Topic: CB750K6 the miraculous running Buffaloe

[lucky]

Well, my fiance named her (him?, whatever) Buffaloe while we were trying to think of names. So being the gentleman, she knows best 

Anyway, according to the PO, this is a bike that just needed "the carbs cleaned". Right.
My list of what I've done so far, which you may have seen a little of in other forums.

New exhaust, as he had a very "harley" sounding exhaust on it, and it really did rumble like a chopper. More on that later.
With this new exhaust came removal of the old spigots, and replacing them with the studs and fins. Thanks to hapakev for the headers!
Ordered a CycleX muffler, the "quiet" supersport. It's pretty restrictive, but I'm not looking to deafen people, and combined with the 4-1 headers, should make for no need to replace jets.
After adjusting valves, I noticed 1-4 didn't seem to spark. Ie none at all. So I ordered some points, got them on today, and VOILA it doesn't sound like a harley anymore, it's amazing how different it is now!!!!  Whoops...
I delved into the electrics, installed a new left hand switch, and I'm going to deal with lots of shoddy connections at some point. Needed a new flasher, and I'm probably just gonna find a bunch of new bullet connectors.
In the process of all this, cross threaded a spark plug, so I've ordered a thread chaser, hopefully to rescue it. It still runs now though, with no loss of compression so I'll just go easy on it until then.

And now, I'm about to adjust the timing and then the carbs, and take it for a spin tomorrow!

BTW, she made lots of awesome popping and gurgling as all that gas from running on 2 cylinders got thrown out of 1 & 4. Guess I have no choice but to get new plugs now, they're almost definitely shot after the abuse they're getting.

Before you adjust the timing, or adjust valves, the cam chain slack must be taken up.

[lucky]

Well, project has come to a grinding halt. Crossthreaded plug number 2, and tried to fix it. Just totally messed it up instead.

Always start spark plugs by hand just turn the socket with extension NO RACHET so you can feel if it is going in correctly. No it will need a time cert installed.

[K5owner]

+1 on Lucky's suggestion to thread em by hand. I also use an anti-sieze compound on the threads (just a little, slighty above the first threads).

[bjbuchanan]

Autozone has free tool rental, just go in and ask for a valve spring compressor to rent. Depending on your local store they may have 2 styles to choose from. You pay up front the total cost of the tool and you got 60 days to return it in one piece. When you do you will be refunded the full cost. Don't worry about losing the receipt either because they can just look it up because it will be warrantied.

I wear those horrid red shirts daily

[70CB750]

+1 on Lucky's suggestion to thread em by hand. I also use an anti-sieze compound on the threads (just a little, slighty above the first threads).

I use a piece of hose to thread them in.  Works wonders on 2 and 3.

[buffaloejon]

Well not really valve-less, but less-one-valve. I'm a dummy, and while trying to change valve guide seals, lost a set of the keepers. And by lost I mean launched across a local lawnmower repair shop. After driving around town for almost an hour trying to find the clamp style valve spring compressor, as I couldn't make the puller style work with the double springs, I ended up at a lawnmower repair place, using one that was *just* a hair too small for the valves. So, I found a little piece tubing to use as a spacer, and the little clamp jumped off the valve cause I wasn't being careful and PEW, they were gone. Heard them clank across the shop, long gone. Little buggers. And I still only changed 3 of the seals... Good thing though, the old ones are all original and hard as rock.

In fewer words, I'm a dweezle and boogered it up.

[K5owner]

Don't fret the small stuff. I've goofed up more stuff than I can remember 

Here's a couple of leads.

$1.49ea +shp *double check to make sure these will work for your bike
http://www.ebay.com/itm/79-HONDA-CB750K-CB750-FOUR-K-VALVE-KEEPER-COTTER-/400262840579?hash=item5d31864103&item=400262840579&pt=Motorcycles_Parts_Accessories&vxp=mtr

$3.14ea +shp
http://www.cyclepartsnation.com/pages/OemParts?aribrand=HOM#/Honda/CB750K_A_%2876%29_MOTORCYCLE%2c_JPN%2c_VIN%23_CB750-2540001_TO_CB750-2575894/VALVE_ROCKER_ARM_%2b_VAVLE/CB750K-76-JPN-A/2Y133416E13341605A

[valt]

Whoop whoop got the head helicoiled! I was at least expecting to leave it at the shop for a couple days, but nope, we got it done right then and there for 25 bucks! But now, what am I supposed to do for the next few months!?

