Topic: K8 Highway Racer - Finished

[JoeCooley]

If this is an 836, can I use the cylinders and head on my k8 cases? That way I don't have to worry with the sprockets not lining up. Ive read that the early k engines had the front sprocket 10mm further inward and I don't think I can make things line up with my bike due to the large rear tire and offset sprockets required.

[JoeCooley]

Started tearing into it. So far I've found a couple curious things.

Three different bolts and nut that don't seem Honda. They are all also 11mm head.


And a missing bolt under the #1


Hmm... let's see what I find.

[JoeCooley]

Well I dug deeper into this "hot cam 836" and guess what? It's not an 836 at all. But no fear, I have a set of 65mm pistons and will just have the cylinders bored.



Also the cam appears stock k2 from what I can tell by looking at other stock cams? Maybe someone can look at it and surprise me with good news?


The head appears to have some polishing in the chambers but it's pretty crude. It also looks like the intake valves have kissed the pistons. So they are probably bent. I will rework it with a little port work, new cycleX valves and springs, and a good Polish in the chambers. Good for a couple hp.


I'll keep you guys updated with the progress.

[madmtnmotors]

Three different bolts and nut that don't seem Honda. They are all also 11mm head.

Those bolt heads are not "11mm" but are 7/16" and are SAE grade 5. Quite the abomination you got there....

[JoeCooley]

Well yeah, the bolts heads are 7/16. The other nuts were various types (nylon locking, non-locking, flanged nuts, etc...). All of these fasteners were removed with an 11mm socket. But yes sir, you're correct.

[madmtnmotors]

Well yeah, the bolts heads are 7/16. The other nuts were various types (nylon locking, non-locking, flanged nuts, etc...). All of these fasteners were removed with an 11mm socket. But yes sir, you're correct.

The markings on the head of the bolts were a clear indication. The threads on those bolts will be SAE as well (not metric threads). The studs at the cam towers look to be rather coarse and I'll wager that they are SAE threads as well.

That sure is a lot of RTV...

[JoeCooley]

That's a good point. I will check the threads on the studs and bolts. I didn't look it over too much last night but will tonight. Hopefully they tapped the holes or used helicoils if the threads are std. If not I guess I have some thinking to do. I might just scrap this head.

[JoeCooley]

Ok so this head and most of the engine is trash. I will salvage the covers and maybe a few other parts. There are numerous bolt holes with destroyed threads and the amount of time and money required to repair is just too much. I picked up a 75 cb750F head on ebay. I've also put in a large order with cycle x and Z1 Enterprises. Hopefully the parts will come in quickly. I really want to start this project next weekend at the hobby shop we have on base. The cylinders are getting dropped of today after work for cleaning/boring.

I'll keep up with the updates for anyone that is still following.

[madmtnmotors]

I might just scrap this head.

Hang on to it for now, spare parts are good to have! You might eventually realize that you can restore the mangled threads once you have repaired a few. If the holes are hogged out too big for a Helicoil repair, then a Time-Sert repair might work better. After you have gotten used to making thread repairs they tend to get easier to do. I surprised myself last weekend when removing the front passenger seat from the wife's car one of the mounting bolts was seized and snapped when trying to remove it. What surprised me was I did not get pissed. I wasn't happy about it, but my first thoughts were how to best approach the extraction process of the remnants, as opposed to throwing things  . I was able to remove the broken portion without drama, but would have been prepared to repair the threads if necessary. 

[JoeCooley]

Yeah I plan to keep most of this engine. Im going to tear this head down and practice my porting skills. That way I have some practice with the die grinder when I get into the 75 F head. I'm not doing anothing extensive port job, mostly just cleanup and polishing. It's been a few years so a little practice will be good.

[koendd]

cool project!

just make sure you don't swap K and F engine parts it's ok.
It can be done but you have to make some adjustments.

[JoeCooley]

This engine will be exactly that.

 K8 - cases, crank, rods, trans
K2 - cylinders, cam, cam towers, camy followers, chrome covers
F1 - 392 head

I will make it all work...

[madmtnmotors]

This engine will be exactly that.

 K8 - cases, crank, rods, trans
K2 - cylinders, cam, cam towers, camy followers, chrome covers
F1 - 392 head

I will make it all work...

No adjustments required for that recipe, everything should fit together without drama. The bike I'm racing now had some similar issues as yours, in that there were a number of bolts missing and some were broken.

