"Poor Kid" 1981 CB750K - first build

Just kidding on the brakes. One of the carrier bolts was slightly loose and it was allowing the caliper to flex. The brake is now secure.

1981 CB750K (getting there now)
 
Congrats on the progress. Before you go adding a failure point with a vacuum actuated petcock, consider capping the vacuum line from the carburetor instead. It means getting religious about turning the fuel off and on, but it's a simpler setup.
 
Because I'm laying in bed reading threads. :) Why do you ask?
 
I understand that a manual fuel valve is a great way to avoid failure of parts AND remove a variable in the fuel delivery system- however I am also not willing to compromise the functionality of my carbs.

If a manual petcock (single output, ON OFF RES) is left in the ON position, it will continue to flow fuel. Forever. Into my NON OE carbs, which came from a GSXR. This is the cause of fuel flooding bowls, then the passages, then the air filters and possibly, the engine. I may also move my vent lines to accommodate the pressure of fuel trying to escape.

The GSXR my carbs came from had a single output petcock with ON, PRI, and OFF positions. In ON, fuel flows ONLY when vacuum from a running engine goes to the petcock, actuating it. PRI is similar to a manual's ON function in that it will fill the float bowls without needing vacuum from the engine. OFF means fucking off. You know, but for readers we must lay this out.

Yeah, I could only use a manual OFF/ON valve in the line and save a ton of money. And I could also experience trouble with cold starts, contaminated oil, etc for the rest of the bike's life... Or I could spend a few more bucks and have these carbs running without variables. I've been attentive to detail on getting it road ready and the last things won't be rushed.

Also, no more exhaust leak- after some fabrication and maneuvering, the split keepers and exhaust are rock solid and sound great.

My reg rec problems continued, but I solved them. I will finalize wiring and do my *last bit of solder soon. No loss of functionality in lights or heat in reg/rec this time. Anyone looking to swap an Electrosport Reg Rec for a SOHC to a DOHC can ask me now.

I nabbed a left crank cover from an Oregonian for only $30 online. Supreme. Fixes the oil leak from PO no. 1's drops. Will prevent me from parking lot oil stains at meets.

So when the petcock is done, I will be done, or at least riding until the end of the summer when I can start worrying about brake swaps and the REAL building. Don't tell me shit about the floats. I swear.
 
Rich I just have been arguing with everyone I meet today about this. It seemed like you had been listening to me talk to a coworker and decided to jump in via Tapatalk. Pretty sure you're the only one reading lol, not enough swapping and body work in here for people to care yet :(

1981 CB750K (getting there now)
 
Re: Re: "Poor Kid" 1981 CB750K - first build

kraptastic k said:
Rich I just have been arguing with everyone I meet today about this. It seemed like you had been listening to me talk to a coworker and decided to jump in via Tapatalk. Pretty sure you're the only one reading lol, not enough swapping and body work in here for people to care yet :(

1981 CB750K (getting there now)

Post ten pictures daily and we of the short attention span will gang up :)

Eliminating the vacuum line will not affect the performance of the carb, but you raise a number of reasons to use it - and good ones, at that. My preference is to KISS rather than retain something more complicated that can fail...but only to a degree. I could walk instead and be less likely to break down. :)
 
As it stands, this will be the appearance of the bike for the season. I plan on making large changes after the first six months of riding, when I have more experience with this bike. So I'm only waiting on a petcock, a starter relay (I blew mine when stashing the wiring around the bike, don't ask) and I have to slap a tail light on it.

It ain't pretty but it is a start.

The bike runs well enough with only fuel from a length of line. I think the petcock will improve the fuel delivery so I can put a final tune on it. Unfortunately, I'm waiting a few weeks to budget for bills etc. So it will be just a few more days. Agonizing days.

1981 CB750K (dying to live)
 
1981 CB750K (messing up replies)
 

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Also, that nasty oil leak is coming from the ignition cover/left crank cover, whatever it is. I snatched a solid replacement from a 79 750K for $34. Some would say it needs polish, I say it fits the general theme of the bike and it stays rough. So, altogether, I will run with the oil leak for about a week and then when all the old gunk is good and kicked up, I'll change the oil and the cover as well. No more oil leaks. Hell yeah!

1981 CB750K with Mikuni BST36SS carbs
 

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Looking good dude, and i agree with not polishing the cover. Leave that to those with fancy schmancy bikes.
 
Thanks for the support. Next bike will have polish, but this one will be nice and gritty with a hint of oil.
 
kraptastic k said:
Thanks for the support. Next bike will have polish, but this one will be nice and gritty with a hint of oil.

If anything it needs to be scuffed up a bit more. Keep rockin! Love the progress!

I'm interested in the details of how the new carbs get set up.
 
Well, I was using another swapper's notes to set these up. A bit bareboned, but I figured it out mostly.

Here's the old link:
http://older-carsandbikes.blogspot.com/2010/10/gsx-r750-caruretor-swap-for-cb750c.html?m=1

The author used some general terms and relative descriptions, which caused me slight hiccups. However, I can answer any questions you might have about the swap as done by me right now... But I suppose all my answers are incredible being that my bike isn't riding status yet. After I snap up the vacuum petcock, I'll be able to speak with credentials.

Uninsured advice by a kid named kraptastic on a bike ten years older than the owner... Trustworthy, eh?

1981 CB750K (really good bluffer)
 
You can have the vacuum petcock from my project if you like. It may need a new diaphram(I'd recommend it.) but it looks like its in good working order. I'm more used to using the one on the tank so I didn't reinstall the vacuum unit after my carb rebuild. Gotta shed weight somewher since this is going to be a race bike. ;D

My petcock on my tank leaked a little fuel when I turned it to ON at first but that went away after some use. I just used the RES position until it cleared up.
 
Your handle has replaced the over used word epic in our home..."how does this look Zeke?" Dad it is Kraptastic! Lol
 
Thanks for the compliments and the reassurance- makes the frustration lessen when I feel accomplished. Today was payday! After rent I'll be able to see how much goes to the "petcock dilemma of 2013." I'm expecting about $200 total...
Glad to see there are people who enjoy my taste.

Hey Pat! I hope I haven't become a bad influence via the forums >:) Tell Zeke that my ride was built on a kraptastic budget! I still gotta meet you two, I feel creepy watching the build via internet when we live in the same town! :3

Soooo... Does anybody care to hear a video of it running when I get the petcock installed?

1981 CB750K (dying to live)
 
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