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Offline JJONES450

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CB 750
« on: June 10, 2011, 09:37:51 AM »
Hey all, Im brand new to this forum, and figured Id get started asap on the new project. I recently got ahold of a cb 750 with a side car that has been sitting for some time. The last year it was registered was 1982. So, I saw the motor was locked up, and brought it home to begin the tear down process. This the first time I have worked on one of these Cb's, so I figured Id join the forum for some answers I know ill need in the future. Im still not too sure what my plan is for the finished product. Last night I pulled the motor out of the frame, and removed the top end, minus the cylinders. The #4 cylinder is rusted so bad that I couldnt break it loose, so I filled the cylinder up with WD-40 to soak for the weekend. Any ideas or info will be greatly appreciated for issues that may arise in the future.
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Offline zzpete

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Re: CB 750
« Reply #1 on: June 10, 2011, 09:43:00 AM »
 :D Hi and welcome! Interesting looking sidecar. This link might help with your stuck piston.
http://forums.sohc4.net/index.php?topic=84354.msg950605#msg950605

Good luck!
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"One of the things that make motorcycling so great because it never fails to give you a feeling of freedom and adventure." - Steve McQueen

Offline MCRider

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Re: CB 750
« Reply #2 on: June 10, 2011, 09:45:36 AM »
Welcome and congrats on bringing one back to life. Tip: A 50/50 mix of acetone and ATF has a penetrating property far in excess of WD-40. This is from a test in an engineering magazine which is on the forum somewhere, but take my word for it.
Much more likely to soak thru the rust than WD-40, though with some luck that may have already done the trick.

After that you may need to whack the top of the piston with a piece of wood like a piece of closet rod or a 1x1 and a hammer.
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Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline JosepyK

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Re: CB 750
« Reply #3 on: June 10, 2011, 09:50:47 AM »
Welcome, the guys here really know their stuff and will help if they can. The search field is your friend, I have a low post count because it answers so many questions quickly.

You're in for it now, in a good way. :D Can't wait to see what you do with it.
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'75 CB750F
'82 CB450SC

Offline Really?

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Re: CB 750
« Reply #4 on: June 10, 2011, 11:54:30 AM »
Interesting!  If you decide to keep it as a hack, check out the build thread for this other hack.  You might find some of the information there helpful.

Venturous's Hack Build Thread - http://forums.sohc4.net/index.php?topic=43173.75

He came darn close to tying for BOTM.  Actually it was darn close that month period! 

BOTM January 2010 - http://forums.sohc4.net/index.php?topic=63268.0
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I don't have a motorcycle, sold it ('85 Yamaha Venture Royale).  Haven't had a CB750 for over 40 years.

The Wife's Bike - 750K5
The Kid's Bike - 750K3

Offline JJONES450

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Re: CB 750
« Reply #5 on: June 10, 2011, 12:49:00 PM »
Hey guys , im wondering if anybody can help me figure out the definate year of this thing. The vin is CB750-111****, and the engine number is CB750E-110****. Thanks for the help
.
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pat english

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Re: CB 750
« Reply #6 on: June 10, 2011, 12:56:06 PM »
i think the last 2 numbers on the frame tag is the year...could be wrong though...

man,you got leave that thing exactly how it is!!!...that side car is freakin sweet!!!
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Offline Really?

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Re: CB 750
« Reply #7 on: June 10, 2011, 01:00:17 PM »
I have looked into doing a hack on my Venture but the prices are way way way out of my reach!  You let that go and you will be pulling your hair out finding another one.  Well, if you wanted to do something like that again.   ;D
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I don't have a motorcycle, sold it ('85 Yamaha Venture Royale).  Haven't had a CB750 for over 40 years.

The Wife's Bike - 750K5
The Kid's Bike - 750K3

Offline JosepyK

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Re: CB 750
« Reply #8 on: June 10, 2011, 01:03:23 PM »
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'75 CB750F
'82 CB450SC

Offline JJONES450

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Re: CB 750
« Reply #9 on: June 13, 2011, 08:24:00 PM »
Still wresteling with the number 4 piston that is locked up. I tried soaking the cylinder with WD-40 for 3 days with no luck. Next I tried the ATF trick, still no luck. On the other hand, I did remove the left hand engine covers after wresteling with some rusted- stripped bolts.
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pat english

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Re: CB 750
« Reply #10 on: June 13, 2011, 08:34:51 PM »
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Offline JJONES450

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Re: CB 750
« Reply #11 on: June 14, 2011, 05:56:56 PM »
Yeah, I tried that with some atf and carb cleaner. I let it burn for about 20-30 mins. Maybe not long enough. Kind funny, im having the problem with the same cylinder.
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Offline JJONES450

