Leaking carbys

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Andrew Deans

Leaking carbys

#1 Post by Andrew Deans » Sun Oct 02, 2005 12:59 pm

Hi<p>A little while ago i replaced the carb float needle valve assemblies because the LH carbys where leaking fuel from the overflow tubes. Fixed the problem for a while however i filled up and noticed some leakage again.<br>Pulled the fuel hose of the carby and found that fuel was flowing in a continuous trickle so maybe the diaphragm , o-ring or spring are gone in the petcock,<p>***Would replacing the spring only resolve the problem or should i do this as a set.<p>Appreciate any help.<p> Regards<br> Andrew<p>
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adeans@geelongcity.vic.gov.au

Ken Smith

Re: Leaking carbys

#2 Post by Ken Smith » Sun Oct 02, 2005 6:42 pm

Do a complete rebuild of the petcock. also check your float levels. The specs in the service manual are incorrect, if you set them at that the carbs will leak out the over flows. If I recall they need to be set 2mm higher (from the carb gasket base) This will probbly fix your probblem as the little leaking from the petcock should not be enough to make the carbs leak.
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RDRZRGTZR@att.net

Paul Springthorpe

Re: Leaking carbys

#3 Post by Paul Springthorpe » Mon Oct 03, 2005 12:39 am

Hi Andrew,<p>Do as Ken says in his post - you are looking for 24mm float height - you will have to tilt the carb to take the float weight off the float valve without going too far and letting gravity give a false float height position if you see what I mean - it should make sense when looking at the float and valve- see the service manual page available at<p>http://www.rzv500r.net/E-Manuals/RZ500N ... html<p>You will note that a float height of 21mm is quoted on this page - it is the old original value - use 24mm - the bike will foul its plugs less, flood less and do better MPG !!! - it will run very slightly weaker so be wary if you have after-market pipes that are on the limit of weakness with a existing 21mm float height.<p>ALso check for rust,dirt and fuel varnish in your tank, fuel lines and fuel tap - check the carbs themselves are also clean inside - not just the float valves - the fuel varnish just spreads around the whole system over time - even if you clean the carbs thoroughly - it will migrate from the tank, tap and fuel lines - Don't ask me how I know !!! - 6 re-builds before I figured it all out !! :-)<p>Cheers<br>Paul
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paul@springthorpe74.freeserve.co.uk

Andrew Deans

Re: Leaking carbys

#4 Post by Andrew Deans » Mon Oct 03, 2005 2:46 am

Hi<p>Appreciate all of your advice. <br>I have a genuine Yamaha manual and there is no mention of any replaceable fuel filter within the system. <br>There are some plates on the bottom of the tank , is this some sort sort of mesh system in here which should be cleaned or give an indication of fuel contamination.<p> Thanks<br>
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adeans@geelongcity.vic.gov.au

Engie

Re: Leaking carbys

#5 Post by Engie » Mon Oct 03, 2005 12:37 pm

There should be a gauze filter in a nylon support that sticks out of the plate that bolts to the bottom of the tank. Maybee it's gone - you would be non the wiser.<p>Look in classic bike magazines for a petrol tank liner. You m/t the tank mix up the stuff and shake it around in the tank and it lines the inside of the tank to stop the very small pieces of rust that can get through a filter and then jam the float needle.<p>Take carb off the bike, remove float bowl. 1st check that the float cannot drop too low to allow the float needle to drop low enougn to twist and jam. <p>Then fill a wok to the brim with water and blow through a tube where the petrol goes into the carb and lower the float into the water until the airflow shuts off. Move the metal bit that presses on the float needle until the air flow cuts off before the water rises to the level of the carb body, with the float bowl off.<p>Well worked a treat for me !
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Paul Springthorpe

Re: Leaking carbys *****WARNING*******

#6 Post by Paul Springthorpe » Tue Oct 04, 2005 5:00 am

>>Then fill a wok to the brim with water and blow through a tube where the petrol goes into the carb and lower the float into the water until the airflow shuts off. Move the metal bit that presses on the float needle until the air flow cuts off before the water rises to the level of the carb body, with the float bowl off.<<<p>Before doing the above ensure that your wife is not only out but unlikely to come home and catch you doing this !!! :-)))))))))<br>Same precaution applies to cleaning carbs out on stainless steel kitchen work surfaces !! , curing paint in kitchen ovens etc,etc<p>Paul<br>
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paul@springthorpe74.freeserve.co.uk

Paul Springthorpe

Re: Leaking carbys *****WARNING*******

#7 Post by Paul Springthorpe » Tue Oct 04, 2005 5:01 am

>>Then fill a wok to the brim with water and blow through a tube where the petrol goes into the carb and lower the float into the water until the airflow shuts off. Move the metal bit that presses on the float needle until the air flow cuts off before the water rises to the level of the carb body, with the float bowl off.<<<p>Before doing the above ensure that your wife is not only out but unlikely to come home and catch you doing this !!! :-)))))))))<br>Same precaution applies to cleaning carbs out on stainless steel kitchen work surfaces !! , curing paint in kitchen ovens etc,etc<p>Paul<br>
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paul@springthorpe74.freeserve.co.uk

