1981 CB750K - Repair/Tune-up

[cdaiscool]

Definitely not dripping. Awesome then. I'll clean it up and go on my merry little way. 

Found 2 places now to do the truing. One said $75 if just tightened up, max of 2 hours if any gotta be replaced. Another said to bring it by tonight/tomorrow (depending when he's free) and he'll look at it then let me know. 

Got a friend coming over Friday with a 10mm socket and 12mm wrench (2 tools I apparently forgot to grab) so I can put it back on. I also have to find a new clip for the master link in my chain - it fell off. The chain also got SUPER slack in it, before I even loosened it up - or at least, I don't think I loosened it up. Meh. 

Now off to do more switch work. 

[shinyribs]

I owned '0' metric wrenches when I got my bike. Northern has a big roll up of metric wrenches for a good price.Sizes range from 6mm to 30mm. It was around $30. They are actually pretty decent wrenches! You'll find the bigger sizes come in handy more often than you would think. 27 mm fits my axle nut-needed for chain adjustments.And the 30mm fits my steering stem nut. Decent kit for the money.

[cdaiscool]

Its literally only a few that I need. Also need to get my hands on a torque wrench. Forgot to bring mine down.

Just got back from the bike mechanic. Seems fairly knowledgeable. He said to check the swing arm bushings. If those are good, then he said he would ride it to see if I am imagining things, and if not try to help me figure out what is going on.

I am hoping to have a place in the next few weeks and will have all my tools with me here. So I may be able to work on the bike here soon. We will see.

[shinyribs]

Ah,I gotcha. A buddy of mine got a torque wrench from H-F. It broke instantly.They swapped it out and its been fine for the last year or so. It reads spot on to my $$$ Craftsman.

[cdaiscool]

Okay.

I have video coming up right now, but its 35 minutes away. I have to be 20 miles from home at 5 am tomorrow, so I'm making this now.

Where does one measure to and from, specifically, when measuring if the sprockets are lined up properly. I have chain noise and the tire stops really quick. Almost like the brakes are applied, but they're not rubbing at all. I don't hear the shoes whatsoever unless I apply them myself.

Do you do it from each tire to the swingarm? Or the sprocket? Now that I'm writing this, I suddenly think it's the same place on the tire to the swingarm. I'm going to go outside and measure that right now.

Also, on the bottom part of the chain, I am doing 1 1/16 slack from end-to-end. That might be a bit tight though.

Swing arm bushings were tight, btw. Absolutely zero play in ANY direction.

Yay! Video is done. Had to send it to FB; Youtube refused to upload it via 3G.

Oh hell. It won't embed. http://www.facebook.com/photo.php?v=10100896449195542

[cdaiscool]

Okay. Measured from rim to swing arm. 2.75" +/- 1/16". Not shabby. Or is that too much?

Chain has 1 1/16" slack while on center stand. Both sides are quite tight, but did not ream on it. I'd guestimate 60 - 80 ft lbs. Just rode it around the block.



Current issues: I have no electronics. No headlight, no brights, no turns, no horn. Left side switch feels as if its about to fall off - apparently I lost a screw somewhere. Entire left side where electronics sit is exposed because the cover fell off a long time ago. I'm guessing it got wet and possibly blew a fuse. Or old juncture points are breaking from the rides. Or something in the switch is going to shit since it's cracked and is kind of loose now due to the missing screw.

As it warms up, it backfires some. Guessing this is due to cylinder #2, and not tuned.

Choke cable is nearly seized. Unsure why. Was hard before, but not nearly seized.

Didn't get a chance to actually ride it to see if the act of putting the wheel on and off fixed my issue. I stayed at 20 mph and 3k rpm in 2nd gear. At that speed, she's light on her feet and quite spry. Though nothing like a 250.

Hopefully, even with these issues, some of them safety related, the guy at least takes it for a quick test ride to check out what's going on with it. Honestly, I'm doubtful, but I can at least try.

And now I have to be up in 5.5 hours, so its bed time for this newbie. G'night guys!

[shinyribs]

Hey bud. A chain will always make a certain amount of noise.It's just nature of the beast. With the bike sitting on the kick stand I adjust mine to 1'' slack. If you adjust it on the center stand,when the bike goes back on the ground it will tighten the chain up quite a bit. An overly tight chain will be louder than a correctly adjusted one. I would recommend checking it on the side stand.If it is too tight,readjust and then check the noise level again.I bet it quietens down.

For aligning the sprockets-If you rear axle spacers are correct ( and I'm sure they are) then all you have to worry about is getting the axle straight in the s-arm.I measure from the canter of the rear axle to the center of the s-arm pivot bolt when I check mine.

