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6t pistons #714322
11/08/17 11:13 pm
11/08/17 11:13 pm
Joined: Sep 2017
Posts: 29
Ireland
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Yeksae Online content OP
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Yeksae  Online Content OP
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Ireland
Hi,

I’m looking to get a pair of +40 6t pistons for 1959 thunderbird. What brand and where have he found good for pistons?

Thanks

John.


John
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Re: 6t pistons [Re: Yeksae] #714327
11/08/17 11:43 pm
11/08/17 11:43 pm
Joined: Aug 2014
Posts: 896
Australia.
L
Les P Online content

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Les P  Online Content

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Joined: Aug 2014
Posts: 896
Australia.
When I was looking for pre unit pistons (1957 TR6) there seemed to be one logical place to shop.
I think they were JCC brand with good USA manufactured piston rings and weight match checked before dispatch, they are a ways from Ireland (as is Australia) but dealing with Dan was well worth the postal distance.

https://fagengine.com/

Re: 6t pistons [Re: Yeksae] #714330
11/09/17 12:09 am
11/09/17 12:09 am
Joined: Nov 2012
Posts: 380
Isle of Wight, UK
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koan58 Online content
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koan58  Online Content
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Isle of Wight, UK
Might take a bit of tracking down. TMS, then TriSupply maybe? Run of the mill say 9:1 easy to find, if you want 7 or so:1, not so easy. I guess that's an alloy head?
TT or Hawaian will hopefully chip in.

Re: 6t pistons [Re: Yeksae] #714331
11/09/17 12:26 am
11/09/17 12:26 am
Joined: Aug 2014
Posts: 896
Australia.
L
Les P Online content

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Les P  Online Content

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Joined: Aug 2014
Posts: 896
Australia.
Finding pistons is not hard including plenty on UK eBay and various websites (30 second web search), finding someone who will supply a good set with decent rings can be the catch.
Even Gandini do low compression .

Re: 6t pistons [Re: Yeksae] #714332
11/09/17 12:39 am
11/09/17 12:39 am
Joined: Sep 2017
Posts: 29
Ireland
Y
Yeksae Online content OP
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Yeksae  Online Content OP
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Posts: 29
Ireland
Iron head and low compression 7:1s is what I’m looking for, hard to tell what’s good or not on eBay 🙁


John
Re: 6t pistons [Re: Yeksae] #714334
11/09/17 1:12 am
11/09/17 1:12 am
Joined: Jun 2007
Posts: 5,597
Maui Hawaii
HawaiianTiger Online content

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Maui Hawaii
I used ordinary JCC unit construction pistons for my 6T with iron head. The CR is pretty low. Not exactly sure how low, but it's a softly tuned motor. When I want standard CR or a little higher, I go with LF Harris pistons, which I believe are JCC's as well, but with the correct domes we need for our pre units.
It's always a good idea to clay the head. You never know who's been messing around with these motors...

Cheers,
Bill

Last edited by HawaiianTiger; 11/09/17 1:13 am.

Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Flying Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
Re: 6t pistons [Re: Yeksae] #714335
11/09/17 1:25 am
11/09/17 1:25 am
Joined: Aug 2014
Posts: 896
Australia.
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Les P Online content

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Les P  Online Content

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Joined: Aug 2014
Posts: 896
Australia.
Originally Posted by Yeksae
Iron head and low compression 7:1s is what I’m looking for, hard to tell what’s good or not on eBay 🙁


Here is a set from 'montysclassicmotorcycles who I have purchased off before (Lucas lenses)

Iron head pistons + 0.040"

What is the deal with the iron head, is it the squish band change like the 500 cc engines ?

Last edited by Les P; 11/09/17 1:29 am. Reason: eBay links not working.
Re: 6t pistons [Re: Yeksae] #714336
11/09/17 1:49 am
11/09/17 1:49 am
Joined: Jun 2007
Posts: 5,597
Maui Hawaii
HawaiianTiger Online content

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Posts: 5,597
Maui Hawaii
The combustion chambers in the iron head are much deeper than the alloy heads, with the unit heads even shallower, so the piston crowns look decidedly different.

And those are the pistons I have used. They work just fine.

Cheers,
Bill


Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Flying Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
Re: 6t pistons [Re: Yeksae] #714352
11/09/17 7:30 am
11/09/17 7:30 am
Joined: Jan 2017
Posts: 261
Pleasant Hill, California USA
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TR7RVMan Offline
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Pleasant Hill, California USA
Hi John, LF Harris makes them. Check their web site for sizes. They seem to be the only ones making them. They don't sell retail, so you'll have to have a retailer order them for you. Seem to be good quality & the rings they come with tend to work quite well.

Be sure to use real break in oil with them.

I actually had a set in my own hands recently at Raber's San Jose, CA USA.

They are often called "unleaded" pistons.

I don't know for sure what the true compression ratio will be with the iron head. It's said to be 7.1:1

Looking at iron head the combustion chamber shape around edges is deeper so I expect them to be 7.1.

I know for sure the alloy head piston is the same blank exactly but is machined around the edge so it doesn't hit the squish band area of alloy head. I'm currently installing these in '69 Bonnie.

I have friend that used these pistons on T140 7.4:1 to very good results. They are the same construction so to speak, but configured for 750. The casting is the same material & interior webbing etc. is the same as the iron head. Bore clearance was set to .0045" to good results. The bonnie 650 bore clearance is .0045 also. That has proven good on several motors.

Again break in oil can be very important. Use Torco TBO 40w. run for 200 miles then go to regular oil. In several cases this combination has given perfect results.

Here's an eBay link to iron head 7.1.


https://www.eBay.com/itm/TRIUMPH-PISTONS-IRON-HEAD-71MM-040-1MM-6T-TIGER-T110-7-1-comp-ratio/132108285863?rt=nc&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D48754%26meid%3D234676220e4048269db881738d6dbd35%26pid%3D100005%26rk%3D6%26rkt%3D6%26sd%3D132165859448&_trksid=p2047675.c100005.m1851

Don


1973 Tiger 750
Re: 6t pistons [Re: Yeksae] #714356
11/09/17 8:28 am
11/09/17 8:28 am
Joined: Sep 2008
Posts: 628
Skudeneshavn Norway
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Stein Roger Online content
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Posts: 628
Skudeneshavn Norway

Re: 6t pistons [Re: Yeksae] #714606
11/11/17 11:46 am
11/11/17 11:46 am
Joined: Sep 2017
Posts: 29
Ireland
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Yeksae Online content OP
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Yeksae  Online Content OP
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Posts: 29
Ireland
Thanks everyone. Found a manual that said could only go +20 could that be right?


John
Re: 6t pistons [Re: Yeksae] #714610
11/11/17 12:50 pm
11/11/17 12:50 pm
Joined: Aug 2001
Posts: 7,117
scotland
triton thrasher Online content
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triton thrasher  Online Content
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Posts: 7,117
scotland
Originally Posted by Yeksae
Thanks everyone. Found a manual that said could only go +20 could that be right?


No, I think you're reading it wrong. 20 thou may be (going by memory) maximum oversize for the 500 cc alloy barrel.

The iron cast iron pre-unit 650 barrel has a 40 thou recommended maximum oversize. +60 thou is usually ok though. I ride one on +60 and it works fine, althouh the studs look a bit close to the bore.


Amateur Loctite enthusiast.

Moderated by  John Healy 


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