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'93 Katana 600 Carbs

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MattE
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Joined: 11 Aug 2017
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PostPosted: 14:47 - 01 Jun 2020    Post subject: '93 Katana 600 Carbs Reply with quote
I have a 1993 katana 600 and have just finished refurbishing the carburettors, I had them ultrasonically cleaned and replaced all O rings and gaskets. I have also re adjusted the fuel screws and float heights however I am still having the problem of excess fuel forcing it's way out through the air box breather hose and pissing all over the floor.

Just to confirm the floats have been tested with both fuel and compressed air and seal at the correct heights however we think it may be sand and grit from the petrol keeping the float open, even when the float bowl is full of petrol so we are installing two small fuel filters. I will provide an update as to whether this resolves the issue. However any further insight would be greatly appreciated.

Thanks Matt

Thanks Matt
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jaffa90
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PostPosted: 00:48 - 02 Jun 2020    Post subject: Reply with quote
Did you replace / renew the needle valves and check / polish their seats.
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Pete.
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PostPosted: 06:24 - 02 Jun 2020    Post subject: Reply with quote
If you've cleaned the carbs as you describe then I guess the filter is the only option. Dunno why you should have sand in the fuel tank in Buckinghamshire.

BTW I think that model was only called a Katana in America. We call it a teapot Smile

There was a UK Katana but that was a proper man's bike.
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jeffyjeff
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PostPosted: 08:47 - 02 Jun 2020    Post subject: Reply with quote
Pete. wrote:
BTW I think that model was only called a Katana in America. We call it a teapot Smile

Actually (not to disparage the motorcycle at all, I almost bought one) in America, they are affectionally referred to as a "Kan-o-tuna". Cool

MattRides wrote:
however I am still having the problem of excess fuel forcing it's way out through the air box breather hose and pissing all over the floor.

Matt, wait a second. Don't the carburetor bowls have their own dedicated overflow tubes? Why would fuel be coming out the air box breather? Normally, there would be engine oil from crankcase pressure entering the airbox (blowby causing high pressure > forcing oil into the airbox and collecting at the bottom of the airbox).
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redeem ouzzer
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PostPosted: 11:58 - 02 Jun 2020    Post subject: Reply with quote
Most Mikuni CV carbs don't have overflow pipes, hence they fill the airbox / sump if anything goes pete tong with a needle valve or fuel tap.
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A100man
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PostPosted: 12:11 - 02 Jun 2020    Post subject: Reply with quote
The problem I have had with more than one set of Mikuni CVs is the o-ring that fits around the brass float valve seat - the one you see when you unscrew the seat. Make sure you fitted the correct item in this position. I think also they are an imperial size.
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MattE
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PostPosted: 14:23 - 02 Jun 2020    Post subject: Reply with quote
MattRides wrote:
however I am still having the problem of excess fuel forcing it's way out through the air box breather hose and pissing all over the floor.

Matt, wait a second. Don't the carburetor bowls have their own dedicated overflow tubes? Why would fuel be coming out the air box breather? Normally, there would be engine oil from crankcase pressure entering the airbox (blowby causing high pressure > forcing oil into the airbox and collecting at the bottom of the airbox).[/quote]

The carbs don't have their own overflow tubes and I have installed a restricted kit making the bike A2 legal which backs excess petrol into the air box and not the cylinders. I can attach pictures as I will be disassembling it again this afternoon.
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MattE
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PostPosted: 14:26 - 02 Jun 2020    Post subject: Reply with quote
jaffa90 wrote:
Did you replace / renew the needle valves and check / polish their seats.


This has been suggested in the American Katana forum I am a part of so this is my next port of call. Thanks for the suggestion Thumbs Up
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jeffyjeff
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PostPosted: 15:20 - 02 Jun 2020    Post subject: Reply with quote
MattRides wrote:
The carbs don't have their own overflow tubes and I have installed a restricted kit making the bike A2 legal which backs excess petrol into the air box and not the cylinders.

Man oh Man!! That sounds like a fire hazard to me! Shocked
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temeluchus
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PostPosted: 15:32 - 02 Jun 2020    Post subject: Reply with quote
A100man wrote:
The problem I have had with more than one set of Mikuni CVs is the o-ring that fits around the brass float valve seat - the one you see when you unscrew the seat. Make sure you fitted the correct item in this position. I think also they are an imperial size.


This.

