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Oh check out the other thread as the 750 of heads sometimes had minor issues that r readily rectified. The pushrod tube bosses in the head are variable Fer depth as well. A rather learned fella was quite gracious. And showed me alot of the info I've passed to you n others . If not for his wisdom I'd be still pulling my hair out.as to the out of shape... yeah you'll find some are even not spaced centered over the crank throws.... they sure r forgiving old engines! Dressing all the flat faces is a great thing. I pull the studs do that myself.
 

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Discussion Starter · #42 ·
Hi all . Back again. Been busy with other stuff that took priority though now have the barrel bored and honed out to plus .040" and new pistons all ready to fit.
Question. I have gone for Harris low compression pistons the same as came with the engine and original fit I believe.
There is nothing stamped on the crowns to indicate orientation front to back. The valve head reccesses , exhaust and inlet appear identical and there's nothing to suggest they should be fitted oa certain way which in my experience is unusual.
Can anyone confirm if there is a recommended orientation ? Thanks for your help and info.
 

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That's a very goid choice, however there is an orientation to their installation. Look into it further.. lf Harris website has more info. No paperwork came w them? Mine have in marked....
 

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Discussion Starter · #44 ·
That's a very goid choice, however there is an orientation to their installation. Look into it further.. lf Harris website has more info. No paperwork came w them? Mine have in marked....
Thanks Brent I will do that. Yes had some paperwork but it was just explaining the ring fitting etc nothing on orientation. (y)
 

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The 750 pistons seem like valve cuts r same, but look closely measure, the smaller cut is exghaust valve, and needs tp tint forward. Just looked at 2 sets, plus a pair of origionals... about .020 difference in width of relief cut. It probably wouldn't make a difference , but.... I'd still try to put larger cut towards rear for the intake valves... measure, yes it's a wonky pita. But I marked mine w a sharpie... once together all well. Mite scribe the inside of skirt if ya ever wanna tear it down again. The jcc are just a bit taller than the lf Harris pistons I have, plus both are lower than the origional pair from this 79 140 I have... easiest way to see that was to put upside down side by side... thickness of the thin oil ring retainer ring difference. Hope this helps.
 

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Discussion Starter · #46 ·
The 750 pistons seem like valve cuts r same, but look closely measure, the smaller cut is exghaust valve, and needs tp tint forward. Just looked at 2 sets, plus a pair of origionals... about .020 difference in width of relief cut. It probably wouldn't make a difference , but.... I'd still try to put larger cut towards rear for the intake valves... measure, yes it's a wonky pita. But I marked mine w a sharpie... once together all well. Mite scribe the inside of skirt if ya ever wanna tear it down again. The jcc are just a bit taller than the lf Harris pistons I have, plus both are lower than the origional pair from this 79 140 I have... easiest way to see that was to put upside down side by side... thickness of the thin oil ring retainer ring difference. Hope this helps.
Many thanks Brett I will check that out when I come to assemble. I did though contact Harris whos main warehouse is no more than a few miles away from where I live and they explained that the engraved/stamped part no etc on the top of the piston should be read the right way up when your sat on the bike.
Your knowledge is always gratefully received though and you may be able to help with the latest query I have regarding the oil pump. What arrived with the engine in boxes was an old style two valve oil pump and I believe this bike should have the later four valve pump. Just need to be 100% sure before I purchase a new pump as this is the later electric start bike. I have read they can be retro fitted to earlier engines with conventional kick start but the inner casing has to be ground away to make way for the bulkier pump body.
Thanks again Brett.
 

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U can put a 2 piston pump onbit, they make a great aftermarket 4 ball pump.. easily retrofitted to earlier engines, it's the cover needing a slight"adjustment " tho the regulator 2 check ball pumps work fine even on the es motors.. yer making more progress than me!! Bestreguards, brent
 

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Discussion Starter · #48 ·
U can put a 2 piston pump onbit, they make a great aftermarket 4 ball pump.. easily retrofitted to earlier engines, it's the cover needing a slight"adjustment " tho the regulator 2 check ball pumps work fine even on the es motors.. yer making more progress than me!! Bestreguards, brent
Thanks Brent much appreciated Pretty sure it should have the four valve pump as thats the type listed in the parts book I downloaded.but its an old bike with a long past and chequered history. Whats holding you up on your build Brent?
 

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The only gain to a 4 valve triumph pump is half of it can clog n it'll still work n keep yer engine alive. The aftermarket 4 valove pumps seem to be held in fairly high reguard. I've a like new 4 valve to put on my 750. As for my lack of progress... heheheheh heheheheh short answer.. life. We allow far too much traffic to get between what we love to do and enjoy in the name of all the crap we hafta do.. work, paying bills.... my to do list is far too long... my wanta do list is not short , but keeps getn pushed off. I've spent 9 years gathering everything to refurbish my 64 ... save new tyres n tubes. Lotsa hours of research to find the correct parts even the paint... I'll be committing sum sorta sacrilege when it's done. It'll have a nacelle from a 64 thunderbird n the large tank too.. the original tank n stuff Fer instruments are all here n in working order, n will be kept safe. I'm so ocd with it I've even got borannis n dls front hub to fit original front end... the 79 n a redhead got in the way, then work n 79 n redhead.... heheheheh seeing the pattern? But I enjoy helping if n wen I can so others can get their scoots back in the wind..
 

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Discussion Starter · #51 ·
Hey have you made any progress?
[/QUOTE
Hi Brent. All been on hold for the last couple of months for various reasons including some illness and my garage workshop being stacked up with building materials for my house extension. Too much dust and disorganised to continue the build but hoping to get back to tackling it soon. Rest assured I will update with pics as I progress. Bound to be returning also for advice on any thing Im not 100% sure about. (y)
 
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