About the drag-Do you have an o-ring chain? O-ring chains have a fair amount of added resistance as compared to a non o-ring chain. My chain now is a non o-ring and I can tell a HUGE difference in how the bike will actually coast now. A new chain will also loosen up after awhile. Maybe 1,000 miles or so? Not real sure on that,but it will loosen up a bit. That could be all you have going on there.

On the no power-Check your fuses.Every time my main fuse has blown it looked perfectly healthy.Also,corrosion on the starter solenoid terminal seems to give some guys trouble.Might be a good thing to check there.

Good luck bud.You're getting things sorted out now!

[cdaiscool]

Awesome. I have a non-Oring chain. And less than 1,000 miles on it. It also probably could use some oil, though that's back in Holland.

I met a new friend last week that has the exact same bike as me, and he has lived in the area for quite a while. He is going to give me his mechanics info tomorrow. He said he's a CB nut. The other guy is also an old Jap bike preferred guy. A review on Google plus said he got their CB350 running like a top. And I had to get a new master link, and that guy also recommended the guy I saw yesterday. He said for newer bikes he would recommend a different guy but mine? Carl. I guess he tunes by ear alone, but his ear tune has been proven to be good on others dyno.

Finally making headway at least.

On Jun 21, 2012 12:32 AM, "shinyribs [via Honda CB750'S]" <[hidden email]> wrote:

Hey bud. A chain will always make a certain amount of noise.It's just nature of the beast. With the bike sitting on the kick stand I adjust mine to 1'' slack.

For aligning the sprockets-If you rear axle spacers are correct ( and I'm sure they are) then all you have to worry about is getting the axle straight in the s-arm.I measure from the canter of the rear axle to the center of the s-arm pivot bolt when I check mine.

About the drag-Do you have an o-ring chain? O-ring chains have a fair amount of added resistance as compared to a non o-ring chain. My chain now is a non o-ring and I can tell a HUGE difference in how the bike will actually coast now. A new chain will also loosen up after awhile. Maybe 1,000 miles or so? Not real sure on that,but it will loosen up a bit. That could be all you have going on there.

Montvale,Virginia
 Piute said it best:  "wheres my 10mm?"
Hellbilly-"that is a great way to tell if you have come to your senses, when you start drilling random holes in things... "

LukeM-"Scooters rock, especially when they're in posse formation. "

Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato

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[rrgunslinger]

Not real sure but I think the book says to adjust the drive chain every 300 miles. 

On Thu, Jun 21, 2012 at 4:22 AM, cdaiscool [via Honda CB750'S] <[hidden email]> wrote:

Awesome. I have a non-Oring chain. And less than 1,000 miles on it. It also probably could use some oil, though that's back in Holland.

I met a new friend last week that has the exact same bike as me, and he has lived in the area for quite a while. He is going to give me his mechanics info tomorrow. He said he's a CB nut. The other guy is also an old Jap bike preferred guy. A review on Google plus said he got their CB350 running like a top. And I had to get a new master link, and that guy also recommended the guy I saw yesterday. He said for newer bikes he would recommend a different guy but mine? Carl. I guess he tunes by ear alone, but his ear tune has been proven to be good on others dyno.

Finally making headway at least.

On Jun 21, 2012 12:32 AM, "shinyribs [via Honda CB750'S]" <[hidden email]> wrote:

Hey bud. A chain will always make a certain amount of noise.It's just nature of the beast. With the bike sitting on the kick stand I adjust mine to 1'' slack.

For aligning the sprockets-If you rear axle spacers are correct ( and I'm sure they are) then all you have to worry about is getting the axle straight in the s-arm.I measure from the canter of the rear axle to the center of the s-arm pivot bolt when I check mine.

About the drag-Do you have an o-ring chain? O-ring chains have a fair amount of added resistance as compared to a non o-ring chain. My chain now is a non o-ring and I can tell a HUGE difference in how the bike will actually coast now. A new chain will also loosen up after awhile. Maybe 1,000 miles or so? Not real sure on that,but it will loosen up a bit. That could be all you have going on there.

Montvale,Virginia
 Piute said it best:  "wheres my 10mm?"
Hellbilly-"that is a great way to tell if you have come to your senses, when you start drilling random holes in things... "

LukeM-"Scooters rock, especially when they're in posse formation. "

Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato

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NAML

Turbos, Hondas, 4-bangers, what could go wrong?

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[cdaiscool]

You're right. And I did, after approximately 300 miles. But since I'm putting the tire back on 'er, I had to adjust now. I will again in 300 more miles. :)

[shinyribs]

I thought it was lube every 300, adjust as needed. :o

[cdaiscool]

Hola guys!