Ken Smith

Re: Leaking carbys *****WARNING*******

#8 Post by Ken Smith » Tue Oct 04, 2005 3:08 pm

So if I'm rebuilding the RZ engine on the kitchen table this could be a probblem????? After 25 years of finally starting to figure out why the wild looks & fits on some of these things! Maybe! should get the fly rod out of the bath tub also. Thanks Paul
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Wyn Belorusky

Re: Leaking carbys *****WARNING*******

#9 Post by Wyn Belorusky » Tue Oct 04, 2005 3:22 pm

But coffee cups are so good at keeping all those little carb parts seperated! Plus, if you drop one of those small parts on that spotless kitchen floor, you'll probably find it.
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RZVWyn@aol.com

Scott

Re: Leaking carbys

#10 Post by Scott » Thu Oct 06, 2005 2:34 pm

My carbs used to leak even after new needle valves, eventually I completely rebuilt the carbs with Keyster carb kits and put a new rubber diaphram in the petcock. Most often I think it was dirt in the carbs (bit of rust in the tank).<p>Posts from the archive that I saved about this issue (can't vouch for their worth):<p>Float jet seals are pooched on that carb.<br>The float jet is a little rubber and brass "rocket ship" looking thing that sits just above the float bowl which has a little button at the bottom with<br>a spring action. The rubber seal goes on occassion. The float seal is supposed to close off the flow of gas into the float bowl when its full.<br>If the seal is pooched and the gas keeps coming, it starts spilling out of the pilot air jets and any where else it can find. This will also happen if<br>the rubber button has lost its spring and it doesn't have enough force to properly close off the jet. <br>****************************************************************<br>-Clamp off the gas line going to that carb.<br>-Drain the float bowl.<br>-With the carb still on the bike, Remove the float bowl.<br>-The float (two black air bladders) should be pushed up gently enough so the button on the float jet moves.<br>-Slowly unclamp the gas line. There should be ABSOLUTELY no gas flowing. Don't push the float all the way to the top to close off the<br>leak. That's how they get screwed in the first place.<br>-If there is no leak even with the slightest amount lift on the float, check the floats themselves. If they have a leak in them, they will<br>not float up and close off the float valve. Emerse them in some gas and check for bubbles (you could use water, but I wouldn't)<br>-You don't have to replace all four, I think the left side ones go faster than the right ones because of the bike's lean. <br>As regards to the YPVS motor turning constantly, I've had that problem too. In my case the cable was sticking and the motor couldn't complete<br>its cycle. I just oiled/WD-40/Duralubed the piss out of the YPVS assembly. I also replaced the throttle cable (but that was for someother reason).<br>****************************************************************88<br>The needles and seats should seal off and not leak when in the fuel valve is in the prime position.<br>The prime position applies fuel head from the tank to the carbs. The run position if the fuel valve is working properly only applies fuel head (pressure)to the carbs when running (vacuum applied to the fuel valve).<br>Better clean or replace the needle seats, and don't forget the possibility that the the seat is not leaking but the o-ring on the OD of the brass body of the inlet needle seat may be leaking. O-ring leakage is not unusal from my recent experience and others on this list.<br>My experience with new seats is that they will hold about 5psi, wet with gas or WD40 , with the carbs upside down and the float in place pushing via gravity on the inlet needle.<br>Don't try this while still installed on the bike HA HA.<br>If they won't hold pressure even 2-3 psi better keep looking or your problems will continue.<br>Have fun. <br>*********************************************************8<p>From my experience of this problem (suffered it a lot !) <br>1/ Most likely, It is sediment from the old and deteriating tank. Give it a good flush out. <br>2/ The float mechanism is a bit iffy, i.e. if you adjust the float height and rotate the carb to check it, you will probably notice that it can stick, this seems to be due to the angle of the valve plate to the valve, it lets the valve drop too far down and it tilts locking itself, you have to take care to keep the angle of the plate as square as poss. sounds complicated but its not, self explanitary when you have a carb in front of you ! <br>I had both the above probs with mine <br>Try turning you petrol tap to prime, it should NEVER overflow (contrary to a nuber of posts over the years on this site) The floats should stop the flow. the petcock in this position is exactly the same as when the engine is running in the normal position. <br>Hope this helps <br>Bryan <br>**************************************************************8<br>About the petcock problem. Before you go and spend $45.00 Can. each on the needle and seats check the o ring around the seat that seals it to the carb body. I had the same problem and this was the cause. The o rings are not sold by themselves so go to a bearing house and match them up. <p><p><p>
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