My CBX1000C Restore Project

[heli_madken]

Fighting with the carbs at the moment. The accelerator jet on No3 was well and truly gummed up and no amount of air pressure would clear it, in the end I ran a few cycles through the Ultrasonic cleaner at its highest temperature and left it to soak overnight in a strong mix of cleaner so sorted that.

Everything has been thoroughly cleaned every jet removed, all passageways checked for clearance etc.

Come to put the carbs back together following Mike Nixons book and I have a strange problem I cant get my head around. Starting with No3 and No4 as per instructions I can join the two carbs no problem. But I can see that as is I would have no chance of synchronising as the sync adjuster is buried between the carbs and looks nothing like mikes picture.

Looking at No1 and No2 in this picture the sync adjuster is in a completely different position -

20220114_113339.jpg

No1 looks correct to me but No2 is pointing in the wrong direction surely? Both butterflies are closed, I haven't touched these at all so whats going wrong?

You can see the issue in this picture, the corresponding fork on No3 matches the sync screw -

20220114_115217.jpg

Any help would be appreciated

[daves79x]

They are correct. You come at the 2-3 and 4-5 adjusters from the rear, right at the scallops in the top carb frames.

Dave

[Jeff Bennetts]

Tool time!

Here’s a link to the inexpensive 90% adj tool,
https://www.amazon.com/Motion-Pro-08-01 ... 9398&psc=1

I have the gear driven adj, more better!
https://www.motionpro.com/product/08-0229

[heli_madken]

They are correct. You come at the 2-3 and 4-5 adjusters from the rear, right at the scallops in the top carb frames.

Dave

Phew thanks Dave, I just cant seem to match Mike's picture but I figure he must have used another pair of carbs other than 3-4, threw me completely off.

Thanks Jeff took the precaution of buying the tool a while back.

[pablotrini67]

I recently completed my 1979 carbs VB 60 A ,they aren't much different than an 82 ,have them sitting on my computer desk ,the way I did it was re-assembled the lower section of each carb with all jets ,floats & bowls assembled ,I f you never removed the carb sync adjuster then they would be correct , start with the # 3 ,install the choke rod ,make sure the spring on the choke rod is installed correctly,it's very easy but hard to explain ,install the choke butterfly on the # 3 carb ,this will hold the rod in place & prevent the spring from moving , if you don't have new screws for the butterfly use some red threadlock , the sync adjuster for the # 3 carb faces up and it's on the right side ,it's on the connector where the two banks of carbs are connected this would be on the engine intake side of the carbs , connect # 2 carb to # 3 ,the # 2 carb sync adjuster faces rear & upwards towards the air intake manifold ,it's difficult to get @ especially when on a bike ,I synced my 82 cbx & requires the special tool , then connect the #1 carb , #1 carb sync adjuster faces up & on the engine manifold side the # 4 carb does not have a sync adjuster as all the other carbs are synced to # 4 , do the same for carbs 4,5,6 then connect the two banks together,before securing all the bracket bolts make sure the choke & carb intake butterflies are moving freely and not sticking ,I found just slightly moving the brackets that secure everything together makes a difference ,once everything looked ok i then assembled the upper parts of each carb ,have attached a photo of the special tool for the syncing , , one picture shows the screwdriver out ,the other picture shows the screwdriver in it's correct place .& of course you will need the vacuum guages for sync the carbs properly , have fun.

[daves79x]

I think the tool Jeff is referring to is the 90 degree screwdriver for adjusting the mixture screws. The tool needed for syncing the carbs is different. K&L carries the long one, as pictured above and you can still get the short one from Honda, I think.

Dave

[Jeff Bennetts]

I think the tool Jeff is referring to is the 90 degree screwdriver for adjusting the mixture screws. The tool needed for syncing the carbs is different. K&L carries the long one, as pictured above and you can still get the short one from Honda, I think.

Dave

Yes Dave is correct, pretty inexpensive and readily available at most MC shops or of course Amazon for $12.00

[pablotrini67]

I think syncing the carbs was almost as difficult as re-building , when I did my 82 carbs & with the freshly re-built 79 carbs I noted how many turns the air screw was out before dissassembly ,it just gives a good reference point ,although final tune it might be different.

[Jeff Bennetts]

I think syncing the carbs was almost as difficult as re-building , when I did my 82 carbs & with the freshly re-built 79 carbs I noted how many turns the air screw was out before dissassembly ,it just gives a good reference point ,although final tune it might be different.

There are so many other factors that can affect a carb sync, your valve adjustment and the condition of them, timing, timing chain stretch, vacuum leaks, weak ignition, whether it’s a waning or waxing moon and how much Scotch you have consumed!

