stuck throttle

hi. looking for help with 750 maxim stuck throttle. cable lubed up. attached at handle the throttle turn free. but as soon as i attach to the carb retainer, the throttle wont turn. is the link at the carbs supposed to be attached to a spring of some kind (mine is not), the link moves freely but i think it should be attached to something to cause the throttle at the handle to snap back . thanks

 

Each carb in the rack has a spring at the adjustment screws. They all pull together and should provide lots of snapback to pull the cable back to idle position.

 

Is the outer cable in its seat.

 

Are you booking the throttle cable to the choke lever instead? Seen it happen on here before.

 

hi Franz,

the choke cable is pulling correctly, i can see the carburetor bar moving - but the throttle link is bot attached and has very free movement, its as if the link has detached from a retaining spring, i might have to take the carbs out to have a look, thanks Ken

 

Can you post a video of what is happening?

 

hi Franz. i will post up video ill get my son to help. i took photos and trying to upload. thanks again

 

I think you need five posts before you can upload photos.

 

do you have the short link cable attached, between the throttle cable and the carb , shown here at the bottom of the picture

 

ah thanks, I cant see that on my bike, ill have a look later -i think something like this has become detached, thanks

 

hi Franz -i will get video soon
Ken

 

Does the throttle shaft turn if you attach a wire to the bracket the throttle cable fits into and pull it? Have the carburettors been rebuilt?

If you remove the throttle cable from the carburettor then turn the twist grip to the fully open position grip the outer cable and pull the inner cable. Does it operate freely?

 

the throttle shaft moves freely with no cable attached but solid when throttle attached at both ends. cable is moving free within cable cover when i twist grip when detached from carb link as in photo. also the throttle link has 2 pivots like an elbow, at the bottom of the link and at the arm where cable attached

 

https://photos.app.goo.gl/oadnBSf1p5B6pQCz9

 

hi franz hope you can open videos i have attached

 

Have you got the throttle cable fitted correctly to the twist grip? I can see your video.

 

Do you have this elbow arrowed on your machine?

 

Is the cable fitted correctly in the twist grip?

 

How many millimetres is there when the cable is attached? How long have you had the bike and was it running before? I am wondering if you have the correct cable or it is attached incorrectly at the twist grip.

 

It appears in the quick videos that he is just flopping the linkage around and not actually opening the throttles. The cable will pull that linkage up to open the throttle plates, the piece is supposed to flop around without a cable as it's on a pivot.

Can you get a video with the cable attached? It seems from my view/best guess that the throttle shaft is frozen. Did this run?

 

https://photos.app.goo.gl/oadnBSf1p5B6pQCz9

ah thanks for your replies. everything appears to be right at the twist grip. my bike has the elbow part that retains the cable. what is the purpose of the large spring next to the elbow. should it move when cable turned to open carbs. thats not happening . thanks

 

hi thanks for your help the spring next to the thottle cable linkage is solid. should i be able to move it manually with screwdriver to open carbs. thanks. correct the thottle shaft is floppy and appears to do nothing

 

Jayrodoh is right about the cable lifting the pivot bar. That spring is one that shuts the throttle shaft. Here are my carburettors with a piece of wire attached. Have the throttle plates ever been removed and refitted? Can you turn the large idle screw at the back of the carburettors clockwise?

 

I tried to upload a video of the mechanism moving and returning under spring pressure but file was too large. Fit a piece of scrap wire as l have in the photos to see if the mechanism is free and not binding up.

 

Is your bracket like this?

 

I wonder if one of the two throttle shaft nuts are too tight binding the throttle shaft and preventing the twist grip opening the throttles?

 

The large spring is one of the springs that shuts the throttle shaft.

 

ah ok well that spring is solid and wont move manually either. carbs out to have a look ?. thanks

 

Yes looks like the throttle shaft is binding. These are from a 750

 

thanks Franz, is this repairable or new set of carbs ? - thanks for your help

 

You should try and repair your carburettors. There is plenty of information on here and many people who have overhauled their carburettors. Can you move the throttle shaft when the carburettors are off the bike? Where are you from in Scotland? The carburettors in the picture were overhauled.

 

hi the throttle shaft doesn't move. only the elbow part that the cable attaches to. haha was wondin where you were. im in ellon aberdeenshire thanks again

 

Remove the carb rack. Something is jammed or the main spring coils are rusted together.

 

Can you turn the idle screw at the back of carburettors? I have been to Ellon years ago l live near Glasgow.

 

fair play. im going to have a poke about at weekend & see what i can see. cheers

 

thanks. thats possible it has sat a while ill take carbs out for a look . thanks

 

Probably something jammed, as the springs are made from stainless steel (I believe), as I've never seen a rusted set (dirty, yes, but never rusted). A number of things can cause the the butterflies to jam:

- incorrect carb rack assembly: if the rack screws were ever loosened (doesn't even require removal of the carbs, just loosening the screws will allow the carbs to walk a bit and get out of linear alignment with each other, and then the brackets on the throttle shafts bind against each other).

- butterfly valves re-installed incorrectly (off-center, or in some cases, upside down).

- extreme oxidation of the carb bodies

- incorrect re-assembly of the throttle shaft, brackets, and springs.......although the springs look all the same, they are actually all different and although you can "force" the spring from (example) carb #1 onto carb #2, you'll end up with either a really loose or a coil-bound spring.

- bent throttle shafts. Rare, but it happens.

- other reasons.

 

I don't know about "extreme oxidation" @chacal , both my Hitachis and one set of Mikunis were seized solid when I got them - UK weather can be harsh...
So I would say not uncommon to see these seized solid..

 

Well, perhaps, if they've set outside for an extended period of time. We've certainly seen carb sets where the shafts/butterflies are seized, but it's never been due to seized throttle shaft return springs, it's always due to some other reason.

The images and video that oscarcat posted don't show any corrosion of the springs.

 

Yes I meant the shafts, not the springs

 

hi franz. got it sussed carbs out and sprayed with carb cleaner. free as a bird . hooked all up now starter button not workin n throttle very slow to snap back. . gettin there. avin a beer n watchin glasto. try again later

 

If you have the original glass tube fuse box replace it with a blade type one. Clean the old fuse clips and check for voltage at the solenoid harness connector. Will it turn over if you bridge the solenoid contacts with a screwdriver? Mabe power is not getting to the start button.

 

cheers franz must be an issue one on the fuses blown