Author Topic: Petcock replacement on the F model  (Read 2129 times)

0 Members and 1 Guest are viewing this topic.

Offline dragracer

  • Really Old Timer ...
  • *******
  • Posts: 5,101
  • CB750F Dragbike
Petcock replacement on the F model
« on: August 20, 2015, 11:37:54 PM »
Well, i just got around to replacing the anemic stock petcock on my F model with a high flow Pingel race petcock. After reflecting on posts by TurboD and Trey where they state a change in performance after upgrading their petcocks, I figured i'd give it a shot myself to see if i could truly tell a difference. I had previously purchased the fuel tank adapter from from Frank (754) but never got around to installing it due to time constraints. I bought two from him, a brass one and an aluminum one and they look great. The only issue i ran into is the outlet is only 1/4" npt and all the standard, easily available Pingel petcocks are 3/8"npt. I had 3 new ones in 3/8" and was hoping i could use one to save a few bucks.  I checked on Lowes website and found an adapter to step up from 1/4" npt male to 3/8" npt female threads. Upon rigging all the pieces together and check fitting it on the bike, the overall length was longer than the stock set up but i had just enough clearance to make it work. I did have to reroute the fuel lines from the carbs a little but i seems okay.

I'll be heading to the Man Cup race at the Rock tomorrow to get parked and help Trey and Bill make some test passes. I'll wait until saturday for the official time trials and race to make my passes. I'm crossing my fingers that i'll pick up some numbers with the extra fuel flow on the top end. I will admit i never noticed any signs of running out of fuel based on the "seat of the pants" feel. We will know come first time run on saturday morning if i was hurting the bikes paerformance because of fuel starvation.

I've attached some picture of the old, leaky, stock petcock and a side by side comparison picture of an old Pingel high flow petcock i had sitting around. Its identical to the new one i actually installed on the bike. Note the inlet and outlet diameters. By the way, the new one is dual outlet but i'm only using one for now and have plugged the other.

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 29,058
Re: Petcock replacement on the F model
« Reply #1 on: August 20, 2015, 11:47:48 PM »
Email me a pic of the petcocks , might need a dual outlet for my alloy tank.
 I don't have an adaptor or drawing near me, but I think there is no meat ot length to go bigger size.
 Don't know if Pingel has flow info but, if you can figure out the flow its probably. Far more for the Pingel than stock.
 You can put it over a 5 gal bucket with a 1/2 gallon or gallon mark and time how long it takes.
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline dragracer

  • Really Old Timer ...
  • *******
  • Posts: 5,101
  • CB750F Dragbike
Re: Petcock replacement on the F model
« Reply #2 on: August 21, 2015, 12:09:45 AM »
Email me a pic of the petcocks , might need a dual outlet for my alloy tank.
 I don't have an adaptor or drawing near me, but I think there is no meat ot length to go bigger size.
 Don't know if Pingel has flow info but, if you can figure out the flow its probably. Far more for the Pingel than stock.
 You can put it over a 5 gal bucket with a 1/2 gallon or gallon mark and time how long it takes.

I think the adapter could be made with a 3/8 outlet. I'm saying that by judging the inlet side to the tank. If you do decide to make one, i'd be interested in 2 of them. It takes up a lot of space using that additional union to step it up from 1/4"npt to 3/8" npt. I'll try to take a picture of it installed on the tank tomorrow.

I can say, it definitely dumps some fuel now. I accidentally turned it to the on position before i got the gas lines on and it flowed out all over the engine and the shop floor before i could react.

Thanks again Frank(754).

Offline dragracer

  • Really Old Timer ...
  • *******
  • Posts: 5,101
  • CB750F Dragbike
Re: Petcock replacement on the F model
« Reply #3 on: August 22, 2015, 09:34:28 PM »
Alright folks, I think replacing the petcock did make a difference with fuel flow. I ran a 10.42@122mph on my first time run this morning. My mph has never been more than 120 and the best 1/4mile ET prior to today was a 10.52. So......it seems I've dropped a tenth on the Et and picked up a little over two mph. I did run into a major problem after the pass. The extra adaptor I added to fit the petcock on the bike lowered the fuel outlet just on top of the number one carb boot. The carb clamp comes together on the top side of the boot. Well, the dang clamp rubbed a cut into the fuel line and it was leaking like crazy when I came back to the staging lanes. Had to thrash to change it out before first round eliminations by working in the lanes with limited tools. I got it done just in time to make the round but I red lighted. Arrgh.  Bought back in and let out of the throttle too early giving my female opponent from Japan the easy win. However, she was very polite and in her limited English, said" thank you".

