Topic: 1978 CB750 Super Sport

[PhilaStandard]

I just got a 78 I just bought a 78’ SS with the intentions of restoring it to at least respectability. I’ve never owned or even know how to ride a motorcycle. I turn the key and I get nothing. I try the kick start and even more nothing ( The engine does turn over)!!
It seems electrical in nature. I have a Haynes and Clymes Manual. In the mean time is there anything I can do.

[UnCrash]

If your battery has no juice, then it will never kick over.

That's the first thing I would check.

[OldSchool_IsCool]

Welcome to the insanity, Phil!

The spark on these bikes is delivered by the coils.  If there is no electricity flowing from the battery to the coils, no spark!  As Crash stats, the battery is the first thing to check.  Wiring and points after that.

On a broader subject, you state that not only are you a new mechanic, you are also a new rider.  PLEASE take both aspects of ownership seriously!  Go slowly, double check everything.  Take a motorcycle safety course.  If you know an old M/C mechanic, try to get him/her over to take a look at your bike, even if it costs you a few beers!  They will catch those subtle yet deadly things that a new owner/mechanic/rider will miss. 

I speak from experience, because my 550K was the first bike I owned, rode and repaired.  Luckily the things I've missed haven't killed me... YET!

[mikedialect]

The 78F and pain a joy and a pain all in one. Good luck and make sure to read, read, read before you ride. Lots of things to go over before you hit the road.

[eldar]

Do a search for "shop manuals" . There are places to download the 78F manual. Get it and use that to help you out.

Your first steps are this:
Check your battery and fuses. Make sure all 3 fuses are good and the battery is fully charged.

Check the points and condensers and set your timing and point gap.
Set your cam chain adjustment according to the manual. Before doing this however remove the adjustment housing and clean it out. There is a powerful spring in here so be careful.
Set your valves and then try it.
This is just a base to start from. You will need to probably clean the carbs and all that too.

[OldSchool_IsCool]

hmmm... lets back up just a bit and not assume too much.  You say "turn the key and nothing"  when the key is in the ON or "P" position you SHOULD get nothing but headlights, oil light and possible neutral and running lights.  That is, until you press the start button on the right grip.  Check also the red KILL switch (also right grip, I believe) it too should be in the "ON" position.  Both the key and the kill switch need to be ON before kick start will allow the engine to fire up.  Full choke may also be needed to richen the fuel mix up to allow her to start.

What is the history on the bike?  Has it been sitting long? 

[drag0n]

hmmm... lets back up just a bit and not assume too much.  You say "turn the key and nothing"  when the key is in the ON or "P" position you SHOULD get nothing but headlights, oil light and possible neutral and running lights.  That is, until you press the start button on the right grip.  Check also the red KILL switch (also right grip, I believe) it too should be in the "ON" position.  Both the key and the kill switch need to be ON before kick start will allow the engine to fire up.  Full choke may also be needed to richen the fuel mix up to allow her to start.

What is the history on the bike?  Has it been sitting long? 

Ok this should maybe be under the moron post but it took me an entire summer of head scratching to figure out this particular combobu in my defense  Like Phila  I was working blind as i'd never had a bike or even ridden one for that matter let aside worked on one

[PhilaStandard]

Thanks for the info. I will now admit that I am a Moron!!!  I read yesterday that you had to pull in the clutch handle and then press the start button. I did so after I got home and the Starter did engage. I could tell that there was no combustion I.E. NO SPARK. Good thing I decided not to buy that starter for $200. After about two unsuccessful attempts at starting her up. The battery crapped out. So I'm getting a new battery this afternoon. It seems like the plugs aren't getting any juice. Could it be as simple as a fuse. Or maybe Ignition coils, points & condensers......??

My Haines and Clymer manual are coming in today. How much will they Help??

[OldSchool_IsCool]

It may be as simple as not having all the switches in the correct positions.  Make sure the key is in either ON or P (most clockwise position or 2nd most clockwise position).  Check also that the kill switch is in the ON position.  Your kill switch likely has 2 off and one on positions.  It's purpose is to cut power to the coils to kill your engine in an emergency, that's why it only takes a sneeze to move it to OFF.  Pull in your clutch or make sure you are in neutral (green light on your instrumant panel).

If you are getting the starter to turn, then it's not the fuse as both the starter relay and the coils are feed via the main fuse.

What is the history on the battery?  If it's relatively new, then spend your $$ on a "battery tender".  A tender is basically a charger that can sense a full battery and turn itself off.  You will want to add a tender to your workshop anyway, so start with that investment and charge your current battery in case it still has life.

