ac auto
New member
I have a stock 96 Vmax 800 with 5200 miles. Was doing some testing on the lake in front of my house. Stock track with 96 picks, new 8bu belt, near perfect conditions gray ice with patches of snow. Running 8200 rpm eventually with about 2000ft to run WOT and safe distance to slow down beyond. Ran over 120 mph om the "dream-o-meter" and it was about 20 degrees out. Waiting for the parts I ordered to go with Yammie's trail clutching so this is a base line. I know i am looking for 8350 rpm and should get that dialed in with the helix and springs. Sunday tried to get a "real" mph by strapping my GPS to the handle bars. Weather warmer 33 degrees and the snow and ice a bit stickier. Ran 120 on the speedo and 109 on the GPS, seems about right. My 04 Viper ran 109 mph on the speedo and 98 on the GPS, so I feel the GPS is fair. My goal is to run 120 MPH in 2000 ft. with a stock Vmax 800 that has been well tuned in every way. Wont be able to do everything this year but I am looking for advice. Am i setting a reasonable goal? Keep in mind I don't expect to run that in all conditions just when everything is just right. planning to change the skid next year. Trails here are groomed and usually hard packed fortunately and besides I usually ride my Viper E/R-S trail riding, so my skid choice would lean towards lighter weight and less rolling resistance. Also looking to improve weight transfer, anything help with the adjustable front struts? or is it all in the skid? I am carrying the torch for the vintage iron in south west Maine and have the best minds here and the Vmax4 forum to draw from. It is only a matter of time before one of my buddies or a stranger shows up on my some what private lake and i want to be ready. I view many of the new sleds as Subaru WRX's and Mitsubishi EVO's and i want to be the guy who pulls the 70' Hemi Cuda out of the barn to show them how it was done and still is! Thanks.
YAMMIEGOD3:16
Active member
peak on the vmax 4 800 was 8150-8450. thats your clutching window. you will never hit a true 120mph with 96 picks. i don,t care what advise you get. just won,t happened. the conditions will have to be perfect for you and this sled. i mean everything from suspension setup, to traction, to clutching, to jetting, driver weight, gearing , omit hyfax, proper belt height, on and on. 3:16x (yammie tony)
toydoc
Member
IMO, you cant hit any good mph on a vmax4 with stock float bowl venting.
The faster you go, the richer it gets. You need to vent to the air box and re-jet, test
The faster you go, the richer it gets. You need to vent to the air box and re-jet, test
ac auto
New member
Thanks for the responses. As far as the 96 picks I agree for acceleration from low speed that just isn't enough. isn't there a point where given enough distance track spin is not much of a factor? I am concerned that the weight of more picks at some point becomes a limiting factor on top speed. I am not opposed to adding/replacing picks it is just the rotating mass that I am concerned with. I come from an auto drag racing background and we would never want to add rotating mass unless completely unavoidable. BTW I weigh 165 lbs. I am interested in the air box venting. My Viper has that stock. Is there a thread explaining the process and jetting changes? For the time being, lets put aside the 120 MPH question as I would like to concentrate on the top speed regardless and see what happens. We are getting snow tomorrow and it will be cold after so the lake conditions won't be optimum for some time. I will still be doing the clutch work this weekend. Thanks.
Bob Vehring
New member
Just for reference I just put in 196. Studs, backers and nuts weight in at just under 15 lb's. Will see how it hooks Sat
Re. the venting, I just ran mine up the steering post hole to just under the bar. did not want to drill the box because sled is clean enough that if we want can return to showroom stock, any problem with that?
Re. the venting, I just ran mine up the steering post hole to just under the bar. did not want to drill the box because sled is clean enough that if we want can return to showroom stock, any problem with that?
ac auto
New member
Finished the clutch set up, redid the carb vents into the air box, glad I did that as I also removed the white plastic clips while the air box was out. Found the outside bowl vent elbow and tube missing on the PTO side carb? Not sure how that may have effected the performance? Should I have to alter the jetting at all? Normal temps here 10-35 degrees.
What does venting to the airbox do? Does it have higher pressure in it vs. atmosphere? Sorry if it's a dumb question.
YAMMIEGOD3:16
Active member
you answered your own post. farr from a dumb question. the vmax 4 was noted for this problem in 1992. jim at dynotech found that very problem when he dynoed the new 92 vmax 4 back than. turned out to be such a problem yamaha looked at it. now your not venting the airbox, your venting your carbs which are vented to outside air. now. if your running a vmax 4 2000 f.t. to achieve 120 mph, i really would not worry about weight. the rotate mass you post about needs to have as much traction as possible, without at least 192 ice picks, this sled is gonna do nothing but wag its tail. 3:16x (yammie tony)
Changes air pressure in the carb bowls. Venting to the airbox provides a more consistent bowl pressure whereas venting to the engine bay will have vastly fluctuating pressures. Generally the airbox is at a lower pressure.
When you move the vents to the airbox on the VMAX4s you will have to increase your mainjet size as they no longer richen up as speed increases...this is because the increasing underhood pressure no longer is pressurizing the float bowls.