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#714322 - 11/08/17 11:13 pm 6t pistons  
Joined: Sep 2017
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Yeksae Online content
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Yeksae  Online Content
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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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#714327 - 11/08/17 11:43 pm Re: 6t pistons [Re: Yeksae]  
Joined: Aug 2014
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Les P Online content
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Les P  Online Content

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Kiwi in 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/

#714330 - 11/09/17 12:09 am Re: 6t pistons [Re: Yeksae]  
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koan58 Offline
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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.

#714331 - 11/09/17 12:26 am Re: 6t pistons [Re: Yeksae]  
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Les P Online content
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Les P  Online Content

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Kiwi in 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 .

#714332 - 11/09/17 12:39 am Re: 6t pistons [Re: Yeksae]  
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Yeksae Online content
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Yeksae  Online Content
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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
#714334 - 11/09/17 1:12 am Re: 6t pistons [Re: Yeksae]  
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HawaiianTiger Online content
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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.
#714335 - 11/09/17 1:25 am Re: 6t pistons [Re: Yeksae]  
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Les P Online content
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Les P  Online Content

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Posts: 822
Kiwi in 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.
#714336 - 11/09/17 1:49 am Re: 6t pistons [Re: Yeksae]  
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HawaiianTiger Online content
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HawaiianTiger  Online Content

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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.
#714352 - 11/09/17 7:30 am Re: 6t pistons [Re: Yeksae]  
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TR7RVMan Offline
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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
#714356 - 11/09/17 8:28 am Re: 6t pistons [Re: Yeksae]  
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Stein Roger Online content
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Stein Roger  Online Content
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Skudeneshavn Norway

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


John
#714610 - 11/11/17 12:50 pm Re: 6t pistons [Re: Yeksae]  
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Posts: 6,895
triton thrasher Online content
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triton thrasher  Online Content
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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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