5 replies to this topic

[Tinkerbelle]

I have always had a problem with my twin SUs leaking from the float bowls randomly. I have just worked out that it is from the built in overflows which allow fuel to spill onto the tops of the float chambers if they overfill. I fitted an inline filter as I suspected dirt was getting in and jamming the needle valve but they still do it randomly.

Anyone know why or have a similar experience?

Thanks

Matt

[dklawson]

If your float valves are at the end of their service life they may not be seating properly and shutting off the fuel flow. Your float level setting may also be a bit high.

There are the original metal-to-metal contact type float valves, Viton tipped float valves, and Grose Jets. I use the Viton tipped valves and am happy with them. Some people have reported that the metal-to-metal valves work best if lapped together using "toothpaste" prior to installation. Both metal-to-metal and Viton tipped float valves have been known to have fit issues where the edges of the moving valve needle may need to be "scraped" just the tiniest bit so they don't stick in place. This is not a major issue, just something to keep in mind.

Grose Jets are VERY different. They use captive steel balls to create the seal when the float is up. They either work or they don't. I have used them with bad results and removed them from my cars. Others may tell you they are the best thing since sliced bread. Again, some work, some don't and I've had bad luck with them sticking shut AND sticking open.

[Tinkerbelle]

Thanks for that Doug,

The carbs are almost new so I ruled out wear. It is not a slight leak either, when they leak they pump out about 10cc of fuel per second, enough to cause a good trickly off of the bottom of the float bowls.

Don't know what type I have, they are plastic floats with no adjustment and a plastic valve piece lined with metal, pointed on one end and spring loaded on the other; which sites within a brass sleeve and activates off of the float.

They are not doing it today, but who knows about tomorrow. To stop it I take the top off of the float bowl and dismantle then reassemble - then all is good for a while.

It is more like the float is getting stuck in the bowl. Next check is for casting burs etc which may foul the float?

Bloody things.

Matt

[dklawson]

Since the parts are new, take a look at whether the needle is being "caught" on the inside of the sleeve due to burrs as you and I both mentioned. If the needle has a metal tip you may also want to consider the "toothpaste lapping" I mentioned earlier. Lapping isn't possible if you have the Viton tipped needles.

The plastic floats aren't really adjustable like the old ones with the metal arms. However, you can tweak them a bit by fitting multiple fiber washers (as necessary) under where the valve sleeve screws into the bowl for the lid. More washers will lower the sleeve and therefore lower the closure point and fuel level.

I removed the Grose Jets from my Mini's carbs after watching the gas pour out of the overflow. I feel your pain.

[Tinkerbelle]

Thanks a lot for help.

My wife's (who is from Va) grandparents used to live in Chapel Hill, now New Bern. I may just have to check out your Minis and bring any bits over you want in July when I am going to see them.

PM me if you want me to bring over any parts (within reason!)

Matt

Edited by Tinkerbelle, 15 April 2009 - 05:26 PM.

[dklawson]

Thanks for the offer Matt.

I postponed my U.K. purchases for several years until the exchange rate became favorable earlier this year. At that time I made my big-ticket purchases from Mini Spares. My immediate parts needs should be OK but again, thank you for your offer.

Let us know what you find out with the float valves.