This motor had busted a piston some time ago with another owner. Then a friend had bought it in pieces. He got sick of fixing it himself so he took it to a motorbike shop to finish it. This is who I bought it from.
When I lifted the head and barrels I found that somebody had put the wrong piston in to replace the junked one. This piston is a Suzuki part but it has no lower land for the oil rings above the wrist pin. It must be designed for different oil rings altogether.
The effect of the piston was that the oil rings have carved out horizontal damage on each side of the barrel about a half inch below the head. The damage is probably 2 mm deep, 5 to 10 mm high, and extends for about two inches wide.
There is also severe vertical scoring on both sides of the barrel where the wrist pin circlip came adrift from one side and damaged that side, then it seems to have gone through the wrist pin to the other side and damaged that as well. In each side bits of it have caught in the unsupported oil rings.
The result is a barrel too badly damaged to repair and a damaged piston that should not even have been in the motor. The bike has also been running way too rich and the carbon build-up was very heavy in all chambers. And the head has some valve guide wear that needs work. And all the rings in the other cylinders are down below their limit as well.
I visited the mechanic who did the work this week to ask what he had done to the bike, but I came away very uninspired and not wanting to return. However, I am in touch with another mechanic who does top class work and will get him to do any machining that I need.
And today I lined up a guy who has a spare GS1000G motor sitting in his shed (with a hole in one piston :?), and another guy who has a spare head that he thinks is a E or S model (a bit more grunt in the cams).
So in a week or so I guess I can put together enough bits to be back on the road with a properly done repair. Then I get the new mechanic to sort out the tuning and the bike will be very happy with me.
Kim
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