[Dabba]

So... I broke the bike out today from winter storage. I basically kept it outside and covered and kept the tank and carbs full of stabil. I didn't drain them hoping the stabil would keep the fuel from gumming up. I was correct because the bike started on the second kick. So I rode it up and down the block, and then about 12 miles into town. Took a break there, and began riding it back. About 10 miles into the return trip my dummy/oil light came on. I limped it over the crest of a hill for another 15 seconds and then cut the engine and coasted down the hill to a safe spot in a parking lot.

Thinking I stupidly forgot to store it topped off on oil, I put two quarts in it, which probably overfilled it a bit. I know, I'm dumb for not checking before jumping off on a ride but I remember topping it off before putting it away, but I guess it could be a little low as it has a leak and I did take it out a few times during a nice week.

I start it again and the dummy light stays on despite having more than enough oil in it. At this point I'm weighing risk vs reward of letting it continue to run and trying to limp it home, and I know I will not be rebuilding this engine even if I had the time and money at this point so.. considering I had no noises or other symptoms I guessed it was a faulty sensor decided to risk it.

The bike runs fine at idle, but as soon as I start to go power drops, RPMS drop despite throttle position and it dies. Then you can kick it right back over and it will run happily while not in gear. As soon as you let off the clutch its start losing power and stalls again. The dummy light is on the entire time. The standard oil leak that I've decided to live with has also appearently gotten much worse because it began smoking like crazy from oil dripping on the power chamber. It usually does, but not to the amount it was after all this started. I couldnt find a definite source but the head and base gaskets looked intact and all I could see was more oil on the underside so thats anyones guess.

To me it seems like I lost compression (idles but won't move), or maybe it has something to do with case pressure? (Oil leak bad enough the dummy light stays on and maybe some compression loss that way?) Faulty light and worsening electrical problem (less likely), or... who knows? It does have a bad headbolt with a helicoil so now I'm wondering if that let go too and the surrounding bolts arent enough to keep a good seal around the head....?

But unless its something simple I think I may be done with this. The case damage to the head bolt threads doesnt make it worth rebuilding to me and I said I'd swap a motor in next time. Unfortantely I'm in PA school and in my clincal years which means full time work as a medical provider and studying so no time or money to deal with this. I know if I sell it I won't get much at all but.. not sure what to do some here. Only has a season on the rebuild I did..

 

[FrisianWheel]

What bike are you riding? Too much oil isn’t good for sure.

 

[Dabba]

The one in my sig, 78 CB400T II

 

[longdistancerider]

I would start by checking the oil level, if it's too full then drain/replace it. I'd find a new oil pressure sending unit and replace that. To replace it means that the right cover has to come off so you can check the oil pump drive chain at that time.
I'm suspecting that the oil pressure sender has failed and also may be the source of your leak.

 

[Dabba]

I would start by checking the oil level, if it's too full then drain/replace it. I'd find a new oil pressure sending unit and replace that. To replace it means that the right cover has to come off so you can check the oil pump drive chain at that time.
I'm suspecting that the oil pressure sender has failed and also may be the source of your leak.

Does that explain the loss of power while in gear though? I'm hesitant to throw time/parts and money at it if it's something more involved.

 

[longdistancerider]

If the oil level is significantly overfull then it could explain the power loss.
It's also possible that the jets have a significant amount of varnish built up on them from being parked. I would also drain the fuel from the tank, add fresh fuel and either Sea Foam or Berryman's B12 to the fuel following the can directions. Then open the carb drain screws followed by petcock and let it flush for a minute. Close drain screws leaving the petcock on and let it sit for an hour then repeat. Try riding again if the oil level was ok or has been corrected.

 

[Dabba]

Okay, this isn't making sense to me.

I went outside just now and started it and it had been sitting parked since last night. It started right up, idled and revved fine in neutral, however the dummy light was still on. I rode it up and down the block through first and second gears with WOT and it accelerated through both gears fine. After doing that a few times I was on another run down the block and all of a sudden the power loss was back, it started bogging and revving down with the throttle held wide open and as soon as I pulled the clutch in it stalled. It took me about almost a minute of kicking it but then I got it started again and the dummy light went off!! I rode it back up and down the block again in WOT and it accelerated through 1st and 2nd fine again like nothing happened. I parked it, checked the oil and looks like I'm about 1-2 quarts high now (So I was never low, however the power loss and dummy light started BEFORE i added any extra oil.)

