Posts
24444
Joined
4/1/2008
Location
US
Edited Date/Time
1/26/2012 10:19am
Crankshaft on the left is an HRC Honda RC125 unit from the late 70's-early 80's. Not exactly sure which year.Polished rod beam, specially machined crank halves, balancing holes are plugged with aluminum plugs as is the hole in the crank pin. Thinking this is what they refer to as "stuffing"? Crank on the right is from an 81 YZ250H (stock). It's loaded with holes, obviously to lighten it up a bit I would guess. Obviously this increases the lower crankcase volume which would lower the lower end compression on the downstroke. What effect would it have on the performance of the bike if the crank was plugged up in the same manner as the one on the left?
Also, this year model used the infamous boost bottle which is still in place on the bike. What effect would it have to remove the boost bottle and replacing the stock intake manifold with a non boost bottle intake?
This is the last year model air cooled YZ250. Doesn't have much bottom end power. Midrange is uninspiring and top end is nearly nonexistent. Needs something in a bad way, just trying to figure where to start.
Also, this year model used the infamous boost bottle which is still in place on the bike. What effect would it have to remove the boost bottle and replacing the stock intake manifold with a non boost bottle intake?
This is the last year model air cooled YZ250. Doesn't have much bottom end power. Midrange is uninspiring and top end is nearly nonexistent. Needs something in a bad way, just trying to figure where to start.
You are correct on the "stuffing of the crank" increasing the pressure on the down stroke & transferring more fuel into the combustion chamber.
You don't even need to use the aluminum plugs, we used to use cork's & epoxy to "stuff" the cranks in the old day's
I don't know what removing the boost bottle would have as I never used one.
I would start with stuffing those giant holes in that crank & maybe cutting a few thousandths off the head to raise the compression.
Also check this out.
http://datafan.com/TunersHandbook/2-strokefiltered.html
here's a link that might help you!
http://datafan.com/TunersHandbook/2-strokefiltered.html
http://www.eric-gorr.com/
The Shop
Just block off the boost bottle port on the reed cage with a small piece of hose with a bolt or something in it to plug it and see what happens. If anything, it may be a bit rich, but you might be able to just lean it out on the needle.
Take the airbox off and while your at it....
Cut the Silencer off at the stinger
and instal the Fire Red colored PowerBand
Post a reply to: Questions for 2 stroke tuners......