Author Topic: 1977 CB750 K7 Resto-mod, Knoxville (Read 97643 times)

enwri · « **Reply #525 on:** July 30, 2015, 06:11:46 PM »

That's more of a pain in the butt with the K7's and K8's than with the earlier K model air boxes.

Same as mine. k7. Someone ground slots on the heads of those long nuts on the bottom half.

AintNoEasyWay · « **Reply #526 on:** July 30, 2015, 06:13:52 PM »

Quote from: Restoration Fan on July 30, 2015, 05:59:11 PM

First things first. Eliminate one thing @ a time.
Take a spare spark plug. Pull the cap off #1 and put the spare plug into the cap. Touch the plug to the engine (make sure fuel isn't on) and see if you get a spark arc'ing over to the engine as you hold in the electric start button. Repeat that process for each spark plug.

If, at the end of this process, you have spark @ all 4 plugs, then spark is most likely not your problem (theoretically, you could have a bad plug and would have to unscrew each plug and test to confirm but the likelihood of that is so small that I would only try that after everything else).

Once you have eliminated spark, then it's most likely a fuel problem. Personally, I'd remove the air box and start the bike without an air filter on it. This lets you visually confirm the slides are completely closed when you have it on full choke.

Also, go get some more fuel. Put enough in there that the the tank is 2/3 full and just eliminate that as a potential source of problems.

Solid advice. Thanks as always, Ron. Just confirmed spark at all four plugs. Move on to carbs?

AintNoEasyWay · « **Reply #527 on:** July 30, 2015, 06:29:40 PM »

Calling it a night. Air box is off & I see that accelerator pump is shooting gas into each carb in the proper way. No issue there.

AintNoEasyWay · « **Reply #528 on:** July 30, 2015, 06:39:51 PM »

Quote from: Restoration Fan on July 30, 2015, 05:59:11 PM

Once you have eliminated spark, then it's most likely a fuel problem. Personally, I'd remove the air box and start the bike without an air filter on it. This lets you visually confirm the slides are completely closed when you have it on full choke.

Also just confirmed that slides close completely at full choke.

enwri · « **Reply #529 on:** July 30, 2015, 06:45:47 PM »

As long as it's sparking at about the right time as well (static timed?) it should at least fire, are you trying the throttle as it cranks? If it's 180 out it will pop and bang but not run,
Did you give no3 a tap to try to stop it flooding?
can you smell fuel on the plugs?
If every thing is clean and set it should just run, if not all you can do is clean and check again until you find something.
Remember those tiny little holes and passages in the carbs?
The rest is mechanical, if it all does what is meant to, (and it should when assembled correctly) the carbs rely on air pressure, pressure differences and fuel being drawn up through those tiny little apertures, little differences in hole size make a huge difference, just being unblocked isn't the same as clean. thousandth's of an inch difference makes a difference. (Jet sizes)
If you have it started already before i've finished writing this then it must be close enough

AintNoEasyWay · « **Reply #530 on:** July 30, 2015, 06:53:36 PM »

Hey enwri, I backed the idle adjuster all the way off because I didn't want to rev it. I was following Hondaman's instructions here: http://forums.sohc4.net/index.php/topic,12686.msg122510.html#msg122510

Kicked it about 40 times & tried to start but never twisted the throttle.

Carb #3 wasn't overflowing from the float bowl drain. I think maybe the gasket isn't seated right or there's a gap somewhere else because it seemed to be flowing down the side of the float bowl.

I did wonder if we maybe have the cam 180 since that was a concern before. But I'm pretty sure we had it 180 at first, then switched it to the correct position.

enwri · « **Reply #531 on:** July 30, 2015, 07:11:04 PM »

You'll know if the ignition timing is 180 out. Big bangs pops and maybe even flame shooting out the carbs and pipe. Don't worry about the cam bit, that's valve timing, it's right, you had it on the right cam timing marks, it won't care if the cam is 180 out, as soon as you turned the crank another 360 to the 1-4 marks that perceived problem disappeared, anything other than exactly 180 and it's trouble though. If you managed to get the tappet gaps set and didn't end up with loose tappets and giant gaps it will be ok.
It may need a bit of throttle to start initially. Backing out the idle screw is just a precaution to stop it from accidentally overrevving on startup.

