Leaky float seats

I bought a set of Mikuni RS34's. The #1 &2 carbs have been leeking from the overflow tubes. it has been ongoing for 2 months. I just got new seats and needles. i replaced them and #2 seams to have stopped leaking but #1 is still leaking. its better but i still get a table spoon or 2 full each day.
Any tips?

Hi Mark,

I know you've been around the bush plenty.

There was a recent thread about polishing the seats. It also described how, in normal operation, a float valve might not open enough to flush out any grit that may be preventing proper sealing.

Have you tried shutting off the fuel a mile or two before you shutdown? That way when you start up again a good flush of fuel rushes in to refill the float bowl and clean the seat.

Is it possible that your tank is dirty and despite your new seats and needles the same old grit is preventing the valves from sealing?

Just a few thoughts.

KZCSI

Those are very good points.I have not tried flushing the seats but it is worth a try. as for the rust in the tank, i do have a fuel filter in the tank(fine metal screen) and in line(pleated paper). even with these, i did see some fine setiment in the float boals . i'm not sure how its getting past the paper inline filter,it seems very fine.But obviously it is.i just bought a new aluminum filter with a stone type media when i was out of town the other day. but when i got it home i noticed the 5/16 nipples are too small of an ID. more like 1/8" holes. my 1300cc's need more flow than that. so im stuck with another spare part i cant use.
I may have to get the tank sealed,even though it looks great inside.
I will try to find the post on polishing the seats.if u come across it please let me know. I have not heard of this. i tried to rub the old needle into its seat but could not get a good grip on the needle. it sits too far down into the seat.
Thanks for the tips.

I am not familiar with the RS product family as pertains to the needles/seats but doubt that polishing will solve your problem. You failed to mention WHEN the overflow is occuring. I bet it is when you park? If so, SHUT THE FUEL OFF and PARK ON CENTERSTAND. No needle/seat is intended to be a fuel shut-off. As far as polishing, it doesn't do any harm but the gas shut-off function in the seat is only the surface on the hole that allows gas to flow and the surface on the needle. This surface must be clean enough to allow seating and it sounds like your tank has grit in it. Are you proud of the tank's paint job? If not, there are a number of ways to deal with grit but if you have a real nice paint job, there are less options.

I am surprised that u say the seats are not meant to shut off the fuel George. I'm sure you must have first hand experience with this .I have not had a bike that leaked when parked before ,so I am surprise to hear u say this.
Yes only leaks when parked. I have no center stand.
I bought a new petcock, and it obviously leaks too. I haven’t found seals for it yet since it is a made in china thing id say. It’s pretty though. lol. i will likely have to buy a new Pingle .
How do u polish the seats? Can u direct me to a post?

You said” Are you proud of the tank's paint job? If not, there are a number of ways to deal with grit but if you have a real nice paint job, there are less options.”
I will have to repaint the tank at some point ,what options are there?

i've had to polish seats before what i did was use toothpaste on a cuetip and spin it around like i was lapping valves i used a polishing type of toothpaste it worked if there are any goughes or score marks it won't but if there is any kind of buildup of varnish or crud it will work, do it until the cuetip comes clean then clean it up and you should be good to go. it's an old trick but one that does work.

While polishing the seats will provide a BETTER seal for the float needle, I repeat, float seats/needles are not intended as fuel shut offs. This is why they added vacuum petcocks in the late 70s. To idiot-proof fuel shut off since many owners forget. While most needle/seat assemblies will shut off fuel OK, they can and will leak and this is normal.

If you have an aftermarket petcock, there really is only one that I can think of that you may have. Look in JP Cycles and see if you can spot it. They sell all the internal parts separately if you want to rebuild the petcock. I would do this on a priority basis.

If you are interested in fixing the root cause of the problem... the rust in the tank, you need to assess how much rust there is. Surface rust can be treated by soaking in a phosphoric acid solution. This makes the rust inert. Flush and refill the tank quickly. I doubt the acid will do the paint any good. If the tank has flaky rust, the process is two stage. First is an acid wash and cleaning... usually tumbling the tank with nuts/bolts inside will help knock off some of the rust. There are lots of threads on this part of the process. If you buy a liner kit, the kit will come with a good acid etch. It is important to follow the instructions to the letter. POR-15 is a good product. Any of these tank cleaning/lining techniques will likely necessitate a repaint of the tank after.

Hi Mark,

WG is right about float valves not being intended to shut off the fuel supply. Their job is to meter it and control the fuel level in the float bowl, not hold back the whole contents of the tank for weeks at a time.

If you tank's contaminated please read this article I wrote about tank cleaning. Perhaps I've been lucky but I've never damaged a paint job with this method.

Rusty Tanks

KZCSI

Thanks guys.
I wasn’t aware that this was a common problem. I've never run into it before myself. But i haven’t had many bikes either, just 10.lol.
Anyway i have got some changes lined up. i just bought another tank that has been lined so that should be the big 1. Also i have just ordered a new petcock valve. Thanks for all of your wise advices guys. I really appreciate it.
I think weve got it covered now.i wont likly know till next year now.We'll see how the weather holds up.