Any reeds for the 670 X?

eazyduzit509 · Oct 10, 2009

I cant seem to find any reeds (like Vforce) for our sleds, mine being a 99 summit 670 X H.O. I'd like to buy some but it dosnt seem like they offer them, so i guess what im asking is are there any reeds from different sleds that we can use (like 700, 600, etc)? THANKS!!!

winter brew · Oct 10, 2009

No reeds....rotary valve

eazyduzit509 · Oct 10, 2009

winter brew said:
No reeds....rotary valve

Please explain.

Zachmandu · Oct 10, 2009

Rotax rotary-valve 101

Well.....there is a reason for that. 670's do not have reeds. You see that round casting on the back of the motor that the carbs attach to? That there my friend is a rotary valve induction. This system was used on all high performance doo's starting way back in the early 70's. Behind that round casting (called the RV cover) is a spinning disc driven off of the crank, with a notch cut-out of it for induction timing. With this set-up, the port is either open, or closed. Some say a better system than any reed-valve set-up. You can change your induction timing by using rotary discs with different size notches (usually expressed in degrees that the notch sweeps across the disc), and/or re-positioning the disc on its mounting gear, changing its position relative to crank position, alowing more fuel/air at different stages of crank position to suit your engine modifications or riding style. One of the most common performance 670 discs is called the 501, which is the last three #'s of its 'Doo part #. You can find aftermarket discs in Dennis Kirk, HP Engineering, etc. Changing the disc is easy, however timing it correctly can be a real pain in the ***, involving a degree wheel and sometimes a dial indicator. Better left to someone who knows what they are doing.

Oh, and BTW, 'Doo DID go to reed-valves on the 600/700/800's for two main reasons - With the rotary valve you are limited on how low and how far back you can mount the engine, and with the new chassis' being developed at the time (ZX), that was a problem. Another huge reason - RER. Electronic reverse will not work with a rotary valve engine.

Hope this clarifys things.

eazyduzit509 · Oct 10, 2009

Zachmandu said:
Well.....there is a reason for that. 670's do not have reeds. You see that round casting on the back of the motor that the carbs attach to? That there my friend is a rotary valve induction. This system was used on all high performance doo's starting way back in the early 70's. Behind that round casting (called the RV cover) is a spinning disc driven off of the crank, with a notch cut-out of it for induction timing. With this set-up, the port is either open, or closed. Some say a better system than any reed-valve set-up. You can change your induction timing by using rotary discs with different size notches (usually expressed in degrees that the notch sweeps across the disc), and/or re-positioning the disc on its mounting gear, changing its position relative to crank position, alowing more fuel/air at different stages of crank position to suit your engine modifications or riding style. One of the most common performance 670 discs is called the 501, which is the last three #'s of its 'Doo part #. You can find aftermarket discs in Dennis Kirk, HP Engineering, etc. Changing the disc is easy, however timing it correctly can be a real pain in the ***, involving a degree wheel and sometimes a dial indicator. Better left to someone who knows what they are doing.

Oh, and BTW, 'Doo DID go to reed-valves on the 600/700/800's for two main reasons - With the rotary valve you are limited on how low and how far back you can mount the engine, and with the new chassis' being developed at the time (ZX), that was a problem. Another huge reason - RER. Electronic reverse will not work with a rotary valve engine.

Hope this clarifys things.

Ahh, thank you much. I had no idea. Ive been riding this sled for 2 yrs and didnt even know. What else can you tell me about them? From what ive read in forums, articles and reviews, they were a pretty fancy sled for the time, with the D.E.S.S. (security) and the (DPM i think) with the carbs adjusting to air temp and such. Very cool.

Ive gutted the airbox, changed the gears and have an MBRP standard can on the way. Other than that, dont know of any performance mods, mabey some clutch work? Which i am also not very educated about...

, i heard we have clickers or something on them but IDK, i should know more but i dont!!!

winter brew · Oct 10, 2009

I can tell you that a 670 done up right will take care of most good running 800's.

eazyduzit509 · Oct 10, 2009

winter brew said:
I can tell you that a 670 done up right will take care of most good running 800's.

Please emphasize. Very interested. I can give my dads 03 800, 159" polaris edge a run for its money, he has a bit more acceleration than me and a bit more top-end. I can get DAMN close but he always pulls away. He's running SLP intake, pipe and can, along with ALOT of bottum end work before we bought it... ( i think it was crank work and such), the guy said he put like $3000 into the sled to get it as reliable as possible, we bought it for $4500-$4800 a year or two ago.

Zachmandu · Oct 10, 2009

Have heard that gutting the airbox on a 670 is not really the way to go, although this seems to be a popular "must do" to the un-initiated. Apparently the 670 is very sensitive to what the carb "sees" as far as induction pressure. Kinda like exhaust back-pressure, but on the intake side. Sure the induction will be louder, making you think that "louder is faster = more power", but in reality, the motor will end up just burning more fuel with very little gain. From what I have read, you will only see gains on a 670 w/ a gutted airbox unless you have porting, pipes, and more radical valve timing. Dyno-Tech did alot of research on this back in the day. I run my old 670 w/ a 501 valve, SLP twins, and the stock airbox.

Zachmandu · Oct 10, 2009

Tunnel-porting, a 501 RV, twin-pipes (ALOT of opinions on whose pipes are the best. I LOVE my SLP's at sea-level - 3000'), and a set of 44's along with the appropriate RV cover.....will work wonders for an old standard 670. There are also 740 big bore kits available as well.

