Hey fellas I was wondering if anyone knows the operating RPM for a 98 MXZ 670 with the FAST twin pipes is at? I can't seem to find anythng for any exhaust stuff on the FAST web site.
I realize that stock it is 7800 RPM but it seems it would go up a bit with the twins?

Originally posted by cwarner@Sep 18 2005, 08:14 PM
Hey fellas I was wondering if anyone knows the operating RPM for a 98 MXZ 670 with the FAST twin pipes is at? I can't seem to find anythng for any exhaust stuff on the FAST web site.
I realize that stock it is 7800 RPM but it seems it would go up a bit with the twins?
432489

Are you running the FAST twins with integral resonators into a FAST muffler. If yes, the installation instructions for the "Eliminator" kit (pod filters, twin pipes and R/valve says clutch for 7900 - 8300 rpm (same as 95 Mach 1 670 with stock twins. My 1998 likes to run 7900 rpm with 44mm carbs set at 1995 jetting 430 PTO 410 MAG @ sea level with a 50 Pilot jet. NOTE: this set up is with pod filters. Will be way too rich at 1/2 - 3/4 throttle running stock air box.

Originally posted by cwarner@Sep 18 2005, 08:14 PM
Hey fellas I was wondering if anyone knows the operating RPM for a 98 MXZ 670 with the FAST twin pipes is at? I can't seem to find anythng for any exhaust stuff on the FAST web site.
I realize that stock it is 7800 RPM but it seems it would go up a bit with the twins?
432489

BTW stock max rpm for 1998 MXz 670 is 7700 rpm

Not sure about the resonators. I bought the sled with the pipes on it. The airbox is stock. I have it clutched to run at 8200 right now and it pulls much harder than at the 7800 it ran at before the clutching.
Do you know where on the web I can find info on these pipes?
Thanks for all the help Doc!

No, I'm sorry but those pipes are and have been out of production for some time and FAST is hard to reach. You could try these (http://www.teamfast.com/locator.html)guys in BC. They might have some old specs or directions for the pipe set up. I bought my pipes used with what was referred to as an eliminator kit. The resonators are a "tin can" looking section welded to the rear of the pipes. If you have a photo of the pipes PM me. From what I've read, the FAST pipes were the best available for the 670. Unfortunately a lot of people burned down their new sleds by installing twin pipes and running stock piston / cylinder clearance which caused seizure when the motor was worked hard and built some heat. Let me know what set up you have and I'll check my notes.

I will run by the storage tomorrow and snap a few pics and see what I got set up on it. I can't remember what he jetting is at. The sled was always running fat until the clutch work and now the plugs look nice and brown like they should. I bought the sled with (ironically) 670 miles on it and now have about 2200, it had the pipes when I bought it. I have run it in all conditions and has been very reliable for my first sled. I love the thing and just want it set up correctly and would actually rather have it a hair fat sometimes instead of closer to lean.

The spec sheet for those pipes said that peak HP was 250-400 RPM over stock. I had to run mine @ 8300 on the stock tach. Tach was out 150 RPM. This gave me 8150 actual. I could not get those pipes to work with the stock box or a gutted box. Needed K&N's to work well. I ran with 410-420 mains with the pods. Fast called for 350 mains with a gutted box, if my memory serves me. The setup sheet did not have jetting for a stock box. Basically they told you to leave the stock pipe on unless you wanted to run a gutted box or pods. The pipes were almost always sold with a 150-80 RV. I found that to be a little much and ran a 501.
The setup clutching included a swap to 145 ramps and gesring down two teeth on the top.

I would recommend the shorty boots, a 501 , .8 mm base with a head shave to get .065 squish. I liked the 145's with a 200-320 spring and solid pins. Get that stock spring out of there if its still in, it wont work.

This is from memory as I gave my sheet away with the pipes.

Cool thanks H.O. I am still trying to get over to get some pics and check what the jetting is. I have done clutching and man that really woke it up. Anyway the thing has never run bad. I check my plugs religiously and they are always brown or a bit on the rich side. I know for sure that the airbox is stock.