Runs good now though!

[JoeCooley]

This engine will be exactly that.

 K8 - cases, crank, rods, trans
K2 - cylinders, cam, cam towers, camy followers, chrome covers
F1 - 392 head

I will make it all work...

No adjustments required for that recipe, everything should fit together without drama. The bike I'm racing now had some similar issues as yours, in that there were a number of bolts missing and some were broken.

Runs good now though!

Thanks for the reassurance. I assumed it would all work do to the head only having .5cc more combustion chamber volume than the 72k. I'm running the 72 block with early style flat 836 pistons which will help maintain the c/r. I will be working the head and milling .010 as suggested by Honda Man in this post.
http://forums.sohc4.net/index.php?topic=7401.0

Are there any major differences in the 78k and 72k camshaft? Which would be better for my build?
There is a 70k sandcast cam on ebay. Is it worth it to use that cam? I read that it is more aggressive than later years.

[madmtnmotors]

I'm using an F1 head with my K8 crankcase and cruzinimage flat top 836 pistons with an F2 cam. Best 1/4 mile so far was 13.38 @ 97mph. I'm a geared a little too tall with the sprockets since I'm just hitting redline in fourth gear at the finish line.  Just installed a Webcam 41 (CycleX CX-1) and will be doing some test and tune at the local track very soon. I will be replacing the baffle in my MAC muffler from the "Z" baffle to a straight through glass pack baffle after a few baseline passes with the new cam. After making a few baseline passes with the new baffle I'll change out the sprockets to try and push redline in fifth gear at the stripe.



I've heard earlier stock cams were a little more aggressive, but I have no first hand experience with them. The Webcam 41 is more aggressive than any of the stock cams AFAIK yet is still fairly mild with good low end response.

[JoeCooley]

Hell yeah! Nice launch!

[JoeCooley]

Just a quick update:

Engine is out an disassembled.
K2 cylinders bored to 65mm with .001-.0008 clearance.
Rings gapped to .010 1st .013 2nd and installed on pistons
Ape studs installed
New cam chain and tensioner installed

I noticed a lot of wear on the k8 (8 bolt) rocker shafts. Appearantly this is common. So I will be using the k2 shafts.
The f1 head still hasn't shown up so I will use my k8 head. Just going to clean it up and slap it on. Then I will do up the f1 head and install latter with the HD springs I have and maybe a cx cam.
I will also be swapping to the chrome covers. I still need to drop the pan on the k8 engine and check the oil pump. The k8 had great oil pressure and looks very fresh inside. Not sure of milage but the cylinders were in great shape and the pistons only have minimal wear on the skirts.

I will upload some photos tmrw. It's late and I'm very tired.

[JoeCooley]

I'm also in dire need of a lower rear engine bolt. The bolt was belt and had to be cut to get it out. If anyone need sandiego has one to spare, it would be great. .

[JoeCooley]

It runs!!! I only rode it about a mile back to the parking garage, but it felt great! Much smoother than before. The sense of accomplishment is amazing. I'll be picking up a lower engine bolt this weekend and then I plan to put a few break-in miles on it. Then an oil change. Im so happy right now! Haha

[SOHC4 Cafe Racer Fan]

Nicely done!

[JoeCooley]

Thanks!

[SOHC4 Cafe Racer Fan]

It's always a HUGE relief after taking an engine apart to have it run (and not leak!).

[JoeCooley]

I've put some breakin miles on it following the hard acceleration/ hard deceleration method.  Now it's time to change the oil.

The power comes on smooth and there's plenty of it. It's so much more responsive than before. The big bore is really taking advantage of the CR Special carbs. The weird part throttle stubble and hesitation is now gone and the idle is much more stable.

Clutch  was kinda slipping before the rebuild, now it really slips! Good thing I have a new CycleX clutch set. That's on the list for tomorrow.

Overall I'm very happy with the bike. I've already gotten tons of compliments from strangers. Not many even know what it is... haha!
Feels good man...

[SOHC4 Cafe Racer Fan]

Such a better ride than that Enfield.

[JoeCooley]

Such a better ride than that Enfield.

Thanks bro!

Special thanks to forum member Ted ( Ricky_racer ) for providing the engine bolt and conversation. It was a pleasure to meet such a good guy and shoot the #$%* for a little bit.
Also, big thanks to this forum and the ton of knowledge it supplies. It's made this project a success.