Fuel in airbox from breather hoses

hello fellow xj’ers,

I have been trying to get my bike running for a couple years, I don’t have a lot of time but I have had time recently...

Anyways, I got it running pretty good, synched the carbs and then all of it sudden it will slowly lower in rpms till it dies. And then I saw fuel in the airbox and got a little scared... I saw that the breather hoses were dripping a little bit of fuel so I’m assuming that’s where it’s coming from... anybody know what’s going on? I cleaned out the petcock and made sure that was working correctly...

Any help is appreciated!

(This is on an 85 XJ700 Maxim, air cooled)

Sebastian

 

Floats are stuck, or the float needles aren't sealing.
Pull carbs. Take them to church. Replace the old viton parts.
IN THE CHURCH OF CLEAN
Even though your carbs have overflow vents, best make sure that no gas got into the crankcase.

 

Thanks k-moe for the quick reply,

I have overhauled the carb and replaced the needles and set the height, could I have done it incorrectly ?

Thanks again,
Sebastian

 

after setting float height did you do a wet set of the carbs?

Setting the fuel levels

 

Here is the set I got from eBay, let me know if it looks correct...?

Deluxe CARBURETOR CARB REPAIR REBUILD KIT YAMAHA XJ750 XJ 750 https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/221822084868

I will do a wet set when I have time, thank you both of you!

Best,
Sebastian

 

As xj550H said, wet setting the float level is critical , especially on the XJ700N which is set at 1 mm +/-1. Some of the aftermarket needles are a little longer than the stock. I replaced mine with brass needles and seats I got from Chacal, and I recommend you do the same. I just cleaned my carbs and they leaked when I checked them on the bench. I removed the bowls, floats and needles a used compressed air through each needle seat, and therefore the entire fuel rail, and that solved the leak problem. I found an easy way to check for leaks is to install the seats, needles and floats, invert the carbs without the bowls, and attach the fuel line. No fuel should flow. If it does then there is a problem with that needle. And/or seat. If there is no fuel flow then lift each float and there should be fuel flow—if not you have a problem with the seat and/or needle. If fuel flows lower the float and the flow should stop—if not then you have a problem with the needle and/or seat.

 

I have no idea what a Y403S main jet needle is for, but it's not an XJ750.
Could be the kit manufacturer's part number I suppose.
The float needles look right, but there are at least two kits out there where they are undersize, and will tilt in the bores. That may be the cause of your trouble.
I'm not fond of the abundance of titanium-nitride coating on what should be brass and nickle-steel parts. Unfortunately that has become the hallmark of cheap parts lately.

 

those kits have gone up in price you could get them for 28 to 38 $ and it is 4 carb sets

 

But they will leak like a sieve, because the needles are the wrong size...………we dropped those sets about 8 years ago (due to this exact problem), I'm surprised that they are still being offered.

 

The brass set Chacal has work perfectly and that's what I recommend. With those, if it leaks then it's not completely clean.