Topic: 1977 CB750 K7 Resto-mod, Knoxville

[AintNoEasyWay]

Chain oil ends up under there too sometimes, The main bearing bolts wept on mine, sealer stopped it.

Hmm... well, I checked the torques last night & they were all good. I'm torquing only to 9 ft-lbs. Should I be doing more? Maybe that's the issue. If not, I'll look to applying some sealer to the gaskets & if I still don't have any luck, I'll try new, hopefully higher quality gaskets.

[enwri]

Don't over torque anything, if you didn't split the cases forget that main bearing bolt bit.
If you can't track it anywhere "upstream" of the final collection point on the gasket seam ( a lot of leaks end up dripping off there.)
A bit of sealer on the gaskets wont hurt.
I tracked a leak all the way up to the gallery plug in the front centre of the top case. hard O ring. Wasn't hard to find, just had to actually look.
My sidestand leaves a dirty little footprint after lubing the chain.

[AintNoEasyWay]

Been having a lot of fun on the bike the last couple weeks. Everything has been going great but I got stuck in a rain storm on Wednesday night & now I'm having some trouble with throttle response. Bike will sometimes die when I twist the throttle & seems to hesitate on occasion as well, especially at bottom end. I pulled up to a stop sign on Thursday night after having been in the rain the night before. Gave it throttle & it died. I pushed the starter button to start the bike back up & the engine didn't even turn over. I rolled it off to the side & waited a couple minutes. Tried it again & it started so I rode it straight home. I'm wondering too now if I also have a short in the wiring somehow from being in the rain?

The bike starts up just fine now, idles well, but still dies with throttle or feels hesitant in revs. From the few threads I've found, it could be an issue with air leaks or possibly accelerator pump?

This bike has stock jetting, air filter, & 4 into 1 exhaust. Again, didn't have any trouble with it until after it sat out in the rain the other night.

Any recommendations for where to start? Thanks guys.

[Desert-SOHC]

Maybe water got into the points cover and the switches. WD-40 = water dispersion formula #40, it will cure it till more water is introduced. Electrical grease at every connection will help keep water out also, that means ALOT of taking apart and cleaning.....then applying the grease and reassemble.

[enwri]

(I pushed the starter button to start the bike back up & the engine didn't even turn over.)
Does that mean not spin on the starter? or it spins but wont start.
The first one is an electrical fault, were the oil light and lights working, if not check earth connections, battery terminals, the solenoid connections, the plug on the ignition switch and the ignition switch itself.
If the lights were still working, and the starter didn't spin the motor, check the solenoid and starter switch, and the earth connections again.
If the starter spun it but it didn't start it could be both electrical  (spark wise) and fuel.
It wont want to keep running trying to idle on three cylinders unless the idle is jacked way up. (watch out if that cylinder comes back online when it has the higher idle setting.)
Run it in the dark and watch for any arcing along the leads or coils, weak spark can have a hard time lighting a denser fuel/air mixture (accelerating)
harder to see but wet plug caps can arc down the inside if they get water trapped in them.
Doesn't hurt to crack the drain screws open on the carbs to check for water, rare but not impossible, it's heavier and comes out first.

[AintNoEasyWay]

Interesting. Thank you guys as always. I just pulled the airbox & have some water sitting in the bottom of it! Also my accelerator pump isn't working properly. I get a mist of fuel out of carb #2, carb #1 sort of drizzles out weakly (not as it should), & I have no gas coming from the nozzles of carbs 3 & 4. I rebuilt the pump along with the carbs last year so not sure how it could go bad so quickly. Maybe the lines are getting blocked?

Update: removed the bottom piece of the accelerator pump (where the spring & ball sit). I'm able to shoot wd-40 through it okay, so no problems there.

