Slightly stuck intake valve? Bad valve springs ( unlikely, but)
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Ninja EX500 carbs on an XS650?
- Thread starter Highside
- Start date
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- Tags
- cafe carburetors custom engine
May be the long way around but if you have the old carbs and they are good
you could mount them and eliminate the engine as the fault.
you could mount them and eliminate the engine as the fault.
Thanks. Compression testing on both cylinders is 145 to 150lb sq in. Bad valve springs, possible but I can't really check that.
For sure I'm in the realms of looking for something very unusual? It crossed my mind that the right side header internal pipe may have collapsed and be blocking exhaust flow?
Thanks. Unfortunately, the BS38 carbs are no good. I spent months and $$$ on them last year before getting the CVK34 carbs. The CVK34 carbs are to replace the BS38s.
I have some of the parts available to rebuild a good set of BS38s. But I think that's only going to happen when I'm completely out of ideas. My next idea is a collapsed inner right side header pipe?
It's a head-scratcher . . .
And the cause of right cylinder misfiring and exhaust smoke pouring from the right side carb? Drum roll.......
Blocked right side down pipe. See picture below where the outer pipe has split, the inner pipe is collapsed. Blowing as hard as I can, I can hardly blow through the pipe. Pushing a brazing rod at either end, it stops after maybe 15cm. No wonder the right side cylinder isn't running properly.
Blocked right side down pipe. See picture below where the outer pipe has split, the inner pipe is collapsed. Blowing as hard as I can, I can hardly blow through the pipe. Pushing a brazing rod at either end, it stops after maybe 15cm. No wonder the right side cylinder isn't running properly.
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Well, it had to be something totally freaking unlikely. Oh, how you must be looking forward to finally getting it right?
Yes, indeed it's a relief finally finding the single issue that has been underlying every other issue that's been "carbs" or "ignition ". That's not say there haven't been issues there. There has.
But while the right side exhaust was blocked, it wasn't going to matter what I did. It simply wasn't going to run right.
Slightly off topic for this thread, but I found a NOS left side header and a rechromed right side one. £800
The joy of double wall headpipes...Are you sure that the pipe is not just blocked by some random debris? (If it was an old RD or other abused 2-stroke, i would suggest the remains of a piston and wrist pin. Don't ask why I wrote that....)
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Thanks, yes I'm sure. Probing the pipe from both ends, the horizontal section of pipe, up round the lower bend. At least 30cm of collapsed inner pipe. By mouth I can only get a tiny amount of air through the pipe. The outer pipe is split from the (presumably) frozen water expansion.
Finger and toes crossed for you on this one.
After all that, completely out of left field.
Good to see you found the source, at least the carbs and electrics shouldn't cause any probs now.
Maybe you could cut open and take a couple of pictures? After all, this is a pretty rare problem 
Thanks. I'm still working on how I'm going to fix this.Maybe you could cut open and take a couple of pictures? After all, this is a pretty rare problem
At the moment, I'm thinking of buying a full replacement after market system to get the bike going. I might actually get to ride it this year?
I am fairly convinced that a repair to the right side header is going to be the best option. Then I'll take pictures as you suggest.
FWIW, all the used headers I can see are junk and expensive. I will keep looking in case I find a decent right side header at a reasonable price.
Fwiw, Motad made a decent 2-1 in stainless. I've got one and it's fine.
Since the mixture screws on the CVK34 carbs are not very accessible on the bike, I ordered a pair of extended screws with a thumb grip. Idea is to make fine adjustments of the mixture screw easy by the road side if required. Seems a good idea. Unfortunately, being Chinesium one of the very fine screw tips is bent. Requested a new one to be sent. See what happens. Borrowed this picture to illustrate what I'm referring to.
Thanks. I have a plan for repairing the original header pipes. I'm not sharing it just yet. It will be a few weeks or months until I do the repair. When I do the repair I will document the work.
