Topic: Diagnosing a tore down motor?? detailed pics...

[whoismattclark]

Hey all,

I'm working on my backup bike today.  Contemplating rebuilding the engine or swapping it with another.

I've never done a top-end rebuild -- it was exhilerating pulling the cylinder head off -- so, I need your help diagnosing the motor.  I have posted some detailed pics of the pistons and the cylinder head.  I'm wondering if a gasket kit alone will be enough to get this 40k+ motor back up and running.  The circumstances of its demise sounded like a blown head gasket, but again, not much experience here....

Check it out at:
http://www.whoismattclark.com/cb550rebuild/rebuildpics.html

[scondon]

First let me say "congratulations" for diving in, gettin' dirty, and crackin' open your first motor. A manual, some patience, and some willingness to learn by mistakes (not that you will make any) is all that's required. Oh, and some tools

   Diagnosing an engine from pictures is next to impossible but I can say "Yep, that looks like the inside of a 40,000 mile engine". Can probably give you some ideas of what to look for if you give a detailed description of problems the motor had when it was running. I've only done 750 motors but there are quite a few skilled 550 mechanics on this site.

      My first top end job was much the same as yours. Questionable motor on my parts bike. I took it apart and put it back together adding just a new gasket set. I gained experience, got 20,000 miles, and only spent $65 on gaskets and $35 on Helicoils. The motor finally failed completely and I gained experience from that. I say do your first engine "on the cheap", if it doesn't work out then go to plan "B"(swap it with another).

     Anyway, no real engine advice here. Just wanted to give you some encouragement and a slap on the back

[supersport_CB400F]

If th engine is shagged .....buy another or spend lot's of money fixing it

[whoismattclark]

     Anyway, no real engine advice here. Just wanted to give you some encouragement and a slap on the back

Thanks bro.  I'm probably going to tinker with this motor on the table.  I have another replacement that had less miles and a broken cam chain guide that I'll throw into the bike.  I'll start a new thread on this later, but could a broken cam chain guide be enough to keep an engine from running?  Or is it usually something worse that went wrong and broke the chain guide?

thanks,
MDC

[whoismattclark]

Can probably give you some ideas of what to look for if you give a detailed description of problems the motor had when it was running.

About this motor:  The bike was riding very hot, and I was in traffic (LA traffic!!!).  Pulled over a few times to cool it off.  Back in traffic.  Running in second gear, revving to get past a car, and SCREETCH....the sound of grinding gears, then coast....Oil light comes on.  Tried kick starting.  Felt like low compression.  A few more kicks, and she started up.  Got a few more blocks then screetch/coast again.  I visually checked the head gasket; it looked darker and oilier near #4 cylinder, but I can't say for sure.  Because of the mileage and unknown history, I thought it was a good candidate for a tear down.

Drained oil, and found no metally bits, but too curious, so pulled off the head....and that's where I am....

[heffay]

if the cam chain guide was somewhere else in the motor yes... could keep it from running, obviously.  but, also if the cam chain was so loose that it slipped... it would keep the motor from running.  so yes, to answer your question.  keep in mind that you asked two questions 

you have only the top end apart? 

[heffay]

sounds like it seized... oil pressure?  now remember, oil light doesn't mean much if the bike is not running... mine is on unless the bike is actually running.

also, screeetch and grinding gears are two totally different sounds.... which is it?

[scondon]

Again, I'm not familliar with the 550 engine but I'd agree with heffay and guess at a siezed engine or oil starvation to the cam or piston. My first rebuild died with a horrible, wailing SKRREEEEEE. I was able to start the bike but it died again a couple miles later "SKRREEEE/coast"   In my case it was the oil feed on one of my cam towers got blocked and the sound was my cam and cam bearings eating each other.

    The oil pressure can drop pretty low at low rpms when the oil/bike is hot. I've got an oil gauge fitted and it will drop to zero loooong before the oil light comes on(problem with my bike,not normal) and since the cam is furthest from the pump it is first to starve. Have a good look at your cam and bearings, pull your cylinder and look at the piston sides and cylinder walls.

[whoismattclark]

I suppose there was only a SCREETCH....the grinding gears might have been my teeth nashing    It was pretty tramatic.  Hard to remember exactly.   

