Topic: 1972 CB450 spewing oil, breaking my heart.

[formasfunction]

I recently bought a 1972 DOHC CB450 and as I was on the expressway driving it home I felt it lose power and as I looked behind me all of my oil was spewing out of the back.  I took the first exit I could find, about five miles later, and as I slowed down the engine died.  Luckily my father was following me (his windshield covered in oil at this point) and just off of the exit we talked about what our options were.  There was a gas station 0.2 miles down the road so after the engine cooled down a little bit we poured a quart of oil in and I quickly rode it down the street until I could pick it up later with a truck (it started right up, btw).

Now, in the aftermath, it's hard to tell exactly where the oil is coming from (oddly enough, the engine is still relatively clean).  I'm assuming I blew a gasket but I was thinking about filling it up with oil again, starting it up in my driveway, and checking for the source.  Is it safe for the engine to run for a few minutes in this condition?  What would you guys recommend?  Luckily the guy I bought it from gave me a complete gasket rebuild set but unfortunately the main gasket in the set is torn so it looks like I'll have to order an entirely new set.

Thanks in advance. I miss my old SOHC CB550 but I'm looking forward to digging into this engine.

[mlinder]

Are you saying you can see no visible exit point for the oil?
GO ahead and put a couple quarts in and run it in your driveway, should be fine. Find the exit point.

[kirkn]

...well, maybe not in the DRIVEWAY, but off in the grass.  Oil makes such a mess on concrete.   

I'm betting on a failed countershaft seal.  I've had two fail on bikes over the years, and they behaved exactly the same way:  loss of oil but no real evidence of it on the motor.  In both cases, I had to add oil and run the motor to see where it oozed out from.

Loss of power, followed by engine dieing, followed by starting back up again doesn't bode too well - sounds like early stages of seizure.  Hopefully you haven't galled cam bearing surfaces or anything else.  Starting back up, though, IS a good sign - it means it isn't galled to the point of being frozen.

Good luck with it,

Kirk

[formasfunction]

Ha, I'll make sure to find a nice patch of grass I'm not too attached to.

What would be a sign that I've done serious damage to the engine, like galling the cam bearing surfaces? Other than the obvious complete seizure, what should I be looking for? And if it has advanced to that point, what are my options?  I appreciate the help already; you guys are great.

[formasfunction]

After filling up the oil and starting her a couple of times, it looks to me like the oil is all coming out of a tube that runs from the top of the engine down to right in between the center stand, which would explain why my engine remained spotless while dumping 3qts on the expressway. Any ideas as to what this means? From the exhaust when she started, it looks like she's burning the oil as well.

[750essess]

If its pumping it out the breather it either had way to much oil in or its got serious blow-by causing the cranckase to be pressurized

[formasfunction]

I don't think there's too much oil in there - the dipstick showed empty and I put 3qts in like the manual said.  However, I failed to mention that I noticed some oil coming out of the "Honda" alternator cover (I think that's what it is) where a previous owner had apparently dropped the bike and the clutch had gouged into it.  There as a small but steady stream coming out of the "A".  Here are a few pics for clarification. Two of the them show the tube where it attaches to the engine, one of them shows where the tube exits on the underside of the bike, and the third shows the leaking engine cover.

[750essess]

yeah thats the breather tube. If you have one, do a compression test.

[kirkn]

How quickly does the oil come out of the breather tube?  Vapor?  Drips?  Pouring?

Vapor or drips, it must need to be ignored for quite awhile before all the oil is gone.  Can't imagine that blowby would cause any more than this and still run!

Pouring out - something else going wrong.  Oil not being allowed to drain back to crankcase?  Too much oil going to head?


A small but steady stream coming from the alternator cover?  Well, if you ignored it for an hour of steady running, how much oil would be lost?  Half a quart?  A quart?  3 quarts?

Hmm...

You're on the right track. 

Kirk

[mlinder]

If the oil return in the head is clogged, it will build up in the head and eventually blow out the tube.

[750essess]

He said it lost power while oil was spewing out the back. It still sounds like he holed a piston or something to me. A compression test will confirm, if compression is ok, look for other problem.

[formasfunction]

Alright, here are a few more tidbits of information.  First off, the only other thing I can think of that I haven't mentioned already is that when I was on the expressway and I opened up the throttle all the way the bike would choke in spurts a little bit, like I was running out of gas.  It didn't seem to matter what speed I was at when I did it but I only ever did it as highway speeds and as soon as I'd roll off the throttle just a little bit it would go back to normal.

