Mikuni drain tube ?

After I did the Raptor petcock mod I could go back to my habit of letting the motor run dry before switching off. But a nasty surprise was waiting for me the next time, when I turned the petcock on to start the engine, the float must have stuck and a lot of gas started flowing out of this hole, which I suppose is a breather. I shut off the gas, and after some tapping it stopped.

 

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But the gas level for flow out of there being well over the intake from the air filter and into the engine, I had to change the oil. 

 

So after this I'm not letting the engine run dry anymore, just a little to ensure no pressure on the needle valve while the bike is at rest.

 

But I'm thinking of a way to make a drain, i guess the drain plug could be fitted with an elbow and a tube of appropriate height, topped with some kind of foam plug to keep dirt out. This tube might even be transparent, for gas level control. This is the drain plug I mean :

 

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I drain the gas almost every time I finish a ride. I have a short rubber hose on the nipple and use the drain screw you show in pic 2

 

BUT that will not prevent the float from sticking when the carb refills with fuel.  Refilling a dry carb is an invitation for the float to stick.  Tap on the carb as it refills is a good practice.

Well I'm not emptying the carb again before I have a drain tube to prevent flooding. Why on earth did Mr Mikuni leave that out ?

I have no idea what that hole is:/ nothing has ever came out mine. Only the overflow pipe when i do endos btw the mikuni carb is not bad :/ i raced a guy who has same as mine apart from the fcr carb yes he pulled away quicker but thats about it there is hardly anything in it. The forum is great to spend money :)

I have no idea what that hole is:/ nothing has ever came out mine. Only the overflow pipe when i do endos btw the mikuni carb is not bad :/ i raced a guy who has same as mine apart from the fcr carb yes he pulled away quicker but thats about it there is hardly anything in it. The forum is great to spend money :)

I'm glad to read your post, since I didn't dare to state that I also find the much rebuked mikuni carb just fine, my bike runs great with it and I see no reason to change.

 

However,  I don't see that it has an overflow pipe, that's its only problem as far as I can see.

There is no high fuel level drain because regulations did not allow fuel to drain on the ground.  That is why all DRZ with  Mikuni carb with no high fuel drain have an automatic fuel shut off valve (vacuum actuated petcock). Some DRZ in other countries with Mikuni do have a drain and manual fuel valves.

I'm glad to read your post, since I didn't dare to state that I also find the much rebuked mikuni carb just fine, my bike runs great with it and I see no reason to change.

However, I don't see that it has an overflow pipe, that's its only problem as far as I can see.

yes mine is uk version therefor it has a overflow pipe and manual petcock whats better.. But yes the mikuni carb is fine once up jetted

There is no high fuel level drain because regulations did not allow fuel to drain on the ground.  That is why all DRZ with  Mikuni carb with no high fuel drain have an automatic fuel shut off valve (vacuum actuated petcock). Some DRZ in other countries with Mikuni do have a drain and manual fuel valves.

Unfortunately that vacuum petcock will fail, look at mine after a few hours. Had the float valve been bad, severe damage to the engine would have ensued. It can be supposed that this has happened to many people.

 

Supermotomad 1, that's good to know, then there must be a plugged hole somewhere in my carb for the overflow pipe. I have an FCR also, and I really didn't notice any difference, they're jetted almost the same. The problem with the Mikuni was that the slider was getting stuck when closed because of some sticky goo that had collected in the grooves it moves in. Once I cleaned that, the jerkiness was gone.

 

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Edited by michaelks

The float bowl could be modified to add the stand pipe and drain.  Might be a bit tricky but doable with the right equipment.

Unfortunately that vacuum petcock will fail, look at mine after a few hours. Had the float valve been bad, severe damage to the engine would have ensued. It can be supposed that this has happened to many people.

Supermotomad 1, that's good to know, then there must be a plugged hole somewhere in my carb for the overflow pipe. I have an FCR also, and I really didn't notice any difference, they're jetted almost the same. The problem with the Mikuni was that the slider was getting stuck when closed because of some sticky goo that had collected in the grooves it moves in. Once I cleaned that, the jerkiness was gone.

Posted Image

looks like piss

The float bowl could be modified to add the stand pipe and drain.  Might be a bit tricky but doable with the right equipment.

So there's no plugged hole somewhere I gather ? I hope I can get the bowl out without removing the carb to take a look. If it can't be done internally in a straightforward manner, I'd think of that external transparent tube, I like the idea of a visible level.

So there's no plugged hole somewhere I gather--- Correct.  You need to add a stand tube to the desired high fuel level and of course a hole for the tube to drain.

 

I hope I can get the bowl out without removing the carb to take a look.---Yes, loosen and twist the carb to the right.

 

I like the idea of a visible level.----- OK, that is doable.

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