1981 CB750K, new rider, not so new bike... hlp plz!!!

[IvyLeague346]

Well I've had her about a year but haven't been able to do nearly a years worth of riding.... To catch you up she's been sitting a couple months because i haven't had the time and don't want to drop $500 to get her fixed at a shop.  I had done that 2 times before and after the second time I felt like the guys weren't really doing their job (entirely).  So at the moment when I try and start her, the choke has to be fully open to get any kind of sputter from the engine. With it closed the lights just dim themselves.  Trying to start up too often and the battery dies. Like the pics says the pods were on previously and the carbs were not tuned for them (something I was expecting the shop to do (sad to say)) they have since been cleaned and the air box is now on.  
I am not entirely sure where to start out, or at all actually.  Any and all help is much appreciated!!!

[seestheday]

Welcome to the forum.

Does the bike start with the choke in, or does it just sputter?

Unless you're ready to either spend a lot of money or spend a lot of time, I advise getting rid of those pods and putting back on a stock air box. These carbs are difficult to tune with pods.

I'm not surprised your shop couldn't tune the carbs well for those pods.

I have the exact same bike with 90k kms on the clock. I rebuilt my top end and carbs myself and now it starts when I almost breath on the starter and pulls like hell when I hop on the throttle.

Do you still have the sos on? If it is failing you may have fuel delivery issues.

[IvyLeague346]

simply put she doesn't start regardless - choke in no sputter just a dimming of the lights choke out sputtering no starting. The pods are off! I forgot to mention that, the air box is back on. I do however have  plenty of time now, still not so much $ but at the time these problems started I was back at school and didn't have the time.  I am not certain as to what the "sos" is...  I am at the moment just cleaning the tank and petcock before big ideas start coming this way. Thanks again!

[seestheday]

Sos is the affectionately named spawn of Satan. Does your fuel line run direct from your peacock to the fuel nipple in between carbs 1 and 2 or does it run into a mess of tubes mount on the carb rail (sos).

Basics of any 4 stroke engine

Suck, squeeze, bang, blow

Suck - are you getting gas?

Loosen the 4 screws on the bottom of the carbs. Fuel should run out of each. That means there is fuel in bowl. Tighten them up and crank the engine a little bit, full choke.

Now pull the plugs. Are they wet with gas? 

If they are wet then check spark, followed by compression.

Sent from my BlackBerry device

From: IvyLeague346 [via Honda CB750'S]

Sent: Sunday, June 2, 2013 12:05 AM

To: seestheday

Subject: Re: 1981 CB750K, new rider, not so new bike... hlp plz!!!

simply put she doesn't start regardless - choke in no sputter just a dimming of the lights choke out sputtering no starting. The pods are off! I forgot to mention that, the air box is back on. I do however have  plenty of time now, still not so much $ but at the time these problems started I was back at school and didn't have the time.  I am not certain as to what the "sos" is...  I am at the moment just cleaning the tank and petcock before big ideas start coming this way. Thanks again!

---

If you reply to this email, your message will be added to the discussion below:

http://honda-cb750-s.456789.n3.nabble.com/1981-CB750K-new-rider-not-so-new-bike-hlp-plz-tp4041627p4041639.html

To unsubscribe from 1981 CB750K, new rider, not so new bike... hlp plz!!!, click here.
NAML

[IvyLeague346]

You must mean this! Or at least I hope.... It was a confusing number when I got the bike. What can be done with this? And thanks again! It'll take me a little while but I'll give all the advice a go!

On Jun 2, 2013 12:55 AM, "seestheday [via Honda CB750'S]" <[hidden email]> wrote:

Sos is the affectionately named spawn of Satan. Does your fuel line run direct from your peacock to the fuel nipple in between carbs 1 and 2 or does it run into a mess of tubes mount on the carb rail (sos).

Basics of any 4 stroke engine

Suck, squeeze, bang, blow

Suck - are you getting gas?

Loosen the 4 screws on the bottom of the carbs. Fuel should run out of each. That means there is fuel in bowl. Tighten them up and crank the engine a little bit, full choke.

Now pull the plugs. Are they wet with gas? 

If they are wet then check spark, followed by compression.

Sent from my BlackBerry device

From: IvyLeague346 [via Honda CB750'S]

Sent: Sunday, June 2, 2013 12:05 AM

To: seestheday

Subject: Re: 1981 CB750K, new rider, not so new bike... hlp plz!!!

simply put she doesn't start regardless - choke in no sputter just a dimming of the lights choke out sputtering no starting. The pods are off! I forgot to mention that, the air box is back on. I do however have  plenty of time now, still not so much $ but at the time these problems started I was back at school and didn't have the time.  I am not certain as to what the "sos" is...  I am at the moment just cleaning the tank and petcock before big ideas start coming this way. Thanks again!