The Haynes and Claymers will be good for general maintenance issues.  Where they tend to come up short is in carboration and technical specs on serious rebuilds.  That's where the Honda shop manual, specific to your year and your model will be invaluable.

[Helo229]

Being as you've never ridden before, might I recommend taking an MSF course. I'm new to biking myself, and I would definitely recommend the coursework/riding sessions.

How ironic that for my first bike I happened on a '76 750F 

Like everyone here said - Turn key, kill switch > run, choke open, fuel petcock > run.

If you're not getting any spark when turning the engine over you might want to check your plugs and wires, on my 750 they had pulled apart. I can't see both coils going out, so be sure to check a plug from each.

Pick yourself up a cheap multitester so you can check for continuity. Remove your left access panel to get to the fuses.
You already said it cranked so we'll skip the starter solenoid.
To check the fuses (and make sure they work), remove each fuse and place the end of each probe to each end of fuses. You should either see a light/hear a buzzer depending on your multitester.
Next, with the fuses removed, test and make sure there is no continuity between each fuse holder with the fuse removed. (I know, fairly stupid to test, but you never know what previous owner might have done)
Lastly, install each fuse and place the probes for your tester on the fuse HOLDER, not the fuse itself. This will make sure all of your contacts are clean.

Next, check your rectifier, it's the multi-tiered stack of square black plates. Disconnect it's harness, place one probe to the red wire, then the other to each yellow wire in turn, then switch the probe connected to the red wire to the black wire and check each yellow lead again. Depending on how it feeds back some connections may not show continuity, which is fine. (as a side note, this is no garuntee that the rectifier is good, it may fail at higher temperatures when you're out on the road)

Finally, on the connector you removed from the regulator, check to ensure continuity between the three yellow wires. This will should show whether the stator coil needs replacing.

All this being said, I'm very new to motorcycles, but do have a fair ammount of experience working on newer vehicles. Testing electrics has never been my strong point, as I really don't have the patience for it, but these simple layman's tests are what helped me troubleshoot my bike. It would be nice if they printed something simple like this in my Clymer's, instead it was a series of complicated tests for Ohms, volts, cycles, etc. Hopefully some of this will be able to help you.

[PhilaStandard]

I will try to do all of that when I get home. There seems to be No spark at all though. The wires and plugs look good. Some one was saying points and condensers were the problem.

[Helo229]

Your points and condensers control the timing of your engine and when each coil fires, so they very well may be at fault. What I posted above is just a quick check-up of your electrical and recharging systems, which I would definitely recommend checking before your first ride. Trust me, first time I got it started and running I did what you're no doubt looking to do - take a ride. Unless you check all that first though, you'll end up like me pushing 600lbs homeward a few miles. 

[firecracker]

I HIGHLY recommend taking the MSF course.  Took it before I even picked up my bike.  The actual "on bike" experience is invaluable.

Welcome!

[OldSchool_IsCool]

Phil,

That's 3 votes for a safety course, and I'm sure you will get MORE votes for it too.  Here is their website.

http://msf-usa.org/

Do it, Man!!  The life you save may be your own!

By the way, the Motorcycle Safety Foundation courses are usually $25-ish and are 3 half day courses.  There are a lot of Hardly dealerships that charge several hundred $$ for the same thing, but thats because they are so used to gouging their customers!

[my78k]

You say there "seems" to be no spark at all...do you know there is no spark? or are you assuming that since it isn't trying to fire that there is no spark?

Check the plugs for spark by removing one and with the HT lead attached hold it near the frame (basically touching it or one of the exhaust headers) and crank it over while looking at the plug end and looking for spark.

I am not saying that it isn't the case but most of my problems with mine have been fuel related (dirty carbs) rather than ignition related.

Aslo, double check your petcock is in the on position (or preferably the reserve position if it is getting low). May want to drop the float bowls too and see the condition of the gas in there and the bowls themselves...

Dennis

[mikedialect]

I HIGHLY recommend taking the MSF course.  Took it before I even picked up my bike.  The actual "on bike" experience is invaluable.

Welcome!

Oh yes, if you've NEVER rode before, go learn on a bike that weighs 1/3 of that 750. Tip their bike over- not yours. You're going to do it. Get it out of the way without damaging your new beauty. It's money well spent. I took the class and the whole time I was calculating how much money I wasted, but I still picked up some valuable info.  Some things I was forced to do over and over again I improved on.

[PhilaStandard]

I just did what one guy suggested and checked the spark against the frame. There was a small arcing but it looked weak should it have been stronger. I got a battery charger and charged the old battery I also have a new battery that I'll be chargin tonight. What should I check next?

