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 Post subject: Carbs wont stop pi$$ing out fuel..........
PostPosted: Thu Jun 14, 2018 3:28 pm 
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Joined: Tue Jan 23, 2018 5:37 pm
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Just trying to finish off the 500, but the carbs wont stop pi$$ing out fuel, despite them being fully rebuilt with new shut off valves, and the float height set to 24mm, as per the revision..............


PLEASE HELP!


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Thu Jun 14, 2018 4:48 pm 
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The only way a carb can piss fuel is if the float valve isn't working properly or the float height is too high. Time to open one up and see what's going on.

I suppose there is one other way and that is if the drain valve is left open, but there is an obvious difference in where the fuel is pissing out.

_________________
1985 RZ500 1GE Spec
1985 RZ500 47X Spec Project Bike
1986 RG500 ATR
1986 NS400R
1987 TZR250
1988 Honda RC31
2007 DL650 VStrom
2014 Triumph Thruxton Modified


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Fri Jun 15, 2018 8:34 am 
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Joined: Thu Nov 17, 2005 7:12 am
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Location: Leicestershire, UK
Did you use OEM or Mikuni float valves and seats ?

Did you check the fuel level in each carb as per the service manual ?

Cheers
Paul


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Mon Jun 18, 2018 7:22 am 
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New shuts used altho kit original Mikuni ones.

Float heights set to 24mm.....just checked float height using the pipe up the side method and it is showing flat heights are too high...

So 24mm is not high enough then....


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Mon Jun 18, 2018 8:25 am 
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Trig wrote:
New shuts used altho kit original Mikuni ones.

Float heights set to 24mm.....just checked float height using the pipe up the side method and it is showing flat heights are too high...

So 24mm is not high enough then....


24mm is roughly correct - can you confirm that you have measured the float height as described in the manual ? The adjustment tang must only just touch the valve - the weight of the float must not bear on it - so you angle the carbs to achieve this.

Good - luck - it’s a miserable process !!

Cheers
Paul


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Fri Jun 22, 2018 6:50 pm 
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Joined: Tue Jan 23, 2018 5:37 pm
Posts: 17
Right..............
Brand new Mikuni shut off valves, and float heights set with the pipe up the side method...................................


And success!!!!!!

There is a difference between the Tourmax shut offs and the Mikuni ones.................



Moral.......buy genuine!


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Wed Oct 03, 2018 3:53 pm 
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Posts: 4
Hello all,

I'm working on an RD500, European spec and have the same problem as mentioned above.
I had the bike standing for 3 years while I was working on the fairing. Finally got the parts painted this summer, so figured it was time to start the bike up.
I had never seen the bike running. Bought it with the tank and carbs drained, so couldn't check at the time of purchase. Bought it in good faith, the guy said it had run normal.
So after three years, I chuck in some fuel (checked the oil, etc.), put the fuel tap on prime for a bit, then to open and gave it a kick.
What do you know, on the second kick the thing fired right up and ran normal. Happy faces all around.

Only downside was that the carbs were a bit on the leaky side. But having stood still for 3 years I thought I would give it a try to see if it would sort itself out.
Well it didn't.
To make a long story short: carbs off, dismantle, lot of dirt, ultrasonic, revised (got the revision sets with the bike), new fuel lines, assembling, still leaking.
Leaks are around the float bowl seal, through the pilot air jet screw and overflow bowl.
Taking the float bowl off, to see if the float needle shuts off: looks OK, float down: fuel runs, float up: fuel stops.

Checking the fuel level with the hose next to the float bowl tells me the fuel level is too high: above the seal of the float bowl where it should be just a few millimeters below.
Adjusting the tang on the floats: got the level below the seal, so OK.
Still leaking! One always, two sometimes and the fourth seemed OK.

In my opinion the new gaskets for the float bowl were not very supple but very hard. Besides that I had trouble (as always) really tightening up the float bowls screws.
Turns out that even at the age of 48 you're not too old to learn. So I learned about the old JIS screws and got me some screwdrivers.
Cut myself some new gaskets for the float bowls from appropriate material and off go the carbs again.

