Author Topic: My 1974 CB750 Boss Maroon auction sale find.  (Read 18652 times)

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Offline dhall57

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My 1974 CB750 Boss Maroon auction sale find.
« on: April 13, 2014, 06:45:36 PM »
Thought I would do this bike a little different and post some stuff here and keep track of some of the work I'll be doing to it to get it on the road. If you've missed the other thread let me give you a quick summary. Low mileage(5291) original bike I bought at a Estate Auction sale a couple weekends ago. Got it from the second owner who had bought in 1976 from the original owner. In 1984 he parked it in his basement and forgot about it after putting only about 3000 miles on it. His doctor told him to stop riding it because of a back problem he had. Being inside all this time bike is in good shape. But it was parked with some gas in it so of course after all this time throttle is stuck and carbs gummed up. Engine was stuck (again from sitting so long) and would not kick over, but have since got free(rather easy)and kicks over smooth after putting some ATF down the plug holes. So I think engine is ok. I hope.

First thing I did today was remove carbs so in the next few days I can start the process soaking, cleaning and getting them back in shape so I can see if she'll start up. Here's some pictures. Have you ever seen carbs in such a mess as this. This explains why the throttle was stuck ??? Knew it wouldn't be pretty but this is worse than what I thought. So this is what happens to gas after 30 years :o Ok who as experience with carbs in this sad shape and condition and what would you say is the correct way to tackle this that will give the best results.


 


« Last Edit: December 08, 2014, 02:37:43 AM by dhall57 »
1970 CB750KO
1971 CB500KO-project bike
1973 CB350G- project bike
1974 CB750K4-project bike
1974 CB750K4
1976 CB750K6
1977 GL1000
1997 Harley Wideglide

Offline flybox1

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #1 on: April 13, 2014, 06:58:13 PM »
Great bike, but yeah, carbs looked like toasty.  Better than water damage I guess ;D
Go at it with carb cleaner spray, simple green, acetone.....and some good brushes.
Maybe even a little heat gun to soften all the hard stuff.
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
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Offline Tews19

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #2 on: April 13, 2014, 07:13:28 PM »
DHall how was it during the auction itself? I did an auction for a 350 sohc a few years ago. My heart was pounding and then when the price got high I bailed. It was fun though while I gave the nods to outbid the other guy.
1969 Honda CB750... Basket case
1970 Honda CB750 survivor.

Offline Greggo

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #3 on: April 13, 2014, 07:18:31 PM »
Great find D!

Offline SOHC4 Cafe Racer Fan

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #4 on: April 13, 2014, 07:48:03 PM »
Great bike.
1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
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"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
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2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
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Offline DennyK

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #5 on: April 13, 2014, 07:49:02 PM »
The bike you found looks great and compared to the carbs I found on my '71 and '74, your set looks pretty good.  I looked into various approaches to clean the carbs and found a guy locally with an ultrasonic cleaner.  He charged me $30 and almost overnight the job was done.  You will of course need to get rebuild kits.  I am just now getting started on that.  There are some real advantages to the ultrasonic approach over soaking.  I delayed cleaning and rebuilding my carbs until I was sure my bike would run; I am not sure that I would approach it the same today.  You can spend a lot of time cleaning just to see if it will run and still have a plugged jet.  Anyway those are my two cents.

Offline dhall57

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #6 on: April 19, 2014, 03:57:54 PM »
Did not touch the carbs just let them sit in cleaner most of the afternoon while rebuilding the rear m/c on the Wang.
Starting to show a little promise.
What they look liked when I took them off
After soaking the afternoon
1970 CB750KO
1971 CB500KO-project bike
1973 CB350G- project bike
1974 CB750K4-project bike
1974 CB750K4
1976 CB750K6
1977 GL1000
1997 Harley Wideglide

Offline 2strokeTrush

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #7 on: April 19, 2014, 07:06:48 PM »
Looking good man!  Great find.  Sub'd
If You Aint First Your Last!!

 350F project-http://forums.sohc4.net/index.php?topic=133079.0

500F Project-http://forums.sohc4.net/index.php?topic=135660.0

Offline DennyK

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #8 on: April 19, 2014, 09:35:14 PM »
I had some good results filling the bowls with Seafoam and letting everything soak for 5 day.  You have made some good progress.  I assume before you go a lot deeper on the carbs you want to make sure it runs.  I also used a 25 - 75 mix of Seafoam and gas when I did my first restart. 

Offline ekpent

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #9 on: April 20, 2014, 03:22:35 AM »
Those carbs will clean up and I don't think you will need any rebuild kits. At the worst maybe a bowl gasket but the stock 750's are ultra durable, even after soaking in carb dunk. At the least though I would break down the rack so I could soak each carb body individually in real carb cleaner and blow out all the passages etc. Try to work a fine wire through the slow jets after the gunk has softened so the carb cleaner will work better through the passage.
  As mentioned and especially when removing the pins for the float from the fragile towers a heat gun will be your friend. Lacquer thinner does a very good job of dissolving that varnish also for jets are other areas such as the pins etc and good penetrating oil with heat hurts nothing and is helpful.

Offline rtbmrgl

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #10 on: April 20, 2014, 08:10:45 AM »
Thought I would do this bike a little different and post some stuff here and keep track of some of the work I'll be doing to it to get it on the road. If you've missed the other thread let me give you a quick summary. Low mileage(5291) original bike I bought at a Estate Auction sale a couple weekends ago. ............................
Great find, Im jealous.
thanks, Mark
Roseville, Ca

Got Points!