---

If you reply to this email, your message will be added to the discussion below:

http://honda-cb750-s.456789.n3.nabble.com/1981-CB750K-new-rider-not-so-new-bike-hlp-plz-tp4041627p4041639.html

To unsubscribe from 1981 CB750K, new rider, not so new bike... hlp plz!!!, click here.
NAML

1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals

My wife's recipe website that I'm trying to help promote: BuffyAndGeorge.com. Yes, I am a lucky man.

My cb750 video site

---

If you reply to this email, your message will be added to the discussion below:

http://honda-cb750-s.456789.n3.nabble.com/1981-CB750K-new-rider-not-so-new-bike-hlp-plz-tp4041627p4041640.html

To unsubscribe from 1981 CB750K, new rider, not so new bike... hlp plz!!!, click here.
NAML

[Hoosier Daddy]

First off, diagnosis is tough on the internet... don't assume we are in your head or there with your bike in front of us. Try and be a precise as possible to help us help you.

IvyLeague346 wrote

...choke in no sputter just a dimming of the lights choke out sputtering no starting....

So with your choke off (knob pushed in), it won't crank over? You say just the lights dim.
Yet when you pull the choke, it cranks?  But only fires at odd times and never starts... right?
Almost sounds electrical to me.

[jbrightwell]

IvyLeague don't give up on that bike!  I too have the same bike and yours looks like its all there.  The folks here give great advice, and it was way over my head when I first started working on mine.  But as SEES says - look for that SOS fuel cut off valve .  Right side, top of carb 4.  Fuel line from left side of tank runs to SOS then back to carbs.  Get rid of it, run a new fuel line WITH A FILTER direct from tank to carbs.  AND clean out that tank - there are bits of rust in it probably, those will keep clogging your carbs.  AND get a charger and keep that battery charged fully!!  All this is what the folks here told me to do when I was overwhelmed with my bike.  Now I am riding.!  

[seestheday]

I wouldn't bypass the sos just yet, but it may be the source of the problem. Check for spark and fuel first, and then we'll figure out where the problem is.

If you do bypass it, don't forget to plug the vacuum teat in between carbs 2-3 towards the front of the carbs.

[Hoosier Daddy]

Heh heh... He said "teat".

[jbrightwell]

SEES I thought I was forgetting something!  I bet a full charge on that battery will help a lot.  IVY LEAGUE I would also suggest the Service Manual that is available from this site.  I downloaded it, and bought one off of ebay along with a Clymer and Cycleserve manual.  I read thru them many times to find out what part these guys were talking about...

[IvyLeague346]

Ahh! I have found this SOS you speak of. I have cleaned out the tank, letting it dry, and petcock as soon as it is done I will check back in with you fine gentlemen and I will look up a couple other manuals and read up in the mean time.  Thanks again guys for sparing the time!
Sos?!

[trapper]

As Hoosier said, we're not there but, from what you're describing it really sounds like a fuel problem. Just for shits and giggles, check your pilot screws too. Make sure they're not screwed all the way in. If that's the case you won't be getting any fuel at all. Someone correct me if I'm wrong here but, I believe with the airbox, these should be about 3/4 turn out. Mine are 1 and 1/4 but I'm jetted. So often these problems end up being something silly that you don't think of.
Case in point, I was working on a CM400 for a customer the other day. He left then came back pushing the bike. Dies out on him. No spark. I went through EVERYTHING. Completely confused. Then just at random I disconnected the kill switch. Boom, she fired right up. Wires got pinched. So, just goes to show. Simple can be the biggest problem.
Good luck

[sgtslag]

You may need to perform a load test on the battery:  take it out, haul it to an auto parts store, and ask them to do the load test -- for free!  If it passes, then make sure it is fully charged (if a flooded lead-acid battery, check the electrolyte levels, topping off each cell with pure, distilled water only -- will require recharging after adding any water!) before working on the bike.  Without enough electrical power, nothing will happen...

Check the battery connection wires:  look for corrosion, green, or otherwise, on the wires.  If they have a white frosting on them, mix some Baking Soda and water, to make a paste; then use an old toothbrush, and clean them with this paste:  the frosting is acid, the Baking Soda paste will neutralize it, as well as remove it from the battery terminals, and the wires.  Clean and dry everything, before re-connecting.

If the wires are showing a lot of broken copper strands poking out, you may need new end connectors.  They typically crimp on, but they need to be securely crimped into place, or they will not conduct high current, causing a voltage drop at that point, robbing the rest of the bike of electrical power.

If the bike sat for more than a couple of months, the gasoline may have gone bad...  The best thing to do, is to drain the gas tank into a proper gas can, then mix that fuel with 1.5 oz of SeaFoam, per gallon, then dump the mixture into a car's gas tank -- fill it up to full, to dilute the old gasoline.  This will safely dispose of the aged gasoline, without issue.

