Topic: 1981 CB650 Custom Start!

[bmx4637]

Hey everyone, I am posting here as a mark of the beginning of my 1981 CB650 custom build. I am trying to get this thing off the ground. In the meantime I am preparing to get some tools and money to start.

I want to make it look very cafe racer, so the stock parts I currently have I may sell eventually so hit me up at any time if interested.

In my signature are the links for my blog build (a bit more organized instead of going through pages of different posts that sometimes go tangent of the original topic). Also there is a link for any contributions to help me out. I have a small bio of me, but basically I am an engineer student majoring in Mechanical Engineering and hopefully double major in aerospace engineering, since I currently work in aviation as an NDT Inspector.

I hope sometime in the near future I will be able to perform fluorescent penetrant inspection on engine parts or frame (such as crankcase, block, etc that are worthy of inspection vs replacement due to it being hard to find) as a service to you guys (I have been doing it for over 4 years so far).

This build will help me gain some experience in being able to someday perform engineering services in frames, engine tuning, NDT etc. as a business.

I appreciate any comments/suggestions and help you guys can collectively share. I look forward to this build, and I hope you do too!







-Alex

[onepieceatatime]

Welcome.

Your cam snd exhaust seem to be missing in the pictures, along with the tank, and a few other things. Did you get them with the bike, or are they items you are going to be looking for?

[bmx4637]

Hey one piece,

I will double check on the cam tonight (I don't remember seeing it so I may need one). but the stock tank I do have (not sure if I will keep that). I also have the stock 4-4 exhaust (def not keeping that).

I have the pics on my blog gallery. I didn't want to clutter the post with a lot of pics.

So check out the blog for it. Thanks

[onepieceatatime]

If you decide not to keep the tank, or side covers, I may be interested in them as well as the stock exhaust depending on my finances when you want to get rid of them.

The cam may be hard to find, a lot of 550 guys use them in their bikes, but they can be found on occasion. I sold my spare already, but have a couple of spare engines. If I decide to part one of them out, then I may have one.

[bmx4637]

ok I found the cam in a box last night. However it has some major defects so I will def need to get a different one:








one piece, you have spare 550 engines or 650 engines? Are any of the cam's from 650 interchangeable with other engines?

and about the tank, side covers, and exhaust, I will def let you know when I have found alternatives to the stock. Then I will sell them.

[onepieceatatime]

one piece, you have spare 550 engines or 650 engines? Are any of the cam's from 650 interchangeable with other engines?

and about the tank, side covers, and exhaust, I will def let you know when I have found alternatives to the stock. Then I will sell them.

I have 2 1980 CB650 projects (one custom and one standard), along with those I have a 1981 CB650 parts bike (which I am going to try to get a title for and rebuild) and 2 spare 1980 CB650 engines.

The cams from the 1979-1982 CB650 engines are interchangeable. I do not know of any other engine that is compatible though. The 650 cam will work in the 550 engine as a mild performance cam, but you wouldn't want to swap the other way.

[bmx4637]

I might want to grab one of your spare engines, after I fully see what condition mine is in.

I'm wondering, since this is my first build, what process is it like in obtaining a title from a parts build in PA? I used to live in Stroudsburg, but here in Florida this bike title is filled up and nobody bothered to actually transfer it, so my name is not on the title nor is the seller. I might need to do a rebuild title or something from parts.

[onepieceatatime]

I was going to the process in this thread, but getting my other 2 projects on the road is priority over that, so it may still be some time before I make the attempt.
http://forums.sohc4.net/index.php?topic=109701.msg1230327#msg1230327

Also, if you start looking for engines, the 79 and 80 are the same, and the 81 and 82 are the same. The heads are different between those 2 sets of years due to Honda using different carbs with different spacing. The earlier 2 are mechanical (PD) carbs, and the newer 2 are vacuum (CV) carbs.

[bmx4637]

nice link. I will see what I can do here in Florida and post everything I go through.

Thanks for the info on the different heads, I really appreciate the shared knowledge.
are there any more differences between the 79-80 and 81-82 engines besides the carbs and carb spacing?
I guess I would need to have an 81-82 spare engine then for my build.

-Alex

[onepieceatatime]

nice link. I will see what I can do here in Florida and post everything I go through.

Thanks for the info on the different heads, I really appreciate the shared knowledge.
are there any more differences between the 79-80 and 81-82 engines besides the carbs and carb spacing?
I guess I would need to have an 81-82 spare engine then for my build.

