the blue spring was better on a full trail mod setup for me too,
i personally found the sled's spring better to suit the response
i was looking for,as stated above,keep inspecting the belt in place,
if the belt held on the straight faces of sheaves,it shouldn't bog
any ways.

 

What elevation are you at and what temps are you running at?

 

I don't know about trusting a guy that sold his polaris and went yamaha!! haha just kidding with ya Bubba

 

I purchased a compression tester and this is what I found.
1. Cold, it is at 145-148 or so pulling with open throttle.
2. Hot, it is at just over 150psi.
Cold, it is much more responsive and actually has throttle response.
Once it warms up, the clutch seems to engage earlier, the motor does not run as smooth on the bottom, and very little power until it gets going, then holy crap, it goes. Im at about sea level, maybe 1000 over or so sometimes. It was about low 50's this morning.
When had the head off the bore looked great and no scars. There is very little piston slap that is typical of a worm Polaris 400. I may look into just ringing it if it is that good.
A little more history on the machine. It is 4 years old and has the original cluch springs in it. It was NOT ridden very much when I got it. But could the springs have gotten bad just being in the clutch over so much time? Is 150 not enough for race mod on race fuel? I'm this close to tear it down this weekend and repiston it. I want it ready for Thunder Alley in June. If I can get out of the hole, watch out. The bike is so light. I can see why it is successful on the mx tracks. I know it is not competitive with true drags, but with non drag quads, its great.

Any other help on why I have no low end power would be great. Change the pilot? Re -ring? Re-piston? Change the primary? HPD blue primary is designed for his race mod, the next step up is for drag only. SO the engagement should be right. Could it be that worn out in four years?

 

I rode everywhere and did everything with the violet spring in the primary clutch. That spring is for maximum acceleration, but that doesnt mean you cant ride it around. I absolutely love the engagement at 5000-5200. The power is there ALL THE TIME.

The top end cant be as bad as you think if the compression doesnt fall off at all when it gets hot. Clutch heat and belt heat will greatly affect how it performs. If the belt has been on it for awhile, dont do a thing until you change it, or at least borrow one from a friend and try it out. When the belt gets worn some it can try to grip the clutch when it gets hot instead of slip like it should. Also if the clutch has a bad flat spot where the belt engages that will cause problems when things heat up.

I have seen way too many times where a belt will fix 90% of bogging or low speed problems on a polaris. I cant stress this enough. Bubba

 

Byt heway Bubba, It has a new kevlar belt and only a slight wear pattern on the clutch sheaves. A lot less than what I have ever run before. I know it is not the belt. The clutches dont get heated up tremendously, just some. I really dont think it is the belt. Possibly the Spring is weak, the jetting is bad on the pilot, the comptression is low, or a combination of all of them. HELP!!1

 

I'd try changing that spring before tearing into the motor dude. It can be manny diferent things. The spring is a start and like bubba I like the higher engagement[img]i/expressions/face-icon-small-cool.gif[/img] Just My @ cents

 

kahnman,there is easy fix you should do to reduce clutch heat by exemple
is to remove,, the long tube plastic still there? you have to remove all this to open up the clutch case holes letting more air to baffle around the clutchs.
the original primary spring wont do any good with a race mods engine,
get at least the violet hpd,and give it a try.
150 psi is pretty low on race mods but still not bad for riding,not worn that bad,i would just inspect cylinders walls and piston skirts of what it looked like depending on what heads you run.
seriously,that stock primary spring must go out!

 

It is not the stock primary, but the blue primary with high engagement. I don't think it is working right. There is no heat as ther is no cover on it on testing. The spring is either old from being in the clutch for four years or the jetting needs fixed, or the compression is bad.

 

Like I said on the phone the compression on a race mod 400 with a 14.5 dome it should be over 160psi. 160 is the minumum it should be. Also check the primary spring for coil binding. If the spring fits tight in the clutch it may be catching the sides of the spring. But it sounds to me like compression it is lacking.