UPDATE:Carbs and a few questions

[KatanaJim]

When we last left out dashing, young mechanic...
My #4 plug was black, And I could not get the bike to idle less than 4k rpms, when warm. I did a valve adjustment, and since you guys recomended checking out the carbs before syncing them, thats what I did.
While doing some light clean up work, I noticed the butterfly for carb #4 was bent!!! It looked like someone poked it (hard) at the bottom. There was a slight crease in it and the bottom half (where the crease was) was about 2mm different than the rest!

Questions:

Could this be the cause of my fouled #4 plug? The way I figure it, By being bent, it was pulling more vacuum and thereby pulling more fuel and running that cyl. rich! (that would explain the high idle as well)

In removing the butterfly, I damaged it a little. I pounded it flat again and the brass expanded a bit, so I was going to machine it back down to size. Is this worth it, or can I find carb parts, like butterflies, somewhere?
Help!!!

[Anonymous]

what number iis on the butter fly 120 125 128 ???? im gonna guess125 since there off a 750 and yes its gonna fit funny since its been bent. wouuld it pull more air and fuel casue its bent open yes.

[trinc]

i would find a good used one ( or buy a used carb & pull it ) but if you stick it in and can get the sync correct - you'd be good to go.

yes it would cause your 1 plug to foul.

tim

[rideitlikeyoustoleit03]

be sure when you put the butterfly back in if you do to use loctite on the screws just so they dont come loose n ruin a motor....... thats just my 2 cents

[The CyberPoet]

I'm going to advice tracking down another set of carbs (used, ebay or send a PM to BraadaJim about the inventory he took from SpecialK) and replacing it. Yes, the bent butterfly would be a highly probable cause. No, you can't expect to get it back into a perfectly acceptible aerodynamic shape.

You might also want to go straight to a vendor of carb parts, such as www.sudco.com or contact Mikuni USA directly.

Cheers
=-= The CyberPoet

[KatanaJim]

It is marked "120", and I cant even locate my model of carb, on the Mikuni or Sudco pages
PS Anybody know what model Mikuni's came on a 91 Kat?

[The CyberPoet]

It is marked "120", and I cant even locate my model of carb, on the Mikuni or Sudco pages
PS Anybody know what model Mikuni's came on a 91 Kat?

Let's check my site... ummm...

http://www.motorcycleanchor.com/katana/katana_tree.html

91 750 came with four BST36SS carbs

Cheers
=-= The CyberPoet

[Trigger]

Have the same problems finding parts for my (4) BSR32, so I broke down and will just order the parts from WWW.Ronayers.com about $200 bucks and I'm done with the CARBS.

[KatanaJim]

Hey sinfulkat!
The butterflies are marked 120, but they measure 36mm across. Interestingly, they measure 37mm top to bottom. I guess I never realized that they are oval and not round...live and learn!!

[Anonymous]

Hey sinfulkat!
The butterflies are marked 120, but they measure 36mm across. Interestingly, they measure 37mm top to bottom. I guess I never realized that they are oval and not round...live and learn!!

hmmmm that strange cuase ive got a set of 36mm carbs sitting here but the butter flys are marked 125 but these are gsxr carbs too i wonder what the diff is with the butter flys being numbered diff cause i dont know ive just notice that diffent size carbs were numbered diff hmmm maybe someone will know strange guess your right learn something new everyday and i got a set of 38mm carbs that have 135 butter flys which i know are bigger and a set of 01 600 carbs that are marked 110 which are
32mm and pre 98 600 carbs are suppose to be 34mm which happen to use the same casting or carb body with a diff bored and internals

[KatanaJim]

Well since I have been unable to locate a new butterfly, I "refubished" my old one. Basicaly, I pounded it flat and filed it back down to the proper dimensions. I am hoping that I can "sync-out" any leaks that it may have. Hell, its gotta be better than when it was bent!!!!

[md86]

Mine on my Kat750 carbs say 120 .