Topic: 1977 CB750 K7 Resto-mod, Knoxville

[Desert-SOHC]

That's where mine is

[AintNoEasyWay]

That's where mine is

Sweet, thanks Desert.

[AintNoEasyWay]

I think this rubber hose from the oil tank connects to the back of the crankcase, correct? Just want to be sure.

Also couldn't resist throwing the tank & seat on... I've got blank side cover emblems that I need to paint & throw on. Also need to remove & touch up those tank badges...

[enwri]

That's looking good,, Does anyone wear engine crash bars now? I like the look, a bit of chrome under the front of the black cases, also handy when someone bumps it over in the carpark.
It should feel and go like a new one now, it's got to go at least 25% better with the main jet back in, to just to start with.

[AintNoEasyWay]

That's looking good,, Does anyone wear engine crash bars now? I like the look, a bit of chrome under the front of the black cases, also handy when someone bumps it over in the carpark.
It should feel and go like a new one now, it's got to go at least 25% better with the main jet back in, to just to start with.

Rarely see engine bars nowadays. I actually wouldn't mind having them on my bike.

Having the main jet in is sure to help! Could one main jet falling out account for the white film on my other three exhaust valves? Would really like to know if I was running the bike too lean or if the problem can be traced to the main jet coming out.

[enwri]

I would have thought the jet missing would have a lot to do with the one dark valve, do you remember which carb it was? hope it was that one.
The plugs being the right colour will tell you more than the valve colour will, (plug will look burnt before the valves burn, If it's extra lean. They only normally burn if there is a slight bend or imperfection in the seat or valve anyway, I think they worked out how to stop them melting in the late 50's, better metallurgy?) 
But you will be checking the plugs once it runs, colour charts on here somewhere.
The exhaust valves always run hotter than the intakes. They used to have a nice white/gray coat of lead dust on them with the old leaded fuel..

[AintNoEasyWay]

I would have thought the jet missing would have a lot to do with the one dark valve, do you remember which carb it was? hope it was that one.
The plugs being the right colour will tell you more than the valve colour will, (plug will look burnt before the valves burn, If it's extra lean.) 
But you will be checking the plugs once it runs, colour charts on here somewhere.
The exhaust valves always run hotter than the intakes. They used to have a nice white/gray coat of lead dust on them with the old leaded fuel..

Interesting. Yes, I'll definitely be checking the plugs once it's running. The one dark valve was #3, which is the same carb the main jet came out of. I just looked at the photos to confirm.

[enwri]

I just went and checked your plug photo, 1,2,4, normal 3 wet.

[Desert-SOHC]

Does anyone wear engine crash bars now? I like the look, a bit of chrome under the front of the black cases, also handy when someone bumps it over in the carpark.

I have them on mine, they were on it when I got it. They are painted black and I haven't removed the paint to see what shape the chrome is in or how scratched they are......lol

[AintNoEasyWay]

Ok, got everything on & set to go except for the air box. Completely forgot how I managed to get it on when I first rebuilt the carbs. It's getting late now & im not making progress getting it on. I'll leave it be for the night & maybe it'll be a quick fix tomorrow after work.

I should add that I split the air box in two & got the top piece in behind the carbs. It's the boots I'm having trouble getting attached to the carbs.

[AintNoEasyWay]

Got the air box on & tried the first start...

No luck. I've got all the ignition wires hooked up correctly. Compression is there because I kicked it over 40-50 times like Hondaman recommends to make sure I've got oil working down into the engine. Oh, & yes, the petcock is on, fuel flowing.

Not sure where else to look. I didn't take the carbs completely apart again when I had them off, but I can't imagine there's a problem there. I barely ran them last year. I could at least take the air box off & make sure the accelerator pump is working.

Now the guess work begins...

[AintNoEasyWay]

Update: just came back to the garage & tried draining my float bowls. Only #1 had gas in it & barely any at that. Took off the tank & turned the peacock on realizing it's barely draining. May need a petcock fix here.