Restoration Fan · « **Reply #532 on:** July 30, 2015, 07:17:17 PM »

Why not take a video of it trying to start and put it on YouTube, then link it here? Maybe someone will be able to help you solve the issue.

enwri · « **Reply #533 on:** July 30, 2015, 07:25:42 PM »

If you make a video, take off the tappet adjuster covers and make sure the valves are actually moving down, if you set them the way you had it first, like you were trying to, the valves wont open and will have giant gaps when the valve should be closed, and have the little gap instead of opening when they should be open.
I thought that got worked out back then though, not sure.

AintNoEasyWay · « **Reply #534 on:** July 31, 2015, 06:40:54 AM »

Quote from: enwri on July 30, 2015, 07:25:42 PM

If you make a video, take off the tappet adjuster covers and make sure the valves are actually moving down, if you set them the way you had it first, like you were trying to, the valves wont open and will have giant gaps when the valve should be closed, and have the little gap instead of opening when they should be open.
I thought that got worked out back then though, not sure.

Yep, worked that out back then & everything was closing/opening properly once we switched the cam over & set the gaps correctly. I'll take a video during my lunch break & throw it up for you guys to see. If I have enough time during lunch i'll get the carbs off & start checking them as well.

It doesn't matter which spark hose/plug cap goes to 1-4 or 2-3 from the coil right? E.g., as long as the hose/cap from 1-4 coil goes to 1 or 4 then it's fine? etc.

enwri · « **Reply #535 on:** July 31, 2015, 07:28:35 AM »

Quote from: AintNoEasyWay on July 31, 2015, 06:40:54 AM

It doesn't matter which spark hose/plug cap goes to 1-4 or 2-3 from the coil right? E.g., as long as the hose/cap from 1-4 coil goes to 1 or 4 then it's fine? etc.

yes, Either lead from Coil 1-4 on cylinders 1 and 4, either lead from coil 2-3 on cylinder 2 and 3

AintNoEasyWay · « **Reply #536 on:** July 31, 2015, 08:39:50 AM »

First start:

All I did was tighten up the idle adjuster on top of the carbs. I had it completely backed off.

My tachometer isn't reading anything though. Maybe I reconnected it wrong.

Have some smoke coming from exhaust around #3. Seems like the tappets are a little clangy. Need to make sure oil is getting up to the top end! I will follow Hondaman again:

Quote

When I rebuild these, I begin by kicking them over about 40-50 times in as much a continuous session as possible (it helps you lose weight!). Then, short bursts of 2-3 seconds of the starter until the oil light goes out. Then, when my leg recovers, I do it a 2nd time, then start it and run, as slowly as it will run, for about a minute.

The kicking/bursting routine will fill the oil filter and the lines, but will not force oil into the bearings the first time. After the second time, it will. The top end will not be oiled until the engine has run for a minute or so, due to air in the system at other points, so don't rev it until it's running pretty smoothly.

Desert-SOHC · « **Reply #537 on:** July 31, 2015, 09:36:52 AM »

Outstanding!!

Seems like your idle is low for full choke though. At full choke on mine I have it adjusted to run at 3,000 rpm. These things are REALLY cold blooded and mine doesn't run decent for about 15 minutes of riding....till its good and warm. You will be doing little adjustments on the first ride so be aware of that. I think I had to adjust my idle3 or 4 times till it warmed up all the way to operating temp, along with small adjustments of the rear brake. Other than that is sounds good...the standard SOHC "chuggle" I call it.

AintNoEasyWay · « **Reply #538 on:** July 31, 2015, 09:39:47 AM »

Quote from: Desert-SOHC on July 31, 2015, 09:36:52 AM

Outstanding!!

Seems like your idle is low for full choke though. At full choke on mine I have it adjusted to run at 3,000 rpm. These things are REALLY cold blooded and mine doesn't run decent for about 15 minutes of riding....till its good and warm. You will be doing little adjustments on the first ride so be aware of that. I think I had to adjust my idle3 or 4 times till it warmed up all the way to operating temp, along with small adjustments of the rear brake. Other than that is sounds good...the standard SOHC "chuggle" I call it.

