Topic: Help with new CB650 Project

[bryanj]

I would say rod bolts went first, unusual for cap to part after a siezure

[Tracksnblades1]

Does reply 38 pictures show a blue journal or is it the gold hue in the pictures making it look that way..?

[76 Supersport]

Here’s a couple pics of the rod journal.

[newday777]

What do you all think broke first? See pictures.

Yikes! That was a major bang. Definitely not something that the previous owner had missed hearing.
Were the bolts missing from the rod bearing cap?

[76 Supersport]

They were withe the primary chain in the oil pan.

[Tracksnblades1]

Difficult on an IPad and in the arm chair but your piston doesn’t look like it was overheated nor does the big end of your rod or crankshaft journal look like it was overheated. The journal look like it still had a film of oil and some varnish still left on it..

Obviously the rod bolts let loose then the the counterweights took the bottom of the piston off and then seized it ….?

How many holes did the rod knock through the cases and head before it quit…?

Looks like the oil never got changed..?

[76 Supersport]

1 and a half? I’ll retake pictures. First pictures marks on outside of case are from me.  Second picture is back of motor under starter.

[76 Supersport]

Here’s the head of the piston that let go.

[bryanj]

Well it went upwards once, too far, when the bolts let go

[newday777]

1 and a half? I’ll retake pictures. First pictures marks on outside of case are from me.  Second picture is back of motor under starter.

I was thinking this morning and wondered if maybe the seller once he heard the rattling motor just pegged the throttle wide open to see how long before it would grenade???

[Tracksnblades1]

I guess my question is, now what? What else at the very least is broken? I did see a case on eBay for 60-70 bucks. If it seized at the bottom maybe the head and valves are still in good shape?

It seems odd to me the hole is between the two intake ports. I would think it’d be in line with the cam chain or in line with the primary chain. Could it be a rod cap or something?

If it was sitting in your garage what would you do with it? I’ve got more time than money and don’t mind a project.

Were you able to determine what caused the hole between the intake ports..?

[calj737]

I guess my question is, now what? What else at the very least is broken? I did see a case on eBay for 60-70 bucks. If it seized at the bottom maybe the head and valves are still in good shape?

It seems odd to me the hole is between the two intake ports. I would think it’d be in line with the cam chain or in line with the primary chain. Could it be a rod cap or something?

If it was sitting in your garage what would you do with it? I’ve got more time than money and don’t mind a project.

Were you able to determine what caused the hole between the intake ports..?

There isn't a hole between the intake per the 2 pictures attached. One hole is on the exhaust side of the lower case from the rod punching thru, the other appears on the intake side, but again, in the lower case behind the starter motor. Unless he has yet another hole in the cylinder head or cylinders somewhere?

In the end, it doesnt really matter. That motor is toast and we can speculate about the "why" but we certainly know the "what". 

[76 Supersport]

Sorry for not being more specific. I meant the hole in the back of the case was between the intake ports if you followed that line up. My thinking was it should be in line with the intakes as that’s where the journals would be on the crank.

[76 Supersport]

There isn't a hole between the intake per the 2 pictures attached. One hole is on the exhaust side of the lower case from the rod punching thru, the other appears on the intake side, but again, in the lower case behind the starter motor. Unless he has yet another hole in the cylinder head or cylinders somewhere?

In the end, it doesnt really matter. That motor is toast and we can speculate about the "why" but we certainly know the "what". 
[/quote]

No other holes. And I agree toast is toast however it happened.

Since everything is apart are any parts worth saving? I’m going the new motor route, but are any parts rare or worth saving from the scrap yard?

[grcamna2]

You can save lots of parts on that.

[jgger]

I think the 550 guys like the 650 cams if they aren't trash.

[76 Supersport]

Ok In that case, I’ll start cleaning things up and see what’s salvageable.

[calj737]

The bare head as a core has value too. It can be rebuilt and improved. The cylinders might be salvageable. No doubt they’d need a bore and hone, but again as a core for someone rebuilding, you might get some $ for them. The rest is probably pure scrap. I doubt anyone would want to invest the money in the crank to repair it from the rod letting go.

[Mark1976]

Post a few pic's of the cam, if its not too badly abused I could be convinced to purchase it.