Topic: CB550, rattling and smoke out the breather hose.

[scartail]

Last night, I was doing about 90 on the freeway with my 1976 CB550. That was the very first time I had taking her that fast. This morning on my communte to work, I hear this loud rattling, and an odd smell when I stopped. Since I was midway in my commute, I didn't know where it was coming from. And previously, I knew of the common clutch rattle issue. But this was much louder.

On my commute back home, suspecting it was more of the clutch related problem, I took the freeway back (less gear changing). So, I'm doing 65 on my commute, and the performance was the same as any other day. When I am at the stop light, I still hear that odd rattle, regardless of engagement of the clutch. I finally get back home, and pull into the garage. Smoke is streaming out of the breather hose. The smell is sharp, more like a clutch burning than oil. But it is coming out of the breather hose.

Performance is as expected. Clutch and gear engagement is as expected.

What do you guys think? Lost a ring land? Piston? Cutch?
My course of action would be a compression test. But I don't have the odd spark plug tool yet. Anything esle I can check in leu of that?

[mattcb350f]

My freshly rebuilt 350F makes a little vapour out the breather tube after she's been working if that makes you feel any better 

I'm really not sure how much is appropriate and hope someone chimes in about it actually.

It may be that you need a thicker oil. I switched from 10w40 to 20w50 and have a little less noise now and less vapour out the breather tube.

 Matt.

[scartail]

It's tough. I'm used to hear some minor rattles, but when I pull the clutch it goes away. And I'm used not smelling anything, other than my rich carbs that is. My spider senses are up on this one. Where can I find the spark plug socket that will fit on this bike. I've had the bike for about 3 mos now, so I haven't collected too much for it.

[Hush]

Bike plugs are a strange size 17mil I think, I had same problem getting a size but Supercheap had a $6 special which works OK.
Hard to get No3 plug out on the 650 without removing tacho cable, not sure about 550?
Could your clutch oil be too thin thereby allowing the clutch to "rattle" once warm and the oil thinned out?
If you never noticed this before maybe something has changed like the weather or season to either hotter or colder!

[mark]

The 550's plugs have an 18mm hex... an 18mm deep socket with the rubber insert from a 5/8" plug socket works just fine. (an actual 18mm spark plug socket can be got from MAC or Snap-on at substantial expense)

Had mine up to 80 in third gear the other day.... no new noises or clouds from the breather.... Of course, any clouds from the breather hose would go unnoticed as the hose is connected to the air filter case and said clouds would just get sent back through to be burned again.............

[scartail]

Scratch an entry.

I had gone out this morning and I couldn't kick start. I had assumed the engine was seized.

I ran out to Sears and picked up 18mm spark plug socket. Worked beautifully, and for 5$ to boot. Anyhow the crank turns over without much resistance now. Hmmm. I guess I can try a cold compression test. I really don't want to start her up just yet.

[TwoTired]

Have you checked your oil level?

[scartail]

Have you checked your oil level?

Checked it. The is plenty of oil.

I did cold compression test.

No. 1: 70 psi.
No. 2: 100 psi.
No. 3: 70 psi.
No. 4: 70 psi.

For the No. 2 cylinder it jump to 100 psi almost immediately. For they others it took about 3 or 4 revs to get that high. What's wrong with No. 2?

Using a stethoscope (sp?), I pinpoint the rattle/noise/GRINDING at the left side of the crank-case. It seems, she will roll over fine for a couple rev, then all the sudden seize. In that state, I can stand on the kickstart lever, and won't even make it budge. It sould more like metal on metal grinding.

What do you guys think?

[martino1972]

sounds like a seized rod or crank bearing to me...

[bryanj]

cam brg or wrist pin

[scartail]

I assume once I get inside, it will be obvious what the problem is.
I went ahead and jump on the task. The motor is sitting inside the frame, with everything disconnected and out of the way (carbs are off too). Now, I'mlooking at the geometry, and I can figure out how to get the motor out. I sure I'll be taking it out from the left. But I see the oil filter and the oil pan between the frame bars.