So, this evening with new seals, new screwdrivers put them back together. Have them on the workbench now (had them on the bike all the other times, what a b#@tch to work on) with an old drinking bottle with fuel hooked up to the pair.
Let them fill and wait. Check the level with the hose and the drain screw: below the seal level, so OK. Everything looks fine, no leaks.

UNTIL after about 10 minutes I see some air bubbles in the hose to the fuel bottle, telling me that there is fuel going down the hose. And indeed there is still fuel leaking.
The good news is the self made float bowl gasket is holding! However fuel is still coming out of the pilot air jet screw. If I check the fuel level again it's way past the seal level.

I don't know why or how but my guess is that the float needle sometimes doesn't work, and sometimes it does. Even though the float needle and seats were changed.
I have the float itself under water now for the night to check if there might be a tiny hole in it.
I'm running out of options here and feeling a tiny bit depressed. I was kinda hoping to get some km in this year but don't see that happening. Still have to mount the freshly painted fairing (missing a fair bit of fasteners and grommets and stuff so this will also take a bit of time) and repair a leaking fork seal.

If ANYONE has ANY ideas, just throw them out here please.
I checked already a bunch of stuff but if it was OK it wouldn't be leaking, so maybe I'm doing something wrong.
I just want to go over everything and get it fixed.
Help is greatly appreciated.

Thanks in advance,
Mad Dog Roger


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Wed Oct 03, 2018 4:58 pm 
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1) Check if your float bowls are on the correct side.
RD500 has 2 different float bowl types - the difference is the position of the overflow pipe.
They have to be out of the center to the right side (bike driving direction).
Reason: On the side stand the bike leans to the left. Left side the fuel level in the float bowl will go up, right side it will go down.
If you mount dem the wrong way it will "leak" when the bike sits on the side stand.

2) Check your fuel tap.
Often the "4 hole seal" is broken and the O-ring of the vacuum plunger is hardened => it`s leaking when it should be closed.
Parts of the seal can go down the fuel lines into the carbs and lead to problems.

3) Check your float valve seats
There is an O-ring which seals the seat to the carb body. Sometimes this O-ring is brittle.
Fuel will bypass the float valves on the outside of the valve seats.
I guess the seats and O-rings are new in your case. Are they assembled with oil? If not the O-ring can be twisted with the same outcome.

4) In case of old valves and valve seats - corrosion and fuel components which will not evaporate.
Forget to ultrasonic clean them, it will not help. Polish the parts with an ear tip and metal polish.
The brass parts have to be shiny and smooth. Same with the sliding faces of the needle.
Never used new parts, polishing them makes them better than new and 100x better than aftermarket parts.

5) Tip of the needle should look fine. Never had one which wasn`t good enough to reuse it.

6) Fuel level according to corrected values. The information in the 1984 service manual is wrong.

7) Float filled with fuel. I think you will not find tiny leaks with water. It has a much higher surface tension than fuel. Fuel will enter much smaller holes.
Put them under fuel and squeeze them. If you see air bubbles there is a hole.
You can also check the weight compared to the other 3.

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My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda CBR 1000 RR SC57
Yamaha R1 RN04


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Wed Oct 03, 2018 5:46 pm 
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Hi Speed Freak,

Thanks for the quick reply.
Ad.1: I'm sure I put them back on the same carb I took them off. I only worked on 1 carb at the time. However that doesn't mean they weren't wrong to start with so I'll definitely check it.
Ad.2: Fuel tap was also revised with a new set from Wemoto. Old rubbers were hard and there were deposits on the back side of the 4 hole seal.
Ad.3: I did use new O-rings, supplied in the kit. I did use oil to mount but still had difficulty seating them, had to tap them in with hammer (gently). In fact there is some small "scraping" from the O-rings. I think I will reseat them with new O-rings just to be sure.
Ad.4: I still have the old parts. They didn't look that bad but since I had the new sets I used that instead. I cleaned them ultrasonic but that doesn't make them shine. So I'll have a go with the ear tip and polish.
Ad.5: The old tips looked fine to me, no markings, nothing worn through or anything but again since I had the new ones...
Ad.6: What are the corrected values then? I'm going by the manual: float height: 21mm ±1mm, fuel level: below the carburetor body: 1.5mm ±1mm.
Ad.7: Thanks for the tip, makes sense. I shook it to maybe hear something inside, but nothing. I'll definitely try fuel, have plenty of that with it spilling everywhere :rolleyes:

Thanks for the input. Already feeling a bit better. Got some things to do now for the coming days.

