Slide and Diaphragm Shaking?

[Angry Rabbit]

I'm in the process of tuning up my BS34 carbs following the carb bible "The XS650 Garage Carburetor Guide.PDF". I've noticed it is running a bit rough when I apply throttle. I popped the air pods off to see if that would help. When I looked in the air intakes, I was surprised to see the slide assembly and the needle shaking up and down violently.

Is this normal? Could it explain why my air pods occasionally get blown off the carbs?

Any help would be appreciated.

thanks, Jim (aka Cranky Bunny)

 

[xjwmx]

It's normal and because there's only vacuum on the intake stroke, The rest of the time it falls. If you ever use a vacuum meter to balance your carbs you'll have to get something like a vice grip and tighten it on the hose until there's just enough opening that the flow becomes steady. Some meters have a feature that does that built in.

 

[gggGary]

This a big part of why Yamaha went to the trouble of making the STOCK airboxes big, using all available space. A large controlled still air box improves how CV carbs run! Search pod on here. Pitch em and get either stock or at least a UNI foam filter. Or prepare to ride a bike that "don't run so good" Yeah there's a lotta guys that prefer fashion to a bike that runs well, it's your choice.

 

[Sci85]

Not to get into a PODs vs stock airbox rehash, but I've done PODs many times as well as friends and from what I have experienced, most issue are due to jetting more than anything. De-restricting the airflow into the carbs will change the A/F ratio and will require jetting changes. In your case, if it's running rough without the PODs, just throwing PODs on will not fix the issue. However, with that said, once jetted properly, I haven't had any issues running good quality individual filters. As gggGary mentioned, I currently prefer the UNI foams. They work well and don't fall off. Note that I did toss the stock BS carbs for a set of Kawasaki EX500 CVK carbs jetted according to the recommendations on the site and the engine ran so much better there's really no comparison. I spent a lot of time jetting the stock carbs with my straight exhaust and UNI filters and it still never felt that great. I highly recommend the swap, especially if you are going to run POD's and/or more open exhaust. Good luck!

 

[xjwmx]

a set of Kawasaki EX500 CVK carbs jetted according to the recommendations on the site and the engine ran so much better there's really no comparison.

I haven't read a good step-by-step on that by somebody who's done it. Did you take pictures? I have read center to center isn't exactly the same is one big thing I guess.

 

[Sci85]

They are a direct swap. You do have to modify the throttle cable holder. There are many ways to do this. There's a huge write up on this swap that covers every question that has ever come up. First step is to read the forum so you know the proper jets and needles to get. This is critical to a good running engine. 2nd, get the UNI Foams or stock airbox. 3rd, you will have to grind down the plate that bolts the two carbs together. Very easy to do. Last, determine how you want to handle your throttle cable. I went with the easiest method and just bent the clamp onto the stock ferule. You will see how this is done in the thread. Again, too easy.

http://www.xs650.com/threads/ninja-ex500-carbs-on-an-xs650.13070/

 

[Angry Rabbit]

Many thanks for the help. I've got the old air box buried under a pile somewhere in the garage. I'll try putting it on and seeing if it helps.

Cranky Bunny

 

[650Skull]

Depending on the jetting...........was it changed for pods.........it may have to be rejetted

 

[gggGary]

BS34 with the stock USA needles like the washer mod. No more than one washer to a needle.

 

[xjwmx]

Many thanks for the help. I've got the old air box buried under a pile somewhere in the garage. I'll try putting it on and seeing if it helps.

Cranky Bunny

I have stock airboxes and maybe they tame the pistons, but honesly I've ridden with bare carbs and there's no major difference in ride. If you aren't satisfied with the ride it's probably something else unless you're really demanding.

 

[TwoManyXS1Bs]

...When I looked in the air intakes, I was surprised to see the slide assembly and the needle shaking up and down violently...

Have a look at rowdyrandy's vid of his slide flutter.
See if yours flutter worse, or less.

(Post #8)
http://www.xs650.com/threads/bogs-down-with-throttle-video.42314/#post-423268

 

[Angry Rabbit]

My slide flutter looks the same as the video. As far as jetting goes, I have started to systematically go through them to see how the bike performs. I know I'm gonna have to do this with the pod filters. I also want to check my timing one more time.

Thanks, CB