Author Topic: 76 CB550 Cafe build (Read 100387 times)

tshrey · « **Reply #475 on:** June 11, 2021, 02:16:40 PM »

One more thing - after a longer ride today I was looking around at stuff with the bike running and noticed a small amount of smoke coming out of the valve breather (that I just have a filter over). I'm guessing that is normal and would usually be piped in to the intake box and burned, but thought I would ask.

tshrey · « **Reply #476 on:** June 18, 2021, 06:23:28 PM »

So very close now. Got insurance, still have my Vermont plate on it (no title when I bought it, that is the easiest way to get an old bike in the system) but now road legal. Need to spend some time with my dslr to get some real pics.

Went for the longest ride I've gone on. New rear suspension makes the ride comfortable and carbs let it idle but the engine just still doesn't feel right. Pulled the plugs when I got back - 1 & 4 are a nice tan, 2 & 3 are sooty. So carbs are good, it has to be ignition. Running Dyna S and their 5.0 ohm coils. When I checked the dynamic timing with a gun I could get a perfectly fine signal on wires 2 and 3. Is it possible for the coil to discharge enough for an inductive pickup to read a signal and not get a good spark on the plug?

I don't have an extra coil to check, I'll start with basic wiring checks. Anything I'm not thinking of?

RAFster122s · « **Reply #477 on:** June 18, 2021, 06:47:43 PM »

Lots of cases of plugs not firing under compression, having both doing it might be highly unlikely. But, that said, cheap test to pop in anew set of plugs to see if it clears the issues. It should temporarily do so until it fouls them again if there is a problem there...sorta. All the brass Keihin? Check your voltages to the coils to ensure the wiring is sound to that coil. Isolate the coil and do a test of each coil's resistance on primary and secondary to see they are sound. Test your your plug caps as well.
That's a start...
Bike looks good.

tshrey · « **Reply #478 on:** June 18, 2021, 08:40:10 PM »

Zero Keihin brass. Carbs are VM34 mikuni's from Murray's Carbs, so one carb for 1&2, one for 3&4. Kinda rules out fueling issue with the cylinder distribution. Also explains why I could never really get it running right with the CR26 kit I had on there if there is an ignition issue.

I'll do as you suggest in the morning. Thanks.

Godffery · « **Reply #479 on:** June 18, 2021, 11:30:05 PM »

Couple things come to mind but can't say for sure they would cause 2 & 3 to fire any different then 1&4.
Never the less; You say you checked the ignition with a timing light, so I assume you are setting that according to the book' right? Well it has been my experience that any of these bikes with modified intake & exhaust require the timing to be advanced about 3 to 5 degrees.
Secondly; The Dyna S retains the stock centrifugal advance unit, and I have found those can loose there effectiveness as the springs stretch and weaken. I herd of some addressing this issue by shortening the spring because new ones are not available separately, but replacing the entire unit might be best.

I hope this might be of some help.

tshrey · « **Reply #480 on:** June 19, 2021, 06:24:45 AM »

The difference between the T and F marks are 10 degrees of advance, right? So I want the bike to fire a few mm to the right of the F mark?

You had mentioned the advancer before, I did exactly what you said and cut off a loop of the spring. Made it work great, it now advances around 3k. Before it was in the advanced area just sitting at idle.

thanks for the input

Godffery · « **Reply #481 on:** June 19, 2021, 09:49:13 AM »

That's about 5 degrees.
http://i190.photobucket.com/albums/z189/uberkafer/b17b41e276d3629854ffc68ca69ffa79_zpsesk0kcrq.jpg

Yes, to the right. So you would turn the timing plate counter clockwise.

tshrey · « **Reply #482 on:** June 19, 2021, 09:58:02 AM »

Well that pic is definitely getting saved, thanks.

So I should move it to fire at about the vertical line of the F to get the advance you recommend.

I'm digging into everything right now. Voltage on coil two was
.2 volts less than 1&4 and then I checked it again and it was .5 less. Freaking screw for the positive terminal was loose. Very embarrassing. I'm now going over and checking resistance and voltage of every other part of this circuit. Also wiped out AutoZone of D7EA plugs, ten of them will hopefully get me through this

Godffery · « **Reply #483 on:** June 19, 2021, 10:29:41 AM »

Yes, that is about right. I will basically go by what performs best, and I use the 'But Dyno' method.

That loose connection could definitely have an effect on your spark. One other thing you could check; The pickups on the Dyna-S ignition is supposes to be set perfectly parallel to one another, but it's always possible they got it off a bit. The paperwork you got with it should give you the static testing method.

tshrey · « **Reply #484 on:** June 22, 2021, 07:36:23 AM »

Timing is now dead on, both at idle and in the advanced setting. Went for another longish ride and plugs are clearly all firing but all way too dark. I'm good on my idle settings (adjust air screw until idle is maximized), it is partial throttle that is the problem. If I roll through the throttle slowly bike is unhappy but once I get near 1/2 throttle it sounds a lot better and pulls pretty good. So first pass today will be raising the clip on the needle a step and going for a ride.

I think at WOT I'm good, everyone has been talking about what little rippers these motors are with some work and I just figured it wasn't running right but I think my expectations are faulty. With ~50 hp and a wet weight of about 340 pounds it will still feel slow as #$%* compared to my MT09 with twice the horsepower and only 50 more pounds.

One thing that feels funny, I asked before and never got a response. When I put every other bike I've had in first gear and then step down on the lever it stops early so I know I'm in first. This thing does not, it travels all the way down. I don't see anything like a missing pin behind the clutch cover, but maybe I left something out internally? Or do these bikes not do that?

