Author Topic: 78 CB750 build - brat seat installed  (Read 10473 times)

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Offline dumpster84

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78 CB750 build - brat seat installed
« on: November 26, 2013, 11:22:35 AM »
Well, I guess I might start a build thread.  Been reading from this site for a while and figure I should contribute.

I've been into "older" style bikes/cars forever I guess.  Maybe I just appreciate older things more and feel like they have more character and takes a different person to be able to keep these antiques (*DMV term) on the road, which is probably why we're all fans of them. I've always liked stuff on two wheels and built up a Honda Ruckus with all kinds of stuff, if anyone knows what that is and wants to see it, let me know and I'll post up some stuff (EFI gy6 big bore etc etc) otherwise, I'll keep it about my motorcycle.

Back in August, I had to burn a month of leave or they were going to take it away from me and luckily, I was able to stay busy by selling my 79 xs650 and buying a 78 cb750 that sat for over 5 years in someone's shed across the state.  So, I drove my little truck over there and snagged it and barely did the speed limit back.




Then had to unload it...definitely a little schetchy, but it worked.





This thing needed some work, as most do after sitting for so long.  It looked pretty crappy, its hard to see, but it had "Ghost flames" painted all over it......geez.  Main list of stuff needed included:
-New tank
-Chain, sprockets
-Charging system
-Carbs rebuilt
-Cables
-M/C rebuilt, caliper, etc
-Timing, Ignition, general tune-up etc

So after many trips to Dime City Cycles, parts were accumulating and progress was being made




Red Kote'd the new gas tank



4-1 header was very rusty and dented all over, so I decided to wrap the exhaust.  First I soaked the header in vinegar and cleaned it up the best I could before I painted it with grill paint and wrapped it. Got rid of the big clunky muffler and threw on a shorty





This was the first attempt at wrapping 4-1, I didn't like how it came out with the two big pockets that would just collect crap and looked terrible, so I re-did it.  I don't have a picture of the second attempt except on the bike.


Pulled the big seat and decided to do the cafe type seat


Knocked out all of the other maintenance and stuff to get it to run and finally got it started!  It's always pretty gratifying to bring something back to life after it was left for dead.  Took it out for the shakedown ride.... I was definitely kinda nervous that it would have some terrible problem and end up killing me, but did alright.  Still had a lot of tuning left, but it ran



Got tired of the pod filters and dealing with losing all power because of a side draft wind, so I bought the tried and true stock air box and threw in a KN filter, tuned and synched the carbs for like the 5th time and BAM, finally got to ride the bike the way it was supposed to feel.  NIGHT AND DAY. 



Put on a ton of miles with this set up, and since then have only done little changes like bars, grips, mirrors, and fixing things here and there, wheel bearings, etc






And this is about how it sits now:


Next up is to change the seat and install a brat-type seat so my wife can ride.  Also, most of the carb bowls were stripped out from the carb bodies and would leak gas, and I tried to ride yesterday until I saw that they were pouring gas out even though they are as tight as I could possibly get them without completely stripping them out, so I ordered a new set of carbs. I'm going overseas in a few months and unfortunately will have to store it for a year and a half.  It's been fun and I've racked up like 1700 miles on it in like 3 months.  I ride with a bunch of guys that all ride their $15-16000 Harley's and I stick out like a sore thumb, but anyone can go to a dealer and buy a brand new bike, most people can't get a 35 year old bike running like a top again and burn ass everywhere.

Sorry it's such a long post. Thanks for looking
« Last Edit: December 05, 2013, 02:40:39 PM by dumpster84 »

Offline Bankerdanny

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Re: 78 CB750 build - sat for 5 years
« Reply #1 on: November 26, 2013, 01:12:05 PM »
Nice job and a good looking rider.

I'm trying to understand your leaking issue though. Where does the fuel come from? I'm a 550 guy, but the carbs on your '78 750 are similar to the ones on my '77 550K.

Where is the fuel coming from? The holes for the bowl screws are placed outside the groove where the bowl o-ring sits. Unless the bowl is cracked there is no reason any fuel should be able to get to the screw holes.

"The problem with quotes on the Internet is that you never know if they're true" - Abraham Lincoln

Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline dumpster84

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Re: 78 CB750 build - sat for 5 years
« Reply #2 on: November 26, 2013, 01:24:43 PM »
Thanks, I appreciate it.  It's definitely not the prettiest or even close to being a show bike, but it runs well and gets ridden like it should.  Paint is in the future as well as a lot of cleaning up and more polishing, but riding safely and reliably was my number one priority since I started so late in the riding season.

