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Unequal carb slide settings


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Hi,

I am about to finish my Banshee build, now I'm puzzled with the carbs.

I have EGT installed and I see the right cylinder running about 80°C cooler than the left one. Also in the lower RPMs it takes a little to get its act together, stuttering a bit.

At first and telling from the spark plugs I thought it was the fuel/air ratio, so I went leaner on the cooler cylinder, with little effect. Then I gradually tightened the throttle cable on the cooler cylinder, thus not changing the fuel/air ratio but increasing the cylinder load altogether. And, surprise, the stuttering went away and the temperatures equalized. In the end, I hat the slider in the right carb set about 1,5mm higher than the slider in the left one.

Then I readjusted the carb slides to equal height again (to make the problem reappear) and went looking for a reason. So I checked this:

  • swapped left/right exhaust pipes (tailpipes only, as they are custom built. elbows are stock) -> no change
  • swapped left/right carbs (choke removed/blocked) -> no change
  • swapped spark plugs and ignition coil leads -> no change
  • checked float levels (first with calipers, then with transparent tubing on the drain studs) -> equal
  • hosed down everything with brake cleaner -> no change in RPM, so probably no air leaks, including the L/H crank seal behind the stator
  • compression tested -> both cylinders equal

So now I am through with about anything that I could probably measure and check...

What on earth...? 🥶

Best regards

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3 hours ago, 375hp banshees said:

U  swap egt senders side to side?

Yup.. before installing them I tied them together with wire and heated them with a torch - they read almost exactly the same.

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Is it ported?

What cylinders

What brand / size carb's ( same ones as before rebuild?)

Did your pipes sit where there could be a nest in one?

Since it runs, choke tube must be on & slides in correct carb. What about correct bowl on correct side?

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Both stock cylinders, no porting, standard bore.

Stock carbs (VM26SS), but can't tell what it was like before the rebuild, did not run at all back then when I got her 🙂

I manufactured my own pipes (basically a 1:1 rebuild of the stock ones, but in stainless). I hope there is no nest in the elbows, though...

Choke tube is on. If on the Banshee they did not do any special effect slides, then they should be in the right way (cut out facing to the filter, as usual). Bowls are correct, the one with the choke jet goes on the left carb that has the choke lever on it (that was off before the rebuild, among a gazillion of other things).

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