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Re: CB 750
« Reply #12 on: June 16, 2011, 06:12:36 PM »
I finally got that piston out and removed the cylinder.... Thank god. The PB Blast worked awesome after letting it sit in the cylinder for the day. Super excited to begin ripping into the motor once I get back from vacation.
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pat english

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Re: CB 750
« Reply #13 on: June 17, 2011, 03:19:56 AM »
jeez...took you long enough...jk ;)..good job
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Offline dhall57

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Re: CB 750
« Reply #14 on: June 17, 2011, 04:29:33 AM »
welcome to the forum jjones. How about more info on your 750. How did you find it, where did you get it etc. If you want to tell us how much did you get it for?  And of course some more pictures.
« Last Edit: June 17, 2011, 05:36:03 AM by dhall57 »
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1970 CB750KO
1971 CB500KO-project bike
1973 CB350G- project bike
1974 CB750K4-project bike
1974 CB750K4
1976 CB750K6
1977 GL1000
1997 Harley Wideglide

Offline JJONES450

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Re: CB 750
« Reply #15 on: June 17, 2011, 09:33:54 PM »
Yeah no problem. My girlfriends uncle (Paul) is in the estate sale business, and he put some pictures online of their next estate sale and the bike was in one of them. I told him id be interested if nobody else was. On the second day of the sale, a guy bought it for $750. When he came to pick it up it didnt fit on his trailer and he kinda wanted to back out of the deal. Since he was a friend of Pauls, he had no problem with it. So, I got a call a couple days later asking if id be interested in it and if so, I could have it for free as long as I fixed it, kept the side car with it and did a small electrical job for him. I couldnt pass it up so I borrowed a trailer and picked it up the next week. Ill post pics of the progress in a few weeks.
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Offline KB02

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Re: CB 750
« Reply #16 on: June 18, 2011, 04:41:32 AM »
When I got my 78 750 the engine was rusted and locked up. I ended up have to split the cases, undo the connecting rod, and hammer the piston out after several weeks of soaking in Kroil. There was no hope in saving the pistons and I had planned to bore it out anyway. (See my avatar pic)
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1978 CB750K Project
2000 Ducati ST2
...and a pedal bike

Join the AMA today!!

My project thread Part I: K8 Project "Parts Bike"
My project thread Part II: Finishing (yeah, right) touches on Project "Parts Bike"

Offline JJONES450

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Re: CB 750
« Reply #17 on: July 08, 2011, 12:49:58 PM »
Hey guys, just thought id give an update. Today I has some time and deciced to split the cases. Everything looked pretty good. I did find that one one of the oil pumps had some minor damage. Im planning on cleaning up all the cases and covers later today.
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Offline JJONES450

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Re: CB 750
« Reply #18 on: July 08, 2011, 12:52:11 PM »
Here is a pic
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Offline JJONES450

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Re: CB 750
« Reply #19 on: July 11, 2011, 03:26:52 PM »
Any advice for cleaning the engine cases and covers? About 4 hrs of cleaning, and felt like I've accomplished nothing.
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Offline CycleRanger

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Re: CB 750
« Reply #20 on: July 11, 2011, 03:49:36 PM »
Take them down the car wash and pressure wash them.
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Offline MCRider

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Re: CB 750
« Reply #21 on: July 11, 2011, 03:53:43 PM »
I've een thru teh same thing. Did the carwash pressure washer. Then got an electric power washer, a little better. A gas pas washer may have done it. But if you're looking to strip the paint, you just about gotta go media blast, like plastic bead blasting. That's what i ended up doing.

If so, you'll spend the time instead of cleaning crud, cleaning out beads from all the nooks and crannies. But its the best job.
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Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline JJONES450

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Re: CB 750
« Reply #22 on: July 11, 2011, 10:31:25 PM »
Thanks guys. I tried a small electric pressure washer the other day, it worked ok. I went and bought some silica sand for the sand blaster, and it worked, but super slow going. I guess this is where patience really works.
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Offline MCRider

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Re: CB 750
« Reply #23 on: July 12, 2011, 05:53:06 AM »
Quote from: JJONES450 on July 11, 2011, 10:31:25 PM
Thanks guys. I tried a small electric pressure washer the other day, it worked ok. I went and bought some silica sand for the sand blaster, and it worked, but super slow going. I guess this is where patience really works.
Once you decide to use media blast, you have committed to an intense cleaning. Use tube brushes in all the holes. The power washer will help overall. Can't leave any grit behind.
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Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline JJONES450

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Re: CB 750
« Reply #24 on: July 12, 2011, 09:37:58 AM »
Right on McRider, Thanks.
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