1981 Carb issue...

Jake2345

Jake2345

XS650 Enthusiast
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Hi guys.
I got a 1981 650, relatively stock, I have a issue with my carbs and it's kinda a weird one....
My bike idles perfectly at about 1100-1300rpm but what I've been having issues with is that my right side carb is running rich and my left is running almost right (I checked the plugs and the left side is slightly tan). I adjusted the mixture and still hasn't helped. I have the floats set at stock height 22mm, the needles are at the second notch. I had 135mm Main Jets in before and the bike was running wwwaaayyy to lean...I'm not sure what else to do...the carbs have been cleaned multiple times.
I have 137.5mm Main Jets, 45 Pilot Jets, pod filters and shorty mufflers.
Any help would be freaking great
Cheers
 
which part of the throttle range are you running rich ? that will determine where you need to address your attention.
 
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Have you checked the condition of the o-rings on the float needle seats? If they go bad, fuel can leak into the bowl around the outside of the seats, over-filling them and causing a rich condition.
 
When we last had the carbs off we checked to see if the choke was sticking and it isn't. Diaphragms are sealed good...yes I believe they are the 34s, the carbs are stock for the bike(other than the jetting), carbs have been checked for sync and are bang on...
The other thing is that all over the RPM range my bike will get this....best way to describe it is like a hiccup, almost like it's not getting enough fuel but it's from about 2000-5000RPM...
 
An important question here is what kind of pods? There are good ones and bad ones. The bad ones can cause all sorts of running and tuning problems, some similar to what you're experiencing.

There are several rubber parts in the BS34 carbs that need to be in good shape for them to operate correctly. The o-ring on the float needle seat is one that I've already mentioned. There is also an o-ring on the mix screw and a rubber plug or cap over the pilot jet. If any of those is bad or missing, you'll have problems.
 
Does this problem occur only when you snap the throttle open ? or does it also happen if you roll the throttle open slowly.
 
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5twins said:
An important question here is what kind of pods? There are good ones and bad ones. The bad ones can cause all sorts of running and tuning problems, some similar to what you're experiencing.

There are several rubber parts in the BS34 carbs that need to be in good shape for them to operate correctly. The o-ring on the float needle seat is one that I've already mentioned. There is also an o-ring on the mix screw and a rubber plug or cap over the pilot jet. If any of those is bad or missing, you'll have problems.
Click to expand...
Last time I checked the rubber plug it was fine.
As for pods this is what they look like(I have a photo of some very similar looking pod filters)
 

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I won't run pleated pods on a CV carb, they tend to block important passages. I get very good results with foam pods, however. I do not oil them, as varying amounts of oil creates a variable that I don't need when jetting. I refuse to buy the theory that something small enough to get past the foam is big enough to harm my motor. Never had a problem with this.
 
So I switched the spark plug wires to the opposite side and now the big doesn't have the hiccup...but if I take it up too about 5000RPM it starts to bog out.
Bike is still running rich though...don't understand that
 
It could be those pods. Besides the pleated element style not working well with CV carbs (makes the incoming air too turbulent), many have a large rubber lip inside the mounting flange to stop them from sliding too far onto the carb. It does do that but can also block the air ports around the outside of the intake bell. You get mostly fuel and not enough air to mix with it. The result is rich running. Try a test run with the filters removed to see if it improves things.
 
5twins said:
It could be those pods. Besides the pleated element style not working well with CV carbs (makes the incoming air too turbulent), many have a large rubber lip inside the mounting flange to stop them from sliding too far onto the carb. It does do that but can also block the air ports around the outside of the intake bell. You get mostly fuel and not enough air to mix with it. The result is rich running. Try a test run with the filters removed to see if it improves things.
Click to expand...
I'll give that a try, thank you
 
5twins said:
It could be those pods. Besides the pleated element style not working well with CV carbs (makes the incoming air too turbulent), many have a large rubber lip inside the mounting flange to stop them from sliding too far onto the carb. It does do that but can also block the air ports around the outside of the intake bell. You get mostly fuel and not enough air to mix with it. The result is rich running. Try a test run with the filters removed to see if it improves things.
Click to expand...
So after running the bike for a few days, I've noticed a few things....at idle the bike sounds great but after a bit the RPM will drop then rise again and once again drop but come back up to a normal rhythm. That is at idle, at speed the bike still gets a little...shall we say surge?
I still have to take the pods off to do that test, however switching the spark plug wires changed how the bike ran as well. I'll keep ya'll updated
 
So after two days of riding...still no change. Actually with the pod filters off the bike is running slightly worse than with them on.
I'm at a loss as too what it could be...
 
well I wrote a whole list of suggestions which you completely ignored .......so i deleted them.
You have a lean mixture problem but you seem to be ignoring that advice also.

You haven't told us exactly what the problem/s are currently so how do you expect anyone to advise you ??

There is nothing wrong with pleated pod filters provided that they do not block the idle air intake or diaphram equalisation vent. They are possibly the worst filter but they work and they keep the dust and road grit out of your engine so they are distinctly better than using no filter at all.
Fitting pod filters and non standard exhausts require you to increase the size of your pilot jet and main jets and needle position to compensate for the additional air flow

By removing the pod filters you could be aggravating an already lean mixture problem.

You either have too much air or you have too little petrol but as you've not told us at what throttle setting the problems occur how can we be sure what could be at fault.?
 
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You may have an electrical problem, not a carb problem. Switching the plug wires side to side shouldn't change anything. You have a single coil with dual outputs. Both plug wires are fired at the same time. Saying that it changed the way the bike ran when you swapped the wires is indicating one plug wire isn't firing as well as the other. You may have a bad plug cap or cap to wire connection. If the plug caps are the originals, you should probably just replace them. The NGK 5K ohm resistor caps are the usual choice. Cut about 1/4" of wire off the plug wires so you're attaching the new caps to some fresh wire.
 
Ok I'm going to but in here and be a bit blunt.

Posting threads asking questions, (right thing to do by the way), and not finishing the threads, (wrong thing to do), when a diagnosis and problems haven't been sorted, then starting another thread that is a carry on from the last is not helping.

This problem could still be related to your electrical problems that haven't been solved in your last 3 threads. The advice and questions from reputed members has been ignored, or maybe you get confused when getting advice from here, your friends father and your mechanic friend.

To much varied input from to many sources and trying to fix to many things at once so there is no cohesion.

Make a list of what has been done in what order and the end result.

As 5twins stated. If a problem changes when swapping the leads over then an electrical issue diagnostic should take president.
 

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