Yanmar 2GM20 pistons

[Compass790]

Does anyone have a 2GM20 piston lying around that they can make a drawing with dimensions of? Or failing that give me a pin height i.e distance from top of piston to centre of pin hole.
Reason I'm asking is I want to find alternative to Yanmar marine pistons as the price is OTT here. Have to figure out if it's worth rebuilding one as they aren't wet sleeved. I haven't bought the engine yet thats why I can't do it myself. Don't want to buy it if I have to buy genuine parts.
Actually want oversize pistons but one step at a time.
Thanks if you can help

[CassidyNZ]

Have you searched eBay for genuine parts? I have long since boycotted the local Yanmar agents due to price and have sourced a host of parts from Japan and the US at better prices. That said, calculation the cost including shipping because what appears cheap often turns into parity for a lot of extra trouble.

Also, check the dealers of small diggers/tractors - many of them use small Yanmars and they’re dealing with tradies and farmers, not us rich boat owners.

Alternately, have you thought of another breed? Like a 2 cylinder Kubota? They’re a whole lot less pricey - in fact I have a good one languishing in my shed.

[Compass790]

Yes I'm the same, haven't bought a single part off Power Equipment & NEVER will. The $630 price for a conrod to go in an 8hp single ruled them out forever to me.
Yes I'm searching ebay but want also dimensions so I can check what China/Taiwan/AliExpress has to see if I can find an aftermarket industrial engine equivalent.
PM me details & price of your Kubota please.
Dont worry if I ever bought a new engine it would be kubota based. Just have a line on a cheap Yanmar 2GM20 but it's cheap because the owner has found out it's not worth rebuilding at Yanmar genuine prices.

[skipperpete]

Originally Posted by Compass790

Does anyone have a 2GM20 piston lying around that they can make a drawing with dimensions of? Or failing that give me a pin height i.e distance from top of piston to centre of pin hole.

Reason I'm asking is I want to find alternative to Yanmar marine pistons as the price is OTT here. Have to figure out if it's worth rebuilding one as they aren't wet sleeved. I haven't bought the engine yet thats why I can't do it myself. Don't want to buy it if I have to buy genuine parts.

Actually want oversize pistons but one step at a time.

Thanks if you can help

Hi Compass790
I have a couple of old pistons from a recent 2GM rebuild, I'll measure em up and post the dimensions when I get to the workshop later today.
The price of Yanmar parts is making rebuilding them almost unviable, this 2GM rebuild cost $AU2,000 just for parts and a recent flooded 4LHA Yanmar was $AU 1,000 per cylinder for the liners and Pistons, alone,rings not included.

[model 10]

Pistons can be fixed. You can knural the skirt and re-cut the top groove for a wider ring. Rings of every size are in the master parts catalogs. Good auto part and machine shops can order this stuff.

[sailorchic34]

Have a good diesel engine shop mill and install sleeves and buy new rings. Cheaper then oversized pistons. Been there done that..

[Compass790]

Originally Posted by sailorchic34

Have a good diesel engine shop mill and install sleeves and buy new rings. Cheaper then oversized pistons. Been there done that..

Trust me it's not cheaper IF you can get the pistons/rings from China & not from Yanmar. I already did this for our YSM8. Thats why I want the dimensions for the 2GM20 piston.
But good thought if I wasn't so limited in funds.

[Compass790]

Originally Posted by skipperpete

Hi Compass790
I have a couple of old pistons from a recent 2GM rebuild, I'll measure em up and post the dimensions when I get to the workshop later today.
The price of Yanmar parts is making rebuilding them almost unviable, this 2GM rebuild cost $AU2,000 just for parts and a recent flooded 4LHA Yanmar was $AU 1,000 per cylinder for the liners and Pistons, alone,rings not included.

Yes it's certainly unviable for me unless I can source parts from China or Taiwan,
The 2GM has 72mm pistons cobber whereas the 2GM20 has 75mm pistons so maybe don't worry as I'm not sure if they have any other differences unless you are sure they dont..
Thanks for the attempt anyway.

[Compass790]

Originally Posted by Ecos

Pistons can be fixed. You can knural the skirt and re-cut the top groove for a wider ring. Rings of every size are in the master parts catalogs. Good auto part and machine shops can order this stuff.

