4L0 head milling

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LC Cnd
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4L0 head milling

#1 Post by LC Cnd » Sun Oct 21, 2018 4:15 pm

What's the optimal depth for shaving the head - recall it was between 0.5-0.6mm from some long ago Dutch technical service bulletin. Also interested in tech info on O-ring installation - would that included shaving the jugs flat also?

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two-stroke-brit
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Re: 4L0 head milling

#2 Post by two-stroke-brit » Sun Oct 21, 2018 6:57 pm

the squish dim for the head i believe is 0.9mm.
mark
350LC,Athena 392 big bore,stock porting,swiss cheese air box,stock reeds,spec11 pipes.(now TSA big bore pipes)
She might not be pretty but she will always be a fun ride


1982 YAMA RD350LC
98KDX 220R
1967 TRIUMPH TIGER
2001 TRIUMPH TT600

Hooligan
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Location: Calgary, Alberta

Re: 4L0 head milling

#3 Post by Hooligan » Mon Oct 22, 2018 8:40 pm

It will always be better if the top of the jugs are perpendicular to the bores and flat, along with the head being flat.

There are two schools of thought on the O-ring groove. Some machine (mill) it into the head but others machine (turn) it into the barrels. The milling operation is way more difficult than the turning operation and prob couldn't be done without a CNC these days. Turning can be done on a hobby lathe, with the addition of a custom work-holding setup.

My engines have the O-ring installed in the barrels, which makes it easier to put everything together IMO. I also think the barrels are a bit more durable than the head in the event things go badly down the road.
'82 RD350LC in '81 colours, OEM pipes, UNI filters
'85 FZ750

LC Cnd
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Re: 4L0 head milling

#4 Post by LC Cnd » Tue Oct 23, 2018 12:53 am

Searched the form for a photo of the o-ring pattern for the machinist I'm working with - canta find one. Must have noted on another site. De-carbonized the interior of the head's domes. Kinda looks like its already been milled - how does one tell for sure?
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Hooligan
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Re: 4L0 head milling

#5 Post by Hooligan » Tue Oct 23, 2018 12:55 am

That looks pretty OEM to me.

The O-ring groove is a flat bottomed groove of sufficient diameter and depth to accommodate the O-ring. Don't remember the exact ring size but it is a standard sized viton O-ring. I bought a bag of 50 of them couple years ago.
'82 RD350LC in '81 colours, OEM pipes, UNI filters
'85 FZ750

Bare
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Re: 4L0 head milling

#6 Post by Bare » Fri Oct 26, 2018 7:16 pm

Typ milling job eliminates that step at the edge of the squish. Remembering it also depends on What cyl Head gasket being used.
Oem v thick Fibre types require more milling to compensate. Current tin plate types being much thinner need less head metal removed .
O ringing the head also means a different amount of milling
"Slinger" in Nova Scotia mills heads and o ring grooves and knows exactly how/what to do onna 350.

LC Cnd
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Re: 4L0 head milling

#7 Post by LC Cnd » Sun Oct 28, 2018 8:19 pm

Attempted to get a hold of Slinger by phone through a nearby relative but learnt he no longer works on bikes as he is too busy working on boat motors currently. Be using OEM gaskets.

Bare
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Re: 4L0 head milling

#8 Post by Bare » Tue Oct 30, 2018 9:19 pm

Surprised by that.. But ? Winter is Down time.
Not a lot of Rec Boating when the waterways are iced

silverstrom
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Re: 4L0 head milling

#9 Post by silverstrom » Wed Oct 31, 2018 12:54 am

I believe he does a lot of fishery work also and their down time is winter, so still plenty for him to do.

Bare
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Re: 4L0 head milling

#10 Post by Bare » Wed Oct 31, 2018 3:23 pm

Credible that the scope of his business has grown.. Good on him.
Suggest http://home.earthlink.net/~scloughn/id14.html" onclick="window.open(this.href);return false;
Scott's been racing and winning :smt002 on 350's.... since 1974.
Unlikely to find better .. anywhere.
Does Excellent work at reasonable prices

LC Cnd
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Re: 4L0 head milling

#11 Post by LC Cnd » Wed Oct 31, 2018 6:23 pm

Yep, looked a Scott's site- impressive resume for motor mods but in California. Found a local machinist who mills banchee heads. Contacted my local Yamaha dealer for OEM head gasket with number 4L1-11181-000. Is there a replacement #?

Bare
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Re: 4L0 head milling

#12 Post by Bare » Thu Nov 01, 2018 1:24 pm

Erm Ok ..Shippings for a crank ~30$ .
Hardly prohibitive, truth be told.

Two types HGs' available: Original 2 mm (too!) thick Fibre ones.
Must be oem! as copies are of variable quality/reliability
OR thin .. 3 layers of stamped metal types.. exactly like the RZ ones.
Aftermarket versions of which are 95 +% as good as OEM. I'd go for the Metal one if only because of Less milling required for reasonable Squish
Plus they are reusable.. repeatedly.. or at least for as long as their stamped in ridges are detectable.
Permatex Coppercoat HG spray is additional reuse insurance.

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