Greetz,
Mad Dog Roger


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Thu Oct 04, 2018 12:56 am 
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I think the correct float height is 24mm. Not 100% sure, can't check the service manual as i'm sitting in the train to work.

You can use the search function.

By the way, don't snap off one of the float pin holders.
They don't need much force and then you need a new carb body (all 4 are different) or a repair.

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My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda CBR 1000 RR SC57
Yamaha R1 RN04


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Thu Oct 04, 2018 4:24 am 
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Location: Toulouse France
Yes, the values for the float height and fuel level have been revised.
Corrected value is 24mm for float height and 3,5mm ±1mm under carburetor body for fuel level


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Thu Oct 04, 2018 4:37 pm 
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Hello all,

Didn't do that much today, on the bike I mean.
My regular ride needed some TLC. The RD is my oldtimer you see. My regular road bike is an NC30 that had a sticking indicator light switch (fixed), broken instrumental panel light (not fixed, impossible to get to without taking the top fairing off) and as it turns out also has a leaking front fork seal.

Did manage to get some measurements on the RD. Float height is 24.5mm on the rear left carb. Left front carb has 26-27mm. Yep one side is 26 and the other side is 27, so it is crooked. Will have to straighten that.
Another thing I noticed. There is supposed to be a small retaining plate to hold the float needle seat in place. This plate is secured by a screw. Well I don't have this plate. Only a screw with a large collar that kinda does the same thing for the float needle seat, only on one side iso halfway around.
I don't think this is a problem, only tells me somebody has been working on the carbs so maybe they are badly adjusted. Just another reason to start from scratch and take nothing for granted.

Keep you posted.

Greetz,
Mad Dog Roger


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Thu Oct 04, 2018 10:02 pm 
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MadDogRoger wrote:
Another thing I noticed. There is supposed to be a small retaining plate to hold the float needle seat in place. This plate is secured by a screw. Well I don't have this plate. Only a screw with a large collar that kinda does the same thing for the float needle seat,


That screw is correct. The parts list is wrong. There is no retaining plate. I have over 40 carburetors here and none have the plate. All have the screw. I just went out and looked at some NOS carbs and they have the screw. I have never seen an RZ500 carb with the retaining plate. All have only the screw holding needle seat in place. What you have there is what you are supposed to have.

The RZ350 and TZR250 (1st gen at least) have that retaining plate. I've rebuilt plenty of both.

_________________
1985 RZ500 1GE Spec
1985 RZ500 47X Spec Project Bike
1986 RG500 ATR
1986 NS400R
1987 TZR250
1988 Honda RC31
2007 DL650 VStrom
2014 Triumph Thruxton Modified


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Sun Oct 07, 2018 3:02 pm 
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Joined: Thu Oct 09, 2014 6:47 pm
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Hi guys,

Quick update. Tried scavenging at work but no 7x1.35, only 7x1.5.
Tried the local parts shop but no luck there either. So ordered them online but have to have them delivered at my parents house. Saves me 4€ in shipping, when 25 O-rings will only cost me 2.5€.
So first wait for the delivery.

Greetz,
Mad Dog Roger


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 Post subject: Re: Carbs wont stop pi$$ing out fuel..........
PostPosted: Mon Oct 08, 2018 7:50 am 
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Posts: 55
Location: U.K.
For what its worth, I had the same problem, I made it work by watching it work. Take the float bowl off so that you can watch the float do its stuff, take the carb into the kitchen, connect a header of water down a plastic pipe to the inlet, fill a bowl of water to the brim and lower the carb float into the water until it shuts off the flow, or doesn't. (I doubt if the difference in density between petrol and water is enough to make much of a difference)

When the float is fully down, and if the shut off valve is worn, the nylon pin can stick by twisting along its shortened inserted length (because it has dropped) and can be the cause of the problem. Even a new valve can stick if it is allowed to drop too much when the float is fully down. Tweak it so it works well, shuts off at good level and doesn't allow the pin to drop far enough to stick.

If the pin sticks when you are out, often a sharp tap on the offending float bowl with a metallic object will free the pin up to get you home.


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