Topic: Total Newb: Starting Issues After Oil Overflow

[matthew.hyndman]

Hey all! Great forum. Disclaimer: I'm new to motorcycles and to mechanics. So I apologize for using non-technical terms or not knowing obvious things I should know as a bike owner.

I've had my 1974 CB750 for about a year now and this is my first time bringing it out after having it stored for the winter. The guy who owned it before me managed a motorcycle shop and took great care of it.

When I kick-started it last weekend (electric start needs repair), it turned over on the second kick! We did some adjusting on the clutch and I gave it a spin around the block to see how the clutch felt. When I did that, oil came out steadily from the overflow tube. I changed the oil and filter before storing it. Turns out I think there was just too much oil in my reserve tank (I put in the 3 q or whatever the manual said, but it was too high on the dipstick).

So, we syphoned out some to get it to the proper level. When I went to start it again, I couldn't get it to turn over. We tried for several hours and in that time I only got it to turn over twice when I was really engaging the throttle. Now I can't get it to turn over at all.

My old man was helping me and thought there was a chance some oil got on the spark plugs, so I ordered a new set and am waiting for them to ship in. If that doesn't help, I'm not really sure what to try next.

Any ideas? Thanks!

(Some eye candy for your time)

[flybox1]

Start with the basics.....we need to know everything is in order BEFORE we start troubleshooting.
3000mi tuneup items.  cam chain adjustment, valve adjustment, timing/advance, carb clean/bench sync, etc.
D8EA plugs are readily available at your local auto parts store.

Overflow tube?  Which one?

[calj737]

And when you say, "won't turn over..." what exactly does that mean? Does the kickstarter cycle the motor? Does it appear the motor is rotating, but not firing?

Likely causes of the latter are fouled plugs, weak battery, no fuel, etc.

[matthew.hyndman]

@flybox1

I honestly don't have the specifics you're asking about (enter embarrassed first-time bike owner). The guy I bought it from had owned it for about a year—he bought it from a dealer (his friend) who had it sitting in a show room for 15+ years. He said in that year he ran regular maintenance and had the carbs cleaned and synced at the shop he managed. He rode it regularly for that year.

I ran it last summer and put about 1k miles on it and never had any issues.

I'll check the manual when I get home to see if I can track down exactly what the overflow tube is called.

@calij737

I'm not 100% sure I know the correct terms to be able to answer your question, but I'll give it a shot. When I use the kickstart, it cycles through but the motor doesn't fire. The battery has been on a tender all winter and is running the rest of the electrical fine. I have a dead solenoid starter switch so I'm waiting for that to ship in before I can replace it... but the electric start has been down for a while now. Bike does have fuel and was stabilized through the winter.

[calj737]

Okay, well that helps some.

Let's check the obvious things:
1. Petcock is ON and there is ample fuel in the tank?
2. KILL switch is set to RUN and key is ON? (don't smirk, this happens)
3. Pull any of the plugs. What do they look like, and more importantly, what do they smell like? Strong odor of fuel? Dry, black, clean as a whistle?

You can "bypass" the solenoid by using a screwdriver to short the 2 large posts (bike in NEUTRAL please!!!). Key ON, RUN switch, try the screwdriver. Should spin the Starter Motor.

You could easily have an issue where you aren't getting voltage to the ignition coils from your KEY or from your KILL/RUN switch. Look under the tank (use a flashlight). You should seethe 2 coils where the spark plug wires trace back. Theres a BLACK/WHITE striped wire. Using a voltmeter, red probe on the BLK/WHT connection, BLACK probe on metal bolt of the frame, key ON, RUN on, what voltage do you get? You should see over 11.9v. If not, you aren't going to fire the coils. You have a wiring issue from the KEY or the RUN/KILL switch.

[matthew.hyndman]

@calj737 thanks for the response!

1) Yes.
2) Yes.
3) Have not pulled the plugs yet. Will do that tonight, but haven't done it on a bike before.

My dad and I were looking at the electric start issue last weekend and we tried bypassing the switch with a screwdriver and we heard some engagement in the starter motor, but it was short and not very strong. It's not like the bike started up, but I'm not sure if you're implying it was supposed to.

