Topic: Throttle mechanism siezed or jammed on a Hondamatic

[drackett_19]

Hey guys, my buddy has a '76 cb750 Hondamatic that we're trying to get on the road. Apparently it ran and operated great when he stored it away in the garage 2 years ago.

After uncovering it he noticed the throttle was really hard to turn and then after a couple twists it siezed in place and the throttle wouldn't turn at all. We thought it might be the cables but we disconnected them and they moving freely.

I tried to open and close the throttle with a screw driver after disconnecting the cables and it won't budge. Its like something is jammed or lodged.

We are considering pulling the carbs off to get a better look, but I figured I'd check here to see if this is a common issue with Hondamatics or if anybody has some suggestions.

cheers.

[750K2]

oh ya.  time to clean the carbs.  the needles are probably stuck.  DON'T try to pry them free with a screw driver... BAD dog, BAD!   drop the carbs, get yourself some carb cleaner and be prepared to see a lot of gunk in the bowls, orifices and passages.  there's a ton of fantastic tips on carb cleaning here on this site.   and as for carb cleaning fluid, there's all kinds of options.  i went to the local auto store and bought a bucket with a soaking tray but that costs about 25 bucks.  there's cheaper alternatives.  try searching for 'simple green'
good luck

[TwoTired]

It's probably the SLIDES that are stuck.  A heat gun or hair dryer on the carb bodies should release them.  But, getting gas or wd-40 on them will keep them free.

May also be the fast idle cam/choke mechanism catching, too.

A screwdriver prying on the slides puts a burr on them and this will definitely Eff them up and make them parts donors.  If you did this, find another hobby where thought isn't required, and have your buddy slap you really hard.

Cheers,

[mystic_1]

Agreed, they're likely gummed up with the residue from evaporated gasoline.  Were the carbs drained for storage?  Was the petcock turned off?

Pull off the carbs, it's the only way to clean them thoroughly.  You do not necessarily have to tear them down all the way, or even to pull them off the rack.  Start by cleaning everything inside the float bowls, and hose down the throttle sliders (front and back through the carb throat) with Gumout carb cleaner, this should dissolve the varnish enough to get them moving.  Regardless of which chemicals you end up using on the carbs, avoid exposing the rubber and plastic parts to it.

cheers
mystic_1

[750K2]

once again i stand corrected.  slides... ya, that's definately what i meant!     TT, you keep me honest.

[TwoTired]

once again i stand corrected.  slides... ya, that's definately what i meant!     TT, you keep me honest.

Or, perhaps I was just "needling" you? 

I usually drop one of the carb bowls before pulling the carbs.  That always gives me an idea about how bad things are inside.  Sometimes, I can get away with a few blasts from aerosol carb cleaner....sometimes.  Otherwise, I put the bowl back on and commence carb bank removal.

Cheers,

[drackett_19]

Okay thanks alot for all the suggestions. He took the tank off but didn't drain the float bowls, so I'm sure its pretty gunked up. We'll pull the rack and get them cleaned up.

A screwdriver prying on the slides puts a burr on them and this will definitely Eff them up and make them parts donors.  If you did this, find another hobby where thought isn't required, and have your buddy slap you really hard.

By slides, do you mean the part that the throttle cable connects to/sits in. If so, the slides are fine.

[TwoTired]

Here you can see the slides in the bore of the carburetor.  You are looking into the carb where the air enters.

The slide on the left is undamaged.  The slide on the right has been damaged by a numbskull (and then filed to move in the bore after the carb body was scored on slide removal).

These are now parts donor carbs and are unlikely to ever see a working motorcycle.  And, the numbskull has a different line of work, (parts counter sales or management, I think).

[750K2]

carbs are the swiss watches of your venerable honda.  finely tuned, they will whisk you along, through the twisties, along country roads, fire up faithfully every time you push the starter and respond to every turn of the throttle.  f*'em up and you'll never get that bike to run as it was born to.  read, my friend, read as much as you can before you open up dem carbs.  get a good book.  soak up the knowledge from the postings on this site.  the bike has waited this long for the right hands to come along.  be those 'right hands'.  look before you leap, learn before you do.  whatever you invest in reading, research and preparation will repay you tenfold.  jumping in with both feet will not only be a waste of time but of a good bike and lots of potential for putting a classic back on the road where it belongs.   good luck!

[drackett_19]

Okay, in that case I didn't put a screw driver anywhere near the slides...nor would i consider it.

Although I don't know the correct terms for some of the parts, i'm not a total stranger to carbs. With the info learned from this site, I've disassembled the carbs on my 550, right down to the emulsion tubes , for a good cleaning and some new rubber and the bike runs like a top. So after doing some more reading on the Hondamatic, hopefully this will go as smooth as that did. I mainly just wanted to ask this Q in case there were some issues unique to the Hondamatic carbs that I should look for.

As always, I appreciate all the help.