Any tips on any of this would be great? I'm looking through the old threads right now. I'm sure there is an awesome write-up on this.

[martino1972]

yeah,dont forget to take the chain off,

[scartail]

yeah,dont forget to take the chain off,

Funny you mentioned that. I spent 10 mins looking for a damn masterlink. It turns out, this one does have one. So, another step inthe process. I'm trying to be effecient at this. But it's my first time every taking a motor apart.

[martino1972]

some people disconnect everything first,drain oil etc.. and then they lay the bike on its side and pop the engine out that way,cause they are pretty heavy if your alone..
put a blanket or something soft underneath,seems like the way to go,i still feel my back from taking out the 750 engine 9 years ago

[brianzenk]

I have the same year bike and have taken the motor apart to replaced the head gaskets.
It sounds like the cam chain tension adjuster could be loose or broken.
That would be the first thing to check to be sure the cam chain is not the problem.
Also be sure the tach and spedo cables are lubed. Dry cables can make noise.
The smoke out the breather hose should be routed back to the stock air filter if
you have one. The fitting is under the battery cage. 
 

[Hush]

Ouch sounds expensive, best of luck and keep asking the important questions, we don't mind.

[martino1972]

no ,we dont mind at all,but.....we want pictures.....lots of pictures,

[scartail]

Ok...

The cam chain didn't seen unsually loose.
I finally got the heads off.
The valve train looks good. Carbon deposites here and there, but nothing suspicious. Spings look good.
I looked down each cylinder. Nice and clean. No gouges or anything.

So, should I go down further?

The noise was coming from the lower left (under No 1/2 cylinders). Could something related to the alternator cause this smoke and noise? Or may just the noise, and the smoke was mere coincidence.

[martino1972]

while you have the head off,spend 5 minutes more and rip the cylinder block off aswell,that way you can inspect,piston,wristpin,connecting rod etc...

[scartail]

while you have the head off,spend 5 minutes more and rip the cylinder block off aswell,that way you can inspect,piston,wristpin,connecting rod etc...

Could everything be re-used? Certainly not the gasket. What of the pins, rings, etc.

[martino1972]

most can be re-used,in general it would be good practice to replace the piston rings....

if you remove the pistons aswell,make sure you number them,piston #1 HAS to go back in hole #1 etc..
some say,replacing the wrist pin clips when removed,ive done both,i replaced them,or sometimes reused them,depending in the shape of them,for them being cheap,i would replace em..

and yes,gaskets and o rings have to be replaced...

[heffay]

i hear the same noises you do.
i also know for fact that my camchain is loose just based on the fact that the tensioner bolt is broken off so there will be no adjust and adjustment never made a difference anyway!  so i just broke it off, perhaps purposefully without comprehending.   
point is... i hear things in this motor that make me wonder.  i've ridden upwards of at least 100+ different bikes and this one sounds the "loosest" (by the way, cb350f).  so, what do i do?  i put new gaskets in to keep the oil in.  i add gas to keep 'er going.  and above all else, i rape the crap out of the throttle and she always wants to go. 
oh, of course, i do the occasional maintenance and safety checks... but i just keep twisting the throttle and have learned to not worry so much about the noise... if i did, i'd have the front brake in pieces right now and wouldn't be considering where to twist to next!     get my drift?

[heffay]

while you have the head off,spend 5 minutes more and rip the cylinder block off aswell,that way you can inspect,piston,wristpin,connecting rod etc...

5 minutes, huh?  could i see a video of you doing said task?   

[martino1972]

while you have the head off,spend 5 minutes more and rip the cylinder block off aswell,that way you can inspect,piston,wristpin,connecting rod etc...

5 minutes, huh?  could i see a video of you doing said task?   

when head is off,theres nothing more holding the cylinder block on,isnt it?
unless im wrong,please tell me if i am..

[heffay]

rings can be a true #$%*  (especially when you have 4 pistons/cylinders)... thats all i have to say.