@750essess
I don't have anything to do a compression test. Are there any makeshift ways I might test that? Also, when it first lost power it was having trouble in 4th so I down shifted to 3rd, got the RPMs up, and then upshifted to back 4th and that seemed to help - would that be a sign that it had lost compression and I was compensating by revving up the RPMs?

@kirkn
As soon as the engine gets going (5seconds after starting) the oil really starts pouring out.  I'd say it puts out about 1/4qt every 10secs when you're on the throttle but that's just a guess. There was a running puddle under the bike in a matter of seconds.
As for the alternator cover, I'd say it's leaking at the rate of half a quart of oil an hour but that's just a guess.  When the bike is on the trail of oil becomes visible down the cover but there's no visible motion to it, if that makes sense - a very small, smooth leak.

@mllnder
How would I check to see if the head is clogged? I don't mind opening her up - I have the cb450 clymer manual and some experience from my old cb550, though I am a novice.

[750essess]

Pull the plugs and hold your thumb over the opening while cranking. its coming out the breather that fast? Does it idle?

[formasfunction]

Yeah, the oil is coming out ridiculously fast and no, it doesn't idle at all; I have to keep on the gas to keep it running.
I'll run out and pull the plugs ASAP and let you know what I find. I might have to wait until my roommate gets home to help me as the kick starter level is stripped and I'm not sure I can get it to turn without using the electric start which is missing the button and has to be triggered with a paperclip. I know, it sounds like the whole thing is falling apart but the rest of the bike seems to be in great condition and even has the original toolkit.

[formasfunction]

So I pulled the plugs to test for compression and started with the throttle side piston. I wasn't sure what it should feel like but I put my thumb over the hole and as I ran the electric starter I could feel a "thud thud" against the pad of my thumb.  Okay, seems good I thought.  Then I moved to the clutch side piston, put my thumb over the hole, and as soon as I hit the starter I thought my thumb was going to be shot to bits.  Okay, so thaaaats what the compression is supposed to feel like.

So, it looks like I have extremely weak compression on the throttle side piston - there was about as much pressure against my thumb on each crank as it's taking to type on my keyboard right now. Also, there was oil on the spark plug for that side but no oil on the plug for the other. What does that mean?  What's the next step?

[kirkn]

A quart a MINUTE  out of the breather??!! 

And no compression on the one side?

And oil-covered spark plug on the side with no compression?


Sorry to hear it.

Yer screwed...



No, really, you're right outside my experience now, and I'm only being flippant at your expense, but it don't look good for the home team...

Kirk

[formasfunction]

Hey, if the Giants can win the Super Bowl...

Seriously though, if it's rebuild-able I don't mind that.  The only thing I'd prefer not hear is that I'll have to go junk yard shopping for an entirely new engine; but hey, if that's the news that's the news.  Thanks for the help up until this point!

[mikedialect]

Sounds like a really good time to start looking for a parts engine or some cheap parts!

I know your pain. BUT in this you will have a rich learning experience and love your bike even more when you're done

[bryanj]

Broken rings and/or holed piston.
Common to shatter rings if you ride a cold enginr hard.
Either way probably best with a set of used cylinders and pistons.

These engines are not the easiest to work on for a novice either

[formasfunction]

Well, I appreciate the help.  I've started looking around for a parts bike and in the mean time I'm going to finally by that craftsman motorcycle jack I've been looking at, take the engine apart, and do a "one of these things is not like the other" since it appears I have one good piston and one bad one. Hopefully I'll at least be able to diagnose the problem that way.

@bryanj
I suppose I don't have anything to lose at this point but even so, that's what an awesome forum like this is for, right? To help us noobs compensate for our lack of knowledge and flippant use of the phrase "that shouldn't be too hard".

[bryanj]

I do have the genuine honda 450 manual, unfortunately this forum is more for the inline fours, but some of us will always try to help. What i really meant was that the 450 was a very unusual design for Honda where you have to split the camchain to remove the head and re-rivet with a new soft link on assembly! Also the head design in the valve spring area is more or less unique.

When they, and the 500 twin, were a current model it was not one any mechanic enthused over when it came into the shop as they were finicky and could spell trouble.

Hope you get it sorted and please email direct if you think i can help
Regards Bryan

[mikedialect]

I do have the genuine honda 450 manual, unfortunately this forum is more for the inline fours, but some of us will always try to help. What i really meant was that the 450 was a very unusual design for Honda where you have to split the camchain to remove the head and re-rivet with a new soft link on assembly! Also the head design in the valve spring area is more or less unique.

When they, and the 500 twin, were a current model it was not one any mechanic enthused over when it came into the shop as they were finicky and could spell trouble.

Hope you get it sorted and please email direct if you think i can help
Regards Bryan

pop over to hondatwins.com- lots of twin lovers there