Hey all, I've been working on a 71 CL350 for the past few months. I thought I finally had all the kinks worked out, but I am now stuck with the bike idling way too high.
The bike has the stock airbox setup, and Keihin 3D model CV carbs.
There is a long list of what I have done to the bike. I replaced both floats, and have adjusted them using the clear tube method and checking the actual level with gas in the bowl, instead of measuring the float height with the bowl off. The level on both floats is about 1/8" from the base of the carb.
The right side carb would leak gas constantly. I ordered a new needle and seat, adjusted the float, and the problem went away.
The right side carb would pop a lot at idle and decel. This was fixed by removing some junk that had accumulated in the intermediate jet.
The left side carbs idle jet #35 was completely plugged. I replaced it with a #38 jet, as it was all I had and I could not clear the stock jet. I am unsure of the size of the right sides idle jet, as I did not replace it when cleaning the carbs. Most likely it is the stock size.
The diaphragm on both carbs look to be in great shape. I double checked on each one recently after running the bike for about a month.
I recently went through both carbs and made sure all passages were clear.
I have adjusted the idle mixture screw between 3/4 of the way out, up to 1 1/2 turns out. It doesn't seem to make much of a difference. This carb does not use an o-ring to seal the screw as far as I know, as there is no groove for an o-ring on the screw itself.
All four valves have been adjusted, and timing set on both cylinders. I had no problems getting the timing set for both of them.
Coils are stock. I've been wanting to replace them, but they still work fine for the time being, and this bike does not get ridden much. Brand new NGK B8ES plugs, with a nice blue spark on each side.
I have adjusted both carb throttle cables so they are not holding the butterflys open. The butterflys look to be closing completely, as well as the slides.
On the left side carb, I did have to disassemble the front throttle assembly, as it was turning very hard. I removed the throttle shaft and blade from the carb, cleaned and lubed everything and stuck it back together.
Compression is equal on both cylinders. 170 psi cold.
Exhaust is stock Scrambler pipes.
Besides idle, the bike runs great. It pulls all the way up to redline with no problems.
As of now, the popping issue has returned on the right cylinder. I suspect more junk could have made it into the carb and plugged up a jet again, but have not yet checked. The bike, when warm, idles at ~4000 rpms. As a test, I removed the spark plug wire from the right side cylinder, and the idle of the left cylinder only was around 3000 rpms. When I repeated this process and removed the left side spark plug wire, the idle dropped to 1000 rpms on the right side cylinder. This causes me to suspect the left side cylinder has an issue. Both idle screws are completely back off, there is enough slack in the throttle cables to keep the butterfly from being open, and both carbs are in sync as far as the throttle opening at the same time.
I sprayed WD40 around the intake boots, with no change in rpms. However, if I spray around the throttle shaft on the left carb, the idle drops quite a bit. On the right side, doing this causes the idle to increase. Could this be a vacuum leak that is causing my problem? The bike will not idle below 3800 rpms now, and I cant back out the idle screws to change this any. I suspect the throttle shaft leak may be my problem, but as far as I can tell, there is no o-ring to seal this off from outside air.
Any suggestions? Thanks!
The bike has the stock airbox setup, and Keihin 3D model CV carbs.
There is a long list of what I have done to the bike. I replaced both floats, and have adjusted them using the clear tube method and checking the actual level with gas in the bowl, instead of measuring the float height with the bowl off. The level on both floats is about 1/8" from the base of the carb.
The right side carb would leak gas constantly. I ordered a new needle and seat, adjusted the float, and the problem went away.
The right side carb would pop a lot at idle and decel. This was fixed by removing some junk that had accumulated in the intermediate jet.
The left side carbs idle jet #35 was completely plugged. I replaced it with a #38 jet, as it was all I had and I could not clear the stock jet. I am unsure of the size of the right sides idle jet, as I did not replace it when cleaning the carbs. Most likely it is the stock size.
The diaphragm on both carbs look to be in great shape. I double checked on each one recently after running the bike for about a month.
I recently went through both carbs and made sure all passages were clear.
I have adjusted the idle mixture screw between 3/4 of the way out, up to 1 1/2 turns out. It doesn't seem to make much of a difference. This carb does not use an o-ring to seal the screw as far as I know, as there is no groove for an o-ring on the screw itself.
All four valves have been adjusted, and timing set on both cylinders. I had no problems getting the timing set for both of them.
Coils are stock. I've been wanting to replace them, but they still work fine for the time being, and this bike does not get ridden much. Brand new NGK B8ES plugs, with a nice blue spark on each side.
I have adjusted both carb throttle cables so they are not holding the butterflys open. The butterflys look to be closing completely, as well as the slides.
On the left side carb, I did have to disassemble the front throttle assembly, as it was turning very hard. I removed the throttle shaft and blade from the carb, cleaned and lubed everything and stuck it back together.
Compression is equal on both cylinders. 170 psi cold.
Exhaust is stock Scrambler pipes.
Besides idle, the bike runs great. It pulls all the way up to redline with no problems.
As of now, the popping issue has returned on the right cylinder. I suspect more junk could have made it into the carb and plugged up a jet again, but have not yet checked. The bike, when warm, idles at ~4000 rpms. As a test, I removed the spark plug wire from the right side cylinder, and the idle of the left cylinder only was around 3000 rpms. When I repeated this process and removed the left side spark plug wire, the idle dropped to 1000 rpms on the right side cylinder. This causes me to suspect the left side cylinder has an issue. Both idle screws are completely back off, there is enough slack in the throttle cables to keep the butterfly from being open, and both carbs are in sync as far as the throttle opening at the same time.
I sprayed WD40 around the intake boots, with no change in rpms. However, if I spray around the throttle shaft on the left carb, the idle drops quite a bit. On the right side, doing this causes the idle to increase. Could this be a vacuum leak that is causing my problem? The bike will not idle below 3800 rpms now, and I cant back out the idle screws to change this any. I suspect the throttle shaft leak may be my problem, but as far as I can tell, there is no o-ring to seal this off from outside air.
Any suggestions? Thanks!