Been a while! Been putting in my time at the new job, been working on my truck, and hanging out with friends. Woodward Dream Cruise was last weekend, and BOY what a blast. Also was good to hear from TOOLS lately. Working on helping him with a request; we'll see where it goes.

I have to admit, he had IMPECCABLE timing. Since I am working on the bike right now and all.

Backstory: I moved to Ypsilanti, and in the move lost my bike cover. And concrete to park the bike on. But due to the heat wave, I erroneously left the bike parked on the grass. Well, one day we got some rain. And more rain. And more rain. It rained a total of 3 times. The 3rd time, it was a nice, gentle, rain-for-couple-days event.

The bike was uncovered. And tipped over.

I got the bike back up, ran and got some wolmanized plywood and a new bike cover (and found my old one a week later!! :mad:) and a few days later, went to ride it. Bike was dead.

Pulled the battery, saw it was low on water, so I filled the water and let it sit on my battery tender for 2 days. It got a full charge. Threw it in, went to start. Still no go. Checked my main fuse. Saw this:



So, I went and got a fuse box and a new fuse, and wired it in per the guy at the local cafe racer shop. Yes, they are called Cafe Racer. And have some G.O.R.G.E.O.U.S. bikes in there.

So, got the bike running after that. However, it died after. Got it some gas, got it fired up, but it was running like crap. Checked out my fueling situation since it seemed as though it was starved for fuel. Found a kink. Fixed kink by adding a fair amount of line and changing route of line. Now it's getting gas. However, it still isn't running well. When I first fire it up, it idles like crap. It idles around 1500 RPM. Even with choke all the way out. It never idles well without choke; with choke in, she drops to 600 and has stalled a couple times on me. So, I pulled out the spark plugs and found fouled plugs. And this:









This is on coils 2 and 4.

I'm going to get new spark plugs. Probably won't get it professionally tuned though. I just can't justify spending $100+ when I'm going to rebuild the motor this winter. Regardless of getting it rebuilt, if something happens, I'll still get it tuned this upcoming Spring.

So I just am looking to know: what would cause this discoloration? Perhaps the fuse was going out, and now that its all fresh and clean, it gave way to another issue, perhaps a regulator issue?

By the way, I still haven't had it up on the highway since Memorial Day. And there are some roads where it feels like its going to kick out on me. Not as many. I sort of think its just me at this point. But I want to get it running better before I take it out on the highway.

[Hellbilly429]

Have you checked the voltage of the bike around 3k rpms? If it's not over 15 volts or under 13 volts the regulator rectifier should be fine. If the bike was running on low voltages or irratic voltages because of that corrosion on your main fuse block it can cause that discoloration in the wires, but it is most likely just because those wires are a light color and any heat can make them discolor. Can check the ohms on the plug wires to make sure that the wires themselves are still in good shape. These bikes foul the plugs so easy when the voltage wavers at all, I know because I have had to clean and replace the plugs often while I was chasing my charging system issues.

[shinyribs]

That brown looks like heat. if the wires are vinyl then they will burn like that pretty easy. Silicone would hold up better,but they can burn,too. But I wouldn't have thought it could ever get hot enough at the coil to burn anything. Not unless the electrical connection on that end is poor and causing the heat build up. Resistance will do that.

Welcome back stranger!

[cdaiscool]

Hmm. It could be a badly done wire. I will pull them and look for any evidence that they may be in there incorrectly. Other than that, if it was a general charging issue I would think that this would be evident in all 4 wires.

Thanks! I will try to keep in touch more. The next few weeks will be quite difficult though, with 20,000 students moving in this week and I am solely responsible for all student networks...

On Aug 26, 2012 2:07 AM, "shinyribs [via Honda CB750'S]" <[hidden email]> wrote:

That brown looks like heat. if the wires are vinyl then they will burn like that pretty easy. Silicone would hold up better,but they can burn,too. But I wouldn't have thought it could ever get hot enough at the coil to burn anything. Not unless the electrical connection on that end is poor and causing the heat build up. Resistance will do that.

Welcome back stranger!

Montvale,Virginia
 Piute said it best:  "wheres my 10mm?"
Hellbilly-"that is a great way to tell if you have come to your senses, when you start drilling random holes in things... "

LukeM-"Scooters rock, especially when they're in posse formation. "

Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
History teaches us that men and nations behave wisely once they have exhausted all other alternatives. ~ Abba Eban

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[TOOLS1]

Are those resistor type wires? These ignitions are not supposed to resistor type wires.
TOOLS

[cdaiscool]

Got them from a CB750 supplier site. Same ones that everyone else uses. I can find the link in a little bit.

