Need to rebuild petcock?

N

nitrofish1

XS400 Addict
Messages
180
Reaction score
0
Points
16
Location
Machesney Park, IL
I removed my fuel tank, and when I tested the petcock on it it seemed to work just fine. Came back to storage a week later and there was a small puddle underneath the petcock, when I left it there in the OFF position. When I hold the tank up, ON and OFF, i t doesn't let any fuel pass, but when I put it on RES, it lets it flow freely. I emptied the tank this way, but should I be concerned with a rebuild? When I bought the bike they changed the oil because there was fuel in it, and after its first ride home I still smell a hint of fuel in the oil.
 
A leaking petcock won't flood your engine by itself. If the float needles are working and sealing properly the bowls will fill and flow will stop. The flooding engine is a totally different issue in my opinion. I would replace the petcock over rebuilding it with a manual one. It's not too much more money and random gas puddles are undesirable. Back when I was looking into this the rebuild kits all seemed sketchy; I had concerns about fitment I believe.
 
bcware said:
A leaking petcock won't flood your engine by itself. If the float needles are working and sealing properly the bowls will fill and flow will stop. The flooding engine is a totally different issue in my opinion. I would replace the petcock over rebuilding it with a manual one. It's not too much more money and random gas puddles are undesirable. Back when I was looking into this the rebuild kits all seemed sketchy; I had concerns about fitment I believe.
Click to expand...

if the carbs are working as they are supposed to, would this stop the gas getting into the oil system, therefore not needing to replace the petcock? possibly a carb rebuild?
 
It may need both.

I am assuming you have the stock vacuum petcock. The vacuum petcock has a few different settings; 'on' and 'res' (reserve) require vacuum created by the engine to allow gas to flow. The last position, 'pri' (prime), does not require vacuum and operates like a manual petcock.

If the carbs are working properly the bowls will fill, the float will rise, and the float needle will seal the float needle seat stopping any excess fuel from entering.

So, yes, if the carbs are working perfectly they will stop excess gas from entering and causing problems. It is, however, considered good practice to turn a manual petcock off, or simply leave a vacuum petcock on 'on' (rather than running it on 'pri') as a safeguard against failure. Since a vacuum petcock requires vacuum in the 'on' position it is considered safe to leave it in this position when the bike is put away.

At the very minimum we can conclude that you've suffered from flooding in the past. Now, this could be the carbs or the gas cap. I would clean both thoroughly, but it doesn't definitively mean there is anything broken or messed up; the entire system is not perfect and flooding can just happen under the right conditions.

The unknown factor is the petcock because you have no idea if the previous owner simply left it on 'pri' all the time, or if they really are leaking in the 'on' or 'res' positions without more information. If it were me I would assume the petcock is a problem and that the previous owner was sensible and used the 'on' position.
 
bcware said:
It may need both.

I am assuming you have the stock vacuum petcock. The vacuum petcock has a few different settings; 'on' and 'res' (reserve) require vacuum created by the engine to allow gas to flow. The last position, 'pri' (prime), does not require vacuum and operates like a manual petcock.

If the carbs are working properly the bowls will fill, the float will rise, and the float needle will seal the float needle seat stopping any excess fuel from entering.

So, yes, if the carbs are working perfectly they will stop excess gas from entering and causing problems. It is, however, considered good practice to turn a manual petcock off, or simply leave a vacuum petcock on 'on' (rather than running it on 'pri') as a safeguard against failure. Since a vacuum petcock requires vacuum in the 'on' position it is considered safe to leave it in this position when the bike is put away.

At the very minimum we can conclude that you've suffered from flooding in the past. Now, this could be the carbs or the gas cap. I would clean both thoroughly, but it doesn't definitively mean there is anything broken or messed up; the entire system is not perfect and flooding can just happen under the right conditions.

