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318 question

23K views 188 replies 30 participants last post by  ptzbrg 
#1 ·
fella close to me has 318 for sale, reasonable price(525). says it runs on 1 cylinder, other wise it looks pretty solid, with deck. opinions on if this is something worth diving into for a project? im not an engine guy but willing to try and learn, thanks Matt.
 

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#3 ·
Matt, for that price it is worth it for a parts tractor. The Onan engines are tanks and can be rebuilt (pricey) but last a long time. If possible, can you get a compression test on the two cylinders?
They should be around 110 to 120psi if good, but I have seen them run good at 95psi. If you have good compression on both equally, then its time to look at electrical issues. You didn't give us the age or Onan model (B43G or P218). From there we can give you more options to look at.
Good Luck,
Bob
 
#4 ·
Matt, I'd go for it. I am not a motor guy either but can stumble my way through it (see my post in the Intermittant Engine Stall thread), at that price you can afford to throw some cash at the engine in it
 
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#14 ·
I did get the 318. Nice gentleman just no time to look into run issue any more. He stated at first he thought was fuel issue he ran some new fuel lines, fuel filter, and cleaned carb. This didn't help. He then pulled head didn't notice anything major, I believe he put on a new head gasket and hasn't messed with
since. He said compression on one side was 30, 40 with oil on it this was before head gasket. I'll probably start with confirming my own compression readings first thing before I decide what's next? Just got it home tonight but did snap a couple pics. It's b43g. Thanks.
 

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#17 ·
Nice find Matt, I'll be following your progress/struggles
 
#22 ·
I'm thinking rings or valves. Do more checking before pulling engine. Crank engine and listen at intake & exhaust manifold for air. When starter stop[s cranking you...hopefully.. will air escaping. do this several times and hope the engine stops cranking near top dead center! If no sounds of air, pull engine, pull heads & pistons. Cylinders usually don't wear too much, from what I've read here, but once rings are out of cylinder, I don't know how to check for wear. Maybe someone else does! Measure cylinder bores and see if to spec. Bob
 
#24 ·
Bob I'm trying what you said but not sure I 100% follow you. I'm cranking and stopping and listening by exhaust and air filter removed above carb. It cranks stops and I would say I hear nothing at exhaust but a 'sound" with ear in air box. A little return?
 
#26 ·
ptz, Could be a burnt intake valve...pretty much uncommon... or a piece of carbon under intake valve...more common! I can't think that you'd "hear" air coming in on the intake stroke, but if valve is not sealing, I'd think you'd hear it on the compression stoke. Your probably going to end of taking head off, so pull intake manifold and crank again. You shouldn't hear/feel any air coming out of port to intake. Bob
 
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