who to build my sport 400?
#11
11-30-2004, 09:43 PM
#13
11-30-2004, 10:19 PM
#14
11-30-2004, 11:39 PM
who to build my sport 400?
Originally posted by: modquad
No offense intended to anyone, or their skills. HPD has years of direct engine dyno time on this particular powerplant. They have the HP, and they have the reliability to go along with it.
My 2c.
No offense intended to anyone, or their skills. HPD has years of direct engine dyno time on this particular powerplant. They have the HP, and they have the reliability to go along with it.
My 2c.
#15
11-30-2004, 11:51 PM
who to build my sport 400?
POSTED BY JAYBLAZER
Who do you guys think I should go through to build my quad the way I want I know all the major players so I don’t need numbers or anything just wondering who would be able to build my quad to do what I want
so here is what I want I want stock clutch engagement I don’t like the pause I also want tons of low end power I don’t care if the quad only goes 55mph as long as it pulls with a good yank the whole way there...do you think I should get porting or should I change gears should I get a stroked motor what do you suggest??
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Jay ,
You have an unusual build request , most always on a modification job on a 400 Polaris engagement RPM is almost always increased due to moving the powerband higher in the RPM band to get more peak power .
To get more real lowend performance at stock engagements there are a few things that will work . However , DO NOT expect better top speed or topend power , it simply isn't going to happen .
Here are a few things I would recomend :
1. Stay with the stock pipe or concider having one of our lowend pipes built . We have discontinued the lowend pipe but I still have the patterns and the building fixture for it , if you have time , I can build one . The lowend pipe we build gets on the pipe way early and pulls noticibly better on the bottom , but it signs off on the top and
bearly can make as much power as a stock pipe . It does what it does well ( start making power early on) but it is no better than stock on the top .
2. Lighten the flywheel ---- Lighten the flywheel (yes you read it right ) Polaris 400's have a heap of stuff on the crank to spin , removing 12 ounces adds a noticable ~zip~ right off idle , few ATV's would get better bottom end from doing this , but your Polaris will .
3. Porting the cylinder will probably do the opposite of what you want to do ....... UNLESS you first have the base machined to LOWER your cylinder and in effect detune the engine . Then after this is done the ports can be recut to make the profiles correct and the timing set to kick in early like you want . Also have the head recut to match and raise the compression up to about 12 to 1 . After this is done the cylinder and head are a matched set and need to stay together and not be swapped to other engines . At the same time have the cylinder rebored , the wear pattern at the top of the cylinder (ring groove) will have to be jumped over by the new piston , it very well may cause problems and a fresh bore will eliminate the problem .
4. Spend $29 on a reed spacer , it may help a bit .
5. Use stock reeds and stock reed cage , no need for a boost bottle either .
After all this is done , you will have a quad that will jump off the line and accellerate pretty well to about 30 mph , it would have a heap of low end power . In a 30 mile per hour roll on race accelerating up to top speed , I doubt that it would run much better than a stock machine . However , it will have the stock engagement you are after and have a ton of low RPM power.
Dennis Shotwell's stroker setup with the timing on the mild side may work even better , but this is something best discussed with Dennis . I would suspect the added stroke ran on the very mild side as far as porting may work well in your application .
Very few poeple want a engine like this , but to get what you want this is the direction you would want to go .
I hope I helped ,
Rick
Who do you guys think I should go through to build my quad the way I want I know all the major players so I don’t need numbers or anything just wondering who would be able to build my quad to do what I want
so here is what I want I want stock clutch engagement I don’t like the pause I also want tons of low end power I don’t care if the quad only goes 55mph as long as it pulls with a good yank the whole way there...do you think I should get porting or should I change gears should I get a stroked motor what do you suggest??
------------------------------------------------------------------------------------------------------------------------------------------------
Jay ,
You have an unusual build request , most always on a modification job on a 400 Polaris engagement RPM is almost always increased due to moving the powerband higher in the RPM band to get more peak power .
To get more real lowend performance at stock engagements there are a few things that will work . However , DO NOT expect better top speed or topend power , it simply isn't going to happen .
Here are a few things I would recomend :
1. Stay with the stock pipe or concider having one of our lowend pipes built . We have discontinued the lowend pipe but I still have the patterns and the building fixture for it , if you have time , I can build one . The lowend pipe we build gets on the pipe way early and pulls noticibly better on the bottom , but it signs off on the top and
bearly can make as much power as a stock pipe . It does what it does well ( start making power early on) but it is no better than stock on the top .
2. Lighten the flywheel ---- Lighten the flywheel (yes you read it right ) Polaris 400's have a heap of stuff on the crank to spin , removing 12 ounces adds a noticable ~zip~ right off idle , few ATV's would get better bottom end from doing this , but your Polaris will .
3. Porting the cylinder will probably do the opposite of what you want to do ....... UNLESS you first have the base machined to LOWER your cylinder and in effect detune the engine . Then after this is done the ports can be recut to make the profiles correct and the timing set to kick in early like you want . Also have the head recut to match and raise the compression up to about 12 to 1 . After this is done the cylinder and head are a matched set and need to stay together and not be swapped to other engines . At the same time have the cylinder rebored , the wear pattern at the top of the cylinder (ring groove) will have to be jumped over by the new piston , it very well may cause problems and a fresh bore will eliminate the problem .
4. Spend $29 on a reed spacer , it may help a bit .
5. Use stock reeds and stock reed cage , no need for a boost bottle either .
After all this is done , you will have a quad that will jump off the line and accellerate pretty well to about 30 mph , it would have a heap of low end power . In a 30 mile per hour roll on race accelerating up to top speed , I doubt that it would run much better than a stock machine . However , it will have the stock engagement you are after and have a ton of low RPM power.
Dennis Shotwell's stroker setup with the timing on the mild side may work even better , but this is something best discussed with Dennis . I would suspect the added stroke ran on the very mild side as far as porting may work well in your application .
Very few poeple want a engine like this , but to get what you want this is the direction you would want to go .
I hope I helped ,
Rick
#17
12-01-2004, 07:35 PM
who to build my sport 400?
Originally posted by: modquad
No offense intended to anyone, or their skills. HPD has years of direct engine dyno time on this particular powerplant. They have the HP, and they have the reliability to go along with it.
My 2c.
No offense intended to anyone, or their skills. HPD has years of direct engine dyno time on this particular powerplant. They have the HP, and they have the reliability to go along with it.
My 2c.
I have to agree with you, but I have always been a little disappointed to see that they contract out the portwork on the Polaris jugs. Darryl needs to get someone to work there and do the porting. That would have it all in one house.
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