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Discussion Starter #1
Can anyone tell me which of the 70's Honda CB's share the same platform?
Actually, how much smaller (if any) is the CB550 platform than the CB750? I am getting ahold of a basket case 71 Kawa H1, and have been reading how terrible the handling, brakes, etc seem to be on those things. I have heard that the CB550, CB400, and CB350 platforms are great handling bikes, and would like to swap the H1 drivetrain in. I have searched around, and not really found any solid info. What would be the best CB platform to attain and fab up for a project like this? I am thinking smaller, lighter, better handling, etc.
Thanks y'all.
 

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quote:
Can anyone tell me which of the 70's Honda CB's share the same platform?
Actually, how much smaller (if any) is the CB550 platform than the CB750? I am getting ahold of a basket case 71 Kawa H1, and have been reading how terrible the handling, brakes, etc seem to be on those things. I have heard that the CB550, CB400, and CB350 platforms are great handling bikes, and would like to swap the H1 drivetrain in. I have searched around, and not really found any solid info. What would be the best CB platform to attain and fab up for a project like this? I am thinking smaller, lighter, better handling, etc.
Thanks y'all.
Putting an h1 motor in a cb frame is a waste of time, there are better alternatives.

As someone who owns both h1's and cb's, let me take this one step at a time.

Kawasaki H1's are not as bad a handeling bikes as you think, 9 times out of 10 the rider is the problem. With an H1 you have a really high strung motor in a frame that is not really setup take the kind of power hit they devlop, so you get all sorts of weird handeling characteristics when really pushing the bike. While riding normally though I would say an h1 doesn't handle any worse than any other 70's bike. The old joke about kawasaki's was that their motorcycle test track had no turns (this was true as it was the WWII runway for kawasaki aircraft) and that is why they never devloped good handeling.
There are 3 generations of h1 frames:

1969-1972: these are what I call open ended frames because the last cross brace on the frame is actually the grab rail which bolts on. These are the frames that devloped the h1's bad reputation for flex and wobble. they are the least braced frame there is and consequently the worst, they are also the best looking.

1973-1975: This is where the h1 became a more refined machine. The 73 h1 actually uses h2 electrics (750cc) so the h2 motor is a direct swap (other years you have to use the h2 harness but it physically bolts in). slightly heavier, I owne one of every year from this era and find that 1) they are decent cafe bikes with attitude in which a lot of frame problems were solved, and 2)I have no business owning a triple as I have manged to blow up every one I own. Seriosuly though this h1 frame is the second strongest frame and is even stronger than the h2 frames from the same year.

1976 KH500: This is the best h1 frame. It is fully gussetted from the factory and has no unwanted flex whatsoever. A lot of drag racers and road racers look for this frame when building their bikes. Jack it up one inch in the rear and drop her an inch in the front and the bike will easily handle with any cb (and sometimes outhandle).

upgrades:

the 1973 and up disc brake front end is the best front end there is. It used to be dual disc was the hot setup but now there are kits to adapt the ex500/zx6 caliper and m/c to these bikes which makes them brake awsome, single disc will outstop any 70's dual disc and a dual disc ex setup is actually overkill (but looks cool). You will need to deck your brake rotors or get 5.5 rotors off a kz650.

Some guys, like myself, have chosen to do fzr400 rear swingarm swaps, and fzr/gsxr front end swaps. This is a lot of work but totally worth it. e-mail me and I'll shot you some pics.

The ultimate setup however, and it is fairly easy to do, is to put a 500 engine in the s1/s2/s3 (250-350-400) frame (the s3 being ideal). It requires a little work ut is well worth it. The bike is more stabel than a standard 500, lighter, the s3 is the best handeling triple ever made (excluding the h1r and h2r roadracers). I have a friend with one, and he never fails to rip my cb750 to shreds with it, I have ridden his and it feels like a scapel for a 70's bike. s3 400s are cheap with blown up engines because the engine parts are discontinued.

everything you ever wanted to know about triples can be found at these two sites:

http://www.kawasakitriplesworldwide.com/

http://kawtriple.com/mraxl/

here is the ex conversion:
http://kawtriple.com/mraxl/caliper/conversions.htm

and the 500 into 400:
http://kawtriple.com/mraxl/khconv/400to500.htm

Now on to your cb question:
don't waste your time putting an h1 into a cb frame, but if you wanted to ruin a perfectly good honda frame use a cb400/4 supersport. A cb750 frame is too much weight to push for an h1 to be a practical engine, same with a 500/550. For an example of this see the 500 plus lbs suzuki waterbuffalo (750cc 2 stroke and just not a screamer).

The cb500/550 is actually a lot smaller than the cb750 although you would never know to look at them side by side. the 50+ lbs weight difference should be an obvious tipoff. the engines are not interchangible and it is a pain in the arse to swap one into the other. A few items interchange like the caliper. If you want to build a real retro screamer, take a cb650 four (up to 1982) engine and put it in a cb500 chassis, then you have the looks of of an early cb500 and the go of the later 650 (which was pretty close to the k3-k6 cb750s).

