One of my riding buds has his 98 Sport all tore down. Sounds like one of the crank bearings froze up on him and locked up the engine. Too bad really....he had a Wiseco piston and all.

Anyway...he asked me while his lower end was in the shop if he should get his cylinder head milled for more compression. I said yes...should give him more power. He has a DG pipe (junk) and muffler and K&N filter with a modded air box and a Wiseco piston, otherwise it is stock.

So how much power will he gain and how much should he have milled off? Still wants to use pump gas. Thanks.

'96 Scrambler 400 4x4
HPD trail pipe
HPD clutch kit
K&N filter
Boyesen Power Reeds
Wiseco piston

 

Raising the compression of a motor is the best way to get HP, and milling the head is the cheapest way. I'm not sure exactly how much HP he will get (depends on who does the work, gas, ect.) but it should result in a noticable difference.

 

I would have to agree with you on that. I too had my machine done over and the primary objective was pump fuel(92) 86.50mm bore 20thou. off the head and trail porting...What a difference.Even my friends were impressed..

 

having the head shaved will also make his powerband 10 times more noticable [img]i/expressions/face-icon-small-wink.gif[/img]trust me i found out the hard way on a buddies scrambler when it left me laying on my back

 

JMO, one of the billet cool heads with the inter-changeable domes and better cooling is a good way to go....heck, might as well get some porting done and really feel it in the seat of the pants. As long as it's torn down, you might as well do it right...that's if the funds are available. Also, the girdling of the cylinder is advised when raising compression, since more stress is placed on the assembly.

Ken

 

<< So how much power will he gain and how much should he have milled off? Still wants to use pump gas. Thanks. >>



Well, none. Simply put you can have the baddest motor out there, but without the proper clutching to make it get to the ground, he's just wasting his money.

I'm thinking like modquad does. A new &quot;Cool Head&quot; with adjustable domes is the way to go. Now if you could get him to get rid of that &quot;Junk Pipe&quot; and get an HPD or RCR setup, he'll be in business.

 

You can't just decide that &quot;10 thou or 20 thou off&quot; is where I want to go. You have to look at the squish band. Yes, you can bring up compression by milling the head, but if you lower your squish band too far, your engine will detonate the rings out of it. On my sled engine, we had 70 thou stock squish....we determined that we never wanted to go below 55 thou squish, but we needed more compression than just cutting the head 15 thou would give us. So we cut the head 40 thou, then machined the squish band back in and blended it to the combustion chamber so the most narrow part of the squish was at 55 thou.

Bottom line: don't do this blindly. You can probably cut 10 or 15 thou off without too much problems.....after that, its a crap shoot unless you get proper measurments.

 

Mike Chero,

Yeah...I told him first he should get himself an HPD pipe, keep the DG muffler, clutch kit and maybe some good reeds to go with the K&amp;N filter.

Then if he wants more power milling the cylinder head and/or cylinder porting should come next.

I just remember .020 as the amount that is removed off the cylinder head....for what reason I am not sure?

Thanks for the input.

'96 Scrambler 400 4x4
HPD trail pipe
HPD clutch kit
K&amp;N filter
Boyesen Power Reeds
Wiseco piston

 

if your buddy wants the head machined properly i would suggest sending it to a place that is very familiar wioth that style head and has done all the research for the most gains.
i would suggest PSI in wild rose wisconsin.Text i gaurantee his satisfaction.these guys are the horsepower gurus.they make some seriuos parts.

 

sorry heres the correct link for PSI www.psi performance.com