99 670 summit

[maxwell]

lol gee thanks modman ill make sure and do that next time hahahaha

now im curious to try this again. only ever ridden 2 670s.

[flabbajabba]

My friends Dad rides a 670x not sure if its a 98 or 99 its a rocket. It took my piped 97 two up

[Modman]

Originally Posted by maxwell

lol gee thanks modman ill make sure and do that next time hahahaha

now im curious to try this again. only ever ridden 2 670s.

LOL - was just joking, maybe your 670 was having an off day or something. Like Magnet said though, some pipes on the 670's were dogs, the HO was the best pipe out there for singles, the Jaws were the best pipes for the twins. Depending on what pipes it had, might have made a big difference. They really like the heat in pipes too, 1230 F is where mine really starts to wake up and make good power, most people don't get enough heat to the pipes to really make the power. The 670 was a hard motor to improve on for big aftermarket power gains. The rotary valve and the head were some of the best areas to make power, pipes were far more difficult to make a large amount of power with.

[Slamnek]

This was my brothers 100% stock.

[maierch]

Originally Posted by Modman

LOL - was just joking, maybe your 670 was having an off day or something. Like Magnet said though, some pipes on the 670's were dogs, the HO was the best pipe out there for singles, the Jaws were the best pipes for the twins. Depending on what pipes it had, might have made a big difference. They really like the heat in pipes too, 1230 F is where mine really starts to wake up and make good power, most people don't get enough heat to the pipes to really make the power. The 670 was a hard motor to improve on for big aftermarket power gains. The rotary valve and the head were some of the best areas to make power, pipes were far more difficult to make a large amount of power with.

Large gains were made on these motors by putting a shorty rotary valve cover on and opening up the cases and the transfer ports into the cylinders. There are mid 90s vintage 670s that will run with XPs. In my experience twin pipes also provided gains however they moved the peak RPM up to 8400 which has diminished the reliability of the cranks in these motors (I went through 3 of them a couple of seasons ago). Also a quick mod for these is to advance the timing all the way, however you have to watch your octane level when you do. With the timing advanced I always ran 50% premium and 50% AvGas.

[Duct tape Doo]

670 have instant throttle response when set up properly, Gutted air box, short rv boots, bored carbs, fattened base gasket, shaved head from .059 to 0.62 squish, 501 intake plate, jaws twin pipes and hold on.
It might not make the power of an 800 HO but very very reliable.
I have 10 seasons without a problem but i did do the crank end bearings and OEM pistons a few years ago as a precaution as i have not needed a chopper flight yet and the PTO end bearing will eventually fail if you keep going.
I have had a 2000 700X, an 2001 800X that had nothing on my 1996 670 non X except better suspension and less flooded carbs.

[jay007]

I know mine is a little older but I have a 97 670 and it has been the most reliable sled imaginable!! had to pull my 05 800 home with it last year!!
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