Topic: 1978 CB750K — Post 836 OIL PRESSURE - Hopefully Good!?

[madmtnmotors]

You will need 20 parts (22 if you count the two nuts for stud extraction) and 4 tools:

>FOUR: New exhaust gaskets (be sure to pick out all the remains of any old gaskets)
>FOUR: Spigots
>EIGHT: Countersunk machine screws
>FOUR: Pipe clamps to clamp the pipe to the spigot
>TWO: 12mm wrenches
>ONE: #3 philips screwdriver (JIS preferred)
>ONE: Pick or flat screwdriver to pry out old gaskets




Crank the nuts together on the stud, flange-to-flange:


The wrench goes on the BOTTOM nut:


Take it ALL the way out:


Then do another one:


Take that one ALL the way out:


Put a new gasket in place, collect the spigot and countersunk machine screws:


Put one screw in:


Put the other screw in:


Viola':




Took longer to document this than it did to do the work. Could probably have all four done in less time than it took to document it.

[SKTP]

You rule!

Thank you, thank you!

I love this forum 

[cheftuskey121]

love the progress so far, those pipes are interesting. since I don't know, what are the benefits to a pipe like that?

[Stev-o]

what are the benefits to a pipe like that?

They look better than old, dented, rusty pipes!

[Garystratos201]

what are the benefits to a pipe like that?

They look better than old, dented, rusty pipes!

Not to mention increased horse power and a totally different sound. Personally I prefer the Stock sound of un-baffled pipes and the true sound of the POWER..........Gary

[SKTP]

I am hoping these pipes are not TOO loud...has anybody actually heard these pipes?

I'm in the middle of moving cities, anticipating a build delay

[754]

 A buddy of mine ran them got them brand new,dont remember it being overly loud.. Sounded good as I recall

[MCRider]

I had them on the bike in my avatar. Course it was many years ago, but my memory was they were melodious. ITs a long baffled megaphone, and it was as near street legal as such things can be, though with a better tone.

[Stev-o]

Will he need to rejet?

[MCRider]

love the progress so far, those pipes are interesting. since I don't know, what are the benefits to a pipe like that?

I bot mine back when they were current pieces, 1971/72. The idea of the wigglies was to get them equal length. This was all the rage at drag strips on hot rods etc.

Russ Collins had the "turbo swirl", everybody had their gimmick.

After many years thoug, no one could really prove one was better than another. The Triple As get my vote for just being out there. They didn't last long, I mean they weren't for sale long. No one ever won any races with them like RC or Kerker did.

[MCRider]

Will he need to rejet?

I can't remember his other mods. But for the pipe alone will need at least a step on the mains.

[SKTP]

My engine is basically stock. New seals, gaskets, cam chain, cleaned, rebuilt, etc...

This is my very first time rebuilding any engine (god I hope it works). If I just slap the previously cleaned stock carbs on to fire it up (hopefully soon) It will run, it will just be underpowered with the wrong jets?

That's my guess...please feel free to chime in and tell me what to expect (assuming I followed the manuals correctly)

thanks

[Syscrush]

If the jets are too small, you'll probably need to use a fair bit of choke to keep it running (as the choke enriches the mixture) - be careful about how much & how hard you run it in a lean condition, though - it's prone to detonation, overheating, and the resultant damage.

[SKTP]

Yikes!

Is there a thread about this somewhere? Starting your bike with new pipes or something?

Detonation sounds bad

Edit: Read this later:
http://forums.sohc4.net/index.php?topic=54193.0

Checked the FAQs...not Carb/4 into 1 FAQs
http://forums.sohc4.net/index.php?board=11.0

[MCRider]

Yikes!

Is there a thread about this somewhere? Starting your bike with new pipes or something?

Detonation sounds bad

No thread that I've seen. But you'll be pretty safe with stock jets for now. With the long megaphone, IIRC it has a full length baffle, with an open core giving it that low down tone without being too loud. YOu can kinda figure loud = rejet.  Those Yosh replicas etc definitley need rejetting

If everything else is stock I'd just run it and see how it performs. I guarantee that back in the day (I was there) people bought aftermarket pipes like candy and never rejetted them. Sure they ran crappy but they were cool. (I'm talking about with other pipes like Jardines, Kerkers etc.)

Before I rebuilt my K1 into the bike in my avatar it was a stocker with the Triple A pipe. IIRC I don't remember rejetting it.  The cafe was an 836 with a ported head and a K0 cam, but stock airbox. Needed a little more on the main jet.

Loved that pipe. The bike was stolen. Went decades before seeing another of those pipes. Then a few here on the forums.

[Syscrush]

Yikes!

