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Discussion Starter · #1 ·
Hi guys,
I rebuilt my 1981 CM 400 A carbs and had taken pictures prior to taking them off where the cables went and were routed on my phone. My phone died and no backup. So I've been searching where the push/pull throttle cables and choke go and mount to the carbs with proper routing.

I have searched the downloadable manuals (thank you) but cant make out where each goes.

I have searched the forum and google but no definitive pictures.

Any help would be helpful.

Done tons of work to the Hondamatic need carbs on to here her run.

Thanks,
Bill
 

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If it's like an 80 cb400t there's one cable with two nuts, one with one nut and a third with no nut (choke cable, don't forget the screw/bracket that clamps it to the throttle bracket). Not too sure about the cable routing though, I think they might be based on the position of the brackets (they're staggered from right to left)

From front to back (engine is front, tail light back): One nut goes in front, two nuts goes second, then third goes at the rear
 

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Discussion Starter · #3 · (Edited)
Awesome thanks your instruction so simple wish I waited and checked before doing it in backwards order.

I did just the opposite throttle works fine if you like the throttle working from bottom to top. lol Hell of a theft deterrent. hahah

I did it backwards. Choke was correct.
but the two nut cable I put first and the one nut in back. Do'hh


Thanks I will fix it tomorrow per your instructions.

On last think. I bought new intake boots mine were in pieces. I installed them and tried to push the airbox back wont go much cant find any screws holding it that I haven't removed. Man what a pain. Not much room and the airbox boots popped out. I'm installing from the left side of the bike facing front.

Is there a correct order on installing the carbs or is a profanity ranted task and need to sqeeze between the airbox boots and intake boots?

Thanks

Will attempt tomorrow..
 

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Here's the cable locations
201_4030-002.JPG
Blue is choke, Green is pull, Red is "push"
This is the choke cable
GEDC2194.jpg
These are the pull and "push" cables. Note that the pull cable has 2 nuts on the ferrule and the "push" cable only has one.
GEDC2195.jpg
The cables are routed just below the CDI unit and thru the middle of the upper engine mount to get proper alignment.
 

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hahaha yeah that would be quite a riding experience. I haven't found an easy way, but I've started using a blunt screwdriver to push the rubber bits that get dislodged after seating the carbs into the intake boots. Just make sure you don't puncture anything with the screwdriver.
 

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Is there a correct order on installing the carbs or is a profanity ranted task and need to sqeeze between the airbox boots and intake boots?

Thanks

Will attempt tomorrow..
Warming up the boots with a hair dryer helps some. Mostly it's bad words used repetitively while struggling with the bloody things.
Carb removal and install from the left side like you're doing. Easiest to install the cables on the carbs first before putting the carbs on
 

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Discussion Starter · #7 ·
Going to giver it another go tomorrow.
I've got a blunt screw driver what I'll plastic dip tonight so it has a rubber coating as to not puncture the boots.
At least i'm out back so nobody can hear me swearing up a storm. lol.

Thanks guys.
Bill
 

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Dont know if this will help but on my 400a I take off the left side top motor mount ,I found the cables work better if run between the top motor mounts. I also remove the change switch to add a little more room on the right side. After mounting the cables pull the choke cable all the way closed so the choke lever wont catch on the left side rubber boot. Slide the carbs in from the left side and when in tilt the carbs down and forward as far as you can then place the rear of the carbs into the bottom of the boots. Note. make sure the clamps are as fer back as you can get them.
With carbs in the bottom of the boots pull back and up as hard as you can and slide the carbs into position. You will still have to work the rubber on to the top of the carbs but with bottom on and most of the sides it will be a lot easier. You dont have to remove the change switch but with my big old hands its just easier to reach in and pull the right side back.

Bill H
 

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Just a thought but you might check the throttle play after installing the cables and before sliding the carbs in . Throttle play should be 2-6mm (.08-.24 in.)

Bill H
 

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Discussion Starter · #10 ·
HI guys,
I got the carbs in and started the bike started right up. Only issue the idle is too fast and couldn't adjust it. So I've taken the carbs back out and need to figure out the factory default idle settings. The two washers on the idle screw weren't split I forgot to do that installing rebuilding the carbs. Stupid mistake hopefully splitting the washers and finding the factory settings will fix the fast idle adjustment . The big idle screw with the spring on the bottom only made the idle go faster.

After this I can it for a ride.
 

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Setting the mixture screws at 2 turns out from fully seated will get it idling. I don't know what you mean by splitting the washers (nvm see post below, I think of that bit as the sync screw).

The important adjustment is the black knob between the carbs that controls the throttle opening, turn it out until the throttle position stops changing, then back in a turn. It should idle reasonably that way, if not turning in opens the throttle (higher idle), out decreases idle. Make sure you sync them while they're off as well, that can do funny things to idle too.

If your sync is way off I learned how to roughly sync by feel today since my homemade tool developed a vacuum leak halfway through syncing. With sync way off, bike wouldn't idle below 1500, the knob had no effect. Had to turn the sync screw in the direction that lowered idle, readjusting to 1200 each time with the knob until I got to approximately the lowest idle. For me these carbs have been easy to get close but a bit of a challenge to get 100% right
 

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On the 400A the idle screw is set at 1 1/2 turns. You can get a close sync by putting a bright light behind the carbs on the bench and set both throttles to close at the same time. The light will let yet you see that they are working together.

With the carbs on the bike I use a small screwdriver cut off to fit under the carbs. a small mirror and a light source to set the screws.

Bill
 

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Discussion Starter · #15 ·
Hi there,
I got the carbs straighten out removed them, split them again, split the washers on the sync screw. reassembled, Bench sync'd then reinstalled them. I did remove the left side motor mount made attaching cables so much easier. Thanks for the tip.

She's now idling nicely she's 1.5 turns in. I had taken the bike for a short ride goes through the two gears. Omg so much fun but looking for clutch ..lol only issue is when I remove the shift side spark plug the engine runs fine no difference in idle however I remove the kick start side and the bike dies. Shouldn't still run when removing the kickstart side plug?

I think this is wrong place to post this so im going to search the forum to see if anyone else has had this issue.
 

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If the engine has a smooth idle, for a twin, and isn't having any issues with misfire at higher rpm then ignore this. Yeah, it does happen and doesn't affect anything as a general rule. I don't have a reason for it and no it doesn't make sense this would occur.
 

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Discussion Starter · #17 ·
Hi Jim,
Yeah no backfire smooth idle smooth acceleration. Could use a real carb sync I think but I dont have the gauges. Looking to start my CB 750 build next. Putting the Hondamatic up on craigslist for sale thanks for your help. I'm going to pick up another 400 or 450 next to keep. You guys helped out so much it was a lot of fun getting this ole girl running and looking good again.
 

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Discussion Starter · #18 ·
HI Guys,
The hondamatic is up on craigslist https://nh.craigslist.org/mcy/d/1981-honda-cm400/6601731713.html

Want another 400 question is any that are 3 inches shorter in the seat? Wife's feet didn't hit ground on the CM400 A.

She used to ride Harleys and lastly an 800 Suzuki intruder but now arthritis it's hard riding anything heavy.

Sorry if this is in the wrong place.
Bill
 

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The seat has @3" of foam on top of the pan. I'd take the seat to an upholstery shop that does MC seats and see what they suggest. Don't go to just any old shop and ask, MC knowledge is needed. I'd guess they could drop the height 1.5-2" easily. Then you could find shorted shocks, stock is 12 5/8", and drop the rear some more. Then you would move the forks up in the triples to match the shorter shocks, 3/4" is max there.
 
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