[AintNoEasyWay]

(I pushed the starter button to start the bike back up & the engine didn't even turn over.)
Does that mean not spin on the starter? or it spins but wont start.
The first one is an electrical fault, were the oil light and lights working, if not check earth connections, battery terminals, the solenoid connections, the plug on the ignition switch and the ignition switch itself.
If the lights were still working, and the starter didn't spin the motor, check the solenoid and starter switch, and the earth connections again.
If the starter spun it but it didn't start it could be both electrical  (spark wise) and fuel.
It wont want to keep running trying to idle on three cylinders unless the idle is jacked way up. (watch out if that cylinder comes back online when it has the higher idle setting.)
Run it in the dark and watch for any arcing along the leads or coils, weak spark can have a hard time lighting a denser fuel/air mixture (accelerating)
harder to see but wet plug caps can arc down the inside if they get water trapped in them.
Doesn't hurt to crack the drain screws open on the carbs to check for water, rare but not impossible, it's heavier and comes out first.

Hey enwri, the starter didn't even turn over. Pressed the button & got absolutely no response at all. I didn't try kick starting it or anything. I assume that would have worked.

Oh yea, Desert. Forgot to mention that I put a PAMCO electronic ignition in it, so points getting wet isn't an issue. I did remove the points cover though, everything there looked good.

[Desert-SOHC]

Hey enwri, the starter didn't even turn over. Pressed the button & got absolutely no response at all. I didn't try kick starting it or anything. I assume that would have worked.

Oh yea, Desert. Forgot to mention that I put a PAMCO electronic ignition in it, so points getting wet isn't an issue. I did remove the points cover though, everything there looked good.

Was there lights on the dash and a headlight? Starting to sound like water in the electrics.

[Restoration Fan]

Nate,
A couple of places you might want to test:
A.  Clutch switch - I don't remember if you rebuilt the left-side controls or not.  But if water somehow got in there and the switch doesn't think it has the clutch engaged, it's not going to start.  This is an unlikely thing IMO, but it's worth checking if everything else doesn't work.
B.  Kill switch - likely culprit I would think.  Check where the black/white wire from the kill switch connects with the wires coming from your PAMCO and the coils.  Make sure these connections are still there and solid.
C.  Ignition switch - make sure your ignition switch block is making good and proper connection.  (Although, if your lights are working when you turned it on, the ignition is probably working)

Ron

[AintNoEasyWay]

I believe the dash lights were on, yes. I'm with you guys & think somehow water has bugged up either the starter button or kill switch. Ron, I agree it's pretty unlikely the clutch switch is at fault here.

I'll look at all this more once I get my accelerator pump back in working condition. I took the carbs off last night & checked all the accessible jets. No trouble there.

Like I said, the two passage ways for the accelerator pump are clear. I'm getting enough fuel from the accelerator pump to squirt into carb 2, but it's weak in 1 & non existent in 3 & 4. I'm guessing the pump isn't strong enough to get to the other carb nozzles.

I changed the pump last year when I rebuilt the carbs, but maybe the pump is a cheap one? What are my options besides going for a new pump or totally disassembling carbs to check the accelerator pump flow tubes?

[Restoration Fan]

What are my options besides going for a new pump or totally disassembling carbs to check the accelerator pump flow tubes?

You could always do like I did and buy a set of round-top carbs to replace those!   

[AintNoEasyWay]

What are my options besides going for a new pump or totally disassembling carbs to check the accelerator pump flow tubes?

You could always do like I did and buy a set of round-top carbs to replace those!   

Haha I figured you'd mention that! How much reworking did you have to do to switch to older carbs?

[AintNoEasyWay]

Just put the wd-40 straw up against the accelerator pump hole in carb #2 & am able to get it to spray through the nozzle of every carb. So that eliminates the tubes being blocked. Thank god I won't have to take the carbs apart again. I guess I'll try putting the pump back in & see if it's working again. If not, I'll order a new one this week.

UPDATE: I threw the carbs back on along with the airbox. Started the bike up again. Still dies right when I twist the throttle. Man, what's going on with this thing?

[Restoration Fan]

How much reworking did you have to do to switch to older carbs?

I had to buy new throttle cables.  Other than that, nothing was different.

