whats up guys, i have a 97 scrambler 400. bought the quad rode it for about 3 or 4 hours. it was running beautiful and then it died on me. i took it apart and the piston was ok except for 2 spots about a half inch wide each which are scored. i eliminated the possibly faulty oil injection (running 32 to 1 castor) bored it, new piston, gaskets bigger main jet with dg pipe. I put it all together, rode it twice, about a half hour total and the same thing happened again!! same 2 spots on the piston (loss of compression). i sent the motor to polaris to have it vacuum tested for any possible air leaks such as the crank seals. it ran perfect before it crapped out! anyone ever hear or encounter anything like this? any help would be very appreciated. thank you

 

Well I cant tell you why the piston is scored but I can tell you that you need to get rid of that piece of crap DG pipe. You just wont feel the power that the 400 actually has with a DG pipe. The DG pipe will actually lose hp on the Dyno. The stock pipe is better. And anytime you add a pipe you NEED to add a clutch kit to perform with the powerband of the pipe. If not you will not hit the powerband when it needs to. The 400 has tons of power to be unleashed and with just a good pipe and clutch kit it will be night and day difference.

Are the cylinder walls scored also? How deep are the scores?

 

Sounds to me that the bore was to tight. What was your ring gap when you put it together? Or you just did not brake in the motor properly.

 

2manytoys, I have a chance to buy a used hot seat pipe for my 400, what are your thoughts on this pipe?? went to there site can't find info on peak rpm?

 

Go to Aaens site and HPD for power curves.
RcR has good prices on HPD pipes. The HSP should be ok but i hear bad things about their clutch kits and cans.

If thats the stock piston you need to put a weiseco in and have it bored, IMO. That is old for the stocker.

Call rick at RCR or PM Bubba297, he does nice work on these motors.

Jim

 

The HSP pipe is ok but there has been issues about build quality on some of the pipes. You will get about the same HP gains as the HPD or AAEN pipes. Just remember if you do get the pipe you MUST get a HSP clutch kit to match or the pipe will not work well. The stock clutch kit will not shift with the powerband of the HSP pipe.

 

I have a tach and lots of clutch parts, what I need to know is what rpm the hsp pipe runs at? thanks

 

If you get the HSP let me know and I will get you the info on the clutch.I have the HSP on my 400 and the only complant I have is it isLOUD

 

ftwflh, can I call you FRITZ ? LOL. A friend had a harley race team FTW RACING. anyhow I got the used HSP pipe, put it on and WOW!!! my r's went from 6100 to 7K with only the pipe change!! mid range and top end are unbelievable. I did loose some bottom end. curiose as to your clutch set up and opinion on r's I'm pulling. aggressive trail port, plugged decomp.hole and cut head. thanks

 

YEA I ride a Harley too[img]i/expressions/face-icon-small-happy.gif[/img] I have the HSP with their kit (the weights are shot)it came with a Brown primary spring a white secondary and a 45-40 helix.I tried a Dalton black/white primary(close to a polaris green)and had no bottom end at all put in the brown and was great.Sill a little bog on bottom but I think if I can get a set of weights or find what size the HSP ones are I can get rid of that spot.As for a tach I dont have one on this 400 yet.But with the kit it should be close to where HSP wants it.