carb synch issues

[squidley63]

I'm trying to get the carbs synched on my 89 fj1200 and I can't seem to get my number 3 cylinder vacuum reading up. I've torn down the carbs a couple of times and have sonic cleaned all the jets and bodies of the carbs and set the float heights according to the instructions on this site.
I pulled the carb boot off and switched it with the adjacent cylinder and the problem did not move with the boot. I'm just stumped as to why I can't seem to get the vacuum of this cylinder up.

I've checked valves and they are a bit tight if anything. The plug looks the same as the others a light brown. The carb is getting gas I checked it with a piece of clear tubing. I just can't figure this out for the life of me.

[movenon]

What sync tool are you using ? I had a leak in one of my lines once that did the same thing (also a kink in the line can do the same). Perhaps spraying some starting fluid around the carb boots / manifold / diaphragm area might give you a clue.

If that fails I would do a compression check just because.  Then check the the manifold to engine connection, there is an O ring there. Inspect the manifold for cracks, and that's it's not leaking around the boots, check the vacuum diaphragm (do a blow test). Of course spraying some starting fluid around those areas should have picked up something. Hope something helps there. 
George

[Firehawk068]

when you turn the syncronizer screw for carbs 3-4, does the vacuum reading for #4 go up and down?

If it does, lower #4 to match #3....................then use the syncronizer screw in between 2 and 3 to  match 1-2 to 3-4...........

It is possible you have 1-2-4 matched, and are trying to raise #3 up to where the others are?  You will never get it there that way..........

Unless it's not this obvious, and you have an internal problem with the carb................I am not sure if pinholes in the diaphragm would cause sync issues?
Perhaps the carb guru could say (SlowOldGuy, his name escapes me right now.......Mr. Rayforth?)

Hopefully it's that obvious a fix 

[ken65]

i personally would get the valves in spec 1st, then start the sync again, IMHO

[squidley63]

Valves are only a thousandth tight(1 of the intakes on cylinder 4 exhaust on cylinder 2). When I tighten up screw between 3 and 4. Four goes down but 3 stays the same.  I have to assume that something is amiss with carb or cylinder 3. I switched boots between 3 and 4 without change so I would say that would eliminate the intake boot or oring  I know that the carb is getting gas in the bowlafter checking with a bit of clear hose. I didn't get a measurement on the level but it seemed to be just under the gasket level.

I'm going to check compression on the cylinders and pull the carbs to try and see if I can find anything wrong with it.

[Dan Filetti]

Four goes down but 3 stays the same.  I have to assume that something is amiss with carb or cylinder 3.

It's been a long time since I held FJ carbs in my hand, but isn't #3 NOT adjustable?  As was alluded to above by Firehawk, when performing a sync, all of the other 3 carbs must be brought in line with #3, as #3 can not be adjusted.  Others know this MUCH better than I, but you may be chasing a red hearing.

Dan

[movenon]

Have you checked for air leaks ?

I prefer to adjust as per the service manual. Try it just using 2 gauges.

1 to 2 (left bank)
3 to 4 (right bank)...
then 1 to 3 (balance the left and right banks together).

And see how she runs.
George

[squidley63]

Sprayed carb cleaner around the boots and got no change in rpm. Unfortunately its supposed to rain the next couple of days so no working on the bike until I catch a break in the weather.

[Firehawk068]

Does the tool you are using have a vacuum measurement scale on it?
Mine read in CmHg scale (or centimeters of mercury)

What vacuum readings are you getting?
I would consider mine to be a "Normal" properly running FJ engine, and when properly synced, all cylinder readings settle around 20 CmHg......
I'm sure most other stock engines would read about the same..(idle speed rpm would probably change this, mine is around 1100 rpm)


Also, before you started the sync process, have you adjusted the idle air mixture screws to where they should be.............these would change your vacuum readings I believe....

I still am miffed by your issue.............when you turn the syncronizer screws, it opens one butterfly, while closing the other one.............
Vacuum readings should go up, as the other cylinder goes down......and vice-versa...........

Look very closely at your synchronizer screws...........there should be 2 little springs on each one (one between the head of the screw and the carb bracket, and one between the carb bracket, and the sister carb bracket) If any of these springs are missing, it would be impossible to sync the carbs........

Hope you get it figured out, and post up what you find.......

[squidley63]

Found out some of the problem at least. My temp tank was low on gas causing some starvation problems. I'm still having an issue with low vacuum. When I get them equal across the board I only have about 5 inches of Hg  I can adjust 1 and 2 to above 10 inches of Hg by loosening up the synch screw between 2 and 3. I can also get 4 up to over 10 inches of Hg by adjusting the screw between 3&4. With the others backed out 3 is about 2.5 inches of Hg and gets to 5 when I level them out.

I've sprayed carb cleaner around the boots and no pickup or anything I've also exchanged the boots on 3&4 with the problem staying with 3. I can't find my adapter for my compression gauge so I haven't checked compression on the cylinders yet.

Next I'm going to open up carb 3 to see if it may still have some gunk in it somehow while I find an adapter for my compression gauge to see if I have an issue there.

[Firehawk068]

what's your idle speed?
If it is really low, your vacuum readings will be low also................
5 inches of Hg = about 12.7 CmHg

Check all of your idle air mixture screws, check your idle speed, then level them all out and see where you are at.........

Have you had the tops off to check to see if the vacuum diaphragms have any pinholes in them?

[dougrs]

I could be wrong but when I synced my carbs earlier this year, I didn't worry about what the actual numbers were at all. What mattered was getting the values equal across the board. It took a few cycles of syncing and then adjusting the idle mixture to get her running really well.

Found out some of the problem at least. My temp tank was low on gas causing some starvation problems. I'm still having an issue with low vacuum. When I get them equal across the board I only have about 5 inches of Hg  I can adjust 1 and 2 to above 10 inches of Hg by loosening up the synch screw between 2 and 3. I can also get 4 up to over 10 inches of Hg by adjusting the screw between 3&4. With the others backed out 3 is about 2.5 inches of Hg and gets to 5 when I level them out.

I've sprayed carb cleaner around the boots and no pickup or anything I've also exchanged the boots on 3&4 with the problem staying with 3. I can't find my adapter for my compression gauge so I haven't checked compression on the cylinders yet.

Next I'm going to open up carb 3 to see if it may still have some gunk in it somehow while I find an adapter for my compression gauge to see if I have an issue there.

[squidley63]

I'm not sure about an acceptable number for synch. I just worry that everything has to be synced down to a carb. I'm used to cars where you look for a number in the 20s at idle.

[fj11.5]

Don't worry about the numbers, just get them the same reading as #2 carb