Had this on two early GSXR1100s, and a set of RS36's, these use the same float valves.
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Shaft
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PostPosted: 14:25 - 03 Jun 2020    Post subject: Re: '93 Katana 600 Carbs Reply with quote
MattRides wrote:
I have a 1993 katana 600 and have just finished refurbishing the carburettors, I had them ultrasonically cleaned and replaced all O rings and gaskets. I have also re adjusted the fuel screws and float heights however I am still having the problem of excess fuel forcing it's way out through the air box breather hose and pissing all over the floor.

Just to confirm the floats have been tested with both fuel and compressed air and seal at the correct heights however we think it may be sand and grit from the petrol keeping the float open, even when the float bowl is full of petrol so we are installing two small fuel filters. I will provide an update as to whether this resolves the issue. However any further insight would be greatly appreciated.

Thanks Matt

Thanks Matt



Vacuum operated fuel tap?

Careful you don't introduce another problem - we've had a few bikes on here (mostly seem to be Suzukis) where putting in a filter means there isn't enough pressure to operate the tap properly, causing restricted/no fuel flow.
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MattE
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PostPosted: 22:28 - 03 Jun 2020    Post subject: Reply with quote
Is this o ring supposed to go on the end of this float needle or have I misunderstood?
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MattE
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PostPosted: 22:34 - 03 Jun 2020    Post subject: Reply with quote
jeffyjeff wrote:
MattRides wrote:
The carbs don't have their own overflow tubes and I have installed a restricted kit making the bike A2 legal which backs excess petrol into the air box and not the cylinders.

Man oh Man!! That sounds like a fire hazard to me! Shocked


See attached pics but the fuel gets pushed backwards due to the restrictor kit then through the small jets in the bottom and out the bottom of the airbox through a tube that ends up underneath the exhaust where it goes on the floor.
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MattE
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PostPosted: 22:38 - 03 Jun 2020    Post subject: Reply with quote
Carb picture
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A100man
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PostPosted: 23:06 - 03 Jun 2020    Post subject: Reply with quote
MattRides wrote:
Is this o ring supposed to go on the end of this float needle or have I misunderstood?


No. The needle faces directly into the brass part of the valve. The brass part is held in place by a small screw and a clamp. If you undo the screw/clamp you can pull out the brass part (chamber) from the carb body. Around the brass part is an o ring. this is the part that goes hard and lets by.

The o ring in your picture looks like part of teh pilot/mixture screw assembly.

This is a bit over the top but might be helpful..

https://www.xjbikes.com/forums/threads/in-the-church-of-clean.14692/#post-120724
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Pete.
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PostPosted: 06:20 - 04 Jun 2020    Post subject: Reply with quote
[quote="A100man"]
MattRides wrote:


This is a bit over the top but might be helpful..


A bit? Talk about chest-puffing.
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A100man
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PostPosted: 19:26 - 04 Jun 2020    Post subject: Reply with quote
Pete. wrote:

A bit? Talk about chest-puffing.


'tis murican..
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MattE
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PostPosted: 12:02 - 06 Jun 2020    Post subject: Reply with quote
A100man wrote:
MattRides wrote:
Is this o ring supposed to go on the end of this float needle or have I misunderstood?


No. The needle faces directly into the brass part of the valve. The brass part is held in place by a small screw and a clamp. If you undo the screw/clamp you can pull out the brass part (chamber) from the carb body. Around the brass part is an o ring. this is the part that goes hard and lets by.

The o ring in your picture looks like part of teh pilot/mixture screw assembly.

This is a bit over the top but might be helpful..

https://www.xjbikes.com/forums/threads/in-the-church-of-clean.14692/#post-120724



Ah my floats are slightly different. I believe the carb model is called Mikuni BT36SS. The float needle slots straight into the float body. I'll attach a picture if I can find one as mine are still on the bike and if possible want to avoid removing them again.
https://www.ebay.com/itm/OEM-SUZUKI-MIKUNI-88-97-KATANA-GSXF-600-CARB-CARBURETOR-FLOAT-NEEDLE-SEAT-/392752002098
This is what the floats I have look like. The dont have a brass seat for the needle as it goes straight into the body.
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Pete.
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PostPosted: 12:31 - 06 Jun 2020    Post subject: Re: '93 Katana 600 Carbs Reply with quote
Shaft wrote:


Vacuum operated fuel tap?

Careful you don't introduce another problem - we've had a few bikes on here (mostly seem to be Suzukis) where putting in a filter means there isn't enough pressure to operate the tap properly, causing restricted/no fuel flow.


Another thing to check is that it's not the float at all but the tap that's leaking via the diaphragm. Remove the small rubber hose off the tap. If there's any trace of petrol on it, strip the tap down and check the diaphragm for holes.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy
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