Author Topic: 1971 honda cb 750 project / Update problem changing oil  (Read 51989 times)

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Offline Garystratos201

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1971 honda cb 750 project / Update problem changing oil
« on: August 19, 2012, 08:30:36 am »
Greetings fellow Honda 750 nuts. I`ve recently been given a 1971 Honda cb750 that has been sitting for over 14 years. My intention is too breath new life into this machine. The engine is locked tight as a drum and I have the engine out. I can handle the disassembly ok but there is a lot of damage to the cooling fins. My first question is what year head is interchangeable with mine without losing any performance. The engine number is 1045093. Thanks in advance.........Gary
« Last Edit: July 23, 2013, 06:45:34 am by Garystratos201 »
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Offline Garystratos201

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Re: 1971 honda cb 750 project
« Reply #1 on: August 21, 2012, 05:10:41 am »
Okay I have the head off and the pistons loose still wondering which heads will work on my 1971 model. Anyone have any info that might help I would appreciate  the help......Gary
« Last Edit: August 27, 2012, 04:48:36 am by Garystratos201 »
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Offline Nikkisixx

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Re: 1970 honda cb 750 project
« Reply #2 on: August 21, 2012, 11:33:56 am »
Hey howdy, kinda quiet in here!  I seem to remember any early model "K" head (70-76) is compatible.  Some performance loss in cam shafts after 70, so you may want to swap that over.  I recall the valves being the same size in the early K heads.  A little port work will overcome any performance changes made in the head.

A good welder can stick some fins back on, and a file will hide his tracks.  Just and option that may be a better route.
It is a proven fact that modifying a SOHC Honda in any way will bring on the apocalypse.

Offline Garystratos201

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Re: 1971 honda cb 750 project
« Reply #3 on: August 21, 2012, 12:44:30 pm »
Thanks for the response Nik. I believe there are way to many fins broken and missing for welder to repair. I have the jugs off now and found everything except the rings to be to be in great shape. Of course I`ll need the cam chain tensioner and the cir clips for the wrist pins and of course the gaskets. anyone know of a good source for oem parts ?      Gary
« Last Edit: August 27, 2012, 04:49:31 am by Garystratos201 »
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Offline Garystratos201

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Re: 1971 honda cb 750 project
« Reply #4 on: August 24, 2012, 04:56:07 am »
Started on the carb yesterday and was very surprised how clean the were. Very little varnish in the float bowls but of course the dust caps and rubber seals around the slides are gone. Slow progress but very satisfying. I really wish I still had the 1971 Honda I sold back in the day. Working on this really brings back memories of all the road trips and friends that were made...........Gary
« Last Edit: August 27, 2012, 04:49:54 am by Garystratos201 »
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Offline Mercutiojb

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Re: 1970 honda cb 750 project
« Reply #5 on: August 25, 2012, 06:37:00 am »
Let's see some photos!

Offline Garystratos201

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Re: 1971 honda cb 750 project
« Reply #6 on: August 27, 2012, 06:35:04 am »
After doing a vin and serial number search I found out that my 1970 was actually a 1971. So I had to go and change the headings in my post. I started taking some photos today i wish I had started taking them, from the beginning  but honestly never thought about it. I guess I was just excited about having and working on the bike. I did find a great looking head on ebay so I`ve got that problem out of the way. Next I need do order rings and a gasket set. Anyone have any recommendations? I dont want to finish my build and wind up with a leaky motor..........Gary

ps; I tried to attach photos but got an error saying entity too large. How do I make them smaller?
« Last Edit: August 27, 2012, 12:16:54 pm by Garystratos201 »
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Offline Garystratos201

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Re: 1971 honda cb 750 project
« Reply #7 on: August 27, 2012, 12:18:07 pm »
Thanks for the advice johnie but I`ve already tried that........still says entity too large.
Oh well I `ll try again later.......Gary
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Offline Tews19

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Re: 1971 honda cb 750 project
« Reply #8 on: August 27, 2012, 12:51:48 pm »
Welcome! Usual phrase, pics or it didn't happen.
1969 Honda CB750... Basket case
1970 Honda CB750 survivor.

Offline Garystratos201

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Re: 1971 honda cb 750 project
« Reply #9 on: August 27, 2012, 01:15:47 pm »
I think I`ve figured out the image thing, I had to reduced the size of the image . This is gonna be a test post to see if it works if it does I`ll have to resize all my images.........Gary
« Last Edit: August 27, 2012, 01:46:38 pm by Garystratos201 »
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Offline Garystratos201

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Re: 1971 honda cb 750 project
« Reply #10 on: August 27, 2012, 02:03:55 pm »
Okay my images are all re-sized,  lets see if this works........Gary
« Last Edit: August 27, 2012, 02:09:54 pm by Garystratos201 »
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Offline Tews19

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Re: 1971 honda cb 750 project/ images attached
« Reply #11 on: August 27, 2012, 03:34:25 pm »
Looks like you dove in head first. Are you planning to make all the parts year correct?
1969 Honda CB750... Basket case
1970 Honda CB750 survivor.