[heli_madken]

Thanks for your help everyone.

The nearest match I can find to Mike's picture is between 1-2 which looks nothing Like 3-4 when following the instructions. I guess he was only making a point about the washers rather than this is how the linkage should look. I guess I am desperate to get this right -

20220114_183042.jpg

I already have the long sync tool from work on other bikes and bought a very nicely made short version a while back.

[Jeff Bennetts]

I know it’s after the horse has left the barn but always take pictures with your phone or IPad before you take it apart. IMHO

[heli_madken]

I did Jeff but none of the pictures seemed to confirm my doubts in relation to the book even though I took at least 20

I think syncing the carbs was almost as difficult as re-building , when I did my 82 carbs & with the freshly re-built 79 carbs I noted how many turns the air screw was out before dissassembly ,it just gives a good reference point ,although final tune it might be different.

I did the same but I am not confident after all the shenanigans that I am close to where they where before. I note Mike Nixon does not like the rod method of bench syncing what are peoples thoughts?

Interesting that all the sync screws still had their yellow seals on so these carbs have never needed to be adjusted

[pablotrini67]

The carbs on the 1979 which I just re-built were the same ,the yellow locking sealant was still visible & looks like they had never been synced ,the bike had 42,000 kms ,I think it's a tune-up procedure that get's overlooked and many people don't bother and yet it can cause alot of issues , even the knocking clutch noise can be caused by out of sync carbs , you can bench sync just by making sure all of the carb butterflies are opening together ,but will need a final check on the running engine.

[Jeff Bennetts]

I did Jeff but none of the pictures seemed to confirm my doubts in relation to the book even though I took at least 20

I think syncing the carbs was almost as difficult as re-building , when I did my 82 carbs & with the freshly re-built 79 carbs I noted how many turns the air screw was out before dissassembly ,it just gives a good reference point ,although final tune it might be different.

I did the same but I am not confident after all the shenanigans that I am close to where they where before. I note Mike Nixon does not like the rod method of bench syncing what are peoples thoughts?

Interesting that all the sync screws still had their yellow seals on so these carbs have never needed to be adjusted

Are you referring to the CarbTune sync tool?

[heli_madken]

Almost there with the carburetors -

20220117_175535.jpg

Setting float heights - totally agree with Mike Nixons approach only trouble is my old eyes just cant cut it, so a while back I came up with an alternative approach using air pressure. Used it on my other bikes and it works a treat.

I designed and 3D printed this -

20220117_174737.jpg

Here are its component parts -

Diagram.png

It is fixed in position using the float bowl screws on a stand as shown here -

20220117_115432.jpg

An air line is attached to the carburetors which has an inline low pressure air gauge, I just use a normal foot pump to apply pressure

This is how it works -

1. The gauge is set to 15.5mm (much like the usual honda tool)
2. The indicator gauge is lined up with the reference marks (white marks in the picture above and below)
3. The gauge is bolted in position
4. Two of the carbs have their floats clamped closed.
5. The knurled knob is turned one full revolution clockwise. In effect at this position the float valve should remain closed.
6. Air is pumped in to give around 0.2 PSI (as little as possible to avoid compressing the damper spring) using the gauge shown as a reference.
7. Turn the knurled knob anti-clockwise, in theory after one revolution (when the white marks line up) air pressure should escape. If it doesn't adjust the float until this happens.

In effect what I am looking for is the exact moment at which the needle valve opens, you immediately see a drop in pressure, you can also hear the hiss as air escapes and feel the rush of air on your fingers.

I am using an M4 coarse thread knurled screw which has a pitch of 0.7mm so if you can get the release point within an 1/8 of a turn either side of the reference mark you will be just 0.08mm out. Takes a while but you can get very accurate, the process is repeated for the other carbs getting them all to the same point.

The advantages are that firstly if the carbs hold the pressure you know that the fuel circuits are not leaking. Secondly judgement is taken out of the equation as you are not using your eyesight and mechanical skill to achieve the result. Lastly all 6 carburetors will be set very closely to the same level.

One other aspect is that you could if you wanted try further settings weaker or richer and have a reference point stored by marking the indicator gauge for future reference.

In practice on my carbs only 5 and 6 where very slightly out, whoever set these floats last had a very good feel for the process and excellent eyes!

Hopefully you wont shoot me down in flames but this has worked on my other bikes a treat. If anyone wants the files to print and make their own gauge let me know.

Another view you can see the white reference marks more clearly -

20220117_120444.jpg