Author Topic: 76 CB550 Cafe build (Read 86152 times)

tshrey · « **Reply #575 on:** June 25, 2021, 08:50:00 PM »

Flipped coils, cleaned up plugs and let it idle for a few minutes with a few revs. Plugs look the same, light and clean on 1&4, darker and a little wet on 2&3. I also took off the connection to the motogadget gauge for the tach pickup (it was on the coil for 2&3) in case that was somehow pulling the coil down. Only thing left in common to those cylinders are plug wires, dyna s or something about the engine itself. It really doesn't seem like the dyna if I can time everything in with a light. I'll probably do a compression check tomorrow since it is easy - engine isn't broken in and it will be cold but if all 4 cylinders read the same it will at least be a sanity check.

RAFster122s · « **Reply #576 on:** June 25, 2021, 09:13:09 PM »

Have you verified fuel levels on carbs 2-3? (Clear tube) compared to 1-4

Maybe it is jetted wrong across the board.1-4 are too lean and 2-3 are too rich.
Any possibility of air leak for 1-4 manifold to head? That cpuld account for leaner running. Something that heat causes it to happen?

Maybe step back and look at it from a different angle.

What kind of manifold is used for the VM carbs?

It looks like you have ruled out the ignition side with coils and plug wires and caps if they ohm out the same or within the range of tolerance.

Just another bite of the elephant to narrow the problem...

tshrey · « **Reply #577 on:** June 25, 2021, 09:32:53 PM »

Carb 1 feeds cylinder 1&2, carb 2 feeds 3&4. That's why I think it almost can't be a fueling issue (not that fueling is perfect, but I don't think they are causing my immediate problem).

tshrey · « **Reply #578 on:** June 28, 2021, 01:49:34 PM »

Small bit of good news, I did a compression test. Cold engine, not broken in but have 160-170 psi on all cylinders.

tshrey · « **Reply #579 on:** June 29, 2021, 10:07:01 PM »

Installed m-Lock tonight, pretty nifty piece of equipment. Rechecked valves, couple intakes were a few thousandths over. Also finally read the instructions for the speedo sensor on the motogadget. It says quite specifically to use only one of the magnets. I stacked both of them together and used that. Also, gap between magnet and pickup is supposed to be less than a mm so I made a mount from layers of carbon fiber and bonded that to my front wheel to get .5mm gap. I'll double check the wheel diameter I used in the gauge, hoping that resolves it.

Also did reading on something I didn't understand, I have a clunking sound at idle. If it was a built car I would say it sounds like piston slap but it isn't consistent enough to be that. Can find a dozen threads on here about it, all recommending the same thing. Keep idle above 1050 (I have it a 900 right now), when the clutch goes in the sound lessens and synch the carbs. I didn't check the clutch thing but that sounds reasonable. Carbs are sync'd using gauge pins (and was told not to touch them) but I think I will hook up my carbtune and see what that results in. Also clearly need to raise my idle.

MRieck · « **Reply #580 on:** June 30, 2021, 05:30:54 AM »

I have never understood the obsession with trying to achieve the sub 1000 RPM idle speed....it certainly doesn't work if any engine upgrades have been performed. The higher idle improves oil pressure which really helps when that oil is heat soaked and thin and smooths the engine out. That super low idle reminds me of the Harley lowest idle contests with the engines turning about 200 RPM

Godffery · « **Reply #581 on:** June 30, 2021, 06:05:32 AM »

Quote from: MRieck on June 30, 2021, 05:30:54 AM

I have never understood the obsession with trying to achieve the sub 1000 RPM idle speed....it certainly doesn't work if any engine upgrades have been performed. The higher idle improves oil pressure which really helps when that oil is heat soaked and thin and smooths the engine out. That super low idle reminds me of the Harley lowest idle contests with the engines turning about 200 RPM

I'll second that.

tshrey · « **Reply #582 on:** June 30, 2021, 06:57:37 AM »

I'm sorry guys, don't beat me up!

The oldest bike I ever had was an 88 Katana and that purred along at a nice typical car idle. My modern bikes are all FI and sound smooth as a sewing machine at 800 rpm. No idea that this thing should idle higher.