There is some spark but no combustion.....................?

Anybody have any ideas??

On another note I had no Idea that bike was going to be so heavy.

[Helo229]

Check to make sure each sparkplug cable is going from the right coil to the right cylinder and the timing. I'm sure there's a post on here somewhere you can search for which will explain it.

If the timing is lined up as are the cables, I would check to make sure that you have compression and the carbs are functioning.

:Edit:
P.S. - Did you see about getting yourself into an MSF course yet? If you haven't, check out this site:

www.ride2die.com

Not to scare you, but realize the consequences of riding without knowledge. These old bikes are big, heavy, difficult to steer/balance (compared to newer sportbikes), and still have all the power it takes for you to make a single mistake and not walk away.

[PhilaStandard]

I think it may be the Carbs there is dark gunky stuff on a small pipe coming out of the bottmom of one. Though it is old the electrical system is not dysfunctional.

[my78k]

Believe it or not but the electrics on these bikes are actually very reliable all things considered...sure stuff can go south but not as much as one would think.

My guess is that spark isn't your issue and fuel is the problem. These bikes are known for carb problems if they have been sitting for any length of time. I would pull the carbs and make sure they are clean (Not reasonably clean but rather spotless!) The idle jets are so small that they get plugged up very easily!

Dennis

As for the MSF course I agree that it is necessary but first let's get this thing running!!!

[PhilaStandard]

I got it too start but I had the throttle open all the way and when I let it go the engine crapped out. My guess it the jets on the carbs is clogged. I bought some carb cleaner. But I don't know the first thing about taking off the carbs. Can I find a rebuild kit anywhere, can i use older CB750 carbs from different bikes. Or is a  thorough cleaning the way to go...........??

[OldSchool_IsCool]

not knowing the history of your bike (how long it has sat, was there gas in it, etc) then yes, a carb cleaning is a good thing to do.  Kits are probably available at around $15-$20 per carb. 

I'm hoping someone who is more familiar with your particular model and year will step up with details and gotchas before you start in on the removal.

[my78k]

To be honest I haven't done a full carb rebuild...I merely pulled the carbs off and popped the bowls off and pulled the idle jets and cleaned it out best I could for the time being mainly because I wasn't sure if the bike was saveable and it made a huge difference! As long as the bowl gaskets are in decent shape you could probably do the same for the timebeing just to see what kind of difference it makes. Admittedly it won't be perfect but it won't cost you more than 4 or 5 bucks for a can of carb cleaner...You should absolutely do a full overhaul at some point but if you are at all tight for money or aren't sure if the bike is going to be a keeper it may help in the interim

Dennis

[mikedialect]

those 78f carb kits were hard to track down..

they have them here: http://www.motorradbay.de/main/honda.php?kat=honda&best_nr=&modell=cb750%20f

My carbs have been pretty damn good since I got the bike and after I synched & tuned them I haven't had to mess with them since. Taking the carbs out and cleaning them is way easier than it sounds. Just be sure to keep all of the parts in order. There are a ton of good web pages detailing what it takes to clean them if you need a visual aid. The clymer manual actually has a good diagram for the F carbs. It's about the only thing that book has been good for so far...well and interesting bathroom reading.

[Wheelhorse77]

I HIGHLY recommend taking the MSF course.  Took it before I even picked up my bike.  The actual "on bike" experience is invaluable.

Welcome!

Oh yes, if you've NEVER rode before, go learn on a bike that weighs 1/3 of that 750. Tip their bike over- not yours. You're going to do it. Get it out of the way without damaging your new beauty. It's money well spent. I took the class and the whole time I was calculating how much money I wasted, but I still picked up some valuable info.  Some things I was forced to do over and over again I improved on.

I guess it depends on the individual. I tried to get into the course but it would fill up in less than a day for the entire summer. It was a joke to get into and it is suppose to be very beneficial. I've ridden dirt bikes in the past so I guess that can account for some learning, I've ridden dirt bikes since about 85 and 2006 went and got the permit portion and rode with an experienced rider using my bike. The next riding season I went to the DMV and went through the cones and all of the exercises on the 750.

I believe that it's people who don't learn how to handle their bikes are the ones that are way more likely to be involved in an accident.

http://www.ridelikeapro.com/

This DVD showed the best advice I have seen. 110 lb women cranking a full dresser, scraping the pegs, through the cones. Like the motorman says, if a woman can handle an 800 lb bike, why can't a manly man get it to perform?

Inadequate training and practice. You want to learn to ride your bike like the dork between your legs.

Oh ya, everyone is out to run you over...keep a sharp eye.