loose. The bike is cold at this time. I then adjusted 1 and 2 the 3 and 4 and left and right banks. After this I noticed the linkage was now resting on the idle adjustment screw so I started it up with the choke and let it warm up. The idle was high so I adjusted the idle screw and got it down to 1000. Don't know what was different from yesterday but it is ok now, however, I still can not use my home made manometer. The only thing I can think of is yesterday I am not sure if I loosened all three screws before starting. I was reading some threads and it was mentioned that if the rpms would not come down it was idling on 3 and 4. I also lubed all of the linkage. Anyway, I feel I am at least back to where I was before I got myself into trouble. Now I will find a real Carbtune and some help and do this right. Thanks for all of your help. The bike was running good before I started this mess, however, had a few pops at idle and me being somewhat of a perfectionist I wanted it perfect. Oh well.

[Marcarl]

Ok, so it looks like even though I was screwed up on front and back etc, (I was going by memory, not actuality) you got things lined up to carry on. And it sounds like you're on the right track. Now what I would check is the amount of play in the throttle cable. To work as per spec's there should be about a 1\16" play in the throttle, measured at the handle. At this point I would lossen that a bit, just to make sure that the cable is not the culprit. Twist your throttle and at the same time look to where it is hooked to the carb. Once you get the feel of where is activates the carb you can look to see how much play there is, or you can do this by feel, one hand on the throttle and one on the carb linkage. Once you have determined that it's not the cable, it could also be the linkage and springs that are holdinng things up, so give them a washdown with wd40 or carb cleaner. maybe that will help lossen things enough for all of it to work as it should.