[oldhatt45]

AintNoEasyWay,

That would explain a couple of things.
Great Gas Mileage (sorry couldn't resist. <G>) and failure to run.
Glad it's something relatively easy to fix!

Charlie

[AintNoEasyWay]

AintNoEasyWay,

That would explain a couple of things.
Great Gas Mileage (sorry couldn't resist. <G>) and failure to run.
Glad it's something relatively easy to fix!

Charlie

Gas mileage has been excellent ever since I started rebuilding the engine. Amazing!

I'm able to shoot wd40 straight through the petcock with no problems though. So not sure what the issue is with it.

[enwri]

inline fuel filter and an air bubble stopping flow?
Tried the reserve setting?

[AintNoEasyWay]

inline fuel filter and an air bubble stopping flow?
Tried the reserve setting?

Yep, the inline filter definitely had a bubble! But even when I took the tank off & tried to drain from just the petcock, barely had flow.

[Restoration Fan]

Nate,
Do you have an auxiliary tank you can use?  When you're trying to start the bike and diagnose problems, it's nice to be able to eliminate the fuel flow from the fuel tank as an issue.

Ron

[enwri]

+1 on the tank.
there's a tube screen in the tank that wont always come out with the tap, can be a restrictor if it's dirty.
can also trap air for a while if the tank has been dry

[AintNoEasyWay]

+1 on the tank.
there's a tube screen in the tank that wont always come out with the tap, can be a restrictor if it's dirty.
can also trap air for a while if the tank has been dry

I changed that screen when I derusted/cleaned the tank. Glanced at it with a flashlight & it's still clean.

Enwri, I switched to reserve & gas flows fine. Maybe I just need to fill the tank up more??  . I didn't put much in it at first. Will try to start it just from reserve maybe? Or should I go ahead & fill tank most of the way?

[AintNoEasyWay]

No bubble when I put it on reserve. Flows much better so guess I just didn't put enough gas in. Still won't start though.

[enwri]

Ahh, the old reserve trick.
 Tried the choke?
Spark at the right plugs at the right time next
Kill switch?

[AintNoEasyWay]

Ahh, the old reserve trick.
 Tried the choke?
Spark at the right plugs at the right time next
Kill switch?

Hahaha! Will have to check spark. Definitely getting gas flow. Have a leak from carb #3 now!! Will pull them now. Agh!

[enwri]

you know you can leave the top half of the airbox on to get them out, easier to get the aibox tubes off and on easier

[Restoration Fan]

First things first.  Eliminate one thing @ a time.
Take a spare spark plug.  Pull the cap off #1 and put the spare plug into the cap.  Touch the plug to the engine (make sure fuel isn't on) and see if you get a spark arc'ing over to the engine as you hold in the electric start button.  Repeat that process for each spark plug. 

If, at the end of this process, you have spark @ all 4 plugs, then spark is most likely not your problem (theoretically, you could have a bad plug and would have to unscrew each plug and test to confirm but the likelihood of that is so small that I would only try that after everything else).

Once you have eliminated spark, then it's most likely a fuel problem.  Personally, I'd remove the air box and start the bike without an air filter on it.  This lets you visually confirm the slides are completely closed when you have it on full choke.

Also, go get some more fuel.  Put enough in there that the the tank is 2/3 full and just eliminate that as a potential source of problems.

[Restoration Fan]

you know you can leave the top half of the airbox on to get them out, easier to get the aibox tubes off and on easier

That's more of a pain in the butt with the K7's and K8's than with the earlier K model air boxes. 

On the air boxes up until 76, the rod that goes down through the bottom connects via a wing nut.  On the K7's and K8's, the rod connects into a molded plastic piece in the bottom of the airbox (that often strips).  Not that you can't do it...it's just a bit more trouble with Nate's bike than it would be with earlier models because you screw it in from the top and that would be hard to do with the top still connected in the bike.