The PD carbs on 77-78's have 3 small bolts that screw into the body and hold the bowls tight to the bodies.  After repeated disassembly and reassembly with countless ham-fisting over torquing these small bolts with fine threads, the threads inside the carb body strip causing the bowls to not form a tight seal and leak fuel (I know that was a huge run on sentence, but whatever, this isn't grammar class, ha).  Earlier carbs have a sweet little hinged lever that holds the bowls on tight.
« Last Edit: November 26, 2013, 02:21:37 PM by dumpster84 »

Offline Bankerdanny

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Re: 78 CB750 build - sat for 5 years
« Reply #3 on: November 26, 2013, 02:29:03 PM »
The '77 550K uses a version of the same PD series carb as your bike, so I am familiar with the general layout (although I think the bowls had 4 screws in my case). With some care you should be able to step up one sze by drilling and tapping the holes.
"The problem with quotes on the Internet is that you never know if they're true" - Abraham Lincoln

Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline dumpster84

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Re: 78 CB750 build - sat for 5 years
« Reply #4 on: November 26, 2013, 02:49:32 PM »
Man, that was my first solution, and it fixed it for a while, but there wasn't much "meat" left to tap.  Several of the bolts were already upped in size by previous owners.  I thought about half-assing a solution by using a gasket sealer or something like that, but got tired of  messing with it.  Then once I went out to the garage yesterday and saw that it was somehow pouring out even worse than it did a couple months ago when I "fixed it", I said screw it and found a decent set on ebay  that I bought for a good price and will just swap my jetting/needles/ etc into.

The owner of the carbs that I bought said none of the bowl bolts were stripped.....but we'll see once I get them.  Either way, I just wanna get back on the road before I leave.  It's gonna be hard to put it away for so long.

Side note- Here's a pic of what I usually have to deal with when I ride with my buddies.....only Non-Harley as usual.  I like it that way though.

Offline Bankerdanny

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Re: 78 CB750 build - sat for 5 years
« Reply #5 on: November 26, 2013, 03:07:10 PM »
I bet every time you stop people walk past your buddy's bikes to get to yours.
"The problem with quotes on the Internet is that you never know if they're true" - Abraham Lincoln

Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline dumpster84

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Re: 78 CB750 build - sat for 5 years
« Reply #6 on: November 26, 2013, 03:19:22 PM »
Haha, yessir, constantly.  I'm sure you've been in that situation many-a-time.  Makes me so happy to ride around with all of these nice bikes that they have huge payments on and all I have to worry about is my 35 year old bike getting me home......wait....it's worth it, right? ;)

Offline hondaman750

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Re: 78 CB750 build - sat for 5 years
« Reply #7 on: November 26, 2013, 03:23:12 PM »
I would like to know where you got that muffler ive been looking everywhere

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Offline dumpster84

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Re: 78 CB750 build - sat for 5 years
« Reply #8 on: November 26, 2013, 03:29:21 PM »
No problem brother, I got it from Dime City Cycles.  Here's the link:
http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-exhaust-parts-stainless-steel-reverse-cone-shorty-motorcycle-muffler-80-2500.html

Not the cheapest one out there, but it was the one I wanted.  Hope it helps

Offline honda_dog

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Re: 78 CB750 build - sat for 5 years
« Reply #9 on: November 27, 2013, 04:14:51 AM »
A well-done project. And thanks for many pictures to look at.
1978 CB750K
1981 CB900F
1978 Suzuki GS1000E
1981 Suzuki GS1100EX
1980 Suzuki GS1000S (Wes Cooley replica)
1982 Suzuki GS1000S Katana
1982 Suzuki GS1100EZ
1983 Suzuki GS1100ED
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Offline hondaman750

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Re: 78 CB750 build - sat for 5 years
« Reply #10 on: November 27, 2013, 10:06:28 AM »
Thank you sir ill get one when I order alls the goodies for my 836

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Offline dumpster84

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Re: 78 CB750 build - sat for 5 years
« Reply #11 on: November 27, 2013, 11:15:11 AM »
Thanks honda dog, glad you liked them. I was worried people would be pissed that there were so many.

Hondaman, no prob bud.

Offline Bankerdanny

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Re: 78 CB750 build - sat for 5 years
« Reply #12 on: November 27, 2013, 12:52:07 PM »
People find plenty of things to complain about here, I don't think I have seen one for too many pictures.
"The problem with quotes on the Internet is that you never know if they're true" - Abraham Lincoln

Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline dumpster84

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Re: 78 CB750 build - sat for 5 years
« Reply #13 on: November 30, 2013, 07:10:51 PM »
Still waiting on my carbs to come in, tracking info isn't working so I hope they were sent.

In the mean time, bought an upswept rear hoop from Harisuluv that came in today!  Super fast shipping, didn't expect it here so soon.  Will probably try to get around to putting it on next week.

