Well I finally got my Ardtail and started the fab work on some of brake mounts:
Brake stay rod bolt welded and started blending
HHB Rear brake pivot and rear master cylinder mouting bracket
Also started on adapting the Keihin CVK carbs from a 2004 EX500 to my old girl:
Here you can see that the throttle cable is moved to in between the carbs rather on the outside of the left hand carb. The EX500 uses a dual throttle cable but has a return spring so my single cable works smooth as silk with no sticking.
Here you can see the idle adjustment screw under and in between the carbs (little black thumb screw)
Here you can see the modification the the upper rear support bar needed to clear the backbone.
Initial thoughts and observations on the EX500 carb swap:
1) As far as mechanical fitment the EX500 carbs are a direct replacement for the BS34's as far as the spigot and intake bell are concerned which means that the carb boots and filters do not need to be changed if you are currently running BS34's.
2) The choke on the EX500 carbs is a cable actuated choke so I had to come up with a creative solution using a little bit of ingenuity. Taking a page out of the BS34 play book I decided to use a spring and ball and created detents in the back side of the choke actuator. On the left hand carb there is an unused hole behind the actuator rod that worked perfectly for a spring and ball, using this hole I now have positive stops for no choke, half choke and full choke. When I take he carbs off for jetting changes I will get pics of the setup.
3) I knew that the jetting would need to be changed from reading the previous posts regarding this swap but wanted to see what it would do right out of the box. With these carbs fitted the bike starts and idles perfectly which really wasn't to much of a surprise as noboody mentioned having to change the pilot jets. Once I confirmed that the pilot circuit was operating at least acceptably and modifying my throttle cable for the new throttle pull position I took her out for a quick spin up and down my road and found that from idle up to about 4k rpms all was ok but at 4k it started breaking up pretty severely which from what I had read was really expected since everything I had read said that the mains need to be leaned out by 1-2 steps. I will have jets in hand tomorrow and will be doing jet swaps and tests to dial it in. The stock jets are 35 pilots and 130 mains. I ordered 38 pilots just for testing purposes and 122, 125 and 128 main jets to get her dialed in.
One thing I noticed is that the carbs weigh considerably less than the stock bs34's just by the weight in my hands. Also the CVK's have built in vaccum barbs which can either be used for vaccum petcocks or for carb sync making it an easy swap for people with bs38's using JBM carb boots.
All in all I think this could be a viable solution for replacement carbs using newer technology which also cleans up the look around the carbs quite a bit and this set of carbs cost only $140. A win win in my book.
