jbrown
jbrown
Hello all.
I am working on a 79 xs400 with what I believe to be bs34 carbs. I was given the bike with the carbs taken apart and tossed in a box. I started by replacing the diaphragms, float needles, bowl gaskets, jets, gave it a good cleaning. The petcock was also rebuilt and new stock air filters were put in. This surprisingly got it running after a fresh battery and new plugs. It ran well enough to go down the road but the throttle response was slow and even slower to return to idle. After the first ride it would die at idle. Turned out to be the idle adjust spring was missing. Found and installed that.
I suspected air leaks were making the slow return to idle so I replaced the manifold boots. No difference. Tried adjusting the carbs needle screw which was set to 3 turns. 3 3/4 seemed the best. I did a crude balancing. By feel of the exhaust pressure. All this and still really slow to return to idle.
After some research I tried trying carb clean on possible leak points. Found a change in idle when I sprayed the throttle butterfly ends. I ordered new throttle shaft seals and choke plungers and seals from Mike's xs. I installed the throttle seals. That went better than expected.
This is the point at which I may have shafted myself. The choke plungers I got were slightly different . The "piston" part of it was identical. The "rod" part was a bit bigger diameter and the groove that those little fork type pieces was different. Working in a machine shop I thought I'd be smart and drill out the retaining nut to
fit the larger plunger rod. All was good until I went to slip the spring (which fits the original plunger rod) on and it is to small.... F!.
Here are the parts
[
So here are my questions.
Are those brass nut/plug things, that hold all the choke plunger business in, available anywhere?
Is the choke plunger area even a place that could leak air causing the slow idle return? (I assumed it was)
Am I on the right track?
Does this make any sense?
Thanks ahead for any input.
I am working on a 79 xs400 with what I believe to be bs34 carbs. I was given the bike with the carbs taken apart and tossed in a box. I started by replacing the diaphragms, float needles, bowl gaskets, jets, gave it a good cleaning. The petcock was also rebuilt and new stock air filters were put in. This surprisingly got it running after a fresh battery and new plugs. It ran well enough to go down the road but the throttle response was slow and even slower to return to idle. After the first ride it would die at idle. Turned out to be the idle adjust spring was missing. Found and installed that.
I suspected air leaks were making the slow return to idle so I replaced the manifold boots. No difference. Tried adjusting the carbs needle screw which was set to 3 turns. 3 3/4 seemed the best. I did a crude balancing. By feel of the exhaust pressure. All this and still really slow to return to idle.
After some research I tried trying carb clean on possible leak points. Found a change in idle when I sprayed the throttle butterfly ends. I ordered new throttle shaft seals and choke plungers and seals from Mike's xs. I installed the throttle seals. That went better than expected.
This is the point at which I may have shafted myself. The choke plungers I got were slightly different . The "piston" part of it was identical. The "rod" part was a bit bigger diameter and the groove that those little fork type pieces was different. Working in a machine shop I thought I'd be smart and drill out the retaining nut to
fit the larger plunger rod. All was good until I went to slip the spring (which fits the original plunger rod) on and it is to small.... F!.
Here are the parts
[
So here are my questions.
Are those brass nut/plug things, that hold all the choke plunger business in, available anywhere?
Is the choke plunger area even a place that could leak air causing the slow idle return? (I assumed it was)
Am I on the right track?
Does this make any sense?
Thanks ahead for any input.
