Author Topic: 76 CB550 Cafe build (Read 95874 times)

MRieck · « **Reply #500 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 #501 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 #502 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 #503 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 #504 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 #505 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

tshrey · « **Reply #506 on:** June 30, 2021, 04:17:18 PM »

Awesome, thanks. I'll order it now.

tshrey · « **Reply #507 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 #508 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 #509 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 #510 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 #511 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 #512 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 #513 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 #514 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 #515 on:** July 14, 2021, 07:42:27 AM »

No one to blame but me

SOHC4 Cafe Racer Fan · « **Reply #516 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 #517 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 #518 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.

tshrey · « **Reply #519 on:** July 14, 2021, 02:56:12 PM »

Redid compression test and with the exception of #1 having stupidly good compression (170) all the other cylinders were at 150-155. Also should say that I checked to make sure that the line for #3 and the carbtune work, I put a mityvac on there and the rod moved up. Going to redo this test and if I get the same result I'll switch ports as well.

Also should say I recently had the exhaust pipes off and decided to give them a nice finish with a scotch brite pad. It is pretty clear from simple discoloration that number 3 is not running.

RAFster122s · « **Reply #520 on:** July 14, 2021, 03:05:22 PM »

Change the plug in #3, some plugs don’t fire under compression, defective. But if that’s a chronic problem then it really is ahead scratcher. Does swapping cylinder 2 & 3 plug wires change the behavior?
Is the exhaust 3 pipe remaining cold?

Definitely must fix this or that fuel is going to wash the rings and end up in the crankcase ruining your lubrication.

Which all leads me to thing you aren’t getting fuel to that cylinder

tshrey · « **Reply #521 on:** July 14, 2021, 07:08:45 PM »

I changed out the plug after doing the compression test, haven't started it back up after. I didn't actually measure the pipe temp, just going by the discoloration of the #3 header it is clearly not getting hot.

What I don't get is how a cylinder with good compression can show zero vacuum. Even without spark, the piston and valves work together to make an air pump and should draw vacuum. I hand cranked the motor with the tappet covers off of #3, things move in the way I would expect them to move.

It can't be fuel, I'm running dual VM34 carbs. The same carb feeding #4 is feeding #3.

Any thoughts on the buzzing in that video?

algophobe · « **Reply #522 on:** July 14, 2021, 10:03:40 PM »

have you switch around the rubber tubing going to the carb sync manometer? could be a hole there or in the carb boot coming from carb to intake. if your compression is good, and the other cylinder sharing the same carb is good then i don't think a leak down test would offer much more info (imho). Also looking back at your prior pics of the carb mounting.. where do you hook up the carb sync to the get the vacuum readings?

tshrey · « **Reply #523 on:** July 15, 2021, 04:15:16 AM »

I didn't, but you're right I should have switched the lines from the manometer as soon as I saw that result. That is on the agenda for today.

I didn't have the spigots installed in any of the old pics, I just did it the other day. If you look at the video you can see them there.

algophobe · « **Reply #524 on:** July 15, 2021, 03:31:46 PM »

Quote from: tshrey on July 15, 2021, 04:15:16 AM

I didn't, but you're right I should have switched the lines from the manometer as soon as I saw that result. That is on the agenda for today.

I didn't have the spigots installed in any of the old pics, I just did it the other day. If you look at the video you can see them there.

also when installing the spigot for vacuum testing did you use any sealants? that might have unintentionally plugged up the channel... ask me how I know. hahahha

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Author Topic: 76 CB550 Cafe build (Read 95874 times)