Was working my 850 hard today. Motor instantley changed pitch VERY VERY HIGH RPM.Took me a few seconds to get her shut down.Govenor linkage came off carb. Got her cranked now it"s popping like stuck valve or crossed wires or timing way off. Pulled valve cover push rods all still moving pulled plugs looked ok. What should I do first compression check, pull head,Govenor cover??? 172 C.I. Gas burner oil pressure OK, Can"t notice any Engine Knock Thanks Jim
- Thread starter 1 leg dog
- Start date
Was working my 850 hard today. Motor instantley changed pitch VERY VERY HIGH RPM.Took me a few seconds to get her shut down.Govenor linkage came off carb. Got her cranked now it"s popping like stuck valve or crossed wires or timing way off. Pulled valve cover push rods all still moving pulled plugs looked ok. What should I do first compression check, pull head,Govenor cover??? 172 C.I. Gas burner oil pressure OK, Can"t notice any Engine Knock Thanks Jim
MarkB_MI
Well-known Member
- Location
- Motown USA
Most likely something's been damaged in the valve train. A compression check will probably indicate one or more bad cylinders; then it's time to pull the head.
I would wonder if the crank to cam timing is messed up. Could have chipped a tooth and be out of time.
If that is good you may have done some bad things with the rods or valves. (heck, if it is bad, you may have hurt rods or valves)
Pull the head. Inspect for bent valves, impact marks on pistons, etc. Check that the pistons are all going up to the same height. Drop the pan, look for chunks.
I did the same thing. Seperate the engine from the transmission. Look at the clutch and pressure plate. It will be in quite a few pieces. The reason for running rough is the pressure plate is in pieces and unbalanced. Do not tear into the engine until you look at the clutch and pressure plate. Starter shaft is proable bent. In my case it bent the hyd tubes in the case. I replaced the pressure side. It had jerked the tube out about .75". I did remove and replace the tube from the front. I cut the tube in two and welded an all 5/16 all thread in it and pulled the rest out. The new tube went in pretty easy. A friend took one out of an SOS case for me. I kept the old pieces of the tube and went to a machine shop and had the replacement tube machined to the correct diameters.
steve n carol
Member
Dog, I wouldn't start at the head. Unless there is something you're not mentioning. I'd start at the distributor cap. Cheaper, easier, quicker too!.
Something that old, spun that fast, could exaggerate a wobble in the dist. shaft and break your dist cap...sl
Something that old, spun that fast, could exaggerate a wobble in the dist. shaft and break your dist cap...sl
Thank's everyone ,It was a real bad experince 5pm stuck in a thicket and real bad weather on the way.Clutch was acting weird, and it does seem like timing is way off.Just drove it far enough to get neighbor yard. When this storm passes and I'm able to get it in side . I'll start with the Dist.(rotor clip),timing, compression check etc.I'm expectng the worse it really hit some high rpm's Never heard a tractor rev that high.Will post update when I get to work on it .Thanks Again
MarkB_MI
Well-known Member
- Location
- Motown USA
The only oversped engine I ever looked at was out of a D6 cat. All of the pushrods were bent and one lifter was broken. I think it had a broken piston as well, although it's been a long time. The bottom end seemed to be fine, but we ended up replacing the whole engine.
I started at all the places that every one has posted. Removed head, removed push rod, removed everything until only the bare block was hanging on the tractor. Finally seperated the tractor and found that the pressure plate, had came apart and sharpnel was every where in the bell housing. I think you are wasting your time if you do not seperate the engine from the bell housing first. The engine would still crank but had a vibration in it that made it sound as if it was out of time.
Ultradog MN
Well-known Member
- Location
- Twin Cities
A lot of good advice here.
But I would not open that engine nor split that tractor till I had done some preliminary checks to it. Check the spark and check the compression at least. Remember it's the simplest things first on this old iron. When you have some clue as to what puked then you tear into it.
Could be something as simple as that much suck pulled a piece of dirt into a jet. I wouldn't tear it apart just yet.
Let us know what you find.
But I would not open that engine nor split that tractor till I had done some preliminary checks to it. Check the spark and check the compression at least. Remember it's the simplest things first on this old iron. When you have some clue as to what puked then you tear into it.
Could be something as simple as that much suck pulled a piece of dirt into a jet. I wouldn't tear it apart just yet.
Let us know what you find.
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