Yes, Ill make a plate and add it under the cylinder. While Im in there with the cases split, Im going to take a really close look at how the reed cage sits and its flow into the cylinder.

Jack, have you tried lightening any flywheels yet? I just finished a friends Lt80 flywheel the other day. That Lt pulled harder off the line than it ever has before. Huge difference. Im not going to list the weights here, because of all the work I have done to it. He has a very mild motor, but now it revs very quickly. He entered his first harescramble race and stomped the competition. I was expecting to see a loss in power somewhere, but it didnt seem to have any down sides.


Gary

 

Oh yea! I've lightened the flywheels. It surely helps. [img]i/expressions/face-icon-small-smile.gif[/img]
The reed cage thing:: This surely can be improved on, but no easy way.I've heard of modding a KX60 cage for the LT.

 

We are thinking along the same lines. If the cases are apart, the mods are easily done. Personally, from using the 20mm keihin carb for awhile now, I think the carb is too big for the reed cage, even ported. When I make the changes, I will try to incorporate a more effecient cage into the mix. I may even go back down in carb size to get a higher velocity instead of volume.


Gary

 

Your correct on the size of carb to cage thing. I used to think that the 20mm was too big. Then I build this Eton and the guy sends me a 28mm (and the cage to go with it). So I go to the Mossbarger site and they say the 90cc's can indeed handle 28mm.
So for us, it's getting a cage that will not restrict like the stock one.
Good thinking [img]i/expressions/face-icon-small-smile.gif[/img]

 

All night long I've been thinking about this rod length thing.
I understand why you want to build your own rod for the knife-edge trial, but The length of the rod +/- I don't understand.
Are you thinking longer or shorter? Either way that don't effect stroke. What am I missing?
What's 1mm equall in thousandths? (I think I know this but I want to confirm)[img]i/expressions/face-icon-small-confused.gif[/img]

 

Jack, 1mm is equal to .03937, or roughly .040 as most like to round off.

 

Ok, I know as well as most on here do that I'm an idiot. So here it goes anyway.

How does the stroker crank work in a 2 cycle? It would appear to me that making the crank swing 6mm or what ever, father down and farther up would change things very drasticly. Would it not bring the piston down and uncover the ports alot more (6mm to be exact) and also for alot longer of a time. In whinch it would loose a tremendous amount of compression and waste unburt fuel? Then theres the up stroke. I realize your talking about spacing the jug up, but would that not make the ports open thing even worse? Would you raise the jug 6mm? If you did, would you not still have to mill a tremendous amount off the head or sleeve? (to get the compression back up) In which case, I know you could reshape the head, but you would also have to do something about the spark plug wouldn't you. I mean changing the combustion chamber that much would really mess up the burn from the plug, would it not? Plus the plug length would also come into effect wouldn't it? Then theres the rod ratio. I know how knife edging works, but wouldn't the added friction on the piston to sleeve wall, from the piston being pushed sideways from the longer stroke, be alot more than that of the rod swinging through the gas/oil mixture. (then again maybe it would offset each other)

DStroyer, I am very glad there are guys like you (and Jack) willing to go the extra mile and spend the time it would take to try and figure these things out. I hope you can get this thing together and give us a ride report some time soon.

KEEP UP THE GOOD WORK!!

 

Hey guys,

Sorry it took me so long to respond, work has been hectic.
Jack, you are correct on the rod length thing. I went back to the research about this and you are right, you dont need to lengthen the rod. It would cancel itself out if done. Good catch!! This is why I posted it in here, to get feedback on this. As for how it works on a 2 smoke. My opinion, , the more volume of fuel and air pulled into the cylinder with vacuum, means more power. The stroked crank will do just that. I may have to play with the transfer and intake port height a little, but personally, from what I have seen, it is not going to affect the cylinder compression. For a 6mm stroke, you would add a 6mm plate under the cylinder, less a base gasket height. The head will not have to be changed since the piston is still coming to the top of the cylinder as if it was stock. Although, to bump the compression up to where I think it should be, I will drastically change the head design. You are correct about altering the spark plug length due to altering the combustion chamber. I will most likely run a shorter plug, since the plug will be drastically closer than stock. Im even looking into fabing my own piston, based on what Ive read about the flow of F/A flows over the surface area of the weisco piston with the rounded dome. It does not seem to be efficient. The flatter the piston, the more effiecient it will be. Take the CR125 piston for instance. They run about 160 psi cylinder pressure stock. So, I think getting a better squish band is a priority to get more ponies. I would just copy the weisco piston, accept add a flat surface on top.

Jack, do you agree about the piston theory? Also, have you resleeved any cylinders yet?

Gary

 

OK, set back and think about this. When you stroke a crank, you are actually just moving the rod big end outward on the crank web just half of what the total stroke will be. If you are going to stroke the bike 6mm, then the piston actually goes down farther 3mm and up farther 3mm. So you would only need a spacer and gasket 3mm total. When stroking a Banshee 4mm, you can get the spacer for the base, or you can get a head gasket spacer for the top of the jug. The later of the 2 is more desireable for most people as it keeps the port timing to more acceptable levels. With the head spacer I have matched the port bottoms to the piston at the bottom of the stroke and done what was needed to get port timing correct. With the case of a 2mm stroke for the LT, I wouldnt see any problem with using a spacer plate for the base, as you would only need .040 to get everything lined up. That would probably work better because you get more crankcase volume too. If you go a lot of stroke be sure the piston ring end gaps dont get into port openings and cause a problem.

asfasasu3, dont confuse a long rod motor with a stroker. You can use a long rod with a stock stroke. The piston pin is relocated to keep the piston height correct. When going long rod, in most cases, it is helpful in 2 ways. The rod angle is improved and the side loading of the piston is actually reduced becasue the pin is farther up in the piston. That frees up power. The second big thing is that your dwell of the piston (how long it stays at the top of the comression stroke) is increased by a fraction of a second and promotes better combustion and power. Hope this helps,Bubba

 

Thanks Bubba,

I apprciate all the info. Its going to take a few tear downs when this is done to get it right.

Gary