Honda Twins banner
1 - 9 of 9 Posts

·
Registered
Joined
·
62 Posts
Discussion Starter · #1 ·
I got my CB500T running last night for the first time. It will idle and run on its own, but there are a couple of things that I've found:

- The choke floats, by which I mean that if it's sitting there idling the choke will slowly work its way to at least half closed. There doesn't seem to be anything with any tension on it to hold it open. Should there be? When I first disassembled it I noticed the choke lever was bent down enough to hit the screw on the air cutoff valve, which means I couldn't use the choke at all. I guess that's why.

- It's backfiring pretty frequently on the right cylinder. I didn't have the air boxes on and I haven't vacuum synched the carbs yet, could either of those be the culprit?

Bonus head scratcher:
- When I pulled the carbs apart I noticed that the pilot jet on the left carb had a hole at the bottom in addition to the holes at the top and horizontally through the side, but the right carb did not have a hole in the bottom. It didn't appear to be a case of a hole being plugged, there just doesn't seem to be one there at all. Is that right?
 

·
Premium Member
Joined
·
2,838 Posts
The lever down opens the choke (turns it off). There should be a little piece of metal under it that holds it in two places, open and closed.

Untitled.jpg
 

·
Registered
Joined
·
2,568 Posts
The lever down opens the choke (turns it off). There should be a little piece of metal under it that holds it in two places, open and closed.

View attachment 271218
See that little cross-point head screw under the choke pivot? That holds that little piece of metal against the lever, so it sticks in those tiny slots cut into it.

If one cylinder is pulling enough harder than the other (carb sync needed), it can cause after-fire in the other, same as closing the throttle at speed.

It sounds like mis-matched pilot jets; they should be the same, with the same number stamped into them. The one without the hole draws fuel from the main jet, which, if your carbs are the same as the 450, is the way it should be.
 

·
Registered
Joined
·
62 Posts
Discussion Starter · #4 ·
OK, I think I see what's going on with the choke. The stop on mine is both bent and turned upside down, so I thought it was just there to keep the lever from pushing too far back when the choke is open. It's a little hard to tell for sure from the picture jd50i posted, but I think I just need to flatten that out and put the bottom hole in the stud and the screw in the upper hole, right? It looks like there is a front and rear location, what's the difference between the two?

As for the pilot jets, is that going to lead to trouble? I know this bike was ridden, and hard, before I bought it, but I don't know at what point anything was done with the carbs. One jet doesn't have a number at all, the other is a 60. I think the one without a number is the one with the hole in the bottom and vice versa, but I'm going off of memory on that. I didn't measure them, but to eyeball them they looked the same, except for the hole in the bottom.

_20181220_180132.jpg _20181220_180210.JPG
 

·
Registered
Joined
·
62 Posts
Discussion Starter · #6 ·
Bend the little tab until it exerts more pressure on the choke shaft-thingy, and keeps the lever in the "notch"
That's exactly what I needed, thanks! I didn't even notice that there were notches on the rotating part of the lever, they were easy to overlook.
 

·
Registered
Joined
·
2,568 Posts
As for the pilot jets, is that going to lead to trouble? I know this bike was ridden, and hard, before I bought it, but I don't know at what point anything was done with the carbs. One jet doesn't have a number at all, the other is a 60. I think the one without a number is the one with the hole in the bottom and vice versa, but I'm going off of memory on that. I didn't measure them, but to eyeball them they looked the same, except for the hole in the bottom.
Are the carbs basically identical? If it ran well before, it could be that one was replaced with a different type, that otherwise works OK. Examine the carb bodies for any numbers stamped into them.
 

·
Registered
Joined
·
62 Posts
Discussion Starter · #8 ·
Are the carbs basically identical? If it ran well before, it could be that one was replaced with a different type, that otherwise works OK. Examine the carb bodies for any numbers stamped into them.
Based on the examination I did when I disassembled them to clean them, they're identical. What I'm going to do is fix a leak in the petcock (d'oh), synch the carbs, then I'll take it for a spin and see how it rides.
 
1 - 9 of 9 Posts
Top