CB500T Rebuilt Motor Shutdown after 10mi

semaj4712

My couch pulls out but I dont
So ok, this may be a premature post because I have not gone back outside and looked at the bike now that it has cooled down...but...

I was riding my bike today for the first time really outside of up and down my street. I have spent the last year having the engine rebuilt and redoing pretty much everything on this bike, as far as I am concerned everything on the bike is brand new. Now while riding the bike, it was riding pretty good with the except of a slight hesitation around 4k in 1st gear but that went away after about 4 miles or so. I was on city streets cruising at around 40 mph and when right about the 10mi marker I hard a screech and the motor dropped in rpm and died. I quickly pulled over and looked the bike over, everything seemed to me like it was how it should be, so I put it in neutral and tried to start it with the push button, and it wouldn't crank over...so then I tried to kick start it, and it did start right up, but then after a second or two the same screech happened and it died, and then after that when kicked over it was really hard to do so and would screech.

My first instinct told me that something is clearly grinding in there and not right, but a close friend and mechanic said it could easily be some sort of oil starvation problem, or at least that's what it sounded like based on what happened.

So I guess first question is, where do I start, I am waiting for the bike to cool down and I am going to take a look at the oil, oil level, and spark plugs to get a gauge on what could have gone wrong, but can anybody think of what other possible problems may have caused this?

Also I know on many mid 70s bikes, mainly suzukis and yamahas, the tach is driven by the oil pump, so would this mean that the oil pump is functioning correctly.

Any help is greatly appreciated, I fully expect although hope I don't need to pull the motor and disassemble it to see what could be the problem.
 
On the 500t engines, the tachometer is driven off of the front (or exhaust) cam.

To me, since you mentioned screeching, it does sound like oil starvation. This can happen for any number of reasons. The most likely is that one of the oil passages to the top of the engine got blocked.

Did you rebuild it? I'm guessing you didn't since you didn't know how the tachometer is driven. Did the person rebuilding it use gasket sealer when they installed the head gasket or the cam covers? If they did, that can easily squeeze out and fill the adjacent oil passages.

On this engine, the oil is pumped up to the top of the engine around two of the long head bolts. It then goes out into the cam covers and then into the cams where it is slung out into the head through tiny holes in the cam.

Probably the easiest thing to try is to take the valve covers off (one at a time) and try running the engine to see if oil is getting to the top end. It should start slinging out shortly after you start the bike so be prepared for a mess.

I'm pretty sure I have a nice diagram of the oiling system at home. I will try and get a pic for you since I can't seem to find one on google.
 
Thank you very much, yea I wasnt sure about the tach and no I did not build it myself. I am not as familiar with motorycycle engines, but know my way around them based on my experience from older V8s.

I will check that out and see if oil is getting to the cams. That diagram will be helpful tho I am sure
 
i dont think you should continue to run it
drop the oil and look for metal is the first thing then go from there
 
xb33bsa said:
i dont think you should continue to run it
drop the oil and look for metal is the first thing then go from there

Agreed. Pull the valve covers on the front and back that are each held with eight 10mm bolts and look for signs of oil starvation after you've checked out the oil for shavings.
 
If nothing shows up in the oil and there aren't obvious signs of galling, though, I would do what Flug said. Buy some towels.
 
Thanks guys, all great advice, I hope to get to this tonight but it happened in the middle of a busy week
 
Nothing against your abilities but if you don't know engines then other than looking for metal and damage is all you can do.
Plus if this is a professional builder they will not want you taking anything apart.
My advice is call the person that built the engine because it is his resposibility to make it right.
Hopefully they will take care of it for you and fix it.
When my race engine was built my builder broke the engine in on his dyno before it was ever taken out on the road or track.
It had many miles of break in time and tuning.

Good luck and hopefully it's not too bad.
 
cklamer said:
Nothing against your abilities but if you don't know engines then other than looking for metal and damage is all you can do.
Plus if this is a professional builder they will not want you taking anything apart.
My advice is call the person that built the engine because it is his resposibility to make it right.
Hopefully they will take care of it for you and fix it.
When my race engine was built my builder broke the engine in on his dyno before it was ever taken out on the road or track.
It had many miles of break in time and tuning.

Good luck and hopefully it's not too bad.

i think this is the best advice so far, if you paid to have the engine built, take it back
 
Here is the diagram I was thinking of.
u3adepu7.jpg



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Hi Semaj,
What did you find out?
Did you contact the person that built the engine and what did they say?

Good Luck!
 
Hey sorry guys, not too active on this forum, I drained the oil and found a really nice metalic flake, sorta like the kind you want painted on the tank, not in the oil...called the builder right away and hes gonna take it and tear it down...id have no problem doing it myself, I would have built it myself but I wanted it done for the summer and this spring I was restoring my finances truck, i guess the good news is i can use the truck to take the engine back over to the builder
 
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