Author Topic: CB750K6 the miraculous running Buffaloe (Read 5744 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.

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Author Topic: CB750K6 the miraculous running Buffaloe (Read 5744 times)