While I have everyone's attention - the 'heavy duty' clutch that I put in this bike is just a stupidly hard pull. Are the plates any different or is it just the springs? Can I use a normal clutch spring set and the HD plates to get some extra holding power?

MRieck · « **Reply #583 on:** June 30, 2021, 09:53:14 AM »

Not beating you up.

You just happened to bring up the point which is one of the pet peeves I have.

RAFster122s · « **Reply #584 on:** June 30, 2021, 02:10:14 PM »

How new is your clutch cable, is it Honda or aftermarket and is it routed correctly. Are the springs std or HD Barnett's and why did you put HD springs in? Was it slipping or you just thought you needed them?
What makes the plates HD?
Who made the clutch kit?

tshrey · « **Reply #585 on:** June 30, 2021, 02:30:15 PM »

It is a custom length clutch cable using the kit from Revival. No sharp bends, well lubricated.

I think I bought a Barnett HD clutch 'kit'. Your question about springs and plates is what I'm asking, if the plates are more aggressive can I use stock strength springs. Entirely possible I don't need it, but I was told everything I had done to the motor would require it. I'm about ready to put a stock one in and just see what happens. I'll try to look through my stuff and see what I bought. That's the trouble with these long builds, the engine work was all three years ago

calj737 · « **Reply #586 on:** June 30, 2021, 02:45:49 PM »

You don’t need an HD clutch. The stock clutch plates and springs will handle far more than the performance gains your engine build creates. A member here, Brent, raced many seasons a heavily built 550 motor with stock clutch parts without incident ever. Take it from him.

tshrey · « **Reply #587 on:** June 30, 2021, 04:17:18 PM »

Awesome, thanks. I'll order it now.

tshrey · « **Reply #588 on:** July 04, 2021, 01:22:47 PM »

Got the stock clutch kit, soaking the plates in oil. Figured I would start it up to warm up the oil before I drained it. Tank on, fuel connected, gas On. Bike fires right up, runs on choke for about 20 seconds and then I take it off choke to let it warm up. Raise the idle screws by half a turn each and pull in the clutch. As you all suggested, all the noises went away. Most of the clunking sound was coming from the transmission, as soon as you pull the clutch in they went away. Then bike dies. Huh. Check over stuff, make sure I didn't forget anything, fires right up again, got the idle set at 1300 rpm. Then dies. This repeats for several minutes. Finally I switch to reserve on the petcock. Runs fine. I guess that is what you get with non-OEM stuff, have to find a petcock that works. Also thinking if it is limiting fuel at idle it could be why it doesn't run consistently when I ride it.

This build started out as an exercise in design and fabrication and has turned into troubleshooting every component of a functioning motorcycle. Anyone have an extra 76 CB550 petcock lying around?

tshrey · « **Reply #589 on:** July 06, 2021, 07:01:04 AM »

So the clutch replacement was a waste of money. Apparently the 'heavy duty' clutch was no such thing, the stock replacement is just as hard to pull. Last thing to try is a different perch, I'm using on from a GSXR750 and if I measure the pivot to cable distance it is longer than the stock perch I have laying around. That will give quicker response but make the lever heavier. Going to try switching that out. I really don't get what has changed with clutches, both of my 900-1000cc bikes had super light cable clutch pulls, literally 3-4x lighter than what this bike with less than half the horsepower has.

RAFster122s · « **Reply #590 on:** July 06, 2021, 07:31:54 AM »

What cable do you have on it now?
If aftermarket, have you lubed it recently? Honda OE cables are smooth and light and should not be lubed. When routed properly they are pretty light.

tshrey · « **Reply #591 on:** July 06, 2021, 08:20:30 AM »

It is the 'build your own' clutch kit from Revival. Stock cable is waaayyy too long with clip-ons. The cable is new, lubed and feels smooth as butter with no load. No bends are anything approaching sharp.

On a stock bike would you classify the clutch as a 1 finger pull? Maybe it is all in the perch, I'll get a chance to check that later today.

tshrey · « **Reply #592 on:** July 11, 2021, 09:05:25 AM »

Bike keeps getting closer to being set on fire before I get to enjoy it.

