Honda MG & MF 750

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Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

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These pistons were originally a special order from JE. I had been talking with Brian Weaver at JE , getting a set of pistons how I wanted was starting to get complicated as JE have lots of sub dealers who have the design rights to their custom piston designs and have to be purchased from the sub dealer, unfortunately those sub dealers are small businesses that only buy in minimum quantities but so you have to wait for them to order once every couple of years and they wont change the ring design, so I got lucky man, old school design is good for me and saved a few bucks but I was prepared to pay bucks for my preferred rings design.
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

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The new old pistons are a bit heavier, they have longer pins and the extra ring, all up around 17 grams heavier but I can live with that, no good having carillo rods if they dont earn their keep, they will be fine with 10K redline.
momec3
Posts: 780
Joined: Tue Mar 01, 2011 10:36 pm
Location: Cedar Grove Qld

Re: Honda MG & MF 750

Post by momec3 »

Yeah beware of that too,
A race engine shop where I once worked were the first to do custom JE pistons for new V6 Commodore engines. To keep ahead of the curb we didn't restrict who could use our design. Got rods done at Carrillo at the same time. The rods were about .006" longer in pin height than std. The pistons .006" shorter. Anyone who then ordered the "std" design style pistons would struggle to find comp with a stock length rod. Keep us ahead of the game for a short while. Ditto the rods.
Lots of little tricks in the background that backyard builders may not be aware and get stung.
CP will do whatever design you want, no restrictions.
Chris
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

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Thought I would have a look at the new pistons,
standard on left
Dynoman JE in Middle and
custom JE on right
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

Image
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

Image
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

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made a long centre pop to mark the centre of the valve on the piston to centre the mill if flycutting.
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

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done all the valve cutaway's
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

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tool to mark the plug centre in case I have to unshroud them
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

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assembled the head, cam , tappets etc , turned it over a couple of times, now to loook at the play doh
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

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measured the play do thickness,
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

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this a kind of a contour map to see where I need to machine.

Inlet valve is good....just need to flycut the 34mm diam to about 38mm

Exhaust is fine , lots of room as both the inlet and exhaust are fly cut to 34mm where the exhaust is only 28mm

The area from edge of piston to the plug is too close from toching to .2 and .3 bit too close

Will have to drill a clearance hole for plug, like the Dynoman JE
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

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time to do a comp check,
Clearance volume......17.2
Swept vol................190.1
CV+SV divide CV = 12.01:1 this is less than the Dyno JE which was 12.2:1

I'll have to think about the piston to head clearance how to machine piston
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Greg Watters
Posts: 760
Joined: Mon Sep 27, 2004 8:57 pm

Re: Honda MG & MF 750

Post by Greg Watters »

being that close and tight clearances offset to one side have you checked the other 3 , nearly like the head is not quite centred on the bores
Johno Senior
Posts: 260
Joined: Mon May 21, 2012 12:17 am
Location: Berri Sth Oz

Re: Honda MG & MF 750

Post by Johno Senior »

Yes Greg,
I thought the same so I did check,

I just got back some info from JE today saying those pistons were ordered by a customer as road racing pistons and he had ground the chamber more hemi shape

not sure why he wanted such large exh releif ?

Out of curiosity I will put in the Dynoman JE piston and check the clearance up around the plug area, if its simliar to the new pistons I will do some milling on one side only rather than lathe the whole dome and lose some comp
I checked under the dome, there is plenty of ally meat there to mill and the ring lands are not close.
cheers johno
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