Also, got a cheap swingarm lift from Harbor Freight tonight for a whopping $19 after a coupon.  Works pretty good, but I was nervous at first, thought it was going to tip over because it was on the kickstand.

Here are some pics because I don't have anything else to say.  Garage is a mess







Offline Tsunami

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Re: 78 CB750 build - sat for 5 years
« Reply #14 on: November 30, 2013, 07:29:18 PM »
Fun reading your project.  Just wanted to say thanks for your service.  Where ever you are going stay safe and stay well so you can come home and finish your bike.
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Offline dumpster84

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Re: 78 CB750 build - sat for 5 years
« Reply #15 on: December 04, 2013, 05:01:24 PM »
Thanks Tsunami, I appreciate the kind words, sir.


Well, got some things done this evening, pretty excited about the results so far and the new look.

Stopped by Dime City Cycles and picked up some stuff for my brakes and grabbed their "DCC Upswept Brat Seat" then went right to work.  I'm not a great welder or fabricator, so back off or I'll kick you in the nuts :o.  Well, not really.  You can say how terrible it is, won't hurt my feelings.

Here are a bunch more pictures, sorry:

First up, the cliche angle grinder with sparks picture, cutting off the stock rear hoop and some of the rear to make room for the hoop.


Hoop cut down to fit, slugs popped in and everything mocked up waiting to be welded.




Welded the hoop on and then I made a bracket to attach the tail light/license plate holder out of scrap from the stock rear hoop.  Cut it to fit, drilled the holes, angled the attachment side, centered it, then prayed the angle was right when I tacked it on, haha.  It's not pretty like a lot of the stuff you guys do on here, but you won't see it anyways and I'm proud of it.  Turned out good the first try, so I welded it on:


Final product, sorry for the #$%*ty picture, light wasn't on my side.


Next on the list for tomorrow, my replacement carbs finally came in today!  I am going to swap everything out in the morning, synch them, and then should be back on the road!  I love the new look that this seat made and my wife is excited to ride with me.  Thanks for looking

Offline dumpster84

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Re: 78 CB750 build - sat for 5 years
« Reply #16 on: December 05, 2013, 08:35:59 AM »
I posted this in elsewhere in hopes to find an answer quicker, but if anyone can help me out, I would reaaally appreciate it:

Hey guys, I just replaced all of my internals from a leaky set of 78 cb750 PD carbs into a good set from a 77 (spring clips to intake stays, instead of being coiled around the linkage shaft).

Here is my dilemma and I really need some insight.  On the "new" set, the idle adjustment screw doesn't even touch the arm that it is supposed to on the linkage shaft, even when fully turned in.  As a reference, I took a picture of both sets of carbs side by side to show the problem.

As you can see, I am putting pressure on the arm that the idle adjustment screw is supposed to make contact with, the screw is also fully turned in and still has a gap.




What is going on here, guys?  Please help me out, I'm at a loss.  Do I have to separate the carbs and pull the linkage shaft because it is installed incorrectly or something? 

Note- I did not install the linkage shaft nor separate any of the carb bodies

Thanks

Offline dumpster84

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Re: 78 CB750 build - PD Carb idle screw issue, help needed
« Reply #17 on: December 05, 2013, 01:53:03 PM »
Problem solved. Finally got it sorted out and reinstalled.  Synched them up real quick and went out for a quick ride, felt great.  Have a few things to wrap up, but it's running again!  Too bad I have to leave it at home all weekend while I'm at work.  More on Monday hopefully.


Offline DaveBarbier

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Re: 78 CB750 build - brat seat installed
« Reply #18 on: December 12, 2013, 06:56:43 AM »
Hey Dumpster, I have a 78' 550 and my bike came with a 4-1 header like yours. I was thinking of getting the exact muffler as you. Question: Is the only thing holding the exhaust to the bike the header bolts or is there a bracket down by the muffler? I'm just curious if you think the header bolts can hold all the weight or if a bracket is needed to help stabilize everything.

Thanks dude, looks awesome. This coming season I'll be riding my cafe/brat 550 with 4 Harley friends I met recently. You and I will be in the same boat pretty much. If they bully me I'll be calling on you to get my back, haha.


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1978 Honda CB550K

Offline dumpster84

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Re: 78 CB750 build - brat seat installed
« Reply #19 on: December 14, 2013, 05:13:28 AM »
Hey Dumpster, I have a 78' 550 and my bike came with a 4-1 header like yours. I was thinking of getting the exact muffler as you. Question: Is the only thing holding the exhaust to the bike the header bolts or is there a bracket down by the muffler? I'm just curious if you think the header bolts can hold all the weight or if a bracket is needed to help stabilize everything.

Thanks dude, looks awesome. This coming season I'll be riding my cafe/brat 550 with 4 Harley friends I met recently. You and I will be in the same boat pretty much. If they bully me I'll be calling on you to get my back, haha.


