Honda CX 500 Forum banner
1 - 12 of 12 Posts

·
Registered
Joined
·
194 Posts
Discussion Starter · #1 ·
Just got finished rebuilding the carbs(for the 2nd time in less then 6 months, thanks to ethanol gas) and when the bike is cold I have to crank up the idle adjustment to get the bike to warm up, for some reason the choke doesn't seem to be working right when it is cold. After it is warmed up if I crank the idle back down to where it should be and then pull the choke out, it dies (which would be normal for a warmed up bike). Checked the linkage and it appears to be working fine (cable pulls the linkage back and forth from a visual inspection). The only "abnormal" issue I had rebuilding the carbs was a broke idle needle tip which I removed and have replaced with new screws assemblies. The hole in the carb body was "slightly" widened on one end, but not much, more liked slightly coned from the tools slipping trying to push the pin out. I realize that may cause a slight issue, but not this symptom I would think. Any ideas. Obviously I have to wait until the bike cools off before trying anything again. By the way, after it is warmed up the bike runs pretty good.
 

·
Registered
Joined
·
1,366 Posts
Adjust the fast idle. Search this forum for fast idle adjustment. It can be done with the carbs on the bike in spite of what the service manual says.

Remove the tank and work from the right side with a long screwdriver to bend the forward of the two fork tines until you get the proper clearance of 0.8mm which is 0.032" NOT 0.047" as the manual says, do the math.

I think the goal is 1500-2500 rpm or so when the choke is pulled.on starting.
 

·
Registered
Joined
·
194 Posts
Discussion Starter · #3 ·
Adjust the fast idle. Search this forum for fast idle adjustment. It can be done with the carbs on the bike in spite of what the service manual says.

Remove the tank and work from the right side with a long screwdriver to bend the forward of the two fork tines until you get the proper clearance of 0.8mm which is 0.032" NOT 0.047" as the manual says, do the math.

I think the goal is 1500-2500 rpm or so when the choke is pulled.on starting.
Is this the tab I need to adjust for the fast idle (see the yellow circle in the photo)? Also, the manual says to "close the throttle valve by turning the throttle stop screw out" where is it?
 

·
Registered
Joined
·
1,366 Posts
Yes, loosen the idle speed screw (black knob) so it is not touching the idle lever, then put your screwdriver or lever in the fork and rotate counterclockwise while trying to keep the forked lever from moving with your other hand. You want 0.032" or 0.8mm clearance between the upper edge of the forked lever and the idle lever above it.
 

·
Registered
Joined
·
194 Posts
Discussion Starter · #6 ·
nice pic by-the-way.
Learned my lesson last time I pulled the carbs out and was trying to rough adjust the throttle cables. Made sure to take a pic this time to be able to reference in the future.
 

·
Registered
Joined
·
194 Posts
Discussion Starter · #8 ·
Update.

Checked the Idle Adjustment and I noticed that the pull cable on the throttle was slightly mis-adjusted, readjusted it and the gap closed down to normal levels as per spec. Went to start it and I still have the same issue. Choke will not increase the RPM's. I can adjust the idle setting and get it to warm up then I have to readjust it for normal temp conditions. Pulling out the choke knob when warm will drop the RPM and cause it to stall. Did a visual inspection and I don't see anything wrong with how it is all connected (of course I am no expert either). Any other ideas?



The choke was working fine prior to the last carb pull, rebuild.



I am to the point if someone will make me a decent offer (1K +) I will sell this headache.





I also had installed a large type 90 degree fuel filter which to me didn't look like it was working right so I swapped it out today with a smaller version that now has good gas flow through it. Not that I thin that was the prob anyway.
 

·
Registered
Joined
·
1,366 Posts
The choke MUST activate the throttle as it is pulled out. Look at

the area of the "fork" and see if the throttle IS moved when the choke is pulled, otherwise closing the choke will just kill the engine unless you add throttle by hand.
 

·
Registered
Joined
·
194 Posts
Discussion Starter · #10 ·
The choke MUST activate the throttle as it is pulled out. Look at

the area of the "fork" and see if the throttle IS moved when the choke is pulled, otherwise closing the choke will just kill the engine unless you add throttle by hand.
I checked that earlier and yes it does move the throttle idle slightly which is all it looks like it would move anyway. Doesn't the choke activate a butterfly inside the choke?



Since the choke does cause a drop in RPM's and will stall the bike if activated when the bike is warm, isn't that a proper indication of the choke working correctly if applied when warm? If so, what would cause an opposite reaction when the bike is cold?
 

·
Registered
Joined
·
1,366 Posts
The choke is designed to do two things: 1) create fast idle, which it does by the forked end of a cam pushing up on the throttle lever and 2) enrichen the mixture in a cold engine by closing the butterfly valves to decrease air intake and increase fuel being sucked into the manifolds. As the engine warms and more efficiently vaporizes fuel the butterfly is gradually opened to lean out the mixture, but the fast idle feature continues to function to some degree until the choke is completely released.

The forked end of the choke cam really does need to be set 0.8mm (0.032") away from the throttle lever when the idle control screw is completely withdrawn from the throttle lever. If this setting does not work, then there is some other carburetor related problem.
 

·
Registered
Joined
·
194 Posts
Discussion Starter · #12 ·
Update: Decided to pull the carbs again because I can find nothing on the adjustment side that appears to be off. The only thing I discovered was that the throttle butterflies were slightly off from each other so I adjusted them to match as far as coverage of the holes in the carb body. Put everything back together and still have the same problem. Choke will not work at all. On this rebuild the only thing I did different than in previous rebuilds was to pull the low jets and clean them. Replaced both rubber plugs (1 kept falling out). Had one of the idle screw tips break off in the carb, which I removed and have replaced both of them. The hole in the crab body which had the stuck tip is slightly coned out.



At this point I am clueless as to what is the problem. The bike runs pretty good as long as I use the idle screw to compensate until the bike warms up, then she will run fine.



Any ideas?
 
1 - 12 of 12 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top