Once this is done, re-fill the bike's tank with fresh gasoline, and 1.5 oz. of SeaFoam, per gallon:  SeaFoam will dissolve varnish in the tank, absorb water, and clean the carbs of minor varnish deposits; it will also stabilize the fuel for up to 12 months.  There is no down-side to using SeaFoam in the fuel system.

When you get the bike running properly, add 1-1.5 oz. of SeaFoam to the crankcase.  Go for a short ride to warm up the oil to 180 F, or higher (minimum operating temperature at which oil suspends crud to be caught by the filter), then drain the oil, and change the filter; add fresh oil, and done.  SeaFoam in the crankcase will dissolve carbon deposits, varnish, and other crud, within engine, and the transmission, turning the oil coal black.  This treatment will only be needed every 20,000-50,000 miles, when using modern detergent oils (SL or higher).  Cheers!

[Cabreco]

In order to rule out fuel delivery, after making sure the plugs aren't fouled, wouldn't it be prudent to just prime the carbs with a small squirt of gas to see if it at least fires?

Next would be check for spark at the plugs (or before).

BTW what repair did the shop do for $500?

[IvyLeague346]

Its taken a little bit to get back to you guys but thanks for everything. Had to go out of town for a wee bit but I'm back!  At the moment I've went through all possible fuels problems and have made sure fuels was getting where it needed to be, I actually did end up bypassing the sos because fuels just wasn't flowing, HOWEVER that was not the issue.  I was starting to believe it may be an electrical issue so i checked for spark and had none... Soooo... as a couple of you fine gents suggested I took the battery to the shop, asked for a load test.... I forgot to mention I actually dont have anything to charge the battery with but do use an external, fully charged battery to crank etc.  getting to the point they came back and said it wasn't even charged - go figure - and said he wouldn't have a problem keeping it over night and performing the load test ... This is currently where I am at now....  Just filling you guys in, and didn't want to leave you hanging after all of the very much appreciated advice, tips and suggestions!

While I wait do you suppose there are any other tests or what not I could perform, while I don't have the battery?
Also I did mention that I bypassed the sos, there was indeed a fuel delivery issue (though not the root of the evil) but after cleaning the petcock (just used b12 and those little arts and crafts pipe cleaners) gas was still flowing even in the off position, so it was just a bit messy hooking up, thought?

[IvyLeague346]

Got my battery back today! full charge passed its load test as well although I am a wee bit stumped again.  Its clearly got a full charege but now all I get is a single click when attempting to start her now, any suggestion, advice???

[Beekeeper]

clean up the connections to the battery, and the solenoid so the power can flow. I don't know how many times I have changed a battery in a hurry, and one electric "snap" and the system is dead.  Clean the connections.

[Hoosier Daddy]

Agreed, also you can bypass the solinoid and see if she cranks. helps eliminate a starter issue.
But I'd be willing to bet after you clean the positive connectionsa at the solinoid, and the starter. Then the ground to the frame / engine case you will be good to go. Last in the likely hood is the starter button... but you say you get a "click" so sounds like solinoid to starter positive lead or the ground (earth) is the issue.

Have you got a volt / ohm meter... or even a 12v test light?

[IvyLeague346]

Well guys, I got a couple new connections to the relay put em on and she fired right up! Can't thank you guys enough! I took her around and did however run into a slight problem. I did end up bypassing the SOS by putting a fuel line straight from the carbs to the tank with a filter. After the test run she began draining fuel from the 1 carbs NONSTOP. I noticed there is a T connection or tube between the 2-3 carbs, does it need to be plugged? I did plug the tube in the front, engine side, of the #2 carb, did I miss something?

[seestheday]

T connection should vent to air. You likely have a stuck float valve.

Sent from my BlackBerry device

From: IvyLeague346 [via Honda CB750'S]

Sent: Wednesday, June 5, 2013 11:51 PM

To: seestheday

Subject: Re: 1981 CB750K, new rider, not so new bike... hlp plz!!!

Well guys, I got a couple new connections to the relay put em on and she fired right up! Can't thank you guys enough! I took her around and did however run into a slight problem. I did end up bypassing the SOS by putting a fuel line straight from the carbs to the tank with a filter. After the test run she began draining fuel from the 1 carbs NONSTOP. I noticed there is a T connection or tube between the 2-3 carbs, does it need to be plugged? I did plug the tube in the front, engine side, of the #2 carb, did I miss something?

---

If you reply to this email, your message will be added to the discussion below:

http://honda-cb750-s.456789.n3.nabble.com/1981-CB750K-new-rider-not-so-new-bike-hlp-plz-tp4041627p4041879.html

To unsubscribe from 1981 CB750K, new rider, not so new bike... hlp plz!!!, click here.
NAML