Here's the first drawing. You can see the angle of wrist pin movement decreased by 1.25 degrees when using a +4 rod. That means less piston slap or chatter. Latter on I'll compute the forces on the cyclinder for a given downward force and compