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Discussion Starter #1
Hi

I am builting a TT1 race bike out of a 750ccm Pantah engine, i am lacking some info regarding the tuning of the bike, i have purchased a set of high comp pistons ø94mm (original ø88mm).
and need to fit them, this is not a major problem just a little milling.

what i need to know is how to adapt the rest of the engine to work with this piston/cylinder combo.

i was thinking about using a 748 crank with carillio conrods does anybody have experience using a 748 crank in different engine models, all info so far indicates it will fit.

when this is solved i need to know the optimal porting and inlet/exhaust diameter. 41mm carbs, 38mm carbs ?
45mm exhaust, 50mm exhaust ?

the work i can do, no problem, but the engineering not so much, if any of you would be kind enough to enlighten me on some of these issues it would be much appriciated.

just for info, i am building the bike on a pierbone TT1 frame with F1 swing arm, the marvis 3 spoke mag wheels of that era. and a Harris TT1 body kit.
i really need those Marchesini mag forks if some one has those.
regarding the engine it is getting the works, so far i have lightened the gears, machined a straigth cut 5 speed gearox.
light flywheel and lightened/polished rocker arms.

any pitfalls, reliability issues vs state of tune. i am chasing a rev happy engine with the peak power at about 9-10.000 rpm.

Best regards.
Christian
 

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Hi Christian,
From your description, it sounds like you are well on your way to building a very interesting motor. My advice to you regarding the porting and such is to research production two valve engines with the same or perhaps more displacement as your 94's will give. From that, you can obtain valve diameters and even cam specs. On carbs, I suspect 41 flat slides may offer the best induction. I know that when I bumped my DB2 from 904 to 944 with Ferraci's hi-comps, they worked well. The expression, "don't re-invent the wheel" comes to mind here. Keep us all posted.

Aah Denmark...spent some time in Aalborg once...a long time ago...very nice folks.
Steve in Florida

Hi

I am builting a TT1 race bike out of a 750ccm Pantah engine, i am lacking some info regarding the tuning of the bike, i have purchased a set of high comp pistons ø94mm (original ø88mm).
and need to fit them, this is not a major problem just a little milling.

what i need to know is how to adapt the rest of the engine to work with this piston/cylinder combo.

i was thinking about using a 748 crank with carillio conrods does anybody have experience using a 748 crank in different engine models, all info so far indicates it will fit.

when this is solved i need to know the optimal porting and inlet/exhaust diameter. 41mm carbs, 38mm carbs ?
45mm exhaust, 50mm exhaust ?

the work i can do, no problem, but the engineering not so much, if any of you would be kind enough to enlighten me on some of these issues it would be much appriciated.

just for info, i am building the bike on a pierbone TT1 frame with F1 swing arm, the marvis 3 spoke mag wheels of that era. and a Harris TT1 body kit.
i really need those Marchesini mag forks if some one has those.
regarding the engine it is getting the works, so far i have lightened the gears, machined a straigth cut 5 speed gearox.
light flywheel and lightened/polished rocker arms.

any pitfalls, reliability issues vs state of tune. i am chasing a rev happy engine with the peak power at about 9-10.000 rpm.

Best regards.
Christian
 

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Discussion Starter #3
Hi Steve

Thanks for the reply.
My point excactly no need to re-invent the wheel, thats why im asking for help.
the 94mm bore will result in a 854ccm over square engine with a relation of about 1,5/1 (bore/stroke).
this should insure the smooth reving nature im looking for.
the problem is i dont know of any 854ccm engines with two valves that i can copy the layout for the valves from.
i know it has been a popular mod for old 750ccm engines bot so far i have had no luck searching the net.
i also have a 1991 900ss whith the 944ccm kit and 41mm flat slides, but as i am 100ccm short of that with the new engine im not sure the 41mm carbs will work. experience anyone ?

Yeah Aalborg is a nice place i lived there for a few years.
i have been around your part of the world as well, fort lorderdale, miami the keys and did a trip from NY to LA a few years back good times.
 

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some thoughts: if you're using a pantah bottom end you'll have 750 stud spacing which will make it very hard to get 94mm cylinders on. the pantah heads will not take valves as large as you want to fit i don't think. the pantah cases crack when you rev them a lot. single phase 748 crank is longer on the alt side than any pantah crank.
 

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CSH,You are better off if you start with a 900 engine because would have to be a magician to get the 94mm pistons to work with the 750 stud spacing.I think 92 was the absolute limit and with that you could almost see the pistons moving in the bores.Using 90mm pistons gives about 820cc and with them the sleeve thickness is on the edge of being too thin.When they get hot the ring sealing suffers and the power drops off noticably.A well built 750 will run just as fast and be much less trouble.All the power is in the cylinder heads anyway. Another option would be to start with an 800 out of one of the later SS's.They have larger valves,stronger cases and FI if you want it.Plus parts are more likely to be available and much cheaper.
 
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