[enwri]

Does the choke make it better or worse?
Was the pump circuit primed after refitting them? might take a few handfulls of throttle (not necessarily running at the time) to fill the hoses up to the nozzles.
You also mentioned water in the airbox, the filter isn't wet is it? should have dried by now anyway.

[AintNoEasyWay]

Does the choke make it better or worse?
Was the pump circuit primed after refitting them? might take a few handfulls of throttle (not necessarily running at the time) to fill the hoses up to the nozzles.
You also mentioned water in the airbox, the filter isn't wet is it? should have dried by now anyway.

Hey enwri, I'll have to try it with the choke up. I'm able to push the choke down quickly when I first start the bike up, just like before. Bike idles fine... only have trouble if I try to rev it.

I can try "priming" it before I start up the bike, but I never had to do that the past few weeks. Curious why that would be the case now. Man, I am getting really good at removing & installing these carbs...

The filter looked dry when I took it apart so I'm not sure if it ever was wet or not.

[AintNoEasyWay]

Bike does rev fine when the choke is up, but when I try to rev during idle it just dies out. Does this point back at the accelerator pump as culprit?

Here's a video of it:

Choke is in. All four pipes are hot.

[Restoration Fan]

Nate,
I know the problem!
Take off that Tennessee t-shirt and put on one from Georgia Tech.  PROBLEM SOLVED, BABY! 

LOL, just kidding.  Have you tried just rolling on the throttle gently to see if it stays cranked as you gently accelerate?  If it does stay cranked doing that, then yes, I would think that it points to the accelerator pump as a likely cause of the problem.

[AintNoEasyWay]

Nate,
I know the problem!
Take off that Tennessee t-shirt and put on one from Georgia Tech.  PROBLEM SOLVED, BABY! 

LOL, just kidding.  Have you tried just rolling on the throttle gently to see if it stays cranked as you gently accelerate?  If it does stay cranked doing that, then yes, I would think that it points to the accelerator pump as a likely cause of the problem.

Hey Ron, any pull of the throttle whatsoever seems to kill the engine. Beginning to wonder if it's something in the starter/kill switch doing all of this... What other carb possibilities could there be?

[Restoration Fan]

It still sounds like a fuel flow problem to me.  The starter/kill switch should be oblivious of any throttle/fuel flow.  It's a switch that's either closed or open. 

Have you tried adjusting your idle higher?  Also, do you have an in-line fuel filter?   If so, is it potentially partially clogged?  If it is, that could cause an issue as more fuel is demanded with the throttle pull...making it starve the engine of fuel.

And are you sure that no water got into the gas tank?  If you have an auxiliary tank, try hooking that up to the carbs instead of the gas tank and see if the problem persists.  Essentially, try to eliminate one potential issue at a time.  But it sure sounds like a fuel flow problem to me.

[enwri]

It does sound like lack of fuel if the choke makes it better, and I forgot about the clutch switch, sounds like that's what stopped it cranking, mines not 100% reliable, moving the lever with the start button in usually gets it cranking.
The little O ring between the bowl and body hasn't swelled and blocked the passage of the fuel has it? doesn't take much, sometimes you can check by loosening the bowl screw closest to it to see if it starts working or leaking out the side. Can do this while they are still on, although the airbox stops you seeing if the pump starts working again.
The check valves can get stuck open by debris, which will stop it working as well.
At least these carbs come off relatively easily.

[AintNoEasyWay]

It still sounds like a fuel flow problem to me.  The starter/kill switch should be oblivious of any throttle/fuel flow.  It's a switch that's either closed or open. 

Have you tried adjusting your idle higher?  Also, do you have an in-line fuel filter?   If so, is it potentially partially clogged?  If it is, that could cause an issue as more fuel is demanded with the throttle pull...making it starve the engine of fuel.

And are you sure that no water got into the gas tank?  If you have an auxiliary tank, try hooking that up to the carbs instead of the gas tank and see if the problem persists.  Essentially, try to eliminate one potential issue at a time.  But it sure sounds like a fuel flow problem to me.