The cb350 four is in my mind an underpowered bike (my 280lbs ass on a sears/gilera 106ss outmuscled my buddys cb350F on a regular basis) and anythign you stick in that frame is an improvement. I don't think it is that great a handler as she runs out of conering clearance way too early, even for a 70's bike. the 400 four supersport is the cb pocket rocket in my opinion. handles nice, lots of upstairs power, cool looks. if you have to ruin a cb, this is the one, but the bike will lose it's most distinctive feature - that kickarse header.

a 1971 h1 restored will bring almost as much as a 1969 diecast cb750, which is a lot in the old jap bike world. If you must destory those beautiful lines by putting the engine in something else, then trade it for a later h1 as the early electrics were junk to boot, even a basket 71 should get you a 74-76 bike in better condition. With the new engine think about an ex250 frame or an 80's ninja 600. Both have had triple motors swapped in and it improves the handling a lot. I would even try an fzr400 if I could find a decent roller for decent money (the sprockets come close to lining up on that one). I know there is a guy in the netherlands who put a 750 in a zx400r chassis, says it handles like a dream. If you are going to spend the effort to do a major swap, why not do it to something that has had decades of refinements. If you must have the vintage looks of an old 70's bike, harris makes a reproduction h1r frame, but be prepared to shell out $1200 for it. Airtech makes the bodywork, and the rest is up to ebay.

there's more but I am tired.





Edited by - Geeto67 on Sep 13 2006 01:19:00 AM
 

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hell, i hate running a cb motor in a cb frame..... it is kinda heavy, ugly and not so strong. i am not a big fan of a pressed steel frame.


dude
 

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quote:
hell, i hate running a cb motor in a cb frame..... it is kinda heavy, ugly and not so strong. i am not a big fan of a pressed steel frame.


dude
yeah I forgot to mention that: all the fours but the cb750 and cb650 have pressed steel front sections, much heavier than the tubular steel frame of the h1 (I have seen street prepped h1's in the mid 300 lbs range - I have even seen one that was 300lbs even but the bike was heavily modified to get that low).

I also didn't mention the cb350 twin because even though the motor will physically fit, it will flex that frame somtheing awful, plus the cb350 is a really good runner with the stock engine.
 

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Discussion Starter #5
Sweet guys, thanks for the info! I guess I just ran across a bunch of bad information. Your input was just what I have been looking for, way to go.
 

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Try swapping a CB engine into a RD350 frame. They're light and handle well. I don't think a CB450 engine will fit in there, but a CB350 engine might. I have an extra frame or three if anyone wants to give it a shot.
 

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Discussion Starter #7
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Try swapping a CB engine into a RD350 frame. They're light and handle well. I don't think a CB450 engine will fit in there, but a CB350 engine might. I have an extra frame or three if anyone wants to give it a shot.
Sweet deal, man.

All this info you guys have put out is great, we should add it into a F.A.Q. thread or something.
<img src=icon_smile_cool.gif border=0 align=middle>
 

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once again I forgot to add (ok I am just trying to beef up my start count the old fashoned way...ahem...branson) that all of kawasaki had a rep for bad handeling. The A1 and A7 as stock bikes were notoriouslty bad handeling bikes as compared with honda superhawks and yr1's of the era. They had a tendency to speed wobble and this firghtened a lot of riders. The 1969-1970 h1 inehrited thsi characteristic and kawasaki fitted them with 2 steering dampners to compensate. by 1971 the bike was back to one steering dampner. The first gen h1's short wheelbase is what makes the bike so twitchy, combined with the 2 stroke power hit and the flexible first gen frame.

Out of curosity, why put a cb350 motor in an rd350 frame? The rd is faster, has as many speed parts as the cb350, and you can't really run it in any racing organization like that. If you are going to put a motor in an rd frame, put in someting like a 90's sport bike motor, really have some fun.

I once saw a guy who put an fzr600 motor in an h1 frame. The dimensions are pretty much the same except for the radiator. Bike was fast as stink. He blew up the h1 motor and had the fzr600 lying around so in it went. Looked cool as hell because he kept all the stock bodywork. Had to gusset the frame and weld new mounts and in she went. I will say this, the bike was much smoother and almost vibration free as compared to the old h1 mill, plus it was a heck of a lot more reliable. I would love to do that one day but the kawi triples guys know where I live and they would surely beat my ass for it.
 

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If someone put a CB350 engine in an RD frame they could put a hurtin on some folks in the SV classes.
That would be a very cool, and probably quite fast combo.
JohnnyB
 

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If someone put a CB350 engine in an RD frame they could put a hurtin on some folks in the SV classes.
That would be a very cool, and probably quite fast combo.
JohnnyB
not familar with the sv classes...explain. how would a cb350 motor have an edge that the rd350 motor wouldn't
 
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