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Carb care

4K views 41 replies 8 participants last post by  izak 
#1 · (Edited)
Did clean the carbs by dismantling all the components and the fuel jets, and by soking in an acetone /thinners mixture, and by aerosol carb cleaner, and by compressed air blown through all the little channels.

With the mixture setting valves/screws turned 2.5 out from fully screwed in, the bike runs perfectly with more responsive power than before the carb cleaning.

I am going to turn the mixture screws in, bit by bit , quarter turns, to see if a leaner mix can save some on fuel.

Question : Is the loss of engine power, and sparkplugs that are to whitely burned, the only ways to detect a air/ fuel mix that is too lean?

Auto part Carburetor Automotive engine part Engine Fuel line


I have it, that by screwing this final mixing screw inwards, causes a bit more UNFILTERED air to mix with the nebulised fuel ,
just before in enters the combustion chambers , via the intakes.

PS . ~ the left side carb's no 78 primary fuel jet was completely blocked , as if is it was welded closed ! I had to open it up with a fine hypodermic needle ,the same size as the opening in the right side's corresonding 78 jet. The secondary jets are no. 112.

The other interresting thing is that my model GL500 has only one fuel tube that connects the float chambers of the two carburaters, not 2 as is shown in the diagram of the FSM.
 
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#33 ·
Final count down: me thinks the set bolt/screw and the locknut combo is not a perfect patent.

If, after the screw is at the right spot on has to lock the bolt, but there is only one bolt that can not be locked to the setting plate nor the setting screw. It can easily be turned it to far and will then push the retaining plate further down to unbalance the butterfly valves again from it's setpoints.

Auto part Fuel line Automotive engine part Engine Carburetor


I have a plan to "lock" the screw to it's nut by applying a few drops of locktide similars on their joining treaded surfaces. Product Plastic bottle Pink Liquid Material property

Which one should I use?

Thanks in advance for inputs!
 
#34 ·
It's not a good design IMHO. You need to learn and anticipate the amount the adjustment will move when the locknut is tightened.

I've had an idea for a while of a conversion to a friction screw.

Threadlock shouldn't really be necessary, but I'd go the blue nutlock if using it.

I'm patient. We learn by doing and by asking.
 
#35 ·
Something don't seem correct on that screw, nut, spring assembly.

There is no way that system will lock into place. Yes, it has been a while since I balanced my carb, but I certainly don't recall that set up. Of course, it could be different from my '81 CXC.......could someone verify if that assembly is correct?
 
#36 · (Edited)
Appears correct. It will lock as the threaded screw is also threaded into the arm.



Just grabbed a set from the shed. Izaks assembly is correct. Bottom to top on the adjuster. Washer, left carbs thick alloy arm, washer, spring, right carbs adjusting plate, nut. ;}
Pic coutesy Larry Cargill.
 
#37 ·
Thanks CXPHREAK. The problem still is that even if the lock nut is turned downwards onto the setting bolt, the position of the setting bolt in relation with the right card's setting arm can make the set screw to displace upwards. Because the arm has a treaded hole in which the settingscrew /bolt 's treads also engage.

I have a gut feel that vibration in the long run will change the setting if the nut on the bolt is not fixed more firmly to the arm.
 
#39 ·
The proper tool for adjusting the balance consists of a tube with a socket on one end and a handle on the other with a screwdriver that fits through the middle. The screwdriver must be a perfect fit in the screw head. (I made my own by welding an 8mm socket onto one end of a tube and a 1/4" nut onto the other; I drilled the threads out of the nut and ground the sides of the screwdriver to fit through.) It is much easier to adjust the balance with this than with a wrench and a screwdriver.

The screwdriver must be held in the screw when you tighten the nut to keep the nut from turning the screw, but even with the best fitting screwdriver there is still a bit of "lash" that will allow the screw to turn with the nut when you tighten it. You can reduce this somewhat by turning the screwdriver counterclockwise a bit to hold the screw and keep it from turning with the nut.

Someone has obviously used a poorly fitting screwdriver and messed up the slot in your adjusting screw (either that or tried to turn it without loosening the nut). You will have to be more careful than usual about holding the screw in place while you tighten the nut.

Once the nut is tightened it will lock against the threads in the arm and will not normally loosen without a wrench. Threadlocker will only make the job unnecessarily difficult the next time.
 
#40 · (Edited)
CXPHREAK and Sidecar Bob: thanks!

If the treads on the inside of the hole in the little arm that accommodates the set screw were stripped completely , the set screw would not have been able to move the arm up or down against the spring under the arm and around the length of the screw.

I hope that the strength of the spring will hold the locknut and set screw in place when all is in operation with the action of the swivelling of the throttle.

Otherwise I will have to dismantle everything to tap and die all the treading of the arm and the locknut and the set screw.
 
#41 ·
The lock nut (actually a jam nut) works by its threads putting pressure on the threads of the screw in the opposite direction to the threads of the primary nut (in this case the threads in the arm). If it is tightened securely (doesn't require a lot of force, just enough to make it tight) it will not loosen again without the use of wrenches.

Every bike in the CX/GL500/650 and many, many more bikes have similar balance screw/jam nut arrangements and they don't loosen off with the movement of the throttle.

The spring has nothing whatsoever to do with the nut staying done up. Jam nuts are used in a lot of other applications where there is no spring anywhere near. The purpose of the spring is to maintain the distance between the arms once the carbs have been balanced.
 
#42 · (Edited)
After balancing the carbs by turning the set screw in and out untill the levels in the fabricated vacuum bottles were precisely equal ( the lock nut was first loosend anticlockwise in relation to the set screw ) , I did turn the lock nut clockwise, untill it came flush with the arm, without disturbing the position of the set screw, by holding it in it's place with the screwdriver's end snugly fitted in its slot. I used a 8mm spanner to ' tighten ' up the lock/jam nut against the arm of the valve.

I think that the treads in the arm is such that, when the locknut is loose, and the set screw is turned clockwise, the arm moves upwards on the set screw and, vice versa; when the set screw is turned anticlockwise the arm moves downwards ?

Of this I am really not sure , because I was so occupied by checking the fluid levels in that bottles at the time, that if a bomb went off behind me, I would not have noticed it ! :D

The treading of the arm must be stripped ( like CXPHREAK says ) , because there is not much resistance if one is tightening the lock nut clockwise onto the arm and the spring.

I did recheck the bottle levels finally ( after applying 3 drops of the locktite onto the nut and screw ) reving the engine a little, and the levels stayed perfectly the same.

At this stage the bike runs and purrs perfectly at idle, and pulls effortlessly and powerfully at all levels of it's revolutions while on the road , so I am satisfied that the balancing of the butterfly valves was done OK by the procedure.

Time only will tell , as per usual :)
 
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