What's weird is that the electric start did work when I first got it (kill switch didn't) but then started to die out over the next few months. But it didn't seem to affect the rest of the bike while I rode it the rest of last summer.

I'll try to get my hands on a voltmeter and run the test you suggested.

Would the issue of not getting voltage to the ignition coils prevent the bike from starting even if I'm using the kick start?

[calj737]

I'll try to get my hands on a voltmeter and run the test you suggested.

Would the issue of not getting voltage to the ignition coils prevent the bike from starting even if I'm using the kick start? YES

You might also take some decent voltage readings at the battery, key OFF. Then again key ON. If the electric start use to work, now doesn't, thats often associated with a degrading battery, or accumulated corrosion/resistance at the solenoid or starter motor circuit.

If you had the headlight burning the entire time you attempted to kick start the bike, you have likely run down the battery anyway. Time to connect it to a battery charger (mind your polarity please!). Don't leave it for days, just 6-8 hours, or overnight. Disconnect it. Then a few hours later, test the voltage with a meter. You can pick up an inexpensive meter at the Auto Parts store for $30 to do all you need (voltage, ohms, and continuity). A good tool to have in your toolbox.

Pulling a plug is easy. Use the spark plug socket on a ratchet wrench. Turn it out. (Remove the spark plug wire from the plug first).

[Jerry Rxman Griffin aka MuthaF'er]

While you're at the auto parts store have them do a load test on your battery after you've charged it fully.

[matthew.hyndman]

Update:

Battery was dead as was my starter solenoid switch. Both have been replaced as well as my spark plugs. Unfortunately, I'm still not having luck.

When I first started the bike with the updates I just mentioned, it did fire up and ran for about 5 seconds before it died. I haven't been able to get it to start since.

Here's a video of what it sounds like when I try to start it. Any ideas on troubleshooting? Looking for a glimmer of hope before I try to clean carbs for the first time.

[ekpent]

 An easy place to start is that you are getting spark at all 4 plugs. Take an extra plug put it in a plug cap grounded to the head/valve cover turn over engine and look for a spark. 1 and 4 fire from one coil and 2 and 3 from the other. Once spark is confirmed you can move on to fuel delivery.  Are you smelling gas like it is severely flooded, have you checked to see how wet the plugs are and are you useing the choke correctly,handle up is choke on,handle down is off.

[calj737]

I would echo that there does NOT sound like any spark is reaching the plugs. Check your KILL/RUN switch is passing 12v to the coils (measure the voltage on the BLK/WHT wire at the coils).

[matthew.hyndman]

I know I should get a voltage reader just to have one but I don't at the moment. If my kill switch has never worked should I assume it's that and order a new one? Or is there hope to repair it if I disassemble?

[calj737]

I'm a NO fan of making assumptions when diagnosing mechanical issues. Go buy a damn voltmeter for Pete's Sake! You can get a decent one for under $30 at the auto parts store.

[ekpent]

I know I should get a voltage reader just to have one but I don't at the moment. If my kill switch has never worked should I assume it's that and order a new one? Or is there hope to repair it if I disassemble?

It will take a whole 2 minutes to lay a plug on the head in the cap and crank it over to check for a spark. If you had a cheap 99 cent test light you could quickly tell if your getting power to the points also,another 2 minute job ! Don't overthink it too much yet just do some easy troubleshooting first as you said you just rode it last week. You were working on the clutch and the points do have a connection on the frame tube by the oil tank and the wires do run under the cover on that side. Is it still plugged together well there at that connection ? Follow the yellow and blue wire from the points cover area and they should have a white clothe shielding around them.

[matthew.hyndman]

Thanks to everyone for the help! I finally got it running.

It ended up being a fuel issue even though I stabilized the fuel and ran it through well before it went into storage. I was only able to get the bike to fire when I ran it on the reserve tank and kept the throttle at high RPMs. I did my best to burn through what sounded like gunk and bad gas, and eventually put in octane treatment and some fresh gas to help burn through the rest of it. The octane treatment seemed to make the difference. 

Now it sounds and runs great!