Looking over the engine a little closer, it appears there was a massive oil leak at some point between the head and cylinders in the front. Pretty thick mess of sand and oil turned into concrete oil-goop. Hopefully once I get the new gaskets put in it won't do that.

So two questions, gasket-sealer or no? And what the heck are the ( little green pieces in my gasket set? They appear to have springs wrapped around them and another metal ring about halfway...

That motor definitely has a bad head gasket leak. If I were you, I would get new/better studs as they tend to stretch and let the head gasket leak. They aren't that expensive or hard to install. For not a lot of money it can definitely save you a ton of headaches.

[buffaloejon]

valt, the reason the head gasket was leaking is because the PO took it apart to replace the original head gasket, and ONLY replaced the head gasket. Every other piece of rubber was original. And when he replaced the gasket, he didn't bother to clean the gasket surfaces whatsoever.

I'm thinking that since I'm stalled (again) anyway, I may ring it, hone it, and deck the gasket surfaces. And new studs, if that's suggested. Found a good machine shop when doing the helicoil, and I'm sure they'd do all of it without much hassle.

[buffaloejon]

Alright, well it's put back together, motor in the frame, and everything done but vacuum synced carbs, finely timed ignition timing, and electrical gremlins found.

Runs quite well, idles at about 1900, revs well about that. 1 is rich, 4 is lean(maybe, maybe not), couldn't be bothered to pull 2 and 3 with a hot exhaust (which speaking of, all 4 are hot, after a short time, all enough to sizzle a wet rag, so they're all firing!!).

So carbs desperately need tuning now, gotta figure out why 1 is rich and 4 looks decent... will look at 2 and 3 shortly.

But, the clutch seems really short, and the friction zone is at the very end of the clutch release... rideable, but obnoxious.

List of things done, mostly for my own good:
New chain
Valves timed, cam tensioned
New valve stem seals
new head, head cover, points cover, starter cover, breather cover gaskets
new 4 orings under cam towers, new pucks
Carbs cleaned
(insert more here, I'm sure some was forgotten)

And of course, gotta have a picture!



Will add some more when I have them, hopefully I'll test drive it tomorrow, didn't feel that ambitious today, terrible day.

[thrutheframe]

Well not really valve-less, but less-one-valve. I'm a dummy, and while trying to change valve guide seals, lost a set of the keepers. And by lost I mean launched across a local lawnmower repair shop. After driving around town for almost an hour trying to find the clamp style valve spring compressor, as I couldn't make the puller style work with the double springs, I ended up at a lawnmower repair place, using one that was *just* a hair too small for the valves. So, I found a little piece tubing to use as a spacer, and the little clamp jumped off the valve cause I wasn't being careful and PEW, they were gone. Heard them clank across the shop, long gone. Little buggers. And I still only changed 3 of the seals... Good thing though, the old ones are all original and hard as rock.

In fewer words, I'm a dweezle and boogered it up.

Don't fret little mistakes.  I rebuilt the oil pump on my 79CB 650 and spent the last three days obsessing over and chasing the cause of a flashing oil pressure light.  It turns out a mis-routed it AND my neutral switch wire. My indicator lights looked like a drag race rolling down the road.  Also, take your time and watch about setting "riding by this date" goals, it will help keep mistakes to a minimum.

[lucky]

Yea that's exactly it, I DID tighten by hand. I get the feeling a PO had already repaired the threads once, because it was WAY to easy to get that thing crossthreaded.

But I'm definitely not abandoning the project, I've wanted a bike for so long its not even funny, and even if this is a big problem, its not big enough to scare me away.

What all does taking the cylinder head off entail? A new head gasket, what else?

Yes ...sounds like it was not your fault. You will need to take the engine out to fix it properly. No way around that .

[lucky]

DO NOT use screw drivers in the engine mounts again!!!
You were lucky this time, but it would be easy to bust the engine mount right off of the case.

[lucky]

This is too scary a thread to read.
You need to get a impact driver and a #2 and a #3 phillips bit.
The screws in the valve cover are #3 phillips.

Before you use those "green things with springs" you need to have the valve guides and valves checked. Othewise a valve job.

You need to get some advice and help from a machine shop. Let them hot tank those cylinders. Get the cylinder walls measured and you will have to have new rings and new pistons if the cylinder walls are crooked.

You get big credit for being brave though.