Throttle cable stuck

Hello everyone,

I am just getting going on full rebuild of my 72 Commando 750 .

Its been sitting (outside under a tarp) for over 12 months and was in a bit of a sad state before but it was running.

Couple of issues,

I cannot turn the accelerator to open the throttle. I have stripped it down an it seem that whatever needs to move in the carb might be stuck? The choke cable opens an closes just fine.

Should I be looking at taking the carb off and rebuilding it or is there something more simple to check first?

also, rusty water mixture coming out of tail pipe when i kick it over?????

Thanks

Just a wag here but... water in the carbs corroded the throttle slides. Intake valve open, water may have entered the cylinder that way. Carb disassembly as a first step. I might be tempted to pull the head too.

Were the spark plugs in place the whole time?

T. E. Lawrence said:

I cannot turn the accelerator to open the throttle. I have stripped it down an it seem that whatever needs to move in the carb might be stuck? The choke cable opens an closes just fine.

Should I be looking at taking the carb off and rebuilding it or is there something more simple to check first?

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There would normally be two carbs and two choke cables so what exactly is this apparently single carb?

Sounds like maybe you are going to have to start at the top and go through everything , I would not think of trying to fire bike up until I had a real good look at everything involved in that exercise , so yah top end off , carb, drain sump see what in it , look down spark plugs , air filter and so on , always better to be very cautious at this stage .... good luck enjoy the process !

maylar said:

Just a wag here but... water in the carbs corroded the throttle slides. Intake valve open, water may have entered the cylinder that way. Carb disassembly as a first step. I might be tempted to pull the head too.

Were the spark plugs in place the whole time?

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yeah, plugs in the whole time.

I read that spraying WD40 into the carbs might help?

L.A.B. said:

There would normally be two carbs and two choke cables so what exactly is this apparently single carb?

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it has duel carbs

You definitely want to pull the carbs off and have a look inside them. Maybe some fine emery or a scuff pad to free them up. And you gotta figure out where the water in the cylinders came from.

maylar said:

You definitely want to pull the carbs off and have a look inside them. Maybe some fine emery or a scuff pad to free them up. And you gotta figure out where the water in the cylinders came from.

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Are there any video tutorials showing the best way of doing that?

Maybe check around your local area for a Club or another Norton owner maybe they could take a first hand look and offer some suggestions .... if bike outside and upswept mufflers on could be rain water laying pipes and not from further into engine, carbs etc. .... got to get a look

The following is a video series detailing a full restoration from a basket case. There are several eposides with carb work and trouble shooting. Unfortunately the author didn't do a great job titling the videos so it is hard to drill into just the relevant ones. There is a "table of content" type video abount mid way through the series.

https://www.youtube.com/channel/UCW-o_oUdFunmUGj1Dz2jEgw

Also check out the Bushman Guide to Amal carb tuning:

http://www.jba.bc.ca/Bushmans Carb Tuning.html


And the technical info "sticky" listing on this site:
https://accessnorton.com/NortonCommando/technical-information.2265/

Not really any tutorials. Normally, with the tank off you can undo the 2 screws at the top of each carb and get the throttle slides out from the top. But if yours are corroded stuck you'll need to take the air cleaner off and persuade the slides to come out. Alternately, you can remove the manifolds from the head and remove the carbs and manifolds with cables still attached. You'll need a cut down Allen key to unscrew the 2 inner manifold bolts.

maylar said:

Not really any tutorials. Normally, with the tank off you can undo the 2 screws at the top of each carb and get the throttle slides out from the top. But if yours are corroded stuck you'll need to take the air cleaner off and persuade the slides to come out. Alternately, you can remove the manifolds from the head and remove the carbs and manifolds with cables still attached. You'll need a cut down Allen key to unscrew the 2 inner manifold bolts.

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thanks, this is really helpful, I will update the post with my progress and add photos

Craig said:

Maybe check around your local area for a Club or another Norton owner maybe they could take a first hand look and offer some suggestions .... if bike outside and upswept mufflers on could be rain water laying pipes and not from further into engine, carbs etc. .... got to get a look

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I think your right about the upswept muffers. I have cranked it a few times and that has cleared all the water.

Craig said:

if bike outside and upswept mufflers on could be rain water laying pipes and not from further into engine, carbs etc. ....

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good call.

T. E. Lawrence said:

Are there any video tutorials showing the best way of doing that?

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“ I have stripped it down an it seem that whatever needs to move in the carb might be stuck?”


Hire a good mechanic. Or bribe with beer a tutor.
Seriously.

Are you sure that the throttle twist grip isn't seized up ? Take the air cleaner off and see if you can lift the slides with your finger.

I use a twin-pull twist grip with separate nylon-lined cables. Some of the older type cables corrode inside and seize

T. E. Lawrence.

Was there an air filer in place while the bike was outside under a tarp? Most likely water in exhaust but not through carbs and cylinders but be methodical and observant as you go about this.

Step at a time and make observations and start with the easy and readily accessible possibilities

I would start by checking carb intakes to see if there is any hint of water.

Is the twist grip is free to twist (a bit) through the slack range of the cable? If no, then start investigating a frozen twist grip. If yes, then move on to the next step.

Once you remove the air filter (assuming it was in place), see if you can lift both slides with your finger, one slide at a time. If the slides are free then I would look at the cable components and the cable splitter to see if something is out of place or fouled up. If one or both slides are stuck or sticking then remove slide covers (two small Phillips screws on top of each carb - assuming you have the factory AMAL) and remove covers with slides and chokes and inspect and clean slides and bores until free. At this juncture you probably should consider taking both carbs off and cleaning and inspecting the, If the slides have in fact stuck you need to be very careful in assessing the conditions, why it occurred and if your remedy has really solved the problem. On occasion I thought I remedied a sticking slide and upon assembly found it was still sticking, sometimes even worse than when I first found it sticking.

If there are indications water may have gone through the carb and into the engine, pull and inspect each plug for water or rust indications. See what you can inside the cylinder barrel through the spark plug hole. There are some inexpensive bore scopes available. Depending upon what crap and corruption you might see in the cylinder, either kick the engine through several times with the plugs out and observe what comes out or pull the head.

If the carbs are old and clapped out, you should seriously consider new replacements. There are some great options out there.

Keep us posted on progress and ask questions.

A stuck throttle can ruin your whole day.

Dances with Shrapnel said:

T. E. Lawrence.

A stuck throttle can ruin your whole day.

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It can ruin a lot of people's day

I was paraphrasing Thucydides who is quoted as saying: “a collision at sea will ruin your entire day”