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Ok guys. Some (many) of you know I took my 79 on its
maiden voyage to Colorado and had nothing but problems the whole trip and
eventually blowwing the motor in Durango only to be Uhauled back to Colorado
Springs and trailered back to Atlanta.
Well I tore her down finally today. Here is what I found and it IS NOT PRETTY!
I dropped #2 Intake valve! It sheered clean off in the intake port and dropped
into the piston. It TOTALLY! Disintegrated the piston and all that is left on #2
rod is a wrist pin. Not a piece of piston left. Of course since the valve
destroyed the piston (new from 900 kit "Steve! got a spare piston and ring
from a 900 kit?") It ate the cylinder walls, and broke off the sleeve of
the cylinder that goes below the base gasket. All of that missing metal had to
go some where so it went out the back of the upper crank case 1/2 (you can put
your whole hand in that hole) and it pushed through the oil splash pan below the
crank and pushed the lower crankcase 1/2 so far it broke off the cast nut
holding the oil filter bolt threads. I also had chunks of aluminum in the
CARBURETOR of all places.
My exchange student son must be deaf not to hear all that racket going on cause
I know it COULD NOT have been any where near quiet.
So here is what I got:
Broken In Valve
Bent and hammered Ex Valve
A WASTED head that I just had a 3 angle valve job done to it. (It may be
salvageable with a new pair of valve guides and a WHOLE BUNCH of shaping and
polishing but there is a HUGE gouge from the valve hammering in there sideways
that I dont' think will come out until the combustion chamber shape is
destroyed. Maybe it could be welded and then shaped.) The seat seems to have
enough shape to survive a grind.
A busted #2 sleeve on the cylinder (but I got the 750 version of the 900 kit
which includes the sleeves which I did not use in the 850 cylinder I decided to
use) which could be re sleeved.
A missing 900cc piston and rings
A TOTALLY hammered #2 rod (I have extras)but the crank and lower rod bearing
seems to have faired the abuse quite well.
A busted and disgusting upper and lower crankcase 1/2.
Probably some damage to oil pump, and trans gears maybe just some alum deposits
and it will probably be ok.
So what to do?
I need a 900cc piston and rings. The head and base gasket are reuseable so I got
lucky there. (It only had 700 miles on it).
I need an upper and lower crankcase 1/2 from a 78/79 (I think the part numbers
were common to those years, gasket set, and oil filter.
I think I have enough of the other busted parts as used from my parts bikes.
My biggest question is WHY DID THAT VALVE DROP???? I have no clue!
I have a head from an 850 with some stripped threads that can be helicoiled for
the valve cover but I have to check out the cam bearing journals. I have rods, I
have crankcase 1/2s from an 850 but I remember there being differences with the
left trans bearing journal size differences that kept the option of using it
last time from being an option. Will have to look at that.
In reality though I was trying to gather enough pieces together to get my 78
750E running. I will check compression on that bike and maybe put it in the F to
get it on the road. But it has been sitting for 10 years. Probably needs
cylinder work. But then I do have a set of 850 pistons that could go in that
bike! That would freshen up any cylinder problems in a worst case scenario. Or
maybe just a hone and rering job.
Oh what to do!
Thanks guys for lending an ear. I will post pics soon on the ytriples-l-pics
site.
Anyone with cases, a piston for a 900, or those other parts listed that want to
help out let me know.
Also anyone know why that valve would have sheered off? Should I buy ALL NEW
VALVES to keep this from happening again?
RobReil.
Disgusted in Atlanta.