1st Ride on my sxViper MTN 77mph @ 8800rpm

[Automed]

Ok! I FINNALLY got to go out and ride my new 2003 sxViper Mountain today.

I was surprised by two things...

1- It pulls real hard of the line (very nice)

2- Top speed was only 77mph at 8800rpm???

Is that normal? I mean yeah it's supposed to be geared low but 77mph wide open on a lake at -15C with 8 inches of snow and that's it?!? 77mph...

120HP and all it will do is 77mph?!?

The sleds compression is a bit questionable I think anyway 100psi (pto) 121psi (center) 119psi (mag) tested with WOT (350miles on the sled)

Other than the holtzman ATACC the sled is stock.

Oh and she's a bitch to start 5-6 pulls most of the time.

Need help please...

I still got warranty till Jan 19, 2005 and I want to get all the bugs fixed.

 

[NORTHMANSX]

yes i would say your compression is very questionable. i know it has staggered compression, with one cylinder being different(pto, i believe) but 100 psi is very low and not good in my opinion. can you try a different compression tester to see what results you get..

 

[Automed]

I had a COMPLTE check up done at the dealer and they came up with very similar compression results (1-2psi). Yes the pto is the one with the lower compression but 100psi come on that's got to be bad...

Please please help the warranty clock is ticking...

 

[NORTHMANSX]

tell your dealer that you want that piston and cylinder checked , definatly low. yamaha is usually good for warrenty, and it could save you alot of money to have them pay for it and not you.

 

[Mtnviper]

Normal compression for the PTO at sea level is usually 110-115 psi. Center and mag 120-125 psi stock. Mountain Vipers are geared fairly low for mountain use. They also have 8 tooth drivers. If your going to be lake racing or riding at low elevations, you may want to gear it up a bit.

 

[terry]

If it is new run it for a while break in period is about 500 miles. 8800 rpm is WAY high...you want it down around 8400 you are losing about 10-15 hp. put a steeper helix like a 51/45 and a silver sec. spring @ 70 deg or 80 and enjoy

 

[kirkswim]

my compression with 2000k on my 02 viper is 140 centre 142 mag, and 132 pto. hope this helps.

 

[Automed]

If it is new run it for a while break in period is about 500 miles. 8800 rpm is WAY high...you want it down around 8400 you are losing about 10-15 hp. put a steeper helix like a 51/45 and a silver sec. spring @ 70 deg or 80 and enjoy

You know I can tear an engine apart and put it back together with no leftover parts pretty easy but clutching is still a mystery to me. I understand the basics but not the fine-tuning part so please help me out here.

1- How do I get the rpm's down
2- One of my ridding buddies mentioned that the belt was riding a bit low in the driven clutch, the outside cogs are even with the outside of the sheaves. (the belt does not stick up out of the driven clutch)
3- what will a 51/45 helix and a silver sec. spring @ 70 deg or 80 do?
4- will these adjustments increase speed?

Thanks for the help...

 

[Automed]

my compression with 2000k on my 02 viper is 140 centre 142 mag, and 132 pto. hope this helps.

Is that a stock engine sounds pretty high?

 

[n2oiroc]

what is your altitude? compression will look low at higher altitudes.

 

[Automed]

Altitude above sea level is 2373 feet

Atmospheric pressure is ~13.71psia

 

[Maim]

kirkswims # are for stock motor. im his brother. only motor related mod he has done is put on mbrp can and engine torque limiter. those where his # from last season. havent checked it yet this year.

 

[yamaholic22]

yea that compression seems high to me too for a stock viper

 

[Automed]

kirkswims # are for stock motor

I t could also just be the gauge what matters is that the difference between the center & mag cylinders is ~0psi and ~10psi for the pto side (lower compression ratio)

I have ~20psi difference between the pto and the other two, that's what's bothering me.

 

[Maim]

that is not enough difference for a tear down. of course kirkswims didnt pull hard untill he got the 1st 1000km on it. vipers seem to take longer to seat right in. we also dont fog our motors for storage . we run em every couple of weeks up to temp during off season. makes a big diff in compression we have found. case in point my dad had 1986 et340t that dealer thought we had heads done on it. when they compression tested that motor it had 20lb more of compression than a brand new motor after break-in. and all that was ever done to that motor was add gas oil and go!