ok boys, i need some help. Just for refresher, I am new to this site and new to scramblers in general. From what i have read, 400 scramblers are suppose to be faster than 500 scramblers stock, and when you mod the 400 it destroys the 500.

Well I consider mine mildly modded. My bike is a 2000 400 scrambler 4x4. I just bought the bike with a blown motor and now the motor is totally rebuilt. Just for reference, my bike looks new, it must have had a real easy life. My buddy on the other hand has a 2000 scrambler 500 4x4. His bike on the other hand is well used. His is stock with the exception of a epi clutch kit. Going through the trails mine feels only slightly if any faster or more powerful. On a road we are about even until 40 mph then I start gradually going by him. Mine might be 4-5 mph faster on the top, but not much different midrange or bottom.



Is that how it should be?

Any suggestions?


thanks


2000 Scrambler 400 4x4
.040 weisco
hpd trail pipe
mildly ported
270 main jet, 34 mikuni
hpd clutch kit
delta v-force reeds
reed spacer
.020 head milled
K&N filter
hpd steering stablizer
ipt wheels
itp mudlites

 

stock for stock yes but with your mods you should be doing better than that..

 

I would think you should be atleast 5-6 bike lenghts in front of him with your mods.

 

yeah, and thats at 45mph with good traction off the start.

 

you will blow him away with those mods,the only thing you might consider
is the throw off that 34 mikuni carb and you'll have a 55 to 60 hp real easy at your
thumb.

 

pipe it, jet it, and filter charger kit and you will be pulling hard along with a clutch kit.

 

The 2 guys I ride with both have modded 400 4x4 scramblers and although mine is not stock the result is about the same, I am right there through all the trails and in a drag they are about a bike length ahead until around 40-45 and they will slowly pull away with a little more top end than mine. The mods they have are the Hot Seat speed kits.

 

ok boys, there must be something massively wrong with my bike. Every where I look on this website you guys are talking about killing 660 raptors. A race between my scrambler and a raptor would be a joke.

Here is somemore info on my bike. When the mechanic rebuilt the motor he said the v-force reeds were a little bent or something, so he installed the pedals the other way when he put the motor back in.

There is also a rattle coming from the rewind side of the motor when the bike is idling. It might just be the pipe rattling against the motor, but it doesn't sound that good. Btw the motor only has about 6 hours on it. I am hoping it is not the counterbalance shaft. After the motor was complete, but not in the bike, there was a little rattle or play in the counterbalance shaft. I took the motor to the dealer and they had never rebuilt a 400 before they said. The noise went away once you turned the crankshaft over fast on the bench, so the polaris mechanic said not to worry about it.

The motor also has 135 psi compression when hot. It has 110 cold. The head has been shaved .020 These bikes are suppose to have 115 stock according to the polaris manual. I am not sure if that is hot or cold.


The mechanic also mildly ported the cylinder. I think he mostly just cleaned up the ports a little. Would this severly make the bike slow if not done right?

The bike really is most depressing low end. My buddies and I mostly ride in mud and trail. When the bike goes through the mud you can really see how its performing. It starts off a little sluggish but when you get on it, it really really has torque. My buddies can't believe how it rips through mud, but it really only excells about 3/4 way through the mud.

I am not a atv guy, but I have driven sleds all my life. The bike seems like its loading up. The main jet is 270 right now. I filled the oil up full on my last ride yesterday, I am going to check how much oil it used and see if it is way too rich. My buddies say it is smoking most of the ride, its running amsoil which is suppose to smoke a lot less than conventional oils.

Maybe its clutching. The primary clutch is in mint shape, except it has a giant groove where the belt would sit with the bike idling. I guess it really isn't in that great of shape. Maybe the belt is having trouble getting over this limit. Are these bikes suppose to use the full primary clutch. How high should the belt ride at full throttle. With my polaris sled, I can get full use of the clutch right up to the top.

I am going to throw this bike on the radar gun this weekend to see exactly how fast it is, so i can post it, and maybe you guys can help.


please help.

 

i have the same engine mods you do and i'm only running a 250 main. what is your pilot jet? i'm running a 25? also 135psi is low for a 12-1 head which is what your .020 shaved head is. you should be able to smoke your buddies 500. all yeah, you can beat a raptor with a trail ported 400, not a match ported 400 which is what your have. the difference between a match port and a trail port is about 8hp. the part about turning the reeds around makes no sense to me.

 

Sounds to me if they bored your cylinder then they did a real loose job.If they did, that would explain the rattling you are hearing. It should have around 145 to 150 pounds of compression for a new top end rebuild with a head milled at .020. Another thing...if they didn't know what they were doing when they ported it.. then yes that can hurt performance too. The bad bottom end performance is probably due to low compression. Flipping the reeds is a common thing to do when they have some time on them. The big groove is from the belt riding there in slow speed situations(and may be one of your biggest problems right now). A new primary is really the only thing that will cure this problem. Do you happen to know what primary spring you are running? It could be a high engaging spring causing it to only run good at the higher throttle ranges. You can run a lower engaging spring and that will help with that but it could be your low compression. How long has it been since you had the top end rebuilt?