Black bomber head

[Tunz]

hi guys, hope I got this posted in the right spot.

I recently purchased a 67 cb450 black bomber. It's got some nasty broken fins on one side where a car backed into it while in a garage. Everything is there for the bike and is in relatively good shape for a 67. Gonna start a restoration! BUT my question is...does anyone know if 67 head would be interchangeable with a 68 or even 70 and so on. I think at least the 68-70 have the same torsion bar set up for the valves??? I checked on a european site that has all bomber parts, but a new head is 700 euros and then shipping to canada!!! wowsers! Lookin on ebay i found a 68 head as well as numerous 70-72 heads that all look like they have the same valve set up. interchangeable or not?? would save me a lot of money if so! I know they changed from a 4 speed to a 5 in 68 i beleive, but I wouldnt expect that that would effect the head much? or would it even be a mild upgrade?

any help would be greatly appreciated!

thanks - Tunz

 

[teazer]

I'm not the expert, but they did have the same torsion bar springs right up to the last CB450K whatever.

Grab one off ebay and if it's not the same, sell it on. I'd be surprised if it changed much. You could check an on-line supplier for a few different years and see if the part number changed much.

 

[DrJ]

All the CB450 double cams use torsion bars for the valves. But wouldn't bet on the heads being the same. The Black Bomber engine is a 4 speed while the 68 K1 and onwards had 5 speed motors.

 

[Tunz]

yeah I knew they changed to a 5 speed in 68 or 69, but I'm wondering how much they would have changed the head. They may have made a few small changes in the head, but as long as it would work, I'd be cool with that. I wanna restore it, but I'm not exactly a Honda purist. If its not an "actual" 67 bomber head, i dont really care. Just want something that is functional and performs/looks better then a bunch of broken fins.

I know I've heard of people fixing broken fins as well, but I heard it can be costly...and these ones r pretty nasty...

 

[teazer]

I have had a few fins welded up by a good welder and then ground back, but it's a lot of work to make them look original. Just grab a head off ebay and see if it's any different. There's a couple of heads on now from 25 bucks with bent fins, 40 looks good and so on.

4-5 speed and 450-500 changed some bits but I'd be surprised if you can't use any head.

 

[Tunz]

right on, thanks man, I just might try it, but I'm not the richest guy out there right now haha, a little hurtin for cash, would be awesome to know for sure if one would work before i ordered one. I do know someone who welds fins up, but not sure how much he'd charge me...haha i wouldnt even care if he just welded on flat rectangle fins, I could grind em to shape...guess I'll have to see! So stoked about the new bike though! Gonna be a fun lil ride!

 

[bluenose bomber]

The heads are not interchangable. While the torsion bars are the same in all 450s and possibly the 500T,not sure on that one. The rest of the top end isn't. Unless, you use everything from the cylinders ( pistons too) up to and including the head, cams etc, you will have troubles in which case it's easier and cheaper to replace the engine with a later 5 speed model, it would bolt right in, and forgo the 4 speed. Even a 500T change out will work, as some feel the gear set is the best of the entire 450-500 series. Go to www.hondatwins.net loads of info on the BB and the 450s in general. Someone there will give you the correct answers to any questions on the BB. A classic, IMHO. I have a 66 BB and love it. rollie

 

[Tunz]

Ok thanks for the info! Not exactly what I was wanting to hear haha, but at least I know my options now. So basically you think any of the 450 engines will fit right in the frame? any one from 65-74 that is. I gotta say the 5 speed would be a bonus! So i guess I'll look for either another whole engine or if i can find a good used set of heads, cylinders and pistons.

I just joined hondatwins...asked a few questions, just waitin for reply.

 

[teazer]

Bluenose, what are the differences in simple terms? Are the barrels significantly different or the piston crowns? I'm trying to understand what the major changes were.

 

[bluenose bomber]

The 4 speed, parts # 283, has a lower compression, 8.5:1 , while the 5 speed, parts # 292, has a higher, 9:1 ,and are interchaneable among the 5 speed 450s. The 500T is different again. The intake/exhaust cams are profiled different between the 4 and 5s. Valve guides and tappes are different in the early 450s from the later ones. Torsion bars are the same, easy swap 282 to 292. Valves have different numbers 283/292 between inlet and exhaust. The valves measure the same between models so, use them if you want.The header pipes on the 5 are different too. The head clamps that holds then in has a different bolt width, wider inthe K1 and on. There are even differences between 283s, therefore the engine ID number is really important to get the correct part for your engine. Most of the 5 speed parts are interchangeable, with a few minor exceptions. It may have been to abrupt to say the heads couldn't be swapped. You can do anything with time, $$ and a good machine shop. It've been better to say its not recommended. Too expensive and too complicated to be worth the bother. Cheaper and a lot less hassle to change the entire engine. Hope this helps. rollie

 

[Tunz]

thanks alot rollie - love all the info! This is the stuff I live for!!

I have a new buddy that I may be visiting on monday who says he can fix broken fins. So I guess I'll see how much he would charge to fix mine...like i say its a pretty nasty section of broken fins. he'd prob have to break more to be able to weld em all. I guess if I could get it done for a 250$ or less range I would be ok with that. If not, I think the chances of me finding a 67 head is gonna be pretty slim. I've looked on ebay and all I can find r later model heads and engines. So Then, I guess the question would be - what is the better motor/year? I've heard from some that 500T has best gear ratio...but also from other honda guys that the 500T tended to have more issues...what they are I dont know. I kinda like the ida of keeping it a 450...keep er a bit lighter and abit more true to the real bomber and all that jazz.

I took apart the carbs to clean at work today and noticed that all the gaskets and brass muct have been changed before it was stored 6 years ago...everything looked basically brand new, including the floats (though they are stamped 67) Also the points looked fairly new considering...gave er a few kicks and got nice nice big blues sparks through some new plugs....but alas, in my excitement to finish the carbs up at work, I must have forgotten on of the mixtures screws on my bench!!! What a piss off!! So wanted to start er up tonight. heres hoping the screw really is sitting on my bench when i go in tomorrow morn. Electric start isnt workin either, but the solenoid is clicking, so im leaning towards a solenoid swap...didnt try crossing it yet or anything, kinda lost my umph once I realized I had forgotten the screw. SO hopefully this weekend I'll hear her roar!! as well, i will post some pics...and maybe a video...if I can get er up and runnin!