69' 450, 71' 450 engine swap?

[jkphila]

im going to try and stuff the motor of my 69 into the body of the 71. Why?
i bought both bikes for super cheap, but they have their issues.
the 71 is in great physical shape but has a hole in one of the cylinder heads. i bought it with the engine already pulled.
the 69 looks like it was stored outside for a long time but the odo reads a mere 4000 miles.
im not ready to do a full tear down of the 71 motor right now, neither the time nor money.
questions
1. i suppose i should get the 69 running before pulling it apart. this thing hasnt been run in 20+ years, are there any special precautions i need to take before trying to get the thing to turn.
2. does anybody see any compatabilty issues with the fit or otherwise?

 

[teddpage]

To get the one to run, make sure that the engine turns over freely. Do a compression check. If you are up around 150 psi on both cylinder, then i'd say go ahead and make sure the carbs are clean and replace the points. Put some fresh fuel in the tank and cross yer fingers.
As for compatibility issues, i dont think there are any. My dad has a 69 and i have a 72 and they are both identical engine wise. They changed a few things like headlight size, the way the seat mounts, front drum to front disc. Aside from that the bikes are identical.

 

[Whitey80]

As an owner of a number of 450's running '68-'72, they are completely interchangeable. Any parts will swap back and forth (in groups, that is. You can't put a disc wheel in an earlier bike without the whole frontend and vice versa.)

PAY ATTENTION: The wiring diagram is the same, but a few of the colors were changed from your old motor to the new, so keep an eye on that bit.

 

[frogman]

69 to 71 LITTLE changed between models. 72 was when it got the changes to the front end, Pre 72 front disk ends are the same as the 750s of the era and have larger brake pads and more contact on the disk. Just so you know.

As far as getting it running, I would pull the inspection covers off the top where the cams are and LIBERALLY lube the hell out of everything in both sides with some GOOD engine oil maybe slather some grease on the cam lobes. CHANGE the oil before you want to run it as what is in it might be two thin to do any good. 450's have plunger style oil pumps that need a decent viscosity to WORK and you will demolish an other wise good engine running 20 year old oil even for a few minutes.

GET a manual, period. These are probably the most complicated twin engines you will get your hands on. Just the valve train alone is super complicated compared to a normal coil spring.

Just for curiosity's sake what's the hole in the head look like?

 

[teddpage]

Not to hijack yer thread, but hey Frogman...are you saying a 750 front brake will work on a 72 450? Im running a 72 450 and my front brake could use some help. Any input here broski?

 

[jkphila]

alright then, that should be enough info to get me started. i'll try to bring all your tips to bear this weekend. as for the hole in the piston, i'll try to get a shot of it and post it up. thanks

 

[frogman]

Not to hijack yer thread, but hey Frogman...are you saying a 750 front brake will work on a 72 450? Im running a 72 450 and my front brake could use some help. Any input here broski?

If you look at the parts fiches you will see that the numbers and the parts changed RIGHT at 1971 model year. Up till then, Honda used the 750 sliders, disk, caliper, and possibly the forks. FOR 72 and up they went with the smaller stuff that the 350s and later 360s had. NONE of the earlier stuff will work with the later aside from the lines. You can swap out the later front end the the earlier OR run down a 750 front end and put it on. COULD go hunt down a DUAL BRAKE system.

Side note, if you get steel braided lines, get your front disk DRILLED and GROUND smooth, (don't turn them) Maybe change the MC to a newer style then that should help make it better.

 

[manualofman]

lol digging the hippy paint job on the tank for the 450 on the right! i hope you're keeping it!