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Low compression in pto
- Thread starter Big Dog Paisley
- Start date
Big Dog Paisley
New Member
Will check the rings. Top of the head appears to be good.
The PTO carb is blowing gas out of it and only will idle. As soon as throttle is engaged engine cuts out.
Could rotary valve timing be to blame for this as well as compression?
The PTO carb is blowing gas out of it and only will idle. As soon as throttle is engaged engine cuts out.
Could rotary valve timing be to blame for this as well as compression?
Big Dog Paisley
New Member
Big Dog Paisley
New Member
Should rotary shaft pull out easily? It seems stuck and won’t pull out.
Spider4real
Active Member
You need a special puller.
OSD ROTARY SHAFT PULLER TOOL (REPLACES 420876488) [OSD420876488] - $23.99
OSD ROTARY SHAFT PULLER TOOL (REPLACES 420876488) [OSD420876488] - $23.99
Big Dog Paisley
New Member
What about that chipped rotary valve? Is my bottom end toast, or do I just need new wheel and shaft?
Spider4real
Active Member
The rotary shaft might be ok. At this stage I would pull the engine and disassemble to inspect. Odds are the broken piece of the rotary valve was blown out the exhaust, but not before it did some damage on its way out. I am not sure what caused the rotary valve to break to begin with. Is there any scoring on the engine block where the rotary valve sits?
Big Dog Paisley
New Member
Nothing I can etch my finger nail on. The cover plate is pretty etched up. Would this be the cause for low compression in my pto cylinder? Are you supposed to be able to turn the rotary shaft by hand? Because if so I cannot…
DaddyLoafin
Active Member
I mean if the piece that broke off got into that cylinder, god only knows what it did in there. Could have messed up the piston rings...idn but unfortunately the only way to find out is pull it apart
Big Dog Paisley
New Member
Sounding like I’ll have to…
DaddyLoafin
Active Member
and the rotary valve shaft is conected to the crank by a gear so if you spin the crank the RV shaft should spin to
Big Dog Paisley
New Member
When I spin the PTO the RV shaft does not move…
DaddyLoafin
Active Member
not an expert, but that cant be good. the gear on the RV shaft is made of brass, so its for it to be stripped of its teeth.
Big Dog Paisley
New Member
You would think I wouldn’t even be able to turn the engine over if that’s so.
DaddyLoafin
Active Member
nah, the crank will spin with that gear stripped, but the RV shaft wont. look at pictures or videos of the bottom end of the engine and you'll see what i mean
Big Dog Paisley
New Member
Literally what I just did lol. Yeah you are very much correct… can’t wait to pull that shaft and see how chewed up it is. If this motor was rebuilt would they have used different sized cylinders? Or can I just order up some spec sized rings?
DaddyLoafin
Active Member
top of the pistons will say like .25 or .5 on them for .25mm over or .5mm over. i looked at your pictures and cant see anything on yours so you might have to get some of that build up off them to see.
Big Dog Paisley
New Member
Thank you for the help with everything it’s very appreciated. This forum has helped more than I can say.
Another question I have is when I turn the engine over by hand it is pretty hard to accomplish. Spark plugs are in but should It turn pretty freely?
DaddyLoafin
Active Member
with spark plugs in, the engine is compressing air and thats making it difficult to spin. with them out it should spin easily
Big Dog Paisley
New Member
Okay, I’ll replace rings, replace RV shaft, and RV degree wheel. Should I bother looking for that chipped piece that came off the degree wheel?
DaddyLoafin
Active Member
your going to have to really inspect the pistons and cylinder walls to make sure there isn't any damage. you really should look inside the cases to maake sure its not in there and didnt cause any damage. plus all that brass from the RV shaft gear had to go somewhere
You really should split the case to clean and inspect everything, especially with the brass gear being all chewed up there will be little pieces of brass shavings all in that RV.
Big Dog Paisley
New Member
Will do. I’ll post back with my findings.