Thanks for that suggestion. Would have to machine myself but would rather find cheap piston & rings ex China/Taiwan or India hence the need for dimensions.

[Compass790]

Actually skipperpete it looks like that the only difference between the 2GM & the 2GM20 pistons may only be the bore dia. as stroke & pin dia are the same.
But maybe a 2GM20 rebuilder will chime in anyway.

[Wotname]

Originally Posted by Compass790

Actually skipperpete it looks like that the only difference between the 2GM & the 2GM20 pistons may only be the bore dia. as stroke & pin dia are the same.
But maybe a 2GM20 rebuilder will chime in anyway.

Another difference between the 2GM and 2GM20 pistons is the 2GM20 pistons are available in an oversize (+0.25mm, IIRC) while the 2GM ones aren't.

The 2GM of course has liners while the 2GM20 doesn't.

[skipperpete]

Originally Posted by Compass790

Yes it's certainly unviable for me unless I can source parts from China or Taiwan,

The 2GM has 72mm pistons cobber whereas the 2GM20 has 75mm pistons so maybe don't worry as I'm not sure if they have any other differences unless you are sure they dont..

Thanks for the attempt anyway.

You're absolutely right about the bore size so I can't be sure that the 2GM20 pin to crown height will be the same ( it's 27.14mm from top of pin bore to top of crown on the 2GM20). My oldest parts manual shows dry liners in the old 2GM and 3GM engines..... never seen one with liners from new.
Good luck with the search for non genuine pistons, I had some success with the JH and TNE series kits from China and zero luck with 4LHA liner kits..but for most rebuilds I only ever used genuine Yanmar bits from Minards in Australia.

[Compass790]

Thanks skipperpete,
That pin to crown height you gave me mite prove useful. I suspect, but don't know, that the only difference is that diameter.
I have actually sent a newYanmar ys8 series liner to Minards for an engine they were rebuilding. They said they are no longer available
Don't like buying from them as they quoted me $360 for used PTO case for a YSM8. I can buy a whole used engine here for less than that.
cheers

[skipperpete]

That measurement is from the top of the piston pin bore, not the centre of the pin.
Yanmar is close to Volvo Penta with parts prices now and it's simply too expensive to rebuild either of these engine brands . The reality is that a modest rebuild is like giving a 95 year old man a heart transplant, sure it'll work but for how long? A proper rebuild is a cylinder head overhaul , all the conrod bolts replaced, new bearings ,new pistons and rings in standard bores, new oil pump, injector pump phase and calibrate... blah blah and its still the same old mounts and electricals, same old jabsco and heat exchanger. Better to just buy a new Beta and start afresh with an engine that we can get parts for.
If you weren't so far away I could gift you an old 2GM20.

[Compass790]

Yes but you have to remember this is mostly a North American forum & their yanmar parts prices are 1/2 of ours.
I rebuilt our YSM8 for about $1100 NZ$,( Parts ONLY) new Beta here about !0,000 NZ$.
I can't begin to guess how many hours I spent on online research & trial & error experiments to save a $. But I've come out the other side with a bit more knowledge & I can help YS8/& 12 series engine owners to escape Yanmars predatory parts pricing at least in Australasia.
Not that I'm doing it for free but if anyone wants to escape my parts pricing to save money they'll soon learn my hourly rate is peanuts.
If you are working yes buy a new engine istead of doing what I did.
Thing is I started on this because the Yanmar agent wanted to charge me $630 for the conrod as I've said in earlier post.
Only escaped that thru CF as Atoll helped me out.
I thought they were taking the p**s but they were SERIOUS.
In life you can often get reamed
BUT sometimes you can't take it. I just thought enough is enough. F U 2

I'm grateful for the offer of the 2GM20 as I KNOW it was offered in the right spirit but I have to know how to evade Yanmars business model which MAYBE to sell engines at a loss & sell parts for a HUGE markup before I would even accept the gift horse.
I don't know as I can't look at their books & wouldn't know what i was seeing anyway
The evidence suggest the disparity between tractor parts prices & marine suggests it's no coincidence tho.
Yes you stated clearly where your piston height was from, I know i just had to add 10mm to get the centre.
CF is great for the people who contribute even if we have our disagreements.
Distracts me from chores tho.