Yanmar 1GM

[bill good]

Need to overhaul yanmar 1gm 7.5hp but no longer able to obtain rings & piston. Somehow one of my engines was rebored or resleeved to 1GM10 specs & I can't find how it was done. Yanmar said in can't be done but that engine has been going for 20yrs without any problems. Anyone done this rebuild?

Thanks

[a64pilot]

Somebody found a piston that matched.
If you worked at Wiseco I'm sure you could, however, just maybe if you got the critical dimensions, maybe you could call them and see if they manufacture a piston that size?
Wiseco is just the ones I used many, many years ago, there are several piston manufacturers I'm sure.

Most of the time manufacturers of any engine when they go to build new engines go to the parts bin and pick valves, rods, Pistons etc that work and they already have as opposed to everything being new, called potato head manufacturing, but it saves mucho money and parts are already available in the system etc. used to be that every GM engine made all used the same valve lifters for example from the little four cylinders up to the big block V8's
Trick of course is finding what other alternate part numbers that piston etc may have.
Sometimes it's modified just a little too, but often you can do that modification as well.

It's just finding the needle in the haystack

[model 10]

Originally Posted by bill good

Need to overhaul yanmar 1gm 7.5hp but no longer able to obtain rings & piston. Somehow one of my engines was rebored or resleeved to 1GM10 specs
Thanks

Why not do do the same thing again? A new sleeve and GM10 piston. There are sleeves for everything because machine shops trim up a new sleeve from anything close. They actually come out better because they are custom to your block.

[a64pilot]

I believe it's getting a piston that is the challenge

[bill good]

What I am trying to do is go with the 1GM10 size. I checked with Yanmar & several dealers & the advice is the block cannot be bored out & a sleeve could not be fitted. It appears that someone has done that to one of the engines in the boat over 20yrs ago & if anyone has done that the same I would like to trace that down. I don't want to get the block bored out only to find it becomes a write off.

Regards

[model 10]

An automotive machine shop will really know. This is what they do every day. And, you have the 20 year old proof that what they can do works. Yanmar would have 0 interest in you putting a -10 piston in your engine.
You will need to assemble the engine correctly as valve to piston clearance can be critical in a diesel.

[Captsteve53]

Most pistons have identification numbers etched/cast/stamped into the interior of the piston as:

Job # : This 6-digit number is located on both custom and off-the-shelf pistons. Use this number to reorder custom pistons and/or locate replacement components for custom pistons (wrist pins/locks/rings).

Shelf Piston Part # : A 6-digit number beginning with P/N indicates an off-the-shelf, catalog item. Use this number to re-order off-the-shelf pistons. Custom pistons will not have this number.

Forging # : This number ONLY identifies the raw forging that was used to manufacture the piston. A large variety of bore sizes, compression heights and other design features can be applied to a single forging.

If yours do not JE pistons (orders@jepistons.com)can usually match from size/use/rings/ etc

Cheers Steve

[hugosalt]

Try contacting Hoye Tractor in Texas, 940 592 0181, they deal with Yanmar motors in tractors, and many motors are same as ours. As I understand it, they buy parts bypassing Yanmar and can sell anywhere. Trick is getting to talk to right individual and being able to
cross reference motor/parts numbers...in any case a good source for Yanmar parts in general.

[bill good]

On closer investigation this one it is bored out to .25mm O/S & that O/S piston & rings are no longer available. However the standard piston & rings are still available. Was hoping to hear that someone had fitted a liner from the 2/3GM series. (1GM no liner - 2&3GM had dry liners). I try not being the first & live in hope someone has been before me.

[a64pilot]

If it's a dry liner, like Guy said go to a good machine shop, they will grab a liner that is too big and long and cut it down to perfect size

[Captsteve53]

Since you are in Brisbane give a mate of mine a ring @ Marine diesel Ltd(Brisbane) (Steve Shale-+61 3390 3633 or +61 401 162 677) I would be very surprised if he wouldn't be able to sort this out for you, he is a John Deere agent but has all sorts of contacts around in the marine diesel equipment area and is a real nice guy to deal with,

Cheers Steve

[Lepke]

Liners are made in many sizes. People that bore engines have access to them. They sleeve engines all the time. The engine is bored to the outside diameter of the sleeve and the inside is bored to match the piston. If the piston is in good shape, it could be sized to the old piston. Rings probably exist, but there are companies that make custom rings. Many companies make custom pistons, especially those that cater to racing.