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CBR900RR Fireblade carb plumbing / connections

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15K views 6 replies 2 participants last post by  jseaman  
J
#1 ·
Right folks, progress is good - tomorrow is a fuelling day. Before I start tearing my hair out trying to figure out what goes where I thought I'd pick your brains

So the stock airbox has two connections, one at the top which seems to be an inlet to a breather and this has an outlet port on the side and the other is on the right hand front as shown in the picture below:



I assume that the small port on the right is a breather from the valve cover here:



Question 1. Is that correct?

My next assumption is that the breather in the airbox connects to the large tube out the centre of the carbs as shown here:



Question 2. When is this overflow ever used?

Question 3. What should connect to the 'outlet' port of the breather on the airbox?

There is a linked breather (?) pipe on the top of the carbs as shown here:



Question 4. Should this vent to atmosphere?

There is another vac line which is already connected on my engine between the two left carbs here:



Question 5. What is this for, PCV?

There is a similar breather on the other side here:



Question 6. Where does this one plumb into? I think it might be one that is used on a standard bike set up to prevent fuel entering the carbs from the tank in which case can I just block it off?

Question 7. And finally, each carb has an outlet port at the bottom. Two of mine are joined together but 2 aren't and none of them go anywhere.

Thanks in advance

James
 
#2 ·
Holy cow James!!! Try any limit your questions to 3 per post!:rotfl:

You're right on with the airbox. The tab on the right from the bottom of the airbox is the crankcase vent from the top right of the cam cover. The very large center pivoting breather hose in the middle of the carbs connects to the sub-air cleaner that bolts to the rear end of the airbox.

The small breathers that come out from the top of the carbs and vent to the right of the carbs to the single tube just vents to atmosphere.

The small hoses on the bottom of the float bowls just drain the fuel in the bowls to the ground. They do nothing and can be removed. They disn't come standard and have been added at some point. They are useless really. Remove them.

The small vacuum hose coming off the cylinder head under the carbs on the right was to activate the original fuel valve on the gas tank. Cap it at the head if your not using a vacuum operated tap.

In your third picture, you're finger is pointing to the main fuel inlet tube. That will connect to your fuel tap.

In the photo above question 5 I can't really see what you mean. The only hose I see is the air bleed coolant hose that goes to the head from the water pump.
 
J
#3 ·
:) Sorry but it tends to come in batches like this! I'll try and keep under 3 this time!!

Apologies for the confusion on pic 3, I think I posted the wrong picture! I wanted to confirm I'd picked the right fuel feed point too which you have done so thanks!

It might well be the air bleed hose! I'll follow it through now and check

1. So the breather on the airbox, when is it used and should it have a connection other than to the middle of the carbs? It seems to have 2 ports which I presumed was inlet -> filter -> somewhere else?

2. All the small hoses that drain the fuel to the ground, presumably they need to be capped off or fuel will merrily drop out?

As usual thanks for taking the time to respond

James
 
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