Topic: Keihin Carb drain screw leaking

[scotty]

I drained the bowls on my carbs, and one of the drain screw looks a little un-semetrical at the end, and it won't seal now.  I think some part of it broke off.  Anyone know where I can buy a drain screw for these Keihin PD46C?  And if that doesn't work, can I just glue it in with JB weld or something?

[ekpent]

Is the gasket seal still there and unbroken for the drain screw?

[brewsky]

You can get them here:
http://www.siriusconinc.com/pro-detail.php?pid=&product_id=1371

Either the price really went up or there is a mistake in the page!
I got a set of 4 from them not too far back and I believe $20 was for the set, not individual screw. Might want to contact them to clarify.

[Bru-tom]

i had the same issue with mine. i went to a local bolt and nut supplier, got some brass screws, went to a o-ring and bearing supplier, got some fuel resistant o-rings, total equivalent to $0.50. shop around before you fork out ridiculous amounts of money for simple things.

[neilc]

Ya mine don't drain if I back off on the screw either

[mrrch]

The drain screws on some Honda power equipment carbs match up. See if your local dealer has a stash of old carbs (we save the old carbs for spare parts/came in handy when I needed a couple of drain screws)

[Jore]

This interests me, but I think my problem is different.

I've noticed that if I leave the petcock open with the bike off, number 2 carb starts dripping gas from the drain pipe, at first I thought the screw was loose, but it's not. I recently replaced the O-rings on all 4 of them.

[ekpent]

This interests me, but I think my problem is different.

I've noticed that if I leave the petcock open with the bike off, number 2 carb starts dripping gas from the drain pipe, at first I thought the screw was loose, but it's not. I recently replaced the O-rings on all 4 of them.

Its probably a float needle and seat that is not sealing perfectly.Not really a problem when riding and probably not an issue when you turn off the petcock when not riding as recommended for these bikes.

[Jore]

so can I ignore it? or what can I do?

[TwoTired]

On the PD46 carbs the drain screw operates like a valve, the tip is kinda pointy, machined, and blocks an orifice located at the bottom of the bowl.  The fuel exit path is into the bowl overflow drains. Other, earlier, Cb550 carbs behave differently.  If the bowl seat is f'd up, perhaps it can be reconditioned buy a machine shop ( or replaced).  If the screw tip is jacked, it won't seal, either.  Maybe the tip can be machined down, or simply replaced.

I don't know what kind of carbs the thread hijacker has, and they are NOT all the same.   So, I can't diagnose that problem.

[Jore]

Really sorry for the thread hijacking.

But my carbs are also keihin (not sure of the type,there on a 75 400)

[TwoTired]

Really sorry for the thread hijacking.

But my carbs are also keihin (not sure of the type,there on a 75 400)

...and this thread began about 78, CB550 Carbs

Anyway, yours is unlikely a drain screw problem, as your carbs are a different design than the PD46.  For yours, either the float valve is leaking from debris, uneven wear, the float height is set for too high a fuel level, or the float pivots are binding/sticking.  May also be a bowl gasket out of place and hindering float movement.

Does it behave differently if the bike is on side stand or main stand?  (Helps narrow down some issues.)

Anyway, it is routine to shut the fuel valve off when the bike is parked.  Modern bikes have engine vacuum operated fuel shut offs.

[Jore]

Sorry once again.

But I might as well ask. I only have a side stand, so no idea what would happen on a centre stand.

[jas67]

So, on the CB400F, should the fuel exit via the overflow tubes when the drain screws are open, or does it come out around the drain screw, making a mess of the engine cases.

I ask this, because I have two CB400F's, one very pretty, one not-so-much.    When I drained the carbs on the not-so-nice one, I expected the fuel to exit via the drain tubes, but it came out around the drain screws, on all four carbs, making a mess of the engine cases.     Because of this, I haven't yet drained the nice one, so the fuel has been sitting there for half the winter getting stale (it does have stabilizer in it), because I didn't want o make a mess of the engine.   I guess I make some sort of catch tool to put under them to drain the fuel into.    I'm thinking some sort of small funnel with a side exit to a hose that I can put into a gas can.