The unknown factor is the petcock because you have no idea if the previous owner simply left it on 'pri' all the time, or if they really are leaking in the 'on' or 'res' positions without more information. If it were me I would assume the petcock is a problem and that the previous owner was sensible and used the 'on' position.
Click to expand...

when i look at it it has on, off, and res positions.

the gas cap i think needs a new gasket, as it will leak if tipped over.

im going to be getting the carbs apart this weekend to check them out, although i may end up rebuilding them in the end.

oldbikebarn has this though

http://www.oldbikebarn.com/Kawasaki...-850-Petcock-Rebuild-Kit?sc=12&category=74247

although its about as much as buying a used one on ebay, but there are some new petcocks that are like 10 bucks that is a two position valve
 
Last edited:
Yeah, don't buy that. I think the manual petcock from partsnmore is only a few dollars more and you get an entire new petcock. A few of us on here use it.
 
The float and valves are not a shut off device. They are for metering fuel.
Even with properly working float valves, the pressure from a full tank of fuel can push past the valves open enough to leak.
This cn be even more pronounced if the tank vents are plugged. Fill up the tank and then park the bike where heat, as in the sun, or a warm garage and it expands the fuel. This pushes past the float valves.
If your carbs are leaking fuel then fix the petcocks.
Leo
 
kinda buzzed through the thread. I had to buy a tank that came with a petcock so I have an extra 81. Not sure what year your bike is but shouldn't matter(I could be wrong I'm a newb). I'm not sure where you're at but I would do my best to get it to you cheap.
 
brownv1 said:
kinda buzzed through the thread. I had to buy a tank that came with a petcock so I have an extra 81. Not sure what year your bike is but shouldn't matter(I could be wrong I'm a newb). I'm not sure where you're at but I would do my best to get it to you cheap.
Click to expand...

I'm in southern illinois, 62901 zip. just pm me with a price and i can paypal ya some for it. youd be saving me a bundle tho. my bike is an 81. may be a few days for the money to transfer to my paypal if thats alright with you, or if youd prefer i can mail some money once i get it on my end. just let me know what u wanna do
 
nitrofish1 said:
I'm in southern illinois, 62901 zip. just pm me with a price and i can paypal ya some for it. youd be saving me a bundle tho. my bike is an 81. may be a few days for the money to transfer to my paypal if thats alright with you, or if youd prefer i can mail some money once i get it on my end. just let me know what u wanna do
Click to expand...
My petcock was leaking on my Dt400 dirt bike,and I went to Lowe's and got a cutoff for a riding mower,put it below the petcock,and no more probs. lha
 
hahaha...not gonna lie I am gonna try that!
I got into my petcock and found the gasket chewd up so I turned it trying to find a part of the gasket that would shut the gas off.Basically tried every hole, tightened back up and waited to see if it would leak. Turned the gasket until I was back at the original position and none of that shut it off completely. Slowed it down a little but didnt stop it completely. Gonna have to buy a replacement or go with the cut-off.
 
lhaolpa said:
My petcock was leaking on my Dt400 dirt bike,and I went to Lowe's and got a cutoff for a riding mower,put it below the petcock,and no more probs. lha
Click to expand...

haha, well i may end up doing this too even with a newer petcock. or i could do this and not buy a new one, just a straight on/off valve would fix that up. itd be pretty well hidden too.
 
bcware said:
Yeah, don't buy that. I think the manual petcock from partsnmore is only a few dollars more and you get an entire new petcock. A few of us on here use it.
Click to expand...

Does anyone know what petcock this is?

I checked partsnmore but I only see repair kits.

Thanks.
 
I'm in the middle of creating a tutorial on how to rebuild your OEM petcock if that's of interest to you. Should be done by the end of next week. Also working on a custom petcock and on/off assembly in one. Will let you know how that goes.
 

Similar threads

G
Air lock in fuel line?
2
Replies
27
Views
2K
gpounce32768
G
clawhamm3r
Pilot Jet Type Identification And Rebuild Kit Questions
Replies
4
Views
469
clawhamm3r
clawhamm3r
S
'77 XS360 Backfiring above 5000 rpm + other issues
Replies
0
Views
59
SimonFordman
S
R
Petcock / filter ?
Replies
7
Views
2K
xschris
X
S
Need help with kickstart
Replies
1
Views
502
barmstrong
B
Back
Top