On Aug 26, 2012 11:50 AM, "TOOLS1 [via Honda CB750'S]" <[hidden email]> wrote:

Are those resistor type wires? These ignitions are not supposed to resistor type wires.
TOOLS

Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
1976 CB 750-A X 2
1977 CB 750-A X 2
1981 CB 750
1995 KZ 1000 P-14
1981 KZ 750 LTD X 2
1973 CB 350
1979 CM 185 Twinstar
1987 Honda TLR 200
1982 Honda XL 80
2005 Yamaha PW 50
South of Edan (Kansas City MO)

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[cdaiscool]

Well, brought it into the shop Tuesday. They said they were striving/goal of 48-hour turnaround time. Called last night, they said they hadn't touched it since they had a couple projects they were trying to get done for today. So their goal was moved to 'by end of the week'. I don't remember if they are open Saturdays or not...


I told them about the other shop, and the compression test in particular. They are doing a 31-point inspection, but likely going to cut the price in half since I have so much new stuff on it. Literally 50% of the stuff they look over, I put new on over the riding season. Oh well...

They are also going to tune the carbs, and try to diagnose the issue with the back end. So we'll see where this ends up.

[cdaiscool]

Okay. Just picked up the bike from the shop.

They checked a bunch of stuff out, didn't tell me much that I didn't already know, and a few things that surprised me. Best surprise?

Compression Results:
Cylinder 1: 155
Cylinder 2: 150
Cylinder 3: 150
Cylinder 4: 150

I told the mechanic on duty today, who races an old Norton, what the old shop said. He just grabbed a compression tester, took out #2's plug (the bad cylinder per the shop in Holland) and did a on-the-spot check for me. Bumped up to 150 quick, and it held. For 15+ seconds. No cranking or anything. So that place was definitely A. lying or B. doing the test incorrectly.

With that said, they did say the throttle cable sheathing is worn, the charging system is weak, and the carbs are dirty. I inquired about this.

Apparently, they were having a tough time getting the bike to run right. Uhh, that's why I was there. They mentioned the boots are worn, old, and cracked. I didn't see the cracks, but it makes sense actually, with how it likes to die at idle.

Picked up all new boots for both sides, plus all new clamps for both sides. I do know the previous owner used worm clamps to hold the boots to the motor. I suspect this is part of the leaking and why it ran like dog crap. 90% of everything is OEM, so hopefully this is the last big thing I gotta buy for it. I also still need to get a centerstand bumpstop so it stops rubbing the chain. I kind of forgot about that. Oops...

They never had a chance to ride it, so they didn't tell me anything regarding the rear wheel. I mentioned it to the mechanic, and he looked over the rear end while I was standing there. Said he saw nothing that'd cause it. I am going to bump up the suspension a tad when I find my suspension tool (I hate having a partially unpacked, AND dirty, garage) and see if that fixes it. If not, I'm going to have them do an official check, then e-mail Shinko again and ask that they replace the tire.

As for the charging system, he said it most likely is corroded wiring. So I am going to start pulling the wiring this winter and clean up the wires. See if I can't refrain from replacing stuff on it.

I wish the bike ran as good as it should. Theoretically, in 1, 1.5 weeks it should be. I'm going to pull the carbs off, replace all the boots and clamps, pull the bowls and look for signs of any issues, run an e-cord from a guitar through all the jets, then put it back together and bring it down to the shop. The guy agreed that, if I do all that, he will tune them and sync them for me. With those compression results, that should make it run like a freaking top.

Except now I've been hit with the mod bug. Now I'm considering swapping out the exhaust, due to the slip cover on mine having issues. Which will require a new tune. :/

[cdaiscool]

Well, spent today getting the carbs off. Yeah, definitely saw some cracking I hadn't previously seen in the boots. So getting those replaced should help. I figured you guys may want to see what carbs look like after maybe 1,000 miles, 2,000 at absolute most.

Overall shot:


Dirtiest of the 4. Bad seal? What can I do to prevent this from happening again?


Carbs 3 and 4:


Carbs 1 and 2. You can tell by the air cut-off hole that squirts the extra fuel in the base:


Carb 2 float bowl:


2 bowls. Unsure which is which (I labeled on the other side):


Final, random bowl:


What all should I specifically look at for looking to see if they're dirty or not? I'm going to run an e-chord string through the jets to make sure all are unplugged. Should I look for anything else? Should I pull the screw out that tunes them and run brake clean or something through it? Is there a simple guide somewhere for cleaning these out?

Also, now that I've pulled the float bowls, do I need to replace these gaskets? Or should they be good yet?