-Alex

That is the only thing I know of different in the engine. The frame, tank, side covers, and seat are different on the 79 and the frame, tank, and side covers are different on the 82 Nighthawk than the rest of the models. The tank on the 80 is the same shape and size on the 80 (all models) as the 81 (all models) and 82 standard model, but the petcock and fuel line size are different. Master brake cylinder is different between the 79-80 and the 81-82 years and also different between the standard and custom models. Forks are different on different years and models, 81 and 82 have air assist forks, and custom forks are different than standard forks which are different from Nighthawk forks. 81 custom had dual disk front brakes, the older ones did not, so the fenders are different also.
That is all I can think of right now, but there is probably more.

[onepieceatatime]

You may also want to check out this site:
http://hondacb650.com/index.php

[bmx4637]

That is the only thing I know of different in the engine. The frame, tank, side covers, and seat are different on the 79 and the frame, tank, and side covers are different on the 82 Nighthawk than the rest of the models. The tank on the 80 is the same shape and size on the 80 (all models) as the 81 (all models) and 82 standard model, but the petcock and fuel line size are different. Master brake cylinder is different between the 79-80 and the 81-82 years and also different between the standard and custom models. Forks are different on different years and models, 81 and 82 have air assist forks, and custom forks are different than standard forks which are different from Nighthawk forks. 81 custom had dual disk front brakes, the older ones did not, so the fenders are different also.
That is all I can think of right now, but there is probably more.

ok so all cb650 engine internals are the same? my frame looks to be in very good condition, but close inspection will be needed to be sure. My fenders I might make myself from fiberglass, as well as a different seat and tank so I'm not too worried about bolt on stock body look.

Other people can contribute too, towards:
1. Obtaining titles
2. interchangeable engine parts between honda CB's



(here is a link to paulages 550/650 hybrid big bore thread: http://forums.sohc4.net/index.php?topic=40414.0 )

Things to highlight:

TRANSMISSION
---all gears fit both main and countershafts, but the 650 1st gear doesn't mate with the 550 kickstarter gear
---all transmission bearings are interchangeable, though there are some slight differences. the countershaft needle bearing on the 650 has a small oil pump built into the outer race/casing for supplying oil to the bearing.
---primary shafts are interchangeable, but the assemblies on them must be mated with their stock cases, as there is a slight difference in spacing between the bearings in the case.
---parts of the shift assembly/ bearing retainers on the clutch side are interchangeable, though I see no advantage to using one over the other.
---the clutch baskets are interchangeable, but the primary gear that mates with the clutch driven gear must match. if using the 650 primary clutch gear with the 550 clutch cover, some material must be removed from the cover in this area to avoid contact.
---the clutch pressure plate needs to match the cover from the same model, as the pushrod assemblies are different.

ENGINE
---both engines use the same hy-vo primary chain
---both cranks fit either case
---both engines have the same barrel and stud spacing
---the slots for the front cam chain guide are in a different location than the 550. all other 650 cam chain parts work with the 550
---the 650 cam will drop into a 550 head with similar results to a mild street performance cam. the 550 cam sprocket must be used, as will the 650 tach, cable, and cam driven gear.
---the exhaust port spacing is the same for both engines
---'79 & '80 cb650 intake ports will mate with SOHC cb550 and cb750 carbs

also as a side note for anybody checking this out: please take a look at the links in my signature, I have a blog and donations can really help me out trying to start this and eventually have a business. Thanks!

-Alex

[bmx4637]

Hey all, I received a cam today    to replace my pitted one 

[bmx4637]

been designing how I want my engine stand to be. However I am planning on moving in about a year, so I am looking for a second job to save money.

I will have to postpone any serious work on this build for now until my next place has a garage

[bmx4637]

Ok, so apparently I am not moving. Therefore, I went to harbor freight with a coupon of 20% off to buy a 1000lb engine stand to move on with my build 









I am currently designing the fitting between the stand and the engine mounts that will allow access to all over the engine without interference. I'll then buy the steel and weld it.

Once I have a good fitting for the stand and engine you guys can let me know if you want one for the cb650, or you can send me some pics/video and measurements of one to fit your engine, like 550,750 and others, and the first one to come with me for a different engine I'll do it for free (just pay for shipping and materials).

I plan on getting a few things here and there every paycheck. My list of things to get contains torque wrenches, calipers, and to make a nut and bolt reference standard for starters.

-Alex

[onepieceatatime]

Here are a couple of links on "custom" engine stand adapters.
http://forums.sohc4.net/index.php?topic=55910.0

http://forums.sohc4.net/index.php?topic=62788.0

I bought the same stand, but have not made anything to put my bike engine on there yet since it is holding the 350 bored 30 over that will be in my truck when I get the time to do it.