Author Topic: 1977 CB750 K7 Resto-mod, Knoxville (Read 97617 times)

calj737 · « **Reply #625 on:** August 25, 2015, 12:24:46 PM »

I'm not sold on that diagnostic process. To me, it's all about the changed variable. If being immersed in a rain storm caused this, then carb setting changes make no sense to me.

Water infiltration into the electrics or fuel are the only realistic options that I would pursue. It's possibly there is contamination/corrosion of the KILL switch and when you roll the throttle it's somehow aggravating the electrics.

AintNoEasyWay · « **Reply #626 on:** August 25, 2015, 01:20:42 PM »

Quote from: calj737 on August 25, 2015, 12:24:46 PM

I'm not sold on that diagnostic process. To me, it's all about the changed variable. If being immersed in a rain storm caused this, then carb setting changes make no sense to me.

Water infiltration into the electrics or fuel are the only realistic options that I would pursue. It's possibly there is contamination/corrosion of the KILL switch and when you roll the throttle it's somehow aggravating the electrics.

Yes, but still very strange that the bike survives a twist of the throttle when the choke is open. Agree? I'll be able to check things again in a couple hours when I get home. Maybe I'll go ahead & inspect the switch some.

calj737 · « **Reply #627 on:** August 25, 2015, 01:43:20 PM »

Yes, that is odd. Safe to assume this behavior did not exist before the rain shower?

Restoration Fan · « **Reply #628 on:** August 25, 2015, 02:30:52 PM »

Yeah, I told Nate that he should try to eliminate one thing at a time.
I suggested he try to ease the idle screw in and increase the rpm's slightly from 1250 to about 1500 or so. Since twisting the throttle kills the engine, I wanted to see if increasing the RPM's via the idle screw would do the same thing. The reasoning: if the engine still stops, it's almost certainly a fuel flow issue.

Assuming that doesn't kill the engine, then I suggested he remove the in-line fuel filter and see if the engine stays running on throttle twist....ruling out whether or not the fuel filter could be the problem. Unlikely, I admit since the bike stays running while under choke.

If that doesn't solve it, then I suggested he remove the air box and try seeing what would happen with no air box on the bike, since he said the air box at one point had water in the bottom. This should eliminate the possibility of a clogged/water-logged air filter as a possible culprit.

You could be right that it's an electric issue but that also wouldn't make sense if it stays running under choke...the vibrations that would cause a switch to not work will be the same under choke or not.

Restoration Fan · « **Reply #629 on:** August 25, 2015, 02:33:00 PM »

Quote from: calj737 on August 25, 2015, 01:43:20 PM

Yes, that is odd. Safe to assume this behavior did not exist before the rain shower?

He said it wasn't doing it prior to the rain shower...he even rode it 20 miles to the music venue. It started on the ride home and got worse after that.

RAFster122s · « **Reply #630 on:** August 25, 2015, 02:46:30 PM »

It is possible that the coincidence of a ocked filter if it wasn't able to rev with choke on. But, he indicated that it is reving when choke is on. I think that he is facing a electrical issues I am baffled by the choke allowing it to rev though. Check out your handlebar switches and unscrew it from the throttle side and see if off choke the issues disappear. If so, then something in the right switches is causing it.
Accelerator pump kicks in later than just off idle? ??

AintNoEasyWay · « **Reply #631 on:** August 25, 2015, 03:31:51 PM »

Ok guys, here's another video for you so you can see the difference in engine response. Today the bike can survive throttle when the choke is in, but you'll hear the engine hesitate & almost kill off when I rev. But when I turn further it catches & the engine stays alive. This is how it was behaving when I rode home after the rain on Wednesday night. I thought I might not make it home.

I'm wondering if maybe the fuel is delayed from the accelerator pump nozzles?

Also, any chance this is due to bad throttle cables? I guess that wouldn't kill the engine completely though...

I unscrewed the right controls RAF before taking this video. I looked inside & also tightened up the adjuster for the cable to remove some play. Maybe this helped the bike stay alive? The mystery continues.

Just an update: I removed the airbox & the bike died instantly it's throttle. But I verified that all the accel pump nozzles are working properly.

calj737 · « **Reply #632 on:** August 25, 2015, 05:00:10 PM »

What do your plugs look like now?

A little hint, if you want us to hear the engine, better to position the camera beside or behind the exhaust; it will produce a more accurate sound for us listeners

Question for you: what are you groping under the right side of the tank for so long during the choke changes?

Can you drain the fuel in the bowls into glass and examine it?

AintNoEasyWay · « **Reply #633 on:** August 25, 2015, 05:11:57 PM »

Quote from: calj737 on August 25, 2015, 05:00:10 PM

What do your plugs look like now?

A little hint, if you want us to hear the engine, better to position the camera beside or behind the exhaust; it will produce a more accurate sound for us listeners

Question for you: what are you groping under the right side of the tank for so long during the choke changes?

Can you drain the fuel in the bowls into glass and examine it?

Good call on the video-taking. I just wanted you guys to see how quickly it died when I twisted the throttle.

Here are photos of plugs 1 & 4. Then a photo of some float bowl fuel I drained into a cup. I promise that's fuel, guys.

I'm groping the idle adjuster screw to see if the RPMs change at all after I rev it.

calj737 · « **Reply #634 on:** August 25, 2015, 06:37:49 PM »

Well, one of your plugs clearly indicates you're not firing on that cylinder. Probably why it runs like poop. The super clean plug is not combusting. Either no gas or no spark. Better pull 2/3 and have a peak.