[lucky]

so can I ignore it? or what can I do?

A leak can also be caused by a cracked overflow tube in the float bowl.
You will need a magnifying glass to see the crack. Even if you are NOT old.
But since you did not tell us what year the bike is it is hard to say.
The 77-78 carb float bowls had a different type drain system.
They had a drain screw but it did not have to be completely removed to drain the bowl.

[TwoTired]

So, on the CB400F, should the fuel exit via the overflow tubes when the drain screws are open, or does it come out around the drain screw, making a mess of the engine cases.

The drain screws don't effect the overflow pipe drain channel on your carbs.  They drain where they screw (sounds dirty, heh heh)

What I use is the tray from an Entenmanns coffee cake offering.   I simply endure the torture of emptying the tray prior to it's main purpose. 

Cheers,

[MoMo]

You most likely have a cracked drain pipe as Lucky said...Larry

[jas67]

So, on the CB400F, should the fuel exit via the overflow tubes when the drain screws are open, or does it come out around the drain screw, making a mess of the engine cases.

The drain screws don't effect the overflow pipe drain channel on your carbs.  They drain where they screw (sounds dirty, heh heh)

What I use is the tray from an Entenmanns coffee cake offering.   I simply endure the torture of emptying the tray prior to it's main purpose. 

Cheers,

Great idea!   I like Entenmann's baked goods.   I'll pick some up on the way home tonight, and the tray will be available for use by the weekend.

[TwoTired]

The 77-78 carb float bowls had a different type drain system.
They had a drain screw but it did not have to be completely removed to drain the bowl.

The drain screw on the non-PD carbs does not have to be completely removed, either.  The brass plug has cross drilled holes. So, in theory,  you only have to unscrew enough to pull the oring off the bowl to drain the carbs.  However, sediment often blocks the small cross drilled holes, and the oring sometimes sticks to the bowl.  In these cases, the plug must be removed completely.

Cheers,

[dave500]

So, on the CB400F, should the fuel exit via the overflow tubes when the drain screws are open, or does it come out around the drain screw, making a mess of the engine cases.

The drain screws don't effect the overflow pipe drain channel on your carbs.  They drain where they screw (sounds dirty, heh heh)

What I use is the tray from an Entenmanns coffee cake offering.   I simply endure the torture of emptying the tray prior to it's main purpose. 

Cheers,

i just bunch a ball of rag under those screws and soak it up as they empty,you dont have to fummble with spilling fuel from a dish then,,the same way you drain holley carb bowls once the bowl screw comes out.

[jas67]

i just bunch a ball of rag under those screws and soak it up as they empty,you dont have to fummble with spilling fuel from a dish then,,the same way you drain holley carb bowls once the bowl screw comes out.

I'd rather drain the fuel into a container to safely dispose of.    What do you do with the fuel-soaked rag when you're done?

I was thinking some kind of "gutter" made from a piece of PVC pipe with caps on the ends, and a small barbed fitting connected to it with a piece of hose on it, so the fuel drains out of the the "gutter" into a closed container via the hose.    This way, I don't have the hazard of fuel sloshing around in a large flat tray.

[dave500]

wow,i love the over thinking of the simple act of draining a cup of fuel,the rag mostly dries out and i throw it away once its fully soiled from say wiping down a filthy drive chain etc.

[flybox1]

next time you smash your hands sliding that motor back in and have to go to the ER, 'borrow' one of those kidney bean-shaped vomit trays (emesis basin) and cut one side down to slide right in and fit under the drains.
luckily my wife is a RN.  she loaned me one 
its also painless to pick one up at a drugstore or staples for less than $1.00

gas can go right through a coffee filter and into your mower.

[seanbarney41]

wow,i love the over thinking of the simple act of draining a cup of fuel,the rag mostly dries out and i throw it away once its fully soiled from say wiping down a filthy drive chain etc.

no #$%*, what did you guys do when you were kids?  Around my neck of the woods it went something like this..."Hey lets use this gasoline to make flaming pentagrams in the street again...I don't want to mow the lawn..."

[Tugboat]

+1!!!