I can buy some of what he is saying. The thing that does concern me is he says opposite of what is commonly known on so many topics.

I wonder about this porting (larger ports and valves don't produce more power??!!?? I think Ron Wood, Pami, etc. would disagree. I believe there could come a point that more flow doesn't help. So, maybe this will help when you hear people stating their head flows more (they bench test and it has better flow). Maybe that doesn't mean it has more power???

 

When I broke my quad in the first thing I did was let it get warm and made sure it was full of oil and then i went streight down to the road an dragged my bro on his rappy about 20 times. If that is what made mine run so well, then i am a FIRM beleiver in the technique, even though I didnt know about it at that time. I just couldnt stand not to put the hammer down!! I figured that was what warrenties are for.

 

High velocity porting is a very interesting concept, and once you understand the multiple phases of the intacke cycle you will understand why velocity is more important to cylinder filling than big hogged out intake tracts or flow bench numbers. I have not read anywhere on motomans site where he is against larger valves.
I am pro big valves, with smaller intake tracts. I have reduced the size of my intake tracs 35% to increase velocity I did the work after 4 stroke wars and am very pleased with the results. When I spoke to gary at 4Stroke wars and saw his head I noticed that it wasn't hogged out, just a little bowl work and porting for efficiency with those big honkin valves. He does not reccommend enlarging ports, just cutting the valve guides back.
moto mans site is controversial , but I kinda pay more attention to the guys at the front of the pack than those bringing up the rear.

Demon- do I really pay you well enough for all those compliments??[img]i/expressions/face-icon-small-smile.gif[/img] we may have to sit down for new contract negotiations.

 

How would lunch do? That is if i can ever get you away from playing with your plastic long enough[img]i/expressions/face-icon-small-happy.gif[/img]. One of these days we need to break away for a few and go check out the 700!!

 

here's a question, and no bashing replies either because this is a discussion, not an argument dammit. you need to read the link in the first post to respond:

How does the pressure get behind the ring to force it out? Okay, so isn't the very same pressure outside the ring trying to force it into the piston groove? There is more surface area on the outside of the ring than the inside, due to the larger o.d., so would it not be easier for the ring to collapse inward, rather than be forced against the cylinder wall?
I'm back on the spring tension of the ring.

Also, is this to say that if you replace your piston you must also regrind the cylinder wall or the new rings will never ever seat, regardless of the method used? if that's the case then just about every DS on this forum with a high compression piston over 11:1 is running lower psi than their 9.7:1 stock.

 

Hitower- that's a great question - send it to motoman and share his response with us.
The way I understand it the spring tension plays an important role to initially seat the ring against the cylinderwall, this creates a void or space behind the ring, maybe .020" or more , pressurized gases will flow to the area of least resistance first which is right behind the top ring. The expanding gases force the ring to flex out and improve the seal beyond what the natural tension of the ring is capable of doing on it's own. Because the initial seal has already been made additional pressure increases just add to better ring seal.
Many of the newer NOS specific piston expand on this by adding small pin hole size vents around the perimeter of the top of the piston
and just below the ring lan to ensure a well pressurized top ring. This enables them to run even higher nitrous charges than ever befor.
My question to those piston designers is... How do you keep the carbon deposits from plugging up most of those holes?

If the ring wasn't spring loaded initially than I believe it would be a toss up as to which side the pressure would act on first.

When I did my first piston swap on my DS, I installed a JE 12.5:1, the rings were brand new but the cylinder was not rehoned.( this was
the reccommendations I received from two notable builders) I broke it in according to traditional break in proceedures and right from the beginning I had oil blow by issues. Many of the folks on this forum have experianced increase blow by as soon as they upgrade their piston, I believe that is a direct result of a piston rings failure to seal properly. Blow by = POWER LOSS
I am running a lower compression piston now JE 12:1, had a newly honed cylinder and blow by is non existant. I can't get away with running a lower octane fuel any more either. Hummmm- better seal ? definately and broke it in according to motomans instructions, proper warm period , get those rings under good pressure etc. I guess you could say I just got lucky but I feel a light honning is ( key word -LIGHT)essential to getting the best seal possible.
I believe that any one with single ring pami piston would need to be certain to break it in properly or blow by will be a major issue. But I like the design of those race minded designs that Pami has- I'm sure they have less power loss to friction than the rest of our piston have.

 

I not smart enough to be in this conversation but i do belive you breakit in as you will ride it[img]i/expressions/face-icon-small-blush.gif[/img]

 

Its all very logical - I buy it. Very much like the way hydraulic seals perform, U-cups that seal against a shaft, the higher the pressure the tighter the seal.

I broke my new bike the traditional way - by the book. I've always had oil blow out my crankcase vent, indicating positive crankcase pressure that is caused from piston blow-by. I recently put in a Pami piston 11.2:1 with new rings, and broke it in like a bat outa hell. Since its install, I have ridden on two hardcore occasions, and I have had no oil deposit on my crankcase breather filter. I've never done a leakdown test on the stock piston, so I can't compare with any certainty, but it would seem that my new piston that was broken in like a bat outa hell sealed better than my original mild break-in, inspite of no honing of the used cylinder wall, although I can see a fresh hone being a plus.
One thing that surprised me when I looked at the cylinder wall, was the spiral hone marks still being so apparent - it looked like new with hardly any wear at all in the nycasil, after 120hrs of use. That's some hard stuff.
Thanks for the link, very interesting.

 

Interesting link Major. I was curious, so I emailed him about 2 strokes. I notice that he says for all 4 stroke engines, just makes me wonder about two strokes. What he says makes sense, I know I did that with my deisel. Pretty much and it seemed to make a difference. I was told by several people that running the diesel hard will help to seat the rings.

I could see maybe not doing that on a two stroke, simply because the crank and low end bearings are not sitting in oil, nor is there an oil pump to make sure oil is being supplied. It has to come from the premix and you might not want to be running the machine real hard until everything is coated nicely with oil.

Just some thoughts. I am no motorcycle builder, so I could be way off base. I will share whatever he says for you guys to see.

Later
Bat

 

Just as a quick throw in, I had never had blow by on my quad till i got sand in the cylinder causing some minor scratches, thus i had blow by and less power.

I have thought alot about the Pami engines problem of having Blow by. Do you think it is possible that due to the fact that the Pami pistons use one less ring than everyother piston out there that that is why they dont seal as good? I think if i was ever to do a pami i would see if it would be possible to get the piston with the same ring setup as lets say the stock one. Just a thought.....blow by seems to be a consistant problem with all of the Pami motors.......Just ask Jeff!!!