JimMcMillan
New member
loss of compression.stripped head,had valve seats reaground,new valves.etc.head refitted. still no comp.but when first valve opens(looking at engine) presumably induction stroke the engine draws air thru exhaust. any answers?
yanmar 1gm10
- Thread starter JimMcMillan
- Start date
chippie
New member
Sounds like the camshaft timing has been upset.
Make sure you are turning the engine over in the right direction.
Make sure you are turning the engine over in the right direction.
JimMcMillan
New member
timing is my main suspect.engine was siezed and took some pressure to move.crankshaft bent?
chippie
New member
I dont know those engines specifically, but it is unlikely that the crankshaft is bent as it will be a fairly large piece of metal. I would look at the drive from the crank to the cam which is probably a chain, but could be gears. It seems that something has let go and lost its correct position. Timing sprockets usually have marks which line up when everything is in its correct place.
I'm assuming that it turns over freely now. Did you find out what caused the seizure in the first place?
Hang in there, I'm sure someone with more specific knowledge will reply to your post.
Cheers.
I'm assuming that it turns over freely now. Did you find out what caused the seizure in the first place?
Hang in there, I'm sure someone with more specific knowledge will reply to your post.
Cheers.
david_bagshaw
Well-known member
Have you reset the valve clearance after reassmbly ?
If yes freshly ground in valves take a little time to bed in, & become gas tight.
how much of a leak ?
David
www.euroboating.net
If yes freshly ground in valves take a little time to bed in, & become gas tight.
how much of a leak ?
David
www.euroboating.net
malcolmx75
New member
it may be stuck piston rings.
paulrossall
New member
I have the service manual which covers the 1GM10(C) (also 2GM20,3GM30 &3GM35). Under timing gear it shows a gear on the crankcase drives both a gear on the camshaft and a gear which drives both the oil and water pump. Unless the gears are incredibley worn , or have somehow been forced to jump then I consider it very unlikely to be the timing to be the cause of the trouble. I would have thought it must be a valve problem but I am no expert.
As someone has said "Are you turnung engine right way? Have you got polarity reversed on starter motor? Would this cause motor to turn wrong way? Have you tried turning engine by starting handle? This is so interesting I almost want to come and help you fix it! (But wife won't let me work much on my boat never mind someone else's). Good luck.
As someone has said "Are you turnung engine right way? Have you got polarity reversed on starter motor? Would this cause motor to turn wrong way? Have you tried turning engine by starting handle? This is so interesting I almost want to come and help you fix it! (But wife won't let me work much on my boat never mind someone else's). Good luck.
toad
New member
I'm not familiar with the Yanmar but on the single cylinder lomardini it is possible, when reassembling the engine, to get the exhaust push rod operating the inlet valve and the inlet push rod operating the exhaust valve. The yanmar being a similar engine, it might be an idea to check that the inlet cam is in fact operating the inlet valve.
JimMcMillan
New member
many thanks to you all.The latest thoughts are..in my efforts to free the engine with the starting handle i have bent,stripped or broken a key or something on the camshaft which is where the starting handle is basically attatched.All will be revealed on Sunday.
david_bagshaw
Well-known member
JimMcMillan
New member
engine unsiezed by force!now stripped timing plate and all ok. so last resort is piston rings.p.s.the vaves and seats were knacked.
jfkal
Active member
Buy the Yanmar repair manual. It explains how to adjust timing and positioning the bits and pieces.
chippie
New member
Try yanmarhelp.com If this is not quite the right address doa google search for it.
pete
Well-known member
Jim
I have the same engine in my boat and after developing a very slight leak of raw water through the cylinder head casting, dripping on the exhaust valve seat it suddenly resulted with no compresion, well away from home, on removal of the cyl head the exhaust valve and seat was well pitted and in an attempt to get home I lapped the valve in with a wobbly stick and valve grinding paste, around 6 hours later I had compression back but on fitting the rocker cover promptly lost compression again, because by re cutting/lapping in the valves they go farther into the head and the valve stem was pressing against the decompressor lever and decompressing the engine, I made 5 cardboard rocker gaskets and used them all to get the clearance back and we got home alright but because of the water leak in the head I had to replace it.
Its easy to check just remove the rocker cover (watch the rockers dont slide out) and turn the engine over by hand if it cures your problem you may be better having new valve seats fitted to reduce pocketing of the valves in the seats. good luck
Pete
I have the same engine in my boat and after developing a very slight leak of raw water through the cylinder head casting, dripping on the exhaust valve seat it suddenly resulted with no compresion, well away from home, on removal of the cyl head the exhaust valve and seat was well pitted and in an attempt to get home I lapped the valve in with a wobbly stick and valve grinding paste, around 6 hours later I had compression back but on fitting the rocker cover promptly lost compression again, because by re cutting/lapping in the valves they go farther into the head and the valve stem was pressing against the decompressor lever and decompressing the engine, I made 5 cardboard rocker gaskets and used them all to get the clearance back and we got home alright but because of the water leak in the head I had to replace it.
Its easy to check just remove the rocker cover (watch the rockers dont slide out) and turn the engine over by hand if it cures your problem you may be better having new valve seats fitted to reduce pocketing of the valves in the seats. good luck
Pete