Offline Garystratos201

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Re: 1971 honda cb 750 project/ images attached
« Reply #12 on: August 28, 2012, 04:56:41 am »
Looks like you dove in head first. Are you planning to make all the parts year correct?

I`m not afraid of the water. lol I am going to keep it mostly year correct as possible with a few exceptions. I plan on custom painting  the tank and side covers just like I did mine back in early 1972. I still nine cans of original honda paint  ' Topaz Fire'. For everyone's benefit I have 40 years experience in the body shop.

I learned something yesterday when I started pressure washing........would have been a lot easier if the bike was still together..........Gary
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Offline Tews19

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Re: 1971 honda cb 750 project/ images attached
« Reply #13 on: August 28, 2012, 05:41:11 am »
Looks like you dove in head first. Are you planning to make all the parts year correct?

I`m not afraid of the water. lol I am going to keep it mostly year correct as possible with a few exceptions. I plan on custom painting  the tank and side covers just like I did mine back in early 1972. I still nine cans of original honda paint  ' Topaz Fire'. For everyone's benefit I have 40 years experience in the body shop.

I learned something yesterday when I started pressure washing........would have been a lot easier if the bike was still together..........Gary

K, on the 71's petcock is on the right, You may have to get a new tank or leave as is and fly with it. ... You may be able to trade someone for the side covers too as yours look to be in nice shape. I have an extra set of proper rear shocks if you are looking to make those year correct as well. Gauges may be the expensive part. Gauges should have the indicators in them.

Keep the updates coming!
« Last Edit: August 28, 2012, 05:43:06 am by Tews19 »
1969 Honda CB750... Basket case
1970 Honda CB750 survivor.

Offline Johnie

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Re: 1971 honda cb 750 project/ images attached
« Reply #14 on: August 28, 2012, 06:02:52 am »
Yah, looks like previous owner did some parts swapping on that bike. Tank is not from 71 nor are the fork ears. The ears on the K1 should be painted like the tank. Bike does have the K1 lift handle by the back shock. Wonder what happened to the rest of the OEM parts? Any chance the PO still has that stuff...gauges, tank, ears, etc. Almost looks like he swapped the entire front end with a newer 750. Check the frame to be sure it is straight and not in an accident. Sure looks like a nice project. Let us know how you come out...
« Last Edit: August 28, 2012, 06:08:27 am by Johnie »
1970 CB750K0 - Candy Ruby Red
1973 CB750K3 - Candy Bacchus Olive
2000 1500 SE Wing (wife's pearl white bike)
1970 Chevy Chevelle SS396 - Cortez Silver

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Offline Tews19

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Re: 1971 honda cb 750 project/ images attached
« Reply #15 on: August 28, 2012, 02:40:01 pm »
I have some painted red K0/K1 fork ears I was planning to use but sold that project the other week. If interested PM. I also have the matching headlight bucket
1969 Honda CB750... Basket case
1970 Honda CB750 survivor.

Offline Garystratos201

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Re: 1971 honda cb 750 project/ images attached
« Reply #16 on: August 28, 2012, 09:01:42 pm »
A little history on the bike. It belonged to my best friend and we used to ride together. At the time I had a shiny new red 1971 red cb750. We traveled a lot. The longest trip was to the Grand Canyon. We were on the road 10 days round trip. He has dropped it the several times through out the years. I knew the fork ears, tank and side covers were from a newer bike but I didnt know about the rear shocks. The frame is fine I have actually rode the bike roughly 13 or fourteen years ago and know what to expect when its running again. If you guys know anyone who wants to trade side cover please let me know. They are in great shape . No cracks just faded.........Gary
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Offline Tews19

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Re: 1971 honda cb 750 project/ images attached
« Reply #17 on: August 29, 2012, 06:50:49 am »
Neat story.. You may look into trading for an earlier set of side covers or sell them outright. Is there any name stamped on top of the rear shocks?
1969 Honda CB750... Basket case
1970 Honda CB750 survivor.

Offline Garystratos201

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Re: 1971 honda cb 750 project/ images attached
« Reply #18 on: August 29, 2012, 07:44:22 am »
Neat story.. You may look into trading for an earlier set of side covers or sell them outright. Is there any name stamped on top of the rear shocks?