Drained the tank to change out the leaking petcock and opened the cap to see this:

Apparently all my careful tank prep was not so great, all the tank liner is bubbling off. The problem is it is very solid stuff. I just spent 45 minute removing the roughly 1/6 section of the tank I can easily get to. No idea how I will get the rest of it out since I can't even see into the left side of the tank. Suggestions? Look for a new tank?

RAFster122s · « **Reply #593 on:** July 11, 2021, 10:00:31 AM »

Acetone takes out some liners (destroys paint too…
Another thing to use is MEK, nasty stuff that also kills paint…

tshrey · « **Reply #594 on:** July 11, 2021, 02:47:05 PM »

I found a tank on ebay for $100. From california, inside is totally rust free. Outside has dents but I'm fine with bodywork and the don't look bad at all. Going to just swish a bunch of alcohol around in my current tank and run it until it leaks or I finish the other one. Because of the extra diameter of the front forks I had to limit their movement or else they would hit the tank. With the new tank I'll pound in some divots to make room for them while I'm doing the body work.

MRieck · « **Reply #595 on:** July 14, 2021, 05:43:42 AM »

Quote from: tshrey on July 11, 2021, 09:05:25 AM

Bike keeps getting closer to being set on fire before I get to enjoy it.

Drained the tank to change out the leaking petcock and opened the cap to see this:

Apparently all my careful tank prep was not so great, all the tank liner is bubbling off. The problem is it is very solid stuff. I just spent 45 minute removing the roughly 1/6 section of the tank I can easily get to. No idea how I will get the rest of it out since I can't even see into the left side of the tank. Suggestions? Look for a new tank?

Did you line the tank or have a shop do it?

tshrey · « **Reply #596 on:** July 14, 2021, 07:42:27 AM »

No one to blame but me

SOHC4 Cafe Racer Fan · « **Reply #597 on:** July 14, 2021, 09:55:14 AM »

I am not sure what product you used to line the tank (Redcoat?), but you may wish to use an epoxy-based liner on you future tank -- not only a good rust preventer but will also withstand ethanol fuels.

FYI - you can take your tank to a reputable radiator shop, who can sandblast and pressure test it for you - and start anew.

tshrey · « **Reply #598 on:** July 14, 2021, 10:23:41 AM »

Looked up my receipts. Caswell Epoxy gas tank sealer in Dragon's Blood. I know the previous owner had put what looked like Kreem in there because a huge thick chunk came out of the bottom when I cleaned it. I'm thinking I must not have cleaned all of that out so the caswell didn't bond to the tank all that great. I can't complain about the caswell itself, what is in the tank is a very strong 1-2mm thick coating and that is part of the issue. It isn't bonded to the tank walls but it is very anchored to the floor so it doesn't want to break up and doesn't want to come out. With the offset fill port I can't get anything into the left side of the tank to pull out sections of it.

For now I'll keep tuning things using a small plastic portable tank and probably move right to the new tank when it gets here saturday. Just seems like a lot less work and irritation.

Thanks for all the ideas.

tshrey · « **Reply #599 on:** July 14, 2021, 01:33:01 PM »

So some actual verifiable data that supports what I think I hear and feel when riding.

First off, made a quick video link that I hope will work for everyone. I'm just wondering what people think of the constant loud buzzing sound. It is definitely coming from the head.

[url]https://photos.app.goo.gl/j4QVgKS12agBsuBh8[\url]

Second, I finally hooked up the carbtune to the vacuum ports I put on the intake manifolds. Zero vacuum on number 3. So it isn't just in my head, this thing is, and probably has been the whole time, running on 3 cylinders. Now the question is how can that be? I have good compression on that cylinder and it holds it (I didn't do what I would call a real leak-down check on it, just a minute or so), I have spark (verified with timing light) and the same carb that feeds #4 feeds that cylinder. I was able to set the valve lash.

I'm heading out now to redo the compression test.

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Author Topic: 76 CB550 Cafe build (Read 86152 times)