I've only been messing with the adjusting screw that sit above the carbs. Not the four idle screws that sit just outside the float bowls. I do have a inline fuel filter, but haven't tried removing it since the rain. Rain could have gotten in the tank, although I'd be surprised how this could happen. Unfortunately I don't have an auxiliary tank, so to go that route, I'd probably empty the tank & just try acetone & air compressor to get it cleaned out.

It does sound like lack of fuel if the choke makes it better, and I forgot about the clutch switch, sounds like that's what stopped it cranking, mines not 100% reliable, moving the lever with the start button in usually gets it cranking.
The little O ring between the bowl and body hasn't swelled and blocked the passage of the fuel has it? doesn't take much, sometimes you can check by loosening the bowl screw closest to it to see if it starts working or leaking out the side. Can do this while they are still on, although the airbox stops you seeing if the pump starts working again.
The check valves can get stuck open by debris, which will stop it working as well.
At least these carbs come off relatively easily.

Enwri, you're referring to the small o ring on carb #2 correct? It didn't seem overly swollen to me. When I put the carbs back on yesterday, I had fuel flowing from all four nozzles again. So the pump seemed to be working properly again.

& yes, they aren't too difficult to remove. Can have them on a bench looking at them in about 10 minutes time now.

[enwri]

It's not the O ring then, water in the fuel is rare, and it sits at the bottom of the bowl where the main jet can dip into it and not allow fuel through. Takes a good "suck" to pull it through and clear, cracking the drain screws will get rid of any water in the bowl, but might not dislodge any trapped in the jet and emulsion tube, handfull of throttle with the choke on will clear it once it has been drained.
Rarely get water in the tank though. It's a long shot.

Water can block inline filters too.

[calj737]

Hold tight. Thinking this through, you say the bike idles and revs fine with choke, but no choke and you turn the throttle and it dies? Those are fairly conflicting symptoms. On one hand it would indicate a very lean condition (likes choke) and then it still should be happy when getting gas. And all this started after the rain storm?

I differ from others about believing water is in the filter, etc. If that were the case, the water would be pulled through with or without the choke and the poor running condition would ultimately clear itself out. I'd turn my attention back towards the ignition. But even that is baffling due to the choke altering the behavior...

With the the choke on, will it rev past 3,500? Without choke, where's the idle, and where's the rev counter when it dies? Does it suddenly die like you flipped a switch, or does it Peter out, or stumble to death?

[AintNoEasyWay]

Hold tight. Thinking this through, you say the bike idles and revs fine with choke, but no choke and you turn the throttle and it dies? Those are fairly conflicting symptoms. On one hand it would indicate a very lean condition (likes choke) and then it still should be happy when getting gas. And all this started after the rain storm?

Hey cal, yes, it revs fine with the choke out, which is why I'm confused. Also confusing is that I didn't have any of this trouble at all until the bike was hit with rain. The rain may not be a cause of all this, but there is solid correlation. I rode the bike about 20 miles to a music venue last wednesday evening, then got trapped inside during a rainstorm lasting a couple hours. When I finally got out, I was barely able to get the bike home, had very strange hesitation with the throttle. Then the next night, same hesitation. By Saturday, any throttle at all instantly kills the engine.

With the the choke on, will it rev past 3,500? Without choke, where's the idle, and where's the rev counter when it dies? Does it suddenly die like you flipped a switch, or does it Peter out, or stumble to death?

I can check this after work today. I believe it does rev past 3500 with the choke pulled out. Without choke, the bike dies suddenly... so at idle RPMs: around 1250. It doesn't peter out, it's as if I just clicked the kill switch or something. Even the slightest twist of the throttle kills it.

I talked with Ron last night & he suggested a 3 part course of elimination. First check how the bike runs if I play with the idle adjusting screws, turning it to idle at higher RPMs (does the engine die out then?), then check the in line fuel filter, then remove the airbox & see how the bike runs without it. Then I could also check the accel pump nozzles. At that point if the problem still isn't solved, I may go ahead & get new gas for the tank as well.