No name stamped on top of the shocks. I started cleaning some of the engine parts yesterday an man is it ever labor intensive. The only way I have found that would remove the discoloration is wet sanding with 320 wet  and then
progressively moving up to finer grit eventually finish with 2000 grit wet.  I`m gonna post some of the work I did yesterday. Almost 3 hours and not finished yet.......Gary
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Offline Kevin D

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Re: 1971 honda cb 750 project/ images attached
« Reply #19 on: August 29, 2012, 01:30:02 pm »
I looked at a couple of your pictures ...
Man those brass floats sure look nice, too bad they're hidden in the float bowls.
Make sure they all float equally.
Seat and taillight also later model, not K1.
The heavy ground wire hooks to the battery negative, not the starter solenoid! The starter motor wire connects to the left solenoid post.
Looks like a replacement fuse holder installed as well.
Sorry, I dont know about head compatibility.

71 CB750 K1
90000 mi
Original Owner
———past———
70 SL100/125/150
70 Candy BlueGreen CB 750 K0
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Former Honda parts kid/counter kid/do all
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Offline Garystratos201

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Re: 1971 honda cb 750 project/ images attached
« Reply #20 on: August 30, 2012, 04:47:35 am »
I looked at a couple of your pictures ...
Man those brass floats sure look nice, too bad they're hidden in the float bowls.
Make sure they all float equally.
Seat and taillight also later model, not K1.
The heavy ground wire hooks to the battery negative, not the starter solenoid! The starter motor wire connects to the left solenoid post.
Looks like a replacement fuse holder installed as well.
Sorry, I dont know about head compatibility.

Thanks for the info Kevin maybe I need to look up a wiring diagram . I havnt done anything to the bike yet I have been concentrating on the engine for now. It appears that my project gets bigger as time passes. I`ve been spending more time researching on the computer than I have actually working.lol
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Offline Prospect

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Re: 1971 honda cb 750 project/ images attached
« Reply #21 on: August 30, 2012, 05:29:34 am »
That looks to be a very early k1.  They started with vin 1044650 so yours is 13 into the k1 model.  So this would be from the "old factory". You'll likely have some K0 parts as honda wasn't strict on exact model changes through the years and some stuff flowed into the next model etc.  I think that head is not worth repairing as there is too much fin damage.  Consider getting one from ebay.  You can get a later model head but as mentioned there will be performance loss.  I'm sure if you post in the wanted section of this forum someone might have one. 

You have a lot of work ahead of you but take your time and do what the budget allows.  Sometimes it's cost prohibitive to go 100% stock and 90% will do fine and not hurt the wallet. 
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1971 CB750K1
1972 CB750K1
1975 CB400F
1975 GL1000 Goldwing
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1957 Harley Davidson Panhead

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Offline Tews19

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Re: 1971 honda cb 750 project/ images attached
« Reply #22 on: August 30, 2012, 06:13:52 am »
That looks to be a very early k1.  They started with vin 1044650 so yours is 13 into the k1 model.  So this would be from the "old factory". You'll likely have some K0 parts as honda wasn't strict on exact model changes through the years and some stuff flowed into the next model etc.  I think that head is not worth repairing as there is too much fin damage.  Consider getting one from ebay.  You can get a later model head but as mentioned there will be performance loss.  I'm sure if you post in the wanted section of this forum someone might have one. 

You have a lot of work ahead of you but take your time and do what the budget allows.  Sometimes it's cost prohibitive to go 100% stock and 90% will do fine and not hurt the wallet.

+1... I would keep those side covers.. Hard to find non busted or cracked ones from any year.

1969 Honda CB750... Basket case
1970 Honda CB750 survivor.

Offline Garystratos201

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Re: 1971 honda cb 750 project/ images attached
« Reply #23 on: August 30, 2012, 01:00:31 pm »
That looks to be a very early k1.  They started with vin 1044650 so yours is 13 into the k1 model.  So this would be from the "old factory". You'll likely have some K0 parts as honda wasn't strict on exact model changes through the years and some stuff flowed into the next model etc.  I think that head is not worth repairing as there is too much fin damage.  Consider getting one from ebay.  You can get a later model head but as mentioned there will be performance loss.  I'm sure if you post in the wanted section of this forum someone might have one. 

You have a lot of work ahead of you but take your time and do what the budget allows.  Sometimes it's cost prohibitive to go 100% stock and 90% will do fine and not hurt the wallet.

Thanks for the info prospect and the advice. There some things I`m going to take care of now. But I`m concentrating on building the engine and paintin the frame first.

Tews no way I would part with the side covers until I found the correct ones. They are in excellent shape paint just faded no cracks or repairs.......Gary
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Offline Garystratos201

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Re: 1971 honda cb 750 project/ images attached
« Reply #24 on: August 30, 2012, 01:04:34 pm »
Neat story.. You may look into trading for an earlier set of side covers or sell them outright. Is there any name stamped on top of the rear shocks?

What name should be on the shocks?..........Gary
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Current ride; Bass boat.... 2005 Ranger 521VX,250 hp Mercury Verado, super charged and direct fuel injected. Not a bass on the lake can out run me !!!