Sorry, didn't mean to freak you out.

Detonation sounds bad

Yes, literally - as in you can hear it happening.  It's also called knocking or pinging.  The circumstance when it's most likely is at WFO pulling from low revs in a high gear.  One episode is very unlikely to do damage, but if you hear/feel it happening, then avoid doing it again until you've enriched the mixture.

I don't know enough about these carbs to know at what RPM/throttle values the choke aka enrichener is active, but in general at low revs, light-to-moderate throttle it will help compensate for a lean condition if you leave the choke on just a bit even after warming up.

[MCRider]

And I hasten to add, it was not my intention to diss Syscrush, what he said is accurate, or any one else who might say you should rejet it.  The proper thing to do is to check the plugs, feel the performance, and rejet accordingly ASAP.

I'm just saying its my experience you will probably be OK to run it in this instance, for a while.

[SKTP]

Looks like I'll be learning about slow jets and mains soon

http://forums.sohc4.net/index.php?topic=106060.0

What do the numbers mean?

[Jerry Rxman Griffin aka MuthaF'er]

There were 4 pages in that link and 16 pages here so I didn't go back but I'll assume you mean jet sizes?

The larger the number, the larger the orifice/opening which allows more fuel flow. The smaller the number then you get less fuel flow.

Lets say you have 40 pilot/slow jets. What you have, and someone correct me if I'm wrong on the actual size, is a jet with a .40mm opening or 40/100ths of a mm. So if you were too rich you'd try a 38 or .38mm or 38/100mm - smaller for less fuel flow.

Same for big jets/fast jets/mains. A 110 would be 1.1mm opening and if you needed more fuel to go richer you'd usually go up 1 normal size and try a 115 or 1.15mm with a larger opening to allow more flow. You may be able to find half sizes if you get THAT good at jetting but it's a science all it's own. ie 112.5 or 117.5

IMO run what you brung first. Try your carbs just as they are, see how it feels, read your plugs and only then make changes based on what you see on the plugs and how it feels. Don't let exhaust sound ie loudness mislead you unless it's total crap sounding. Only change one jet at a time ie do not change fast AND slow jets at the same time. Do one across all 4 until you get the feel right then move on to the other if necessary. When you get to the mid-range "jetting" you actually deal with needles. This is another ballgame as you have to take the carbs apart on most of our carbs. On these you move the needles up by lowering the clip one notch to make it richer by allowing more fuel to go through the needle jet or raising the clip to drop the needle lower into the needle jet to decrease fuel flow. Hope you don't have to mess with these. I'm not even going to bring up slow jets at this point as the screws may do what you need in that range just like needles and big jets overlap in certain rpm ranges.

Grasp the concept first then try your carbs just as they are. You may be good without learnings carbs 101.

I'm taking the easy and more precise way out with my new carbs. I've found and spoken with 2 dyno guys the past 2 days. I'll pay them to put the bike on their dyno amd measure the air/fuel ratio in my 4 to 1 pipe and they will tell me what size jets to use. Max jetting/max HP. Few bucks but well worth it to avoid the time and frustration of doing it wrong or not doing it the best it can be. Plus they give you a cool dyno chart 

   

[SKTP]

Thanks....

Can anybody recommend a Dyno place in the Long Beach, CA area?

This bike is going to be a daily driver. I want it to purrrrrr

[SKTP]

What am I missing? When the wrench turns the bottom one, I just crank them both off?

[Jerry Rxman Griffin aka MuthaF'er]

Exhaust studs are the worst. Penetrant lube, heat, double nut, smack the end of the stud, air wrench, etc. You're doing that part correct. You may need some vise grips on the shaft too. 

Let's hear from someone that does this more than once every 40 years though.

[madmtnmotors]

Exhaust studs are the worst. Penetrant lube, heat, double nut, smack the end of the stud, air wrench, etc. You're doing that part correct. You may need some vise grips on the shaft too. 

Let's hear from someone that does this more than once every 40 years though.

+1

The elements are not kind to dissimilar metals.

[MCRider]

What am I missing? When the wrench turns the bottom one, I just crank them both off?

If both nuts are turning, you don't have them jammed together tight enough. The whole strategy relies on you putting the threads in such a bind that the nuts can't turn and instead the stud turns. While it very often works, I've never been a fan and instead prefer a proper stud puller.

[Syscrush]

If both nuts are turning, you don't have them jammed together tight enough. The whole strategy relies on you putting the threads in such a bind that the nuts can't turn and instead the stud turns.

What he said.  If you can put some heat on the head, too, that will help.  Tapping the end of the stud with a hammer can also help break up the corrosion that's holding them together.