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Discussion Starter · #1 ·
What are the good mods for a 650 motor. I'm going to rebuild my 1970 TR6 bottom end with a 1966 head. I need new pistons, head work, pretty much redo everthing. I hope to keep the same cam if I don't need to change it. How can I get the best power out the motor. What manuel will I need, a 1966 or 1970 does it make a difference. What's the est. amount that I'm look at on parts.

Wes thanks for the info on the T100 mod to a 650. Can this same mod be done to a 650 to a 750? Any addtional info.
 

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Galaxie500XL said:
What are the good mods for a 650 motor. I'm going to rebuild my 1970 TR6 bottom end with a 1966 head. I need new pistons, head work, pretty much redo everthing. I hope to keep the same cam if I don't need to change it. How can I get the best power out the motor. What manuel will I need, a 1966 or 1970 does it make a difference. What's the est. amount that I'm look at on parts.

Wes thanks for the info on the T100 mod to a 650. Can this same mod be done to a 650 to a 750? Any addtional info.
Performance:
- lumpier cam
- higher compression ratio
- dual carb head
- Mikuni carburetors
- Port & polish the head
- Lighten valve train components - pushrods, rockers, adjusters, etc.
- Belt drive primary

Reliability/Streetability
- keep engine internals stock
- electronic ignition (boyer)
- updated charging system (sparx)
- external oil filter
- single carb head

$$$
-how fast do you want to go? :D
-how much work are you doing yourself?

650 vs 750
- can't drop a 750 cylinder on a 650 without case machining and changing the rods - spigot diameters are different and 750 cylinders and rods are shorter
- 650 cylinder could feasibly be bored .200" over to 750 spec - I personally haven't seen it done
 

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Big Bore kits are made for the Trump 650 to bump it to750, but you cannot bore out the 650 jug to be a 750. Morgo also made a kit to bump a later T140 (natural 750) to an 850. Most kits nowadays are designed so that rebalancing of the crank is not necessary. Most of the reason why the earliest kits (Sonny Routt) blew up was not because of the kit itself not matching up with the balance on the crank, but becasue the big giant cast pistons were VERY heavy. if you have ever held one in your hand you will know what the difference is. Not sure why the 500s had so much meat on them, but they do. Also unfortunately you cannot drop a 650 jug on a 500 set of cases either. Bolt pattern as well as bore and stroke all different. Same for a T140 jug, you cannot put it on an earlier 650 set of cases without modifications. Different stroke.


Best bet is to build a pretty stock motor. Stock cams were quite zippy, especially in the later R models. Megacycle sells a "Hot Street and TT" cam that is zippier but still streetable if you gotta go with different cams, just remember that the cam bushings can be a major pain with new cams. But you are adding about $350 to your build budget with any hot cam, more if you walk into the wrong BritBike Store. Use a higher compression piston. Drop on a Big Bore kit and that will make you super-zippy. I blow off stock Evos on a 1965 650 Triumph pretty easily with no mods whatsoever light to light. It is all power to weight ratio, with a chopper you got NO weight. Most Evos are dragging about 10,000 extra pounds around. Not sure about the bigger motors nowadays but the Trumps always beat the Big Twins in the early days. Sportsters were more competitive with the Triumphs and it was always neck and neck back in the day Sporty versus Triumph. Bigger inches does not always mean more speed.
 

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Discussion Starter · #4 ·
What are good pistons to use for the build? I know most people that rebuild Norton's like Hepolites. I'm sure it's the same with Triumphs, but I have a friend that said he likes Taiwan's pistons, and he doesn't have problems with it, but I don't want to go cheap if it's going to cost me more in the long run.


I'm on a budget, my Norton has been eat up on my cash flow$$$$.
 

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Discussion Starter · #5 ·
What brand of piston would be good?

Galaxie500XL said:
What are good pistons to use for the build? I know most people that rebuild Norton's like Hepolites. I'm sure it's the same with Triumphs, but I have a friend that said he likes Taiwan's pistons, and he doesn't have problems with it, but I don't want to go cheap if it's going to cost me more in the long run.


I'm on a budget, my Norton has been eat up on my cash flow$$$$.
 
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