Hey guys~
This past weekend I went to a 1000' ice drag strip and my Scrambler would only manage 55.4mph. After reading all these posts about the 400 doing between 65 and 70, I am starting to wonder if I am needing to rebuild my topend. The machine is going on 5 years old and has about 2800 miles on the speedometer. It still has great power off the line(partly due to clutch kit), but seems to die off quickly after 50mph. Is it time for the rebuild?

 

Did you have the tires studded?

 

1000 feet is not a long distance for top speed runs. No doubt many of the runs referring to top speed on 400 were made on a smooth ribbon of asphalt.

 

Im sure the tires were spinning a great deal the whole way to.

 

How? cold was it 2-strokes run lean in colder air temps which greatly reduce top end speed

 

Hey guys~
To answer some questions...Yes my tires were studded. 184 sheetmetal screws per tire. They did spin off the line, but hooked up great after about 50 feet. I had the carb jetted with a 250 main, so it was shouldn't have been running too lean. Thew temp was about 20-25 degrees. On Sunday, they even backed up the radar gun so we had closer to the full 1/4 mile(about 1300 feet) so everybody could get higher speeds! Still, 1000 feet or 1300 feet, I still only managed 55.4mph as my best run.

 

ok, ok, ok, before you tear your motor down and i know what you want to by what? i'm reading but do a compression test, make sure you warm the engine up first then when you crank the motor over hold throttle open being it's a 2-stoke record it'sfirst reading and then it's second (needle jumps twice on compression gauge) reading should be no less than 100psi

 

Remember, there are more variables at work here than simply engine horsepower. How old is your belt? You clutching mods could also be reducing top end. Chain too tight or loose. Even chain lube and wheel bearing, axle grease cold could cause more friction on a cold day. Also don't forget it will take some power to pull those studs up out of the ice too. Are you wearing a big snowmobile suit and sitting up in the wind? All these things and more can reduce top end. All I'm saying is don't make the mistake many do and blame the motor right off the bat!

 

harescrambler~
I did the compression test...had between 110 and 115. compression obviously isn't the problem!

Robculp~
Original clutch belt was checked about 3 months ago...less than 1/32 inch of wear. I still put in a new belt. Clutching mods may have affected top speed. I am using a HotSeat chain tensioner so the chain is not running with a lot of slack. I had oiled all 3 chains the night before. I am highly aware about loose/bulky clothes cause big drag as speed increases(riding TW200), so I wore fairly tight clothing, ducked down behind handlebars, and pulled in 1 arm. I don't know. Maybe 55mph is all the 96' model was capable of. I remember a shootout dirtwheels did between the 95 scrambler and the Wolverine. They said both machines topped out close to 50mph! I'm getting the HPD pipe soon, so that should make it quicker.