CT90 Carb and Throttle cable Help!

M

MYTRAILHATESME!

New Member
I just put a new carb on my 1971 CT90. We installed it no problem, but when we put the throttle cable and pin in then started it the engine revved extremly high (with the throttle closed) and wouldn't change when I opened/closed the throttle. The internet hasnt been very heplful so I was wondering if anyone had any ideas as to what the problem might be.

Note: We did not change the cable or the topset.
 
motodevo

motodevo

Active Member
barry's got it i reckon, common mistake for a noob(we have all done it atleast once), carb barrell fits in 2 ways, only drops down enough in one of those positions though. If you have the airfilter off the barrell should drop all the way down leaving only a small(like 1mm or so) gap. It the barrel was installed correctly then perhaps the cable is too short.
 
R

ReneO

New Member
Barry said:
You most likely have the slide 180 deg off.
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What do you mean slid 180• off ? I’m very new to this I put on a new throttle cable and had the slide line up with the handle and had proper feel to it with rotation but my husband went to test drive my bike that I have been working on the throttle got stuck wide open and he now looks like meat loaf with a busted hand😪
 
Old Guy Too Many Bikes

Old Guy Too Many Bikes

Well-Known Member
Remove the carb so that you can see the slide from the intake side. With the cable disconnected, the slide should be in its bottom position, and you should be able to slide it up with your finger. Verify that with the cable attached, as you rotate the throttle, you should see the slide move up. If the cable is too short, then the slide will not return to its bottom position. Some carbs have a threaded collar on the top that can adjust the amount of free play on the cable. If the problem is elsewhere, check the cable routing and for binding.
 
R

ReneO

New Member
Old Guy Too Many Bikes said:
Remove the carb so that you can see the slide from the intake side. With the cable disconnected, the slide should be in its bottom position, and you should be able to slide it up with your finger. Verify that with the cable attached, as you rotate the throttle, you should see the slide move up. If the cable is too short, then the slide will not return to its bottom position. Some carbs have a threaded collar on the top that can adjust the amount of free play on the cable. If the problem is elsewhere, check the cable routing and for binding.
Click to expand...
My cable returns to the bottom. It does have a slide coller on the top. What should I be looking for if I adjust it. I have not adjusted yet at all I just installed it and made sure everything moved how it was supposed to.
 
Old Guy Too Many Bikes

Old Guy Too Many Bikes

Well-Known Member
You say your cable returns to the bottom. But does your carb slide return to the bottom with the cable attached? Can you rotate the twist grip and watch the slide move up and return when you release the twist grip without binding. You should have about 1/8" free play on the twist grip before the slide starts to move. This play can be adjusted with the threaded collar on the top of the carb. Also check your idle adjustment screw on the side of the carb. It's threaded and as you turn it clockwise, it raises the slide and the idle.
 
R

ReneO

New Member
Okay so I think the new cable is to long I did t buy it myself it came with the bike when I bought it and has just been hanging out I didn’t pay much attention to it and though that he would have the right size I compared it to the old one that I replaced and it’s a few inches longer. Their is a long drag time before the twist handle in gaged. If I open it all the way it will stay that way in till I twist it back down fully then it will close 🤔do you think that’s why it could have stayed open?
 
Old Guy Too Many Bikes

Old Guy Too Many Bikes

Well-Known Member
Yes, it sounds like your carb slide does not drop down. Either the problem is either the carb or the cable binding. Remove the cable from the carb and check to see if the slide moves freely and and spring returns it down. Check your cable while it's disconnected from the carb, to make sure it does not bind. If your cable is too long, there's lots of household garage items you can repurpose to take up the cable slack.
 
C

CL90Flash

New Member
Before, you install the carborator slide look at the bottom of it where the needle is, the part of the slide that looks like it was cut at an angle faces towards the air filter. There is a slot in the slide that will line up with a pin made into the carborator body,this pin is located inside the slide barrel about midway down ,the carborator slide slot normally where the cable is connected to the cable needs to index this pin when installing slide this will keep slide in proper position after installing slide work it with throttle be sure it works freely don't overtighten carb mount bolts this can cause slide to bind . Tighten mount bolts evenly tight after carborator is installed be sure carborator slide works smooth top to bottom when working throttle. Hope this helps enjoy the ride.
 
B

b52bombardier1

Well-Known Member
Yes, an over-tightened carb flange can warp the carb body and the slide won't move. Its a fine line between clever and stupid here with respect to an over-tightened condition and vacuum leaks.

Rick
 
N

-Nate

Active Member
@ Rick ;

I'm stupid because I think riding a beat up forty year old Motocycle is a good idea..... ;).

CT90.AUTOCLUTCH.ASSEBLY.jpg
 
N

-Nate

Active Member
Well ;

My ex M.I.L. wasn't bad but I sure as hell like my old CT's more......

A Honda CT90 is like a goat or mule ~ it can and will go anywhere you want it to .

Not terribly fast but easily and safely .

I agree an S90 is sexy, I used to have several but the overall utility of the CT won me over ~ interestingly enough, an S90 doesn't handle any better than a CT does .

Few ever put their CT's to a high speed twisty test .

My son did and it was breathtaking, amazing and frightening to watch ~ he has a skill set that allows him to ride *much* faster than anyone else I know .

Watching him keep up with sports cars going down hill was frightening but he did it easily .

WHEW .

Plus of course, even before I became an old man I had the milk crate firmly attached to the rack, it turns out a Coleman cooler fits snugly in the rack and carries a lot of ice and waters....
 
N

-Nate

Active Member
Yep ~

I bought my first CM91 (90CC Passport) off an old motor home for $150 ~ it actually made it 5 miles or so before crapping out .
 
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