Author Topic: CB750K6 the miraculous running Buffaloe (Read 5815 times)

buffaloejon · « **on:** October 06, 2011, 03:36:13 PM »

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.

MattInVA · « **Reply #1 on:** October 06, 2011, 05:07:46 PM »

Nah, they just need to dry off. Save the new plugs for when you get it all sorted out.

buffaloejon · « **Reply #2 on:** October 06, 2011, 05:38:15 PM »

Yah, I'm gonna use that thread chaser tomorrow, and get the timing right, and then take her for a short ride, sync the carbs, and then take her on a real ride, sticking to back roads, seeing as I'm not titled or anything.

And then I'll get her titled and ready to go in the next month!

Greggo · « **Reply #3 on:** October 06, 2011, 05:42:31 PM »

I'm doing a '76K as well...By the way...WE LIKE PICTURES HERE

buffaloejon · « **Reply #4 on:** October 06, 2011, 05:53:36 PM »

Duly noted, here are a few. The only recent ones are the ones with no tank or seat. Once she's put back together this weekend, lots of pics will be taken. And videos.

edit: Whoops, how'd that dog get in there!?

She's my (not so) little helper.

buffaloejon · « **Reply #5 on:** October 06, 2011, 06:24:00 PM »

This is my homemade Carb sync tool that I will attempt to use tomorrow. I used marvel fuel additive so if it gets sucked in no big deal.

edit: for some reason the picture is sideways... it obviously sits rotated 90 degrees. The levels aren't right cause its not done equalizing yet.

Greggo · « **Reply #6 on:** October 06, 2011, 06:41:53 PM »

Hey, you've got a 16" rear too. I don't like the gap it leaves under the rear fender...I'm trying to find a stocker.

buffaloejon · « **Reply #7 on:** October 07, 2011, 03:27:51 PM »

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

lucky · « **Reply #8 on:** October 07, 2011, 03:37:10 PM »

Quote from: buffaloejon on October 07, 2011, 03:27:51 PM

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

I was afraid of that. Always install plugs by hand so you can feel them. Never use a rachet or speed handle.
You only get one chance to fix that kind of problem.
Now you will need to remove the cylinder head and cam.
Will you abandon the project?
Maybe another forum member will buy it and fix the cylinder head.

buffaloejon · « **Reply #9 on:** October 07, 2011, 03:53:54 PM »

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?

scunny · « **Reply #10 on:** October 07, 2011, 03:56:30 PM »

base gasket as well.

luceja · « **Reply #11 on:** October 07, 2011, 04:07:45 PM »

Quote from: buffaloejon on October 07, 2011, 03:53:54 PM

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?

I think removing the old gasket and cleaning up the surfaces are your big hurdles in taking the head and cylinder block off. Other than that, it's learning the steps to dissemble and assemble the valvetrain, camchain etc.

As far as the gaskets go, getting the old gasket off without marring the mating surfaces was difficult for me on my 550 project. I actually found that aircraft stripper and a fresh razor, lightly burnished to avoid it catching the aluminum was somewhat effective, but I'm pretty sure that's not the right method and wouldn't suggest it. I ended up having a machine shop clean up the surfaces of the head and the cylinder block just in case. Other members may have had more success with other methods, maybe it depends on the state of the old gasket. My current project's PO clearly took the wrong route - whatever abrasive method they used ruined the head's flatness. Be careful about using any power tool or strong abrasive.

Greggo · « **Reply #12 on:** October 07, 2011, 04:22:39 PM »

Quote from: buffaloejon on October 07, 2011, 03:53:54 PM

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?