AintNoEasyWay · « **Reply #635 on:** August 25, 2015, 09:13:33 PM »

Quote from: calj737 on August 25, 2015, 06:37:49 PM

Well, one of your plugs clearly indicates you're not firing on that cylinder. Probably why it runs like poop. The super clean plug is not combusting. Either no gas or no spark. Better pull 2/3 and have a peak.

That'd be #1 that's not firing. I was having trouble with this cylinder not firing when I first started the new engine. It didn't look like this last Thursday when I pulled it to check it. I believe it was running at that time. I haven't checked that I have spark on all four plugs recently, but I do know that all four pipes were hot yesterday (didn't check today). I'll pull 2& 3 for a look today.

calj737 · « **Reply #636 on:** August 26, 2015, 04:03:33 AM »

If #1 looks like that, and all four pipes were hot, you've got a fuel issue on #1. No way around that. Running the choke and idling, #1 would look like #4.

enwri · « **Reply #637 on:** August 26, 2015, 08:20:50 AM »

Quote from: AintNoEasyWay on August 25, 2015, 03:31:51 PM

Today the bike can survive throttle when the choke is in,

Plug caps and leads drying out?

Do you use ethanol mix fuel? I haven't had much experience with it. Does water stay separated out or absorb into the alcohol?

Restoration Fan · « **Reply #638 on:** August 26, 2015, 08:56:35 AM »

He uses ethanol-free gas.

AintNoEasyWay · « **Reply #639 on:** August 26, 2015, 09:47:45 AM »

Quote from: enwri on August 26, 2015, 08:20:50 AM

Quote from: AintNoEasyWay on August 25, 2015, 03:31:51 PM
Today the bike can survive throttle when the choke is in,
Plug caps and leads drying out?

Do you use ethanol mix fuel? I haven't had much experience with it. Does water stay separated out or absorb into the alcohol?

Haha, Ron knows me best. Yes, I use ethanol-free, 100% gas.

Not sure that the plug caps are really drying out. Last Saturday the bike was stuttering with throttle, then I took off the airbox & it seemed like the accel pump nozzles weren't working quite like they should. So I took the carbs off & checked the jets & went ahead & got the accel pump back to normal. Then once I put the carbs back on, the bike would die with throttle (choke in) no matter what.

For whatever reason, yesterday it was back to behaving as it was before I removed the carbs Saturday, which is that hesitation/almost dying until i get back 1/4 turn of throttle.

Restoration Fan · « **Reply #640 on:** August 26, 2015, 09:51:31 AM »

Nate,
When we spoke you mentioned that you didn't remove the main jets. You might want to take those out and clean them...make sure there's no garbage or debris in there causing the hesitation on throttle roll.

AintNoEasyWay · « **Reply #641 on:** August 26, 2015, 10:33:43 AM »

Quote from: Restoration Fan on August 26, 2015, 09:51:31 AM

Nate,
When we spoke you mentioned that you didn't remove the main jets. You might want to take those out and clean them...make sure there's no garbage or debris in there causing the hesitation on throttle roll.

Yep, that'll be my next move probably. When I get home tonight I'll check plugs 2 & 3, then go from there. What an awesome week of weather I'm missing!

AintNoEasyWay · « **Reply #642 on:** August 27, 2015, 04:17:38 PM »

Ok guys, finally got to take a look at these 2 & 3 plugs. They look great to me. What do you guys think?

calj737 · « **Reply #643 on:** August 27, 2015, 04:25:20 PM »

Now solve the fuel issue on #1

AintNoEasyWay · « **Reply #644 on:** August 28, 2015, 06:41:20 AM »

Quote from: calj737 on August 27, 2015, 04:25:20 PM

Now solve the fuel issue on #1

Sounds good, cal. Should I just pull all the jets & clean them all thoroughly?

Here's one more video I did:

I put the camera behind the exhaust for this one.

calj737 · « **Reply #645 on:** August 28, 2015, 09:18:22 AM »

I'd still prefer to see a fuel level on 1&2 as comparison.

AintNoEasyWay · « **Reply #646 on:** August 28, 2015, 09:46:12 AM »

Quote from: calj737 on August 28, 2015, 09:18:22 AM

I'd still prefer to see a fuel level on 1&2 as comparison.

Not sure what you mean here. Could you clarify?

calj737 · « **Reply #647 on:** August 28, 2015, 09:52:26 AM »

clear tube method.

AintNoEasyWay · « **Reply #648 on:** August 28, 2015, 06:18:01 PM »

Fuel levels still looked good when I checked this evening. The bike was still hesitating as before when I started it up tonight. I decided, what the hell, before taking the carbs off I'll put some sea foam in the tank. Did that & now the bike runs fine. I took it around the block & for about a 7 mile ride just before dark. Tomorrow I'll try it on a longer 20 mile ride & see how that goes.

Maybe I had water in my tank or a clogged jet & the sea foam took care of it? Really not sure what to say about this, guys... Wish I had a better answer for what happened. Fuel that I drained from my bowls into a white cup did have a small amount of debris in it, so I think I'll clean the tank out as thoroughly as possible within the next week or so.

Restoration Fan · « **Reply #649 on:** August 28, 2015, 06:33:36 PM »

Hmmm....bad fuel, huh? Too bad no one suggested you dump out the fuel and just put new fuel in there.

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Author Topic: 1977 CB750 K7 Resto-mod, Knoxville (Read 97617 times)