I am at a loss with this considering the symptoms are intermittent. I'm wondering if this is more of my original problem and it's the CDI failing. The random coming and going of the problems makes me think electrical rather than mechanical or fuel.

(I am still very temped to park this and buy a local '92 CB750 nighthawk for 1500 for the time being, I like the bike but it's killing me)

 

[longdistancerider]

Get the oil level corrected and try one more time. As the pistons go up/down they create a positive crankcase pressure, with the engine overfull you may be experiencing positive pressure working against the piston where it's normally vented out the breather hose on the valve cover.

 

[Dabba]

I'll give it a shot. I may buy the other bike anyway if it looks good and hasnt been sitting to be a reliable daily rider while I tinker with this. If it works out it will likely sit a year or so until I find myself a place with a headed garage so I can tinker with it more as a hobby and not rushed necessity because I want a rideable bike I don't mind messing with it but it's adding more stress in my life than taking!

I'll keep you updated. I need to solve this mystery eventually.

 

[Old Okie]

I can not even imagine riding a bike WOT with the oil light on.
But then, I am just an old fart, what do i know???

 

[Dabba]

I decided the light was likely broken and it truly wasnt low on pressure. In any case seizing the motor would not change much of my situation with it at this point so

 

[JamesPal]

I think you should listen to LDR. I will break this down into simple to understand terms:
Too much oil = oil leaks and loss of power
Old gas sitting outside through the winter = loss of power

Too much oil will increase the oil level in the engine. This will get the oil up into the swept area of the crank. This puts a drag on the crank and will froth up the oil like a latte. The froth will increase the pressure in the bottom end and over power the seals.

Modern gasoline consists around 10% ethanol. Ethanol is hygroscopic. Hygroscopic means tending to absorb moisture from the air. When the bike sits outside the barometric air pressure changes will breathe fresh air into the gas tank. Barometric changes are usually associated with storms (rain and snow) so your old gas will fill up with water. This can get bad enough for water to form at the bottom of the tank. The engine can even suck the water into a pick up.

Buying another bike is not going to fix this problem. Quit being lazy and go fix the bike.

 

[Dabba]

Buying another bike is not going to fix this problem. Quit being lazy and go fix the bike.[/FONT]

I appreciate all the knowledge and advice except for this. Frankly, you have no idea what situation I'm in as far as time and resources available to continue to work on this bike. And while the issue may just be gas, (It's not the oil because it did the same thing before it was overfilled), it also may not, and this bike has a history of continuing to have issues after I try to fix it. My main objective is to have a reliable motorcycle to ride, not a project that will leave me on the side of the road. I'm currently on clinical rotations for my PA which is a full time job plus studying after work, I do not have time for this anymore. If I still have the bike in a year when I'm settled with a heated garage, then that's fine. Until then, I need something to release stress, not cause it.

 

[intrepid]

How about a couple of simple things to try: first drain all the gas out of the tank and put in fresh fuel after you remove and clean your fuel tank strainer.

 

[80cb400t]

If you want a reliable motorcycle to ride your best option is go to a dealership and buy a new bike with a warranty

If that's too expensive, you're going to have to either luck out with a used one (cheap bikes are cheap for a reason) or patiently learn to fix what you've got.

If you're a PA surely you have some sort of science background, use a process of elimination to troubleshoot. Bikes are simpler than humans, there's no placebo effects or psychosomatic symptoms. If it's not working, there's an explanation that can be found with a little digging.

 

[Dabba]

I have actually been approaching this as I would a patient. Given the history and current symptoms I still suspect electrical. However of I were to continue i would change the oil and gas on top of testing the timing with a timing light.

However that said I picked up a 92 nighthawk 750 for 1500. It has 30k miles on it and it never sat for extended periods. I think I was able to spot a good deal and pick well from my experience working on this bike so for that I'm grateful. I wanted my next bike to be a 78 CB750 but this is close enough. Overall it's very solid.

So being I don't have a big attachment to this twin even though it was my first street bike I'm selling it
I'm not in any particular need to so if I still have it when I settle I'll continue to repair or replace the motor then I'll cafe it. That was the original plan after upgrading anyway. I just upgraded a year earlier than expected but I think that night hawk is worth twice of what I paid!

 

[80cb400t]

That does look like it's in good condition and those are supposed to be good bikes, I hope it works out for you