I have only taken off the head.  I have not taken off the block because I don't own ring compressors at the moment to get it back on.

Forgive my ignorance, but if the motor seized what needs to be done to fix the damage?  Do the damaged pistons need to be replaced, sanded down?  Cyliders bored, or just cleaned?  Rings changed?

[Gordon]

You don't need a ring compressor to get the cylinders back on.  Just your fingers aided by the fact that the bottom of the cylinder bore is tapered outward is plenty good enough.  In fact, on these engines it seems like a ring compressor would only make things more difficult. 

[whoismattclark]

You don't need a ring compressor to get the cylinders back on.  Just your fingers aided by the fact that the bottom of the cylinder bore is tapered outward is plenty good enough.  In fact, on these engines it seems like a ring compressor would only make things more difficult. 

Well then, expect pics of the block and pistons on Sat morn.  How exciting...is it wrong that I'm kinda glad I blew this motor, so I could tear into it with abandon?

thanks so much, guys...
MDC

[heffay]

hey... while you got the bike apart maybe you could sand down that exhaust header and use some bbq paint!   

also, looking at that... is that a vance and hines in your avatar... the thought occured to me perhaps you are jetted lean and running the bike hotter than it should be.  how's your carburetion?

[whoismattclark]

hey... while you got the bike apart maybe you could sand down that exhaust header and use some bbq paint!   

also, looking at that... is that a vance and hines in your avatar... the thought occured to me perhaps you are jetted lean and running the bike hotter than it should be.  how's your carburetion?

That's a different bike.  It's for sale on Craigslist right now.  And I did give it a spray with silver Hi-Temp Rustoleum.  Take a look:
http://losangeles.craigslist.org/mcy/135494260.html
http://bikepics.com/members/whoismattclark/
Actually, it does need a re-spray, hah!  Love the Vance & Hines sound (and it bolted right on!  pulled off an ninja ex500 junkyard find).  I think the I got its jetting pretty close, but no more time to tinker on that one....need to sell to fund the reviving of this bike.  Wife and Uncle Sam said I can only afford one bike at a time.

As far as causes for the seizure: I think there was a lot going on.  Too lean, inaccurate timing, valves needing adjustment, old oil...I was spending more time working on the other bike and neglecting basics on this one and learning/self-teaching along the way.

[whoismattclark]

I pulled the block and added some pics of the Pistons.  Don't have good pics of the cylinder walls yet, but working on it.

Check it out at:
http://www.whoismattclark.com/cb550rebuild/rebuildpics.html

Looks like possible seizure or scoring marks on all four pistons, intake and exhaust side, though I am knew to diagnosing internal engine components (brand new, first look at pistons of any kind).  I'm using this website pics as a guide.  Rings seem good.  Springy and moveable.

thoughts???

[TwoTired]

Do we need to tell you that you need 4 new pistons, rings, and likely and over bore?

Is this the same engine that was giving you oil light indications?.  If you have an oiling problem, new cylinders won't cure that.  In fact, you can destroy a new engine with poor oiling.  Better check out your oil pump clearances, too.

Cheers,

[whoismattclark]

Do we need to tell you that you need 4 new pistons, rings, and likely and over bore?

Is this the same engine that was giving you oil light indications?.  If you have an oiling problem, new cylinders won't cure that.  In fact, you can destroy a new engine with poor oiling.  Better check out your oil pump clearances, too.

Cheers,

Different engine, TT, but thanks for remembering.

And yes, I need to be told about the bad news, because it's not immediately obvious to me that the cylinders are trashed, due to my lack of experience.  Do the scoring marks just create too much friction in the cylinders to run these pistons ever again?

I have another engine that I believe to be good, so the news is not so bad.  This tear down is for educational purposes only.  It would be fun to gain the experience of getting it running again, but is by no means a necessity.

[TwoTired]

If the bores are still smooth and shiney, then they need to be measured with an internal micrometer, for wear, taper, and roundness.

If they are within tolerance, then a cylinder hone, new pistons and rings would get you going again.

I'd still check the oil pump and for an exact cause of the overheating and engine seizure.

Cheers,