Shtonecb500 · « **Reply #485 on:** June 22, 2021, 01:05:35 PM »

Quote from: tshrey on June 22, 2021, 07:36:23 AM

Timing is now dead on, both at idle and in the advanced setting. Went for another longish ride and plugs are clearly all firing but all way too dark. I'm good on my idle settings (adjust air screw until idle is maximized), it is partial throttle that is the problem. If I roll through the throttle slowly bike is unhappy but once I get near 1/2 throttle it sounds a lot better and pulls pretty good. So first pass today will be raising the clip on the needle a step and going for a ride.

I think at WOT I'm good, everyone has been talking about what little rippers these motors are with some work and I just figured it wasn't running right but I think my expectations are faulty. With ~50 hp and a wet weight of about 340 pounds it will still feel slow as #$%* compared to my MT09 with twice the horsepower and only 50 more pounds.

One thing that feels funny, I asked before and never got a response. When I put every other bike I've had in first gear and then step down on the lever it stops early so I know I'm in first. This thing does not, it travels all the way down. I don't see anything like a missing pin behind the clutch cover, but maybe I left something out internally? Or do these bikes not do that?

What do you mean travels all the way down, it travels like ur brake lever travels?
little rippers compared maybe to the 750, I love my 550 more than my 750, none of these bikes really get going until 3rd, if ur coming of a MT09 then ur prolly just going to be disappointed all the way around. You built a very nice bike though, love the grey frame in the natural light and your attention to detail.

tshrey · « **Reply #486 on:** June 22, 2021, 01:22:51 PM »

Thanks for the compliment. I'm sure it will be fun, I just had unrealistic expectations I guess

What I mean by lever travel is downshifting from any gear to the one below it the lever moves about an inch. In every other bike I've ever owned once you are in first gear if you step on the lever it doesn't move down at all, like there is a stop somewhere in the mechanism letting you know you are in first. This bike moves down the full inch even in first, so I'm never sure I'm there when down shifting at a stop unless I see the neutral indicator light for a sec as I move through it.

Shtonecb500 · « **Reply #487 on:** June 22, 2021, 01:26:53 PM »

Quote from: tshrey on June 22, 2021, 01:22:51 PM

Thanks for the compliment. I'm sure it will be fun, I just had unrealistic expectations I guess

What I mean by lever travel is downshifting from any gear to the one below it the lever moves about an inch. In every other bike I've ever owned once you are in first gear if you step on the lever it doesn't move down at all, like there is a stop somewhere in the mechanism letting you know you are in first. This bike moves down the full inch even in first, so I'm never sure I'm there when down shifting at a stop unless I see the neutral indicator light for a sec as I move through it.

Ohhhhh, no it shouldn't do that.

tshrey · « **Reply #488 on:** June 22, 2021, 01:37:54 PM »

Yeah, I kind of figured that. Unfortunately I don't see any mechanism in the clutch cover that would do that, so it must be something in the case that does it, not sure if I can get to it without pulling the whole motor apart.

tshrey · « **Reply #489 on:** June 23, 2021, 07:59:33 AM »

That's what I figured. I spent last night looking over all my pics and the factory service manual to see what I could have left out that would let it act like that. I guess I will be pulling the engine out at some point and the bottom case off to see what I did wrong. No hurry on that since it works fine.

Shtonecb500 · « **Reply #490 on:** June 23, 2021, 06:42:47 PM »

Quote from: tshrey on June 23, 2021, 07:59:33 AM

That's what I figured. I spent last night looking over all my pics and the factory service manual to see what I could have left out that would let it act like that. I guess I will be pulling the engine out at some point and the bottom case off to see what I did wrong. No hurry on that since it works fine.

I’m on my bike now, it absolutely does drop an inch if u hit it and you are already in first, that’s
Normal. Sorry I confused you dude.

tshrey · « **Reply #491 on:** June 23, 2021, 06:48:34 PM »

Hey thanks, you just saved me about 20 hours of work

tshrey · « **Reply #492 on:** June 25, 2021, 12:06:53 PM »

Dialed in idle circuit and tested the other night with fresh plugs. That now at least I am confident of, plugs all looked perfect. After that change rolling on the throttle slowly (just sitting there, no load) the engine hesitated. So I raised the needles (lowered clip 1 slot). That fixed the issue and I went for a ride. Better, but still just doesn't feel right. Whacking the throttle open and giving the bike the beans it feels good.

Pulled the plugs when I got back and found this

Reminder, I'm using a VM34 kit from Murray's Carbs, so cylinders 1&2 are on one carb and 3&4 are on the other. Based on that I would say that I still have ignition issues under load. Timing checks out perfectly. Coil and HT leads fully check out with a meter but I guess the next step is to swap coils and use fresh plugs to see if the problem moves to the other cylinders.

RAFster122s · « **Reply #493 on:** June 25, 2021, 12:48:08 PM »

Plug chops need to run at speed/throttle settings you are checking and then hit kill switch to get an accurate read on the plugs. That is after you have it fresh plugs in… otherwise the idle or low speed puts deposits on the plugs which obscures your readings. Typically the bike is warmed up and you do the plug swap then immediately go to the test level and sustain that speed/throttle for several minutes to get the read on fresh plugs.

tshrey · « **Reply #494 on:** June 25, 2021, 02:50:56 PM »

I get that, but my idle plugs looked good. Then I went for a ride and cylinders 2&3 look sooty as hell and 1&4 don't. I'm not trying to tune the carb setup, I'm just saying there must be something wrong with ignition if cylinders fed by the same carb but different coils look totally different.

If I find something wrong then I have to try to figure out where I can drive to do the plug chops at throttle settings other than idle, it isn't easy living around people.

tshrey · « **Reply #495 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 #496 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 #497 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 #498 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 #499 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.

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Author Topic: 76 CB550 Cafe build (Read 100387 times)