Offline MRieck

  • Really Old Timer ...
  • *******
  • Posts: 10,560
  • Big ideas....
Re: Petcock replacement on the F model
« Reply #4 on: August 22, 2015, 09:39:28 PM »
Frank
 I currently use a 1/4" Pingel and have another sitting on a shelf....they don't have to be 3/8". I had to drill a small hole in my F gas cap to prevent vapor lock. That thing has flowed awesome.
Mike
Owner of the "Million Dollar CB"

Offline dragracer

  • Really Old Timer ...
  • *******
  • Posts: 5,101
  • CB750F Dragbike
Re: Petcock replacement on the F model
« Reply #5 on: August 22, 2015, 11:45:49 PM »
Mike, I had 3 brand new 3/8 Pingel petcocks. It was hard for me to spend that $106 for a 1/4 when all I needed was a $4 adapter to make it work. Plus time was running out and the new one wouldn't have gotten to me before leaving for the race on Friday. I would have used the 1/4" otherwise. Anything is better than the tiny stock petcock outlet. Picking up the mph and lowering the ET was worth the aggravation. As my friend Bull would say, I ran my personal best on that pass. 

Offline dragracer

  • Really Old Timer ...
  • *******
  • Posts: 5,101
  • CB750F Dragbike
Re: Petcock replacement on the F model
« Reply #6 on: August 23, 2015, 12:07:55 AM »
Uhh, that was supposed to be Bill, not Bull

Offline Retro Rocket

  • Eggs are hard due too a
  • Really Old Timer ...
  • *******
  • Posts: 19,279
  • ROCK & ROLL
Re: Petcock replacement on the F model
« Reply #7 on: August 23, 2015, 02:30:19 AM »
Interesting, the old drag bike i bought had two outlets to the carbs, one on either side of the tank, the fittings had been brazed into the tank...
« Last Edit: August 30, 2015, 02:27:22 PM by Retro Rocket »
750 K2 1000cc
750 F1 970cc
750 Bitsa 900cc
If You can't fix it with a hammer, You've got an electrical problem.

Offline MRieck

  • Really Old Timer ...
  • *******
  • Posts: 10,560
  • Big ideas....
Re: Petcock replacement on the F model
« Reply #8 on: August 23, 2015, 06:24:41 AM »
Mike, I had 3 brand new 3/8 Pingel petcocks. It was hard for me to spend that $106 for a 1/4 when all I needed was a $4 adapter to make it work. Plus time was running out and the new one wouldn't have gotten to me before leaving for the race on Friday. I would have used the 1/4" otherwise. Anything is better than the tiny stock petcock outlet. Picking up the mph and lowering the ET was worth the aggravation. As my friend Bull would say, I ran my personal best on that pass.
I understand Frank. ;) I agree about the stock unit especially the one on the late F tanks......like a cocktail straw. I am happy about the personal best as well. ;)
Owner of the "Million Dollar CB"

Offline TurboD

  • Hot Shot
  • ***
  • Posts: 680
Re: Petcock replacement on the F model
« Reply #9 on: August 23, 2015, 07:45:36 AM »
Congrats on a new PB. Edging closer to the 9's.  ;D

Offline dragracer

  • Really Old Timer ...
  • *******
  • Posts: 5,101
  • CB750F Dragbike
Re: Petcock replacement on the F model
« Reply #10 on: August 23, 2015, 09:20:34 AM »
Congrats on a new PB. Edging closer to the 9's.  ;D

If I had a Mike Reick head like my friend Bill, there's a chance with the right conditions, I might knock on the door of a nine second pass. Uhhhh, wishful thinking. Lol. I'm bracket racing so I'm cool with going slow.

Offline NalleyRacing

  • Hot Shot
  • ***
  • Posts: 497
  • 1972 Cb750K dragbike Instagram: Drag_racer736
Re: Petcock replacement on the F model
« Reply #11 on: August 30, 2015, 09:15:33 AM »

Offline Jerry Rxman Griffin aka MuthaF'er

  • This MuthaF'er is getting to be a
  • Really Old Timer ...
  • *******
  • Posts: 14,902
  • Bought her new 4/75
Re: Petcock replacement on the F model
« Reply #12 on: August 30, 2015, 11:10:09 AM »
Congrats on a new PB. Edging closer to the 9's.  ;D

If I had a Mike Reick head like my friend Bill, there's a chance with the right conditions, I might knock on the door of a nine second pass. Uhhhh, wishful thinking. Lol. I'm bracket racing so I'm cool with going slow.

Yeah Mike, that sounds like a subtle hint to me ;-) Frank needs 9's!!
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)