1973 CB500 back yard find 1243 orig mi,  http://forums.sohc4.net/index.php?topic=124285.0
1976 CB750 Restoring,        http://forums.sohc4.net/index.php?topic=132997

Offline Johnie

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #11 on: April 20, 2014, 09:32:21 AM »
She is coming along good hall! Patience...especially if you have issues getting the float pins out.
1970 CB750K0 - Candy Ruby Red
1973 CB750K3 - Candy Bacchus Olive or Sunflake Orange
1970 Chevy Chevelle SS396 - Cortez Silver
1976 GL1000 Sulphur Yellow

Oshkosh, WI  USA

Offline dhall57

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #12 on: April 20, 2014, 11:41:22 PM »
These carb jets remind me of the movie Ghostbusters and when they all get slimed.
I took it easy screwing these out and thought every thing was good and didn't realize until after the fact that tip end of pilot jet for #4 carb broke off and is still in carb.

1970 CB750KO
1971 CB500KO-project bike
1973 CB350G- project bike
1974 CB750K4-project bike
1974 CB750K4
1976 CB750K6
1977 GL1000
1997 Harley Wideglide

Offline ekpent

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #13 on: April 21, 2014, 04:41:18 AM »
You should be able to get that out once they have a good soak. Looks like you have all the threads. Heat gun will soften that varnish or that is one of the reasons I would like to see you break that rack down and give each carb body a good dunk/soak before trying to remove that stuff.  Have you removed the slides yet. ?  Don't force those or the needle jet mount plate can get bent  up. Often the needle also gets "glued" in the carb body.

PS- I should have an extra slow jet around for you when you put it back together.   ;)
« Last Edit: April 21, 2014, 04:43:15 AM by ekpent »

Offline BLEAMA

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #14 on: April 21, 2014, 05:40:10 AM »
That is a great find!   Way better than water damage!  Must have been a nice basement!

Offline HondanutRider

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #15 on: April 21, 2014, 07:24:43 AM »
Rather than carb cleaner, I've found that lacquer thinner works better at dissolving old gunk off carbs.

Offline ekpent

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #16 on: April 21, 2014, 09:00:24 AM »
Rather than carb cleaner, I've found that lacquer thinner works better at dissolving old gunk off carbs.
Rather than carb cleaner, I've found that lacquer thinner works better at dissolving old gunk off carbs.
Yeah I made a note of that back up a little. It does cut that gunk very well and is good to soak those jets in, plus it smells great, love it in the morning  8)   :P

Offline rtbmrgl

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #17 on: April 21, 2014, 01:40:06 PM »
Ekpent is right about the heat gun. My 500 had been sitting for maybe 30yrs, the slides were completely stuck, after hitting with heat gun they dropped out. From that point is was all down hill.
thanks, Mark
Roseville, Ca

Got Points!

1973 CB500 back yard find 1243 orig mi,  http://forums.sohc4.net/index.php?topic=124285.0
1976 CB750 Restoring,        http://forums.sohc4.net/index.php?topic=132997

Offline DennyK

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #18 on: April 21, 2014, 04:37:39 PM »
Consider removing the floats and check them for leaks, I found that a couple of mine from this vintage had small cracks and took on fuel.  Also again I would suggest you fins an ultrasonic cleaner and save yourself a lot of work.

Offline Johnie

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #19 on: April 21, 2014, 04:45:28 PM »
And one other side note...check the float bowl standpipes for cracks.
1970 CB750K0 - Candy Ruby Red
1973 CB750K3 - Candy Bacchus Olive or Sunflake Orange
1970 Chevy Chevelle SS396 - Cortez Silver
1976 GL1000 Sulphur Yellow

Oshkosh, WI  USA

Offline dhall57

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #20 on: April 25, 2014, 07:47:08 PM »
Make a little head way on the K4 when I got home tonight. Took carbs off rack and got slides out. Still got a more cleaning to do but I think these carbs are going to be just fine ;)
« Last Edit: April 25, 2014, 07:49:30 PM by dhall57 »
1970 CB750KO
1971 CB500KO-project bike
1973 CB350G- project bike
1974 CB750K4-project bike
1974 CB750K4
1976 CB750K6
1977 GL1000
1997 Harley Wideglide

Offline rtbmrgl

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #21 on: April 25, 2014, 09:48:49 PM »
Make a little head way on the K4 when I got home tonight. Took carbs off rack and got slides out. Still got a more cleaning to do but I think these carbs are going to be just fine ;)
Looks good from way over here in No. Calif. and I have bad eyes.  :o
thanks, Mark
Roseville, Ca

Got Points!

1973 CB500 back yard find 1243 orig mi,  http://forums.sohc4.net/index.php?topic=124285.0
1976 CB750 Restoring,        http://forums.sohc4.net/index.php?topic=132997

Offline ekpent

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #22 on: April 26, 2014, 09:35:31 AM »
Did that little bit of broken slow jet fall out for you or easy to pick out ?

Offline dhall57

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #23 on: June 02, 2014, 05:50:41 PM »
Haven't done much on my K4. Been busy with my Goldwing since getting it on the road and still doing things to it. Just enjoy riding it ;D

Going to be finishing the K4 carbs shortly. Got bowl gaskets order.

 Wanted to do something so I took off #1 and #2 341's to start cleaning them up.
 Plenty nasty with 30 years of grud on them, but also plenty solid. Think they will clean up good, and when done think they will look almost new.


1970 CB750KO
1971 CB500KO-project bike
1973 CB350G- project bike
1974 CB750K4-project bike
1974 CB750K4
1976 CB750K6
1977 GL1000
1997 Harley Wideglide

Offline Tews19

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Re: My 1974 CB750 Boss Maroon auction sale find.
« Reply #24 on: June 02, 2014, 07:18:17 PM »
Hmm. That one pipe should be interesting. 
1969 Honda CB750... Basket case
1970 Honda CB750 survivor.