1992 slingshot carbs and routing

[Hooligan666]

Hi all.

I've recently acquired an 1992 slingshot.

I noticed both fuel lines where connected to the back of the petcock....no vacuum hose on top as all 4 points are blanked off with a rubber cap...no fuel line spacer/connector on the middle vacuum tube and the breather hose from crankcase was just sat in it.

Bike currently doesn't run and I plan on getting it up and running

I take it the bike is vacuum fed and if so Where's best to connect the vacuum hose on?it's strange as all 4 carbs arnt connected up..just 1 and 2. ..3 and 4 so not sure how the vacuum Will work when there's no hose there for it and the petcock has 2 fuel lines to it.

As I've learnt the fuel lines have a t piece joint and one line coming off that to the petcock so leads me to think there's a vacuum pipe some where?.

Also why would the breather pipe just be sat in the breather t joint in the middle of the carbs?. 

I get Impression the bike hasn't been sorted properly and hasn't ran with the previous owner during the build.

Routing and pics of where tubes go will help me understand what I need to do etc on the build from other peoples slingshots will be much appreciated 

Cheers all.

 

[Dezza]

One of the carb rubbers should have a take-off for the vacuum for the OEM fuel tap. The take-offs on the carbs are for connecting your Carbtune when balancing the carbs. Be carefull faffing with these as they break easily. The top breather thingy would have a hose connected with the other end going into the airbox.

[Panos]

If those carbs are 40mm you will need the airbox for them to work .

 

[Hooligan666]

3 minutes ago, Panos said:

If those carbs are 40mm you will need the airbox for them to work .

 

I.d?

[Panos]

1 minute ago, Hooligan666 said:

I.d?

Yes measure the i.d on the side where they fit on the rubbers on cylinder head , 92 model uses bst 40mm .

They are very tricky to tune without an airbox .

[Hooligan666]

16 minutes ago, Panos said:

Yes measure the i.d on the side where they fit on the rubbers on cylinder head , 92 model uses bst 40mm .

They are very tricky to tune without an airbox .

I'm getting almost between 39-40 almost.

It's currently has cone filters and the r6 rear end on it so won't be able to fit the original airbox on it

[Hooligan666]

Just now, Hooligan666 said:

I'm getting almost between 39-40 almost.

It's currently has cone filters and the r6 rear end on it so won't be able to fit the original airbox on it

I'll be sending it to a dyno centre with a rolling road to get it done right once I have it up and running

[Upshotknothole]

Save your time and money and get some flat slides for it. Way easier to tune without the airbox. Shouldn't be too hard to sell those 40mm carbs. Those carbs don't like not having an air box, and none of the BST carbs like those individual pod filters. Either some BST38s off a 750 or RS36/RS38 carbs.

[Jonny]

7 hours ago, Dezza said:

One of the carb rubbers should have a take-off for the vacuum for the OEM fuel tap. The take-offs on the carbs are for connecting your Carbtune when balancing the carbs. Be carefull faffing with these as they break easily. The top breather thingy would have a hose connected with the other end going into the airbox.

I have an 1100L and the vacuum take off comes from carb 2. I thought they were all done like that?

[Upshotknothole]

4 minutes ago, Jonny said:

I have an 1100L and the vacuum take off comes from carb 2. I thought they were all done like that?

Depends on the year. M and N 1100/750 came off the #4 intake. 

[Dezza]

750L,M also have a spigot for the vacuum take-off on carb rubber 4.

[Jonny]

7 hours ago, Dezza said:

750L,M also have a spigot for the vacuum take-off on carb rubber 4.

Don’t suppose it really matters. IMHO, 2 is probably the closest so probably best.

[rodneya]

What does the petcock look like?

If it is not stock it may not need a vacuum line at all.

[Wee Man]

Dont know if this helps, the standard setup for fuel lines.

[Upshotknothole]

In addition to the two fuel lines going to the carbs, there's that large open vent line that normally goes to the air box, that can get a length of hose and a small breather filter. Then there are two smaller vent lines that come out just above the fuel lines and those go to a smaller filter that sits on top of the valve cover. Vacuum line should come off the #4 intake boot if you still have a stock petcock. But once again, either consider fitting an air box with these carbs, trade them for some BST 38s, or get some flat slides.

[Wee Man]

This might help too.

[Upshotknothole]

I guess I do have a photo of mine. God I hate all the extra crap that comes with running the fairings. My valve cover filter was modified to take the two other vent lines as well as the main one. I'd forgotten that went in there as well. Also need to swap the petcock and get rid of that T fitting in my fuel lines.

This is a 750M/N