Sounds like the motor will have to come out of the frame, that's a bummer. Do a search on 'engine removal' here to find some great tips for getting it out successfully, and painlessly. I'd try to find another running motor to just swap in if you can. It's great to have a spare motor with these bikes too. I'm looking for a spare to build up a hi-po motor. Just a suggestion, but they're not too expensive - just find one that turns over freely.

buffaloejon · « **Reply #13 on:** November 27, 2011, 09:55:15 AM »

Well, made some progress on everything over the last little bit. Mostly today. I've decided to just pull the head off and take it into a machine shop to get it helicoiled, or whatever they can do to it... I may even helicoil both inside plugs just for the heck of it... Much harder to crossthread a steel insert than an aluminum head...

Drained the oil, removed airbox, carbs... seat, gas tank... oh and the exhaust system that I just put on. Studs, that good stuff. Much easier this time though, no impact driver required.

Removed the chain. What a pain that was, maybe I was doing something wrong. I had to take the cover off where the shifter arm is, and then the cover behind that to get to it. Good thing I looked the chain over though, it was in pretty bad condition. Several of the links were stuck pretty good.

Now all I gotta do is get the oil filter off, which I'm sure will coat my floor in oil again, and then as far as I can tell the engine will be ready to come out.

One question though, there's a couple large wire bundles going into the transmission, one just unplugs from the wire harness, but the second goes to the starter relay... Do I have to unplug it from the starter relay and pull it from there, or does it unplug from the engine in a simpler place?

And I've got some pictures at the link below, more to come soon!
www.photobucket.com/buffaloejon

buffaloejon · « **Reply #14 on:** November 29, 2011, 01:45:59 PM »

Welp, ordered lots o' parts on cyber monday, thanks Bike Bandit!

Ordered the rear rubber thing that holds the gas tank on, mine was busted all to h***, a full Athena gasket set, oil filter, and new exhaust gaskets. Also noticed on the bike that PO has a brand new starter motor in her... So I've got a feeling she won't need any major work anytime soon, unless I booger up taking off the head to helicoil.

Can anyone tell me about the gasket sets... Do they have everything I might need to get the head back on nice and clean?

buffaloejon · « **Reply #15 on:** December 04, 2011, 09:59:09 AM »

Whoop whoop, got the engine out! Took three people, and we used several heavy screwdrivers as handles in the mounting points to pick her up and get her out... After trying the dump method, got jammed in there pretty good so we picked it back up and wiggled it out... Didn't really make the frame any worse than it already is...

That engine is one big mother.

buffaloejon · « **Reply #16 on:** December 10, 2011, 11:36:00 AM »

Well, made real good progress. The head is off, came off really easily once I got everything loose, it was all really straightforward...

Except for this. The FIRST bolt I get to on the cam breather cover, is impossibly stuck... So I was pretty peeved, and just drilled as much off as I could get, and then broke the bolt and screwed it right out. Broke the cover though, I'm gonna try and JB Weld and then sand it. Since it needs painting anyway, should disappear pretty easily.

But this is what the cylinders look like underneath that head. Pretty dirty, but my engine-knowledgeable buddy is gonna come help me put it all back together, and he's gonna be the judge on whether anything looks real bad.

K5owner · « **Reply #17 on:** December 10, 2011, 12:20:31 PM »

Looks like your progressing nicely. The pistons don't look that bad, but make sure you get a quality base & head gasket. Replace the rubber gaskets and inspect/clean the oil passage orifices. There's o-rings to replace, so take your time, ask questions if needed.

Here's a link to the engine rebuild on my 750. Click through the photos until you get to the ones you can use.
https://picasaweb.google.com/107470341290124962680/1975CB750EngineRebuildRestoration?authkey=Gv1sRgCPD1m_26vJv90wE

I'm glad you're repairing it. You'll have a great ride when you're done.
Thanks for sharing
-Ray

buffaloejon · « **Reply #18 on:** December 10, 2011, 12:27:22 PM »

I removed the camshaft, wasn't aware I could do this WITHOUT doing that... But either way, I've ordered an Athena full gasket set, it'll get here on Tuesday, and I'm assuming that it'll have most everything. I know I need those 6 pucks that go underneath the camshaft towers, but aside from that, I'll have to wait and see what's in that set.

