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Discussion Starter · #1 ·
hey everyone i have a stock 1990 indy 400, my buddy and i have the same sled but i am just a little faster so we decide to do a little cheap build off and race them again next year. im looking for your advice on clutching. mine boged really bad so i took the secondary apart and tightend the red spring one hole and made a huge differnce,but looking to make some changes to the stock drive spring and weights. there is a light blue spring in it now. the sled has over 6500 miles the spedo broke before i got it so im sure its due for a service. we are only looking to spend liek 350 on our build off nothing crazy. is there any other items i sould look at for more low-mid end speed. i really would love to get it alittle louder but is that possible with out spending liek $450 on aftermaket pipes if even made? let me know what you guys think or if any of you guys have done to your own 400's these our our beaters but i have more fun riding it then my newer edges.
 

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Myself I,d start by gutting the airbox and play with the clutching.Maybe through in a clutch kit.As for louder I,m sure you can cut open the exhaust and remove the sound deadening material and weld it back together.
 

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Take the money and spend it on rebuilds for both clutches. Your best chance of gaining anything for a lower powered sled with that many miles for the price tag you have is to concentrate on clutching and make sure everything is up to spec and running smooth. If clutching is off then the sled will run poorly. After rebuilding look into replacing the springs in both clutches. You can make the sled louder, but you won't gain a thing.
 

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put a 500 top end on it and leave the 400 heads....shhhhhhhhhh!!
alsi if you really want pipes i have a set kinda beat up but will work and will definately make some noise, theyre slps.
if youre in the lower 48 pipes shipped to your door $160.
and i agree with everyone clutching is key.
 

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Discussion Starter · #5 ·
im not really looking to gain anyhting with the exhaust being louder, just for a little sound. does anyone have any kinds of suggestions for the clutching keep it all stock just rebuild it? i had a leaky oil injection tank and i am removing it . when doing this do i have to jet any differnt for oild and gas being mixed? also when im taking some of the sound det. material out of the exhaust and gutting the air box any suggestions on jetting for that?
 

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Discussion Starter · #6 ·
im thinking of doing a pory and polish sould i just smooth out things or someone metioned gasket matching it . any suggestions?
 

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prospolaris said:
im not really looking to gain anyhting with the exhaust being louder, just for a little sound. does anyone have any kinds of suggestions for the clutching keep it all stock just rebuild it? i had a leaky oil injection tank and i am removing it . when doing this do i have to jet any differnt for oild and gas being mixed? also when im taking some of the sound det. material out of the exhaust and gutting the air box any suggestions on jetting for that?
Gutting the airbox will lean it out a bit but you should be easily ok with the stock jetting.Just check the plugs after a wot ride.I,ve yet to see a problem with the stock jetting after gutting an airbox.
As far as the port and polishing,I,d be real conservative if you try it,maybe knive the intake ports.Unless you know what your doing you might lose performance as it can alter your power curve.
 

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Discussion Starter · #8 ·
ok so may be ill just leave it a lone with the porting. thanks alot i got the sled tore down to just a frame everythingis out of itso im goign to start the build up on t now as soon as my parts come in. anyone put a clutch kit in a 400.. what brand works good?
 

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clutch and gears, these sleds are over geared from the factory, you can easily drop 2 teeth on the top. as far as clutching, get a 36 degree helix out of a 600, blue spring with 2 shims, and 51.5 gram weights. I have found that these run better without the air box gutted. advance you timing a couple degrees, that will give you a little better throttle response. mill your head 20-30 thousandths. I had this setup on my old indy 400, it was a very quick machine. you will be happy.
 
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