TOPIC:

I think the bolt hole spacing on the GPz is going to be 44mm. the 650 SR should be 44mm as well. The petcock on my 81 csr is 34mm & uses a smaller o-ring where it meets the tank than the gpz. I'm assuming the larger gpz o-ring would indicate a wider bolt hole spacing. Partzilla shows a photo with the o-rings next to a ruler.

Also from partzilla, the GPz uses the same petcock as the 82-2005 1000P police which I think use a 44mm pingel adapter plate. a pingel fuel valve w adapter plate would be another option, but be wary of the fuel valve extending too far down & contacting the carb top. not sure.

martin_csr wrote: I think the bolt hole spacing on the GPz is going to be 44mm. the 650 SR should be 44mm as well. The petcock on my 81 csr is 34mm & uses a smaller o-ring where it meets the tank than the gpz. I'm assuming the larger gpz o-ring would indicate a wider bolt hole spacing. Partzilla shows a photo with the o-rings next to a ruler.

Also from partzilla, the GPz uses the same petcock as the 82-2005 1000P police which I think those models use a 44mm pingel adapter plate. a pingel fuel valve w adapter plate would be another option, but be wary of the fuel valve extending too far down & contacting the carb top. not sure.

Thank you Martin, I have been combing through Partzilla several hours a day myself and love that site. I have been compiling a list of stock OEM parts as well as aftermarket parts meant for "other" models or makes but actually DO fit the A1-A3 ZX750's so I just added this petcock to the list, thank you!

Will post what I find as soon as I have more info.

Brett

Ok so got some info, hopefully can help others who may have questions on this as well. Confirmed that my bolt hole spacing is 44mm as expected. Thanks to spending some time and searching through some Concours message boards I confirmed that the bolt hole spacing for the Concours 1000's are also 44mm. Via comparison on Partzilla I also confirmed that the petcock a are nearly the same, the main difference is that the outlet on the C10 points in a different direction than my GPz (towards the back tire instead of straight down if the diagrams are to be trusted) and that the bolt pattern for the dial face (that has On, Prime and Res engraved on it) is clocked slightly differently. Lastly I contacted Murph from the C10 vacuum to manual petcock conversion kit that Martin posted in one of the other petcock threads DOES maintain the reserve function and doesn't cut it out. So based on all of this info I think I'm going to try the spring stretch trick on my old tank and replace the rubber parts to get it riding right now and in a few weeks order the C10 billet kit so that I can install and modify the face mounting points on my replacement tank that I will be dropping on the bike in the next month or so.

Hope this helps clarify and answer some questions that were hanging out there about this. Will post up results and pics of both the spring stretch trick on my old petcock and the finished product with my replacement tank and petcock when the time comes.

Brett

Verly interestink.
Steve

Rebuilding petcock is pretty simple and parts are cheap. Find instructions. Aluminum plate has to be sanded with 1000 or 2000 final sandpaper grit.

car5car wrote: Rebuilding petcock is pretty simple and parts are cheap. Find instructions. Aluminum plate has to be sanded with 1000 or 2000 final sandpaper grit.

Correct depending on your conversion method. The method you are discussing this the one my Pops used on his 79' SR650, my particular method involved only two modifications; 1) stretch the plunger spring to double its normal length (26mm stretched to 52mm) and then clean/remove ethanol oxidation and deposits and polish plunger seat surface, 2) plug the vacuum port coming out of the petcock assembly and plug vacuum port on carburetor.

I plugged mine via JB Weld over the nipple on the petcock so that I could retain the vacuum hose for a factory look and keep the hose attached just non-functional.

That being said, I have yet to be able to test it as after installing and hooking up the carb bank and everything else I did yesterday, to test the starter and fire her up we used a hanging fuel bottle and did not employ the petcock. I have another full day scheduled in the garage next Thursday again and should be able to wrap up the two remaining tasks of doing a dynamic running sync in the carbs to tune them perfectly, and flush and replace the brake fluid and bleed the lines. Once all that's done she will be in riding condition and I can confirm petcock conversion results. Once I have definitive results I will post back in here again but won't be for 6 more days I suspect.

- Brett

Be mindful that a rear exit outlet my not work to make the bend back to the carb. The fuel line is gonna have a hard time coming back clear of the air box. I ditched the rear exit one I tried on a 650. Even with a 90 degree elbow and elbow molded tubing it did not work to my liking. R YMMV

Appreciate the thought and heads up, I should have been clearer but I am using the main body of my original petcock and adapting the conversion kit that is meant for the C10 to my GPz. That way the outlet and everything is still the same just the guts and billet face/lever are new. I will have to drill new mounting holes for the billet face so it will bolt onto the slightly differently clocked face meant for the C10, of that makes sense.

- Brett

Just wanted to update and reply that blocking the vacuum ports (one on carb and one on petcock) and stretching the internal spring to twice its length works PERFECTLY for me, not a single problem so far and worked exactly as intended. Cant confirm for other models of petcock, but this one was nice and worked well for me

Brett

For a 79 650SR all you need is a 77 manual petcock direct bolt in, outlet same location looks just like stock
Have had this on my 78 since 1983 when i tired of fixing the piece of junk vacuum stock one,was turned on to this by an old
Kaw racer/mechanic, Since then I have changed over 7 bikes with no problems. When I see a 76-77 manual petcock on ebay I buy it for future use

ezrider714 wrote: For a 79 650SR all you need is a 77 manual petcock direct bolt in, outlet same location looks just like stock
Have had this on my 78 since 1983 when i tired of fixing the piece of junk vacuum stock one,was turned on to this by an old
Kaw racer/mechanic, Since then I have changed over 7 bikes with no problems. When I see a 76-77 manual petcock on ebay I buy it for future use

Didn't know that thanks, and will pass that along to Pops who I am sure will be interested to know too!

Thank you,
Brett