Topic: K7 engine on a '76 frame?

[apocalypsebob]

I am thoroughly confused by the search function here, so if anyone knows of a thread that has already beaten this subject to dead-horse status, by all means point me in that direction please.

But I have a '77 SOHC engine that I have been slowly bringing back from the dead. In fact, I have the majority of a basket case for the 77, minus a frame and front end. I finally have a lead on a titled frame in my area, but it is from a '76. I understand that 77/78 had a different chain clearance. I was wonder if it is at all possible to mate the K7 engine to the 76 frame? I have been told that if I wanted to hardtail the bike, I can get a particular section that will work for me. But what if I want to build more of a stock-style bike? Is there a laundry list of considerations and changes that would need to be made? Certain parts that will have to be replaced with pre-77 parts? Or is it just not going to work period? Any help or pointing me in the right direction is greatly appreciated

[ekpent]

Cheapest way I think would be an offset sprocket but you will get other useful suggestions from folks who have actually done it. Is the bottom end of the engine apart right now by chance ?

[750K]

The 77-78's have the sprockets offset a few mm's, I can't remember how many. So you'll need the sprocket carrier from a 77-78 rear wheel and you'll have to fab a longer upper rear shock mount on the left hand side of the 76 frame. That way you get the clearance for the chain and left rear shock, I think the rear swing arm is a tad wider so most likely you'll need a 77-78 swing arm, axle and rear wheel spacers. The rear rims were the same iirc, the 77 motor will bolt right up to the 76 I think as well. I haven't done this but remember reading up on the differences between pre and post 77 bikes when I bought my 77k a few years ago. Someone will chime in if I'm wrong or forgot anything. I'd keep the pd style carbs of the 77 for the accelerator pump but finding new carb to manifold rubbers can be a #$%*.

[apocalypsebob]

... I'd keep the pd style carbs of the 77 for the accelerator pump but finding new carb to manifold rubbers can be a #$%*.

haha, and wouldn't you know it - i only have three of the carb boots!!

[750K]

Carb boot 1 & 3 are still available from Honda, 2 & 4 are NLA. You can flip a set of 1 & 3's and they will work but it's not 100% at the correct angle once flipped. It works though, I did that till I found a good set of #2 & 4's. They pop up on eBay from time to time.

[Tugboat]

Here's the lowdown:
http://forums.sohc4.net/index.php?topic=103649.0

[apocalypsebob]

Ok - first, THANKS, haha. My head is spinning but ... i'm definitely in the right place! So let me see if I have it right ...

I have (more or less) a complete basket case of a 77k MINUS the frame.  So I have the 77K rear wheel, swingarm, and sprocket & carrier.

My frame, however, is a 74K frame.


So if I understood that correctly, I will be ok if I'm running the 77K rear wheel/sprocket/swingarm as well?

If so - what is my best option for rear shocks? Is there an aftermarket solution - or will I need to find OEM - and if so from which year?
Thanks - I'm getting there!


This would be a whole lot easier if everyone hadn't torn these things into a million pieces, lost half the pieces, then sold the rest of them to us from their back yards twenty years later!!!


... but it wouldn't be half as fun!

[Tugboat]

Your sprocket carrier & swing arm are 10mm wider than on the earlier bikes. To compensate, the 77/78K's (and F's) had a 10mm shoulder where the LH shock attaches to the frame, so that the shock stays perpendicular to the ground. Otherwise it would be crooked, dig? Your 74K frame does not have this shoulder and thus, if you were to install the 77K swing arm & wheel, your shock would not line up correctly.

To make this work, you'll need an earlier wheel/sprocket carrier, an earlier swing arm and the 10mm offset sprocket from CycleX.