Yamaha 420 inboard diesel

Paddyd51 · 04 April 2015, 20:03

Anyone know of a supplier of Pistons or other parts for Yamaha 420 inboard turbo diesel 245hp.

biffer · 05 April 2015, 07:38

Pistons probably weren't made by yamaha as its a Toyota block, would suggest you go to a engineering company or show one to toyota

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willk · 05 April 2015, 09:50

I don't. You may find this interesting however: Yamaha ME420STI Sterndrive - Diveworks Charters, Fishingdownunder, Whakatane, New Zealand

Paddyd51 · 05 April 2015, 10:19

This seems to be a normal misconception. Block casting is Toyota but machined by Yamaha to suit their slightly smaller Pistons which have numerous bore grades and compression heights which are coded on crank and rods. Standard Toyota Pistons last about 1 hr due to extremely high compression ratio and boost.

biffer · 05 April 2015, 11:44

Quote:

Originally Posted by Paddyd51

This seems to be a normal misconception. Block casting is Toyota but machined by Yamaha to suit their slightly smaller Pistons which have numerous bore grades and compression heights which are coded on crank and rods. Standard Toyota Pistons last about 1 hr due to extremely high compression ratio and boost.

I don't mean this in a nasty way but how do you machine for a smaller piston, the block isn't liners, neither yamaha or Toyota make there own Pistons, just like the rest of the bits on the engine, injector pump for one, turbo as well, you've got to find where they used to buy them from, the compression isn't the problem, it's the bigger turbo

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yam man · 05 April 2015, 13:49

The engine block is built up by Toyota 1hdt 12v / 1hdft 24v Yamaha supply Toyota with the Pistons an rings an big end bearings that's it the rest is Toyota . The engine block in then shipped to Yamaha to be marinised .The bores size are the same an grading A,B,C . All the engines iv striped an rebuilt have been b . The crank mains an big ends are graded 2 . By taken number of the crank ladder an the crank an added the numbers to get the right shell . But to be honest if an engine has done 1000hrs the crank an the bores are worn which means the grading is out the window .
Pistons (forged) have to be Yamaha (ART) an the rings due to the high boost pressure .The rest ie shells can be a good quality aftermarket make . Hope this helps

Brian · 05 April 2015, 14:37

My understanding is that "a certain N Ireland boatbuilder", not a million miles away from Cushendall, has a whole stock of bibs and bobs for Yamaha engines.

You could try asking one of our moderators for his phone no.

biffer · 05 April 2015, 15:48

I think he would have volunteered his services by now surely

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yam man · 05 April 2015, 16:10

The Pistons are not that expensive from Yamaha now they used £500 or so plus vat but the last batch I bought was around £250 inc vat . Still a rip off

yam man · 05 April 2015, 16:10

That's each

Ian M · 05 April 2015, 16:56

Bl@@dy he!!

cptsideways · 05 April 2015, 19:34

I'd be looking at stock Toyota pistons & get them machined to the specs of the Yam ones, especially if lower compression. Stock pistons are cheap for the cruiser engines from Milners 4x4.

Engine Piston Set (6) Std (no Rings) for Toyota Uk Land Cruiser HDJ80 - 4.2TD 1990-1998 UK/IMPORT

yam man · 06 April 2015, 08:19

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Give it a couple of hours of running

Roger Barr · 06 April 2015, 08:48

I rebuilt an ME370 a few years ago and sourced the pistons via Kilmarnock Engine services, they reground the crank, cut the valve seats, skimmed the head, etc for me. They got them from A truck part supplier in Germany.
Different engine, but maybe worth a call?
Cheers Barry

paraicm · 01 September 2015, 19:00

Would it be possible to use a good 1hd ft engine block and use my original yamaha pistons with new rings .the bores are rusty on my old engine I was told .its a 432 sti 285hp version .yam man might be able to point me in the right direction .

kubcat · 01 September 2015, 22:08

There are companies in the U.S. that will make pistons for you at a reasonable price. I got some made for my Porsche by JP Pistons about 15 years ago and I have done almost a million kilometres with them. They were a quarter the price than from Porsche and I got a custom compression ratio.

They do a lot of racing vehicles so make top quality stuff.

Probably not the first option, but certainly an option.

Paddyd51 · 05 September 2015, 09:27

Not sure about 432 but all 422's use 1HDT block bore grade 2. Probably is the same since yanmar 6lp 315hp uses this block also. PM me for technical detail and sensible part source

otilly · 09 September 2015, 12:11

wiseco can make any piston yoy want. Google them

Paddyd51 · 13 September 2015, 07:32

Beware after market land cruiser Pistons. Some out there are not up to the higher cylinder temperatures.
Sure the combustion chambers can be CNC machined to lower CR but gudgeon pins are not as strong which would be the weak link in a 432 unit. Art Pistons used by Yam are nothing special in construction and accept a Toyota top ring but 2nd ring is thinner as is oil control. We regroove to accept an OE ring set, complex!!
Building one of these is more complex than your normal diesel with loads of very important tolerances and in particular a block change means a calculation for head gasket thickness.