And I definitely want to make sure everything is ok before I put it back together and get it in the bike... This has been a hard process so far and I want to get a little riding in. I'm planning on doing all this again next winter and painting the cases, frame, etc. I'm wondering if I can paint everything without cracking the cases? It really all depends on what I find when I finally ride it in the spring.

K5owner · « **Reply #19 on:** December 10, 2011, 01:02:01 PM »

You can paint the case/engine without taking it apart. Some have soda blasted their's clean and then applied the paint. Just make sure to seal & mask off as needed.

buffaloejon · « **Reply #20 on:** December 16, 2011, 02:19:04 PM »

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...

scunny · « **Reply #21 on:** December 16, 2011, 02:23:02 PM »

you will have 8 of those "green things" they are your valve guide seals
I install the gaskets dry.

buffaloejon · « **Reply #22 on:** December 16, 2011, 02:38:18 PM »

That's what I was thinking, something to do with valves. There are lots of o-rings in the kit that I have no idea what they go to, so I'm just going to replace everything that I can find in the top end with new.

Is it absolutely necessary to replace the valve guide seals? Or rather, would you recommend it? I'm not thinking this engine has ever been rebuilt (saying this because the cam tower pucks were all rock hard), but the head seperated from the cylinders ridiculsouly easily and the gasket wasn't stuck to either surface... Selective gasket-replacement by the PO I'm thinking. The reason I ask that is, wouldn't I need a valve spring compressor? I've heard the Autozone rental compressor is junk.

scunny · « **Reply #23 on:** December 16, 2011, 02:56:44 PM »

I would replace them while you are in there. can't help you on the valve compressor, don't know whats available in your country.

K5owner · « **Reply #24 on:** December 16, 2011, 03:37:22 PM »

I would replace the valve seals also. Most of the auto parts stores have the compressor, and usually they charge less than $10, which you'll get back after you return it. I've "rented" tools from Autozone & Advance Auto without buying parts.

As for the gaskets; I don't use sealers, but do check the surface for straightness. Any machine shop can do this. Shouldn't cost that much.

lucky · « **Reply #25 on:** December 19, 2011, 03:05:31 PM »

Quote from: buffaloejon on October 06, 2011, 03:36:13 PM

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 · « **Reply #26 on:** December 19, 2011, 03:09:42 PM »

Quote from: buffaloejon on October 07, 2011, 03:27:51 PM

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 · « **Reply #27 on:** December 19, 2011, 03:21:31 PM »

+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 · « **Reply #28 on:** December 19, 2011, 09:43:59 PM »

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 · « **Reply #29 on:** December 21, 2011, 04:10:13 AM »

Quote from: K5owner on December 19, 2011, 03:21:31 PM

+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 · « **Reply #30 on:** December 30, 2011, 02:20:24 PM »

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 · « **Reply #31 on:** December 30, 2011, 02:56:10 PM »

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 · « **Reply #32 on:** December 31, 2011, 12:20:11 AM »

Quote from: buffaloejon on December 16, 2011, 02:19:04 PM

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 · « **Reply #33 on:** December 31, 2011, 07:13:05 AM »

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 · « **Reply #34 on:** March 28, 2012, 04:36:19 PM »

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 · « **Reply #35 on:** March 28, 2012, 05:14:56 PM »

Quote from: buffaloejon on December 30, 2011, 02:20:24 PM

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 · « **Reply #36 on:** March 31, 2012, 07:25:13 AM »

Quote from: buffaloejon on October 07, 2011, 03:53:54 PM

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 · « **Reply #37 on:** March 31, 2012, 07:31:44 AM »

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 · « **Reply #38 on:** March 31, 2012, 07:39:26 AM »

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.

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Author Topic: CB750K6 the miraculous running Buffaloe (Read 5815 times)