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1978 Honda CB550K

Thanks friend, if you have any problems with Harley Doucherson's messing with you, I got you.  (JK about the "douche=davidson" thing, if I could afford one, I'd have one as well).  Just be ready for your friends to get jealous when everyone walks right past their $15,000 bikes and come straight to you and your 35 year old ~$1,000 bike to talk and ask questions, haha.

As far as the header and muffler set up, I do not have a bracket holding it on.  The header bolts are indeed all that hold it on.  I was worried about this when I was putting it all together because I took a very crappy crude looking bracket off of the back when it had the old muffler on, so I thought it would need one fabbed up.  So far, I haven't had any problems with it.  The muffler itself is very light and much lighter than the megaphone type that I took off, so hopefully it's alright.

Offline DaveBarbier

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Re: 78 CB750 build - brat seat installed
« Reply #20 on: December 14, 2013, 06:48:07 AM »
Hey Dumpster, I have a 78' 550 and my bike came with a 4-1 header like yours. I was thinking of getting the exact muffler as you. Question: Is the only thing holding the exhaust to the bike the header bolts or is there a bracket down by the muffler? I'm just curious if you think the header bolts can hold all the weight or if a bracket is needed to help stabilize everything.

Thanks dude, looks awesome. This coming season I'll be riding my cafe/brat 550 with 4 Harley friends I met recently. You and I will be in the same boat pretty much. If they bully me I'll be calling on you to get my back, haha.


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1978 Honda CB550K

Thanks friend, if you have any problems with Harley Doucherson's messing with you, I got you.  (JK about the "douche=davidson" thing, if I could afford one, I'd have one as well).  Just be ready for your friends to get jealous when everyone walks right past their $15,000 bikes and come straight to you and your 35 year old ~$1,000 bike to talk and ask questions, haha.

As far as the header and muffler set up, I do not have a bracket holding it on.  The header bolts are indeed all that hold it on.  I was worried about this when I was putting it all together because I took a very crappy crude looking bracket off of the back when it had the old muffler on, so I thought it would need one fabbed up.  So far, I haven't had any problems with it.  The muffler itself is very light and much lighter than the megaphone type that I took off, so hopefully it's alright.

Ha, yeah we'll see what these guys think about my old Honda once it's taking all the attention. Once he saw it my buddy already is thinking of a vintage bike of some kind.

Thanks for the muffler info. Once I get it I'll be able to see how strong that stuff is. A bracket could only help in this situation but maybe it's not absolutely necessary.


---
1978 Honda CB550K

Offline Buster68

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Re: 78 CB750 build - brat seat installed
« Reply #21 on: December 14, 2013, 03:26:44 PM »
Bike looks good! I think I have the same 4-into-1 exhaust on my Cb750 K8. I meant to order the same 12" shorty exhaust from DCC, but somehow screwed up (or they did) and got the longer one. My question is whether you are running that shorty without some kind of a welded support tab, or a tab from the collar? I couldn't see one in the pictures - aren't you worried about the weight of the exhaust muffler being unsupported?
1978 CB750K - in process of cafe conversion
1953 Harley Panhead chopper
1993 Harley FXR
Previous:
1978 Yamaha XS650 cafe
1977 CB750F cafe
1997 KTM 950 Adventure
1998 Honda VTR1000
1986 Harley-Davidson 1200 cafe
1990 Harley Evo rigid chopper
1998 Suzuki TL1000R

Offline dumpster84

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Re: 78 CB750 build - brat seat installed
« Reply #22 on: December 14, 2013, 03:52:29 PM »
Hey Buster, bummer about getting the wrong muffler, I'm sure those guys would swap it out for you if you asked, probably be some shipping costs though...

That's funny you asked about the muffler/header not being supported, DaveBarbier just asked the same question a few posts up.  To answer your question, No I'm not using a bracket, I intended to originally, but to be honest, it is pretty secure.  The shorty muffler is very light, especially compared to the big clunky blown out megaphone that I replaced it with.  THAT muffler did have a bracket.  I check the header constantly to see if there is any play in it and so far so good.  8 exhaust studs/nuts holding the collars on the header provide quite a bit of support and a pretty strong mounting point.

Should I be concerned with this?  Am I the only one running a 4-1 header without a support tab?

Offline KrautKoffin

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Re: 78 CB750 build - brat seat installed
« Reply #23 on: December 14, 2013, 04:23:56 PM »
How did you mount your seat?
74 cb550
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Offline dumpster84

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Re: 78 CB750 build - brat seat installed
« Reply #24 on: December 14, 2013, 04:25:23 PM »
How did you mount your seat?

Which one?  The cafe one or the brat seat?