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Fuel leak

When I start my bike (Trident 900 1991) fuel pours out. As far as I can see, it's coming from either the right-hand carb, or the pipe that feeds it - I can't see which. It stops when I turn the engine off. While the bike runs, it sounds like it's only firing on two cylinders.

Any idea of likely cause? Time to remove the carbs again I guess.

Fuel valve

If I turn the fuel selector so that the flat bit is at the bottom, it leaks even with the motor switched off. When it's in the other two positions (flat bit on the left or at the top) it doesn't leak. This seems weird to me because I thought the tap positions were like this:

Flat bit at top (ie pointer would be down) - Prime
Flat bit on left (ie pointer would be right) - On
Flat bit at bottom (ie pointer would be up)- Reserve

I'm wondering whether my bike has a non-standard plastic pointer from another bike - I expected fuel to come out when it's in the Prime position - does it look standard in the pic?



 

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fuel float

you push it in for prime. sounds like a float is stuck , letting fuel flow freely, which would be why it leaks when running with tap on ,and leaks off with tap on res.
 

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Discussion Starter #3
Interesting about pushing in to prime... I've seen this referred to elsewhere on the forum, but my owner's handbook doesn't mention it. Equally, the picture of the fuel knob in the handbook looks different to mine.
 

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Your petcock looks standard to me. I don't know positions without the knob, but all the way left is Prime, all the way right is Reserve, and in between is On.

Watch the movement and you'll see the valve move in as you turn to prime. As I recall there's an internal ramp that accomplishes this.

The fuel leak sound's like shot float needle valve seats in a carburetor.
 

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sounds like you are leaking fuel whenever you have either vacum pressure (i. e. engine is running, fuel is in reserve or on position with flat bit at bottom or right) or when you put the fuel valve in the prime position (i.e, engine off, no vacum, flat bit at the top). Sailfish has it right, or you have a stuck float letting the fuel flow freely.
 

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You will want to check and see if you have a vacuum operated petcock. I'm not sure about the pre 95 models but my 95 Sprint has one. If you pull the tank you will likely find a vacuum hose running from the left hand manifold vacuum port to the backside of the petcock. That will explain why the leak only occurs while the engine is running.Now onto the problem, it sounds like you have a leaking float needle and seat. Could be as simple as crap not letting the needle seat or it is worn.Time to yank the carbs.
 

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Would I be right in saying if it is the float valve sticking that the fuel would be leaking from the breather hose....and if it's not leaking from the breather then it's probably a fuel line that's leaking....that way you could eliminate the cause before pulling the carbs...???
 

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If it is fuel it has to be either a line or the float valve. If you are refering to the breather nipple on the bottom of the air box it is possible the carb is overflowing and fuel is coming up the needle jet and running into the airbox. If the breather hose is still connected and fuel is seeping at the airbox then you probably have an engine full of fuel too! Or at least oil contaminated with fuel,if the petcock was left on prime. Check the level and smell the oil. if it smells like fuel, drain it and remove the plugs and turn the engine over with the ign. disabled. fuel will blow out of the cylinder that had the leaking float.Failure to disable the ignition will possibly cause the loss of your eyebrows,motorcycle ,garage, and or home. Proceed with caution! Don't ask how I know this. And you still will have to pull the carbs.
 

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Fuel leak
<...>
If I turn the fuel selector so that the flat bit is at the bottom, it leaks even with the motor switched off. When it's in the other two positions (flat bit on the left or at the top) it doesn't leak. This seems weird to me because I thought the tap positions were like this:

Flat bit at top (ie pointer would be down) - Prime
Flat bit on left (ie pointer would be right) - On
Flat bit at bottom (ie pointer would be up)- Reserve
<...>
IIRC, & I think I do 'cause it's muscle memory related to the motor cutting out at speed in traffic, pointer *down* is RES & up is PRI.

Cheers, HTH,
-Kit
 

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Sounds like a fuel line came unhooked from the petc0ck.

Your photo shows the knob in the "On" position.
When the flat side is on top, you will be using "Reserve."
When the flat side is on bottom, you will be using "Prime."

I will be ordering another dial shortly, as mine just cracked at that flat side. My fix will be to fabricate a metal collar, and press it onto the backside of the dial. Hopefully, it will reinforce this area against future breakage. If that doesn't work, I'll find a close match in metal...I'll bet there is similar in a marine application.
 

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I just replaced my fuel tap and knob. I went and shape some pieces from some Oak and then used JB weld to hold them in place.
 

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Discussion Starter #18
I've pulled the carbs, and Mot and Alterna were right. Fuel line to #2/3 split where it joins the carbs.

So, nice cheap fix then, just get a length of fuel hose off ebay, right?

'Fraid not, because I sheared off the throttle cable adjuster when removing the cable from the carbs, and then broke the plastic T piece on the carbs when removing the old fuel pipe:mad:

Presumably that means I need to replace the whole throttle cable? (can't see how I'd get the adjuster off, even if I could buy one).

Likewise, it will be a trip to the dealer to get a new T-piece, and split the carbs to fit it. Anyone got any experience of doing this (Mikuni carbs), or know the cheapest place to get a throttle cable? (I'm in the UK)
 

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Glad to hear that the problem is simple, too bad the brittle plastic got you.

Since the carbs are out, you really should replace the float needle valve seats. If they've never been done then you're over-due.
 

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FFS that is bad news...good news is no one really bids on Mikuni carbs on ebay so they can be had for 30 quid..ish sometimes so it may be easier just to replace them...?

I've got a spare throttle cable for the Speed Triple but I think it will be too short for your Trident...happy to measure up or canibullize (sp) if needed.

All the best
Mot
 
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