engine rebuild of GS450LE - need a little advice

[Anonymous]

I'm rebuilding my 450 over this winter. It started with an innocent comoression check that showed 90 psi each side that jumped to 130ish with oil in the cylinders. It did have starting issues beofre I got into this anyway I digress.

With much aggravation I've removed the cylinder head, cams, and block. God bless the inventor of the rubber mallet!

The inside of the cylinders look okay, I'm having them de-glazed anyhow. My question is the pistons themselves appear to be rubbed. Its present on both pistons, back worse than front only on the part below the wrist pin, well below the rings themselves. (The whole reason for the teardown was to replace these and to learn a little about motorcycle innards)

Is this something I need to worry about? Can/should I try to buff these off?

thanks for your help...Sam

[SqDancerLynn1]

Some light scuffing can be expected in a high milage engine so don't worry about it. What I have done sometimes is to soak the pistons in carb cleaner. Make sure the ring grouves are clean. You can use a broken ring to clean the grouve if you need to

[Anonymous]

Thanks for the advice. Its not a high mileage engine though, just a neglected one. there's only 16500km (~10300miles) on the clock. i get the impression that this is the first serious maintenance it has seen in a long time.

Sam

Some light scuffing can be expected in a high milage engine so don't worry about it. What I have done sometimes is to soak the pistons in carb cleaner. Make sure the ring grouves are clean. You can use a broken ring to clean the grouve if you need to

[Anonymous]

Sam,
How did the bike run with that kind of compression? I'm just curious as to how motors degrade in performance over age.

As for the scuffing, when the piston is pushed down by the burning gas it gets pushed sideways because of the connecting rod holding it back. It is normal to get scuffing and even oval cylinders after time. Your manual will be able to tell you what the service limit is. I wish I had my Cavaliers pistons with me as I could explain it a bit better but after 200,000km and a head that had been shaved twice there was considerable polishing of the pistons.

Steve

[blo]

when restoring the engine pay attention to the ring-groove clearance, as well as ring gap and cylinder wear. All these thing will affect the compression.
I had the same compression on my -81 GS450ex, and after doing the head and piston rings it did not become that much better, turned out to be to much groove clearance.
Good luck

[Anonymous]

It had starting troubles, but once running seemed to run well enough. I don't have a reference having never owned a properly running 450 twin. Having said that, it pulled well from 5000rpm on up. No misfires, stutters or weird noises.

Sam

Sam,
How did the bike run with that kind of compression? I'm just curious as to how motors degrade in performance over age.

As for the scuffing, when the piston is pushed down by the burning gas it gets pushed sideways because of the connecting rod holding it back. It is normal to get scuffing and even oval cylinders after time. Your manual will be able to tell you what the service limit is. I wish I had my Cavaliers pistons with me as I could explain it a bit better but after 200,000km and a head that had been shaved twice there was considerable polishing of the pistons.

Steve