I also have a 501 valve sitting on the self ready to go in as well.

 

Sorry man but I struggle with throwing that kind of money at a sled that old. Especially when there will still be sleds out there that will beat you on the lake. If you were able to get the parts ultra cheap I might consider it. Otherwise I would put the money towards a newer and bigger sled.

 

how about, big bore kit 82 mm and 74 mm stroke. that would make about 780 cc motor. then tunnel port, HO spec the cylinder. I don't know how much power that would produce but a regular 670 done up tunnel port, cylinder porting and single pipe should be good for 140 hp. give or take a bit. If you look maize's build which I do believe it was a 670, he made 130 ish. The first one is kinda what tossing around. just need some money. as much as people that say it'll be too much money, wouldn't it be nice to pull up in '670' and showing who the boss is! kinda like my sleeper sled, 1994 mxz 470 with a 670 in it and not stock either. It's magical, to see the young bucks thinking they are going put the boots to the old girl and they realize they've been had. Priceless.

 

As far as buying a newer sled that's out of the question. I don't like the chassis and the older sled ride different. My buddy's dad did a big bore kit and it's fast but not many people are still selling that stuff it was hard for him to find. Also if any body knows what twin pipes will fit I would appreciate it. As far as cost I'll do the porting and polishing my self. Carbs I can find cheap. The cost will come for pipes and gaskets and carbs which is no we're close to a new sled price which I know I did not explain in my first post. But running an 8mm gasket I will have to get the head milled which will add to the cost. I'm not trying to be the fastest I just wanna go faster. "Shake and bake"

 

Long live the 670's !!! I hear ya. I love putting a whoop on newer and bigger sleds with my 670.I have a bunch of the upgrades that you want (except the porting and polishing) Try and find a old mach 1 670 at the end of the season and you will get basically what you want.Then just tinker with that.

 

Long live the 670's !!! I hear ya. I love putting a whoop on newer and bigger sleds with my 670.I have a bunch of the upgrades that you want (except the porting and polishing) Try and find a old mach 1 670 at the end of the season and you will get basically what you want.Then just tinker with that.

I have a 700 built from a 670 that has never been beat by a 700 of any kind, I also own a 787 cc stroked and bored 670 engine built by Union Bay that engine is not a feasible engine to build the crank failed two years ago and the quote for having a new crank built was $3500.!

I have Jaws, Decker's. Fast, Crank Shop and power pipes for the 670 engine they all have there advantages depending on how you use them or What RPM you want to run!

 

I run a lot of trails but I do drag ass once and a while. My low end has plenty of power. So which pipes do u recommend for high rpm power.

 

I run a lot of trails but I do drag "edit for bad language" once and a while. My low end has plenty of power. So which pipes do u recommend for high rpm power.

Twins.Just about any set of twin pipes on the 670 wakes the motor up in the higher rpm's.(when tuned right) I have only ran the stock mach 1 twins but they work well.I have not noticed any problems in any of the rpm range but like i said they are the factory pipes on the factory setup. Pipes and cans are one of the biggest argument starters when it comes to sleds. Any new set of pipes are pretty darn expensive for a few ponies or a loss of a few ponies depending on who you talk to and what side of the bed they woke up on that particular day.And there is alot more than just throwing pipes on hammering the go fast lever. in my opinion the factory doo pipes just work really well. I have modded my factory pipes but have never bought aftermarket exhaust for my sleds. But will not ever run stock exhaust on anything else i drive/ride.

 

We'll I could do a y pipe mod but with running 44mm carbs and don't know if the single exhaust would choke the motor

 

my 670 ho runs single exhaust with 44mm carbs and it factory ported. so you wont have any issues running a single pipe .and i agree with you %100 on the new sled thing they sucks in every way possible . if i had a new free sled i would pull the motor and rear suspension and throw the rest away .

 

On your HO what ports are ported I my just go that way with a single exhaust

 

cylinders are ported along with intake ports has flat top pistons and high compression head from factory

 

What octane do u run

 

91 always

 

Min octane is 91 with the mach 1 and h.o..

 

What clutch spring and weights for primary and what is your secondary set up

 

If I was to build a 670 I would run HO crank case cyl pistons and head with reg 670 crank stator flywheel trigger Cdi . If you don't want the dess . Personally I like it because unless you tow my sled it won't start.

 

Are the cases on the HO ported

 

I got a 200/290 primary with 280 ramps solid pins clickers on #4 secondary got beigh spring on b5 22 -23lbs preload . So far so good I'm still working on clutching the thing thought

 

Ho cases are factory ported along with cylinders all factory

 

Only thing aftermarket on my sled is mbrp can

 

I'll be going to roller cat clutch next season thought skidoo secondarys suck after you put a roller on it

 

http://www.dootalk.com/forums/topic/995074-mods-for-98-670/#entry11031961
Check out this post... It says something a lil different for clutching scroll down to the don emery area

 

So if I bump up to 44s and do some porting as well as 501 and 8mm base gasket , mill head and do exhaust mod I will have to run 91?

 

probably. I run 93 to be safe.