I have a leaking petcock. I've tried rebuilding it, cleaning it etc, I've added a little more tension to the wave washer, there's no damage or wear evident, and whilst at first it looked hopeful, after a run, I've found it still leaks. A new petcock is too expensive. I've read bad reviews of the repair kits that are available (?). I see the inline fuel tap (Briggs and Stratton -ouch!) option. Nice, cheap and cheerful, -It may come to that.
Regarding this mod:
http://www.usa2strokers.com/forum/forum ... dification
Removing the vacuum system - obviously this works for some people, but can someone explain why/how it works? Surely if the petcock leaks it must be caused by the rubber seal gasket and or a weak wave washer that 'makes' the seal, irrespective of the vacuum line? How does bypassing the vacuum line fix the leak?
That leaky RZ petcock, fuel tap.
Re: That leaky RZ petcock, fuel tap.
Jools; When you say it is "leaking", do you mean that it is allowing fuel to pass through with no vacuum applied, OR that fuel is actually dripping out of the body?
I'm not sure whether this will be of any help, but my view is that vacuum-operated fuel taps are just unnecessary complication - more parts to develop faults. Also, vacuum-operated taps have the disadvantage (for me, at least) that the carb float bowls cannot be run dry before parking the bike.
My KR-1, TZR and SDR all came with vacuum-operated fuel taps, but I've changed them all for "normal" on-off-reserve gravity-fed taps and blanked off the vacuum ports on the carbs.
If the RZ fuel tap is made by Taiyo Giken, you will almost certainly be able to find a direct replacement of the on-off-reserve type.
Does your tap look like this http://www.ebay.co.uk/itm/YAMAHA-RZ350- ... 1425527509?
If so, does it attach with M6 bolts, 34mm between centres? If it does, you could try the Yamaha 21V (shorter) or 5LP (longer) tap (Part Nos.21V-24500 and 5LP-24500). Either of these should cost about $30-40 new plus postage for the genuine article from various Ebay sellers.
Some info and photos of the 5LP tap - http://www.kr-1s.co.uk/forum/viewtopic. ... p&start=30. The 21V tap is almost identical, but shorter (won't clear the seam on the KR-1 tank in the photos).
For your interest, this is the ZXR750 tap, where the tap is not mounted directly on the tank - http://pure2strokespirit.net/forums/ind ... 3#msg12453. I used this tap on my TZR 1KT. There are several different variants, but most are similar. This tap cost me about $25 secondhand. The seals were OK, but new ones can be obtained quite easily, as they are common to many Taiyo Giken taps (main seal is the same as the Yamaha 21V and 5LP taps). I'm using a similar tap on my SDR.
If buying one of these taps new, I'd suggest buying genuine, as some of the aftermarket ones have internal passages much smaller than genuine ones. If you need any dimensions or part numbers for replacement seals, please let me know!
Regards,
James
I'm not sure whether this will be of any help, but my view is that vacuum-operated fuel taps are just unnecessary complication - more parts to develop faults. Also, vacuum-operated taps have the disadvantage (for me, at least) that the carb float bowls cannot be run dry before parking the bike.
My KR-1, TZR and SDR all came with vacuum-operated fuel taps, but I've changed them all for "normal" on-off-reserve gravity-fed taps and blanked off the vacuum ports on the carbs.
If the RZ fuel tap is made by Taiyo Giken, you will almost certainly be able to find a direct replacement of the on-off-reserve type.
Does your tap look like this http://www.ebay.co.uk/itm/YAMAHA-RZ350- ... 1425527509?
If so, does it attach with M6 bolts, 34mm between centres? If it does, you could try the Yamaha 21V (shorter) or 5LP (longer) tap (Part Nos.21V-24500 and 5LP-24500). Either of these should cost about $30-40 new plus postage for the genuine article from various Ebay sellers.
Some info and photos of the 5LP tap - http://www.kr-1s.co.uk/forum/viewtopic. ... p&start=30. The 21V tap is almost identical, but shorter (won't clear the seam on the KR-1 tank in the photos).
For your interest, this is the ZXR750 tap, where the tap is not mounted directly on the tank - http://pure2strokespirit.net/forums/ind ... 3#msg12453. I used this tap on my TZR 1KT. There are several different variants, but most are similar. This tap cost me about $25 secondhand. The seals were OK, but new ones can be obtained quite easily, as they are common to many Taiyo Giken taps (main seal is the same as the Yamaha 21V and 5LP taps). I'm using a similar tap on my SDR.
