If I polish and SLIGHTLY shave the head on my '97 Honda 300 4X will I have any gain in low end torque? Also, will it allow too much slack in the timing chain and/or throw the timing off in the motor?

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Shane

'97 Honda 300 4X - Vamped, Locked, & Lifted

 

Porting will give you better top end and throttle response -- at the expense of torque.

You could go in and just CLEAN UP the casting flaws but don't remove any extra material unless you plan on increasing your displacement.

If you shaved the head a small enough amount to not affect chain tension and cam timing, it wouldn't be enough to increase compression to the point you'd notice a difference.

Pam

 

Pam,

So my best bet would be to go with a higher compression piston 10.25:1 and "polish" the inside of the head, correct?

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Shane

'97 Honda 300 4X - Vamped, Locked, & Lifted

 

I had my motocross bike ported and the company that did it had several flavors of porting to choose from: Top end, Low to mid, and moderate power gains throughout the entire power band.

I think the moderate power gains mod just cleaned up the casting flaws. The others modify port timing and compression.

You could also use thinner top end gaskets. This will increas the compression for better low to mid power. You might have to use a higher octane gas, octane booster or race gas if you increase compression too much. I use Cometic gaskets for my dirt bike. They're a few thousandths thinner than stock gaskets. I don't know if Cometic makes gaskets for an ATV but its worth a try.

 

I had alot of head porting done on my 250X and I was told that polishing is not a good idea for a bike with no fuel pump. The reason for this was the fuel atomizes poorly and with "drip" (slightly exaggerated) into the cylinder with will cause a poor mixture and loss of power. If the inside of the head is keep just alittle rough, that is enough resistance for the fuel to stop dripping into the cylinder.

You might want to get a little more info on this. Call CT or White Bros. tech support and see if they can give you some advice. www.ctracing.com, numbers are on the web site.

 

Please excuse the wonderful grammer.

 

I have all my off road vehicles ported. The cylinder intake is made rough to better atomize the air/fuel mixture. The transfer ports and exhaust ports are polished to improve flow.

Pro-action is a company that does this for me. They also have a carb mod for $80. that grinds a swirl in the carb opening. This also better atomizes the fuel/air. Reviews I've read on the modification says its definitely worth the money.

Dave

 

Shane,

Yea, If you go with a slightly higher compression piston and have someone do a clean-up on the ports, it'll help a little. We're talking maybe 5-8% at most -- but it might feel like more because you'd have better throttle response.

If you decide to get the porting done, make sure it's done by a REPUTABLE shop, and make sure they use a flow bench. Also, a 3-angle valve grind can help quite a bit towards making a port job work well (this can add another 15-20% more flow!). The most important thing with porting -- a good port job will help performance somewhat, but a bad port job will KILL torque and cause all kinds of jetting problems.

If you don't want to shell out $250 - $400 bucks on porting right now, I'd just leave it alone!

Better perfomance for the average trail rider can be gained from going bigger on the piston -- say 2mm over stock size. That'll give you about a 20% gain in HP.

Pam

 

Pam,

Thanks. An oversized piston would be my cheapest alternative, but I don't think that it'll give me what I'm looking for. If I am going to spend $300.00 plus on a head job I would rather invest in the Powroll big bore kit and boost up the cc's.

Thanks everyone for your input.

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Shane

'97 Honda 300 4X - Vamped, Locked, & Lifted

 

Headwork on a 4 stroke can get expensive, but the ends do justify the means.

I had my 400cc Wicked Warrior engine work done at Powroll, and was treated very well, (even if we did have a few problems along the way, eh Pam?)

My Warrior head had the 3-way valve job, H/D springs with Titanium retainers, .430/.430 lift cam up from .380/.382 stock, and yes it was ported and polished. Flow bench data before and after shows the facts. Approximately 10% more flow across the board, with almost 30% more on the intake during low RPMs though the exhaust was a flat gain across the board.

I read this 30% flow on intake as the ability of the engine to suck in a larger fuel charge for bigger combustion.

Big bucks? yeah, worth it? All depends on how deep your wallet is to begin with. Speed costs money, how fast do you want to go?




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Da Heapster - Seattle 1994 Bitchin Banshee 1993 400cc Wicked Warrior 1992 4x4 Busted Big Bear 300 h.p. V10 Dodge "Quad" Cab