Your sled already being an HO, has the 44's, some port work from the factory, and a more efficient head design. As you will find, there are not many twin pipes available for this engine, and the ones that you come across are all high-altitude pipes. I say stick a nice sounding can on it and enjoy it.

A 670 CAN be built to keep up with an 800, BUT, by the time you get there money and time-wise, you could have just BOUGHT an 800. My .02...

eazyduzit509 · Oct 10, 2009

Zachmandu said:
Tunnel-porting, a 501 RV, twin-pipes (ALOT of opinions on whose pipes are the best. I LOVE my SLP's at sea-level - 3000'), and a set of 44's along with the appropriate RV cover.....will work wonders for an old standard 670. There are also 740 big bore kits available as well.

Your sled already being an HO, has the 44's, some port work from the factory, and a more efficient head design. As you will find, there are not many twin pipes available for this engine, and the ones that you come across are all high-altitude pipes. I say stick a nice sounding can on it and enjoy it.

A 670 CAN be built to keep up with an 800, BUT, by the time you get there money and time-wise, you could have just BOUGHT an 800. My .02...

I see. So as for mods im pretty much done unless i put a bunch of time and money into it? Ive got a few hundred dollars to play with, ive already bought the can, and soon to buy some simmons... Any other (farely easy) recomendations for a few hundred bucks or less? It sounds like im pretty much reached my limit unless i open er up.

Zachmandu · Oct 10, 2009

Put a can on it and enjoy it!

DaveB · Oct 10, 2009

What Zach said. But learn some clutching....races are won and lost with clutching. You said you don't know what "clickers" are? You need to learn. You might be able to beat your ol man with a simple clicker change.

ak · Oct 10, 2009

Some easy horsepwer for the 670 x and 670 is a 501 rotary valve and shorter carb boots. The shorter the intake the more power, many used a short intake cover for the rotary valve but to use this cover you lose your oil injection.

winter brew · Oct 10, 2009

Shoot me a PM with your weight, altitude you ride, track length etc.....I will give you a clutch setup that may be all you need to hang with the old man's 800. It will be much less tha $300 and most parts you can get from your dealer. . :beer;

wildcard28 · Oct 10, 2009

A can. on that motor would be cool, I checked around all over and couldn`t seem to find one for a descent price, but I did talk to HPS and they can make one it is spendy but after talkin to him on the phone he would be the one I would choose. next would be a MBRP they seem to be a bit quieter.

I also read alot on gutting the air box and of what i found it`s not worth it.
everyone seemed to gut there airbox, not like how it performed and then needed to find another one cause they hacked up the old one, Lol

Very good info zachmandu.

eazyduzit509 · Oct 10, 2009

Can someone explain clutches to me? I dont really know how they work or how they can be adjusted... I feel noobish, but lets here it!

wildcard28 · Oct 10, 2009

Here is some good readin.

http://www.gates.com/brochure.cfm?brochure=1033&location_id=3850

http://www.snowtechmagazine.com/articles/2001/clutch/cltchtun.php

eazyduzit509 · Oct 10, 2009

Off topic, but does anyone know if the Rox sled treads from a 99-03 MXZ (ZX chassis) will fit the S chassi? Thanks again!

Zachmandu · Oct 11, 2009

Oh-h-h-h......! shorty intake boots... how did I forget THAT one?? Lol! One of the performance shops, (suffering from old-timers, can't remember who) used to offer an "induction tune-up kit" or something like that. It included a set of shorty intake boots, and a 501 RV. Maybe somebody remembers who it was.

Get ahold of WinterBrew for a good clutch set-up. DaveB is right - the right clutching will also wake up your sled and make you THINK you added a bunch of power. Big thing is to not over-rev a stock 670. Power drops like a rock and belt heat becomes an issue. If my foggy memory serves me correctly, I think that your target rpm is right around 7900/8000 rpm. Years ago Big John gave me a clutch set-up that worked miracles with my 98x. I was destroying belts left and right until he set me straight. Sled is still kicking butt and taking names ten years later! Got that info somewhere around here...

Clickers - The three bolts around the perimeter of your primary clutch. (actually on the governor cup) They really do not "click", but are an adjustable eccentric bolt that changes the angle of your TRA ramps therefore changing rpm. You have a ten mm nut, attached to the end of a bolt whose head is sunk into the casting. Loosen the nut, and you can push the bolt head out of the casting enough to turn it. The bolt head has a line on it, the casting having corrosponding #'s going from 1 to 6. You can spin the bolt one way or the other, increasing or decreasing your top rpm. #1 being the lowest, #6 being the highest. Each # is approximately 200 rpm gain or loss, depending if you go up or down. Say you are on clicker #3, and running 8100 rpm. Well, you are OVER your target rpm. re-adjust your clickers to #2, which in theory, should bring you down 200 rpm to 7900, which is your target on a stock 670. Handy to use to change clutching depending on conditions - warm or cold air temps, dry powder or wet heavy snow, etc. There are aftermarket spring-loaded clickers available that do not require the use of tools. Ask WinterBrew about them if interested.

If somebody needs a stock airbox, un-cut, I have a couple laying around, along with some various RV discs, and some Aaen twins. I also have an old Don Emory can (vary similar to MBRP) that is pretty hammered, but still salvagable. Had it on my '98x. Hm-mm-m-m.... thinking about all the 670 stuff I have laying around... PM me with a wish list, never know what I might have. Cases, cylinders, etc... time to clean out the shop.

eazyduzit509 · Oct 11, 2009

Thanks for all the info. I'll see what i can do!

Any reeds for the 670 X?

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