If buying one of these taps new, I'd suggest buying genuine, as some of the aftermarket ones have internal passages much smaller than genuine ones. If you need any dimensions or part numbers for replacement seals, please let me know!
Regards,
James
Re: That leaky RZ petcock, fuel tap.
James thanks for that post, very useful advice.
Yes, the petrol was dripping out of the outlet nozzle.
I'm getting an in-line on-off tap - a 'Festo' brand 6mm inline ball-valve, which are used in industrial applications and model jet turbine aircraft applications, they are compact, efficient, good quality.
In the meantime I've tried another fix to the petcock which has worked (SO FAR !) I pulled the tap backplate off, which gives access to the fine spring that holds pressure on the vacuum plunger which has the small o-ring into the aperture which stops fuel flow. I thought maybe if the spring has lost some tension it might fail to hold it with enough pressure to seal the hole. So I gently pulled the spring to lengthen it a bit. Reassembled, and it works well so far, -it's stopped the drip from the fuel tap outlet.
I know some people convert the petcock to delete the vacuum system, a mate of mine has converted plenty of fuel taps, he drives in a suitably sized bearing ball into the hole to blank off the vacuum.
Re: your link to the RZ tap -that tap looks fairly similar but is not the same, the RZ (RD ypvs) tap has an extension which connects to the tap 'knob' which fits through a hole in the sidepanel. The filter arrangement is quite different by the look of it. (And whilst the price is reasonable enough, the postage cost is a ripoff (approx $70 to Australia).
I'lll look into the other info too, thanks again.
Cheers James,
-Jools
Yes, the petrol was dripping out of the outlet nozzle.
I'm getting an in-line on-off tap - a 'Festo' brand 6mm inline ball-valve, which are used in industrial applications and model jet turbine aircraft applications, they are compact, efficient, good quality.
In the meantime I've tried another fix to the petcock which has worked (SO FAR !) I pulled the tap backplate off, which gives access to the fine spring that holds pressure on the vacuum plunger which has the small o-ring into the aperture which stops fuel flow. I thought maybe if the spring has lost some tension it might fail to hold it with enough pressure to seal the hole. So I gently pulled the spring to lengthen it a bit. Reassembled, and it works well so far, -it's stopped the drip from the fuel tap outlet.
I know some people convert the petcock to delete the vacuum system, a mate of mine has converted plenty of fuel taps, he drives in a suitably sized bearing ball into the hole to blank off the vacuum.
Re: your link to the RZ tap -that tap looks fairly similar but is not the same, the RZ (RD ypvs) tap has an extension which connects to the tap 'knob' which fits through a hole in the sidepanel. The filter arrangement is quite different by the look of it. (And whilst the price is reasonable enough, the postage cost is a ripoff (approx $70 to Australia).
I'lll look into the other info too, thanks again.
Cheers James,
-Jools
Re: That leaky RZ petcock, fuel tap.
Spot on Jools - I have no end of issues with vacuum tap on one of my bikes - I think that is the issue. You replace the vacuum valve (i.e. the black thing with the nozzle on it and the rubber ring) but not the spring as this isn't usually in the kit. However the spring is old and probably doesn't have the tension to push the new rubber thick seal in to stop the flow off vacuum - hence the dribble.
Re: That leaky RZ petcock, fuel tap.
No problem Jools - hope you find a cost effective solution. You're right about excessive postage charges, although some sellers do offer postage at a more reasonable price.
If your existing tap has M6 bolts at 34mm between centres, there are LOADS of taps which may fit. Buying secondhand is a good option, especially if you know a motorcycle wrecker who doesn't mind you rummaging through the stock!
Your Festo ball valve could be an interesting option - let us know how you get on!
Regards,
James
If your existing tap has M6 bolts at 34mm between centres, there are LOADS of taps which may fit. Buying secondhand is a good option, especially if you know a motorcycle wrecker who doesn't mind you rummaging through the stock!
Your Festo ball valve could be an interesting option - let us know how you get on!
Regards,
James
Re: That leaky RZ petcock, fuel tap.
Bugger! After all that my 'fix' didn't fix it at all.
So I've got to buy a couple of float needle valves... I've always thought the viton tipped ones would be better than the brass tipped ones, -anyone have ideas on this?
So I've got to buy a couple of float needle valves... I've always thought the viton tipped ones would be better than the brass tipped ones, -anyone have ideas on this?