Thanks, Desert. I had it running for about a month last summer & did some short riding before I started having a bunch of problems with it & pulled the engine. Back then, I could get it to idle with the choke in at about 1750. Can't remember what it idled at with the choke out. I need to get that tach working so I can know for sure.

Desert-SOHC · « **Reply #539 on:** July 31, 2015, 09:47:20 AM »

Get out there an ride it now!!!!!

Restoration Fan · « **Reply #540 on:** July 31, 2015, 11:58:55 AM »

OUTSTANDING!

A September ride is looking like a sure thing now, Nate!

AintNoEasyWay · « **Reply #541 on:** July 31, 2015, 02:43:02 PM »

Came back after work to try idling the bike for a minute & get oil up into the top end. #1 exhaust seems cold but the other pipes are hot. It also started smoking some out the exhaust & around the carbs. Air box is still off & I haven't tuned the carbs yet. Any advice on how to proceed would be great!

I checked the oil tank & over half of the oil that I just filled it up with is gone. I assume it worked down into the engine. So I filled the oil tank back up again.

Desert-SOHC · « **Reply #542 on:** July 31, 2015, 03:17:26 PM »

With a first startup there might be a little "burn-off" so that may be where the smoke is coming from. Sounds like #1 isn't firing or is starving for fuel, either way the problem needs to be found before continuing. Pull the plug and see if its wet.

AintNoEasyWay · « **Reply #543 on:** July 31, 2015, 03:33:36 PM »

Quote from: Desert-SOHC on July 31, 2015, 03:17:26 PM

With a first startup there might be a little "burn-off" so that may be where the smoke is coming from. Sounds like #1 isn't firing or is starving for fuel, either way the problem needs to be found before continuing. Pull the plug and see if its wet.

Ok first picture is plug #1. Does look wet on the threads but not on the actual plug. Photo two is plug #4.

AintNoEasyWay · « **Reply #544 on:** July 31, 2015, 05:06:37 PM »

Here's a better photo, 1 to 4 left to right.

Although #1 pipe isn't getting hot, I just checked & it still has spark.

calj737 · « **Reply #545 on:** July 31, 2015, 05:17:49 PM »

looks badly fouled from start up. Id say clean those plugs up really well, and see if #1 comes alive.

AintNoEasyWay · « **Reply #546 on:** July 31, 2015, 05:50:05 PM »

Quote from: calj737 on July 31, 2015, 05:17:49 PM

looks badly fouled from start up. Id say clean those plugs up really well, and see if #1 comes alive.

What could cause a plug to foul at start up, cal?

calj737 · « **Reply #547 on:** July 31, 2015, 05:52:10 PM »

Easy enough. If you used oil during assembly to slide your pistons together, then residue is still present in the cylinder. Rings hadn't fully sealed. Fuel level off badly before you got her fired. Lots of options. Use a torch and heat the tip enough to clean it up. Should fire. If so, splurge and buy a new set of 4

enwri · « **Reply #548 on:** July 31, 2015, 08:29:32 PM »

Are those are the old plugs?, lash out and get new ones, they will show up how each carb is performing easier.
did you clear tube it or bench sync it after you had all the bodies apart last time?
Maybe just check the level in the one that's not getting hot, or try screwing the mixture screw in and out to see if it picks up and fires. As they move out it gets a little more fuel at idle, in is less, can show if idle jets are dirty, if no effect, something is blocked or its flooding. Or the plug is dead.

Or the slide on that one is closed already before the others,(not synced) give it a bit of a rev to see if it picks up.

Desert-SOHC · « **Reply #549 on:** July 31, 2015, 09:47:13 PM »

Quote from: enwri on July 31, 2015, 08:29:32 PM

As they move out it gets a little more fuel at idle, in is less

Aren't PD's the other way? Out lean in rich?

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Author Topic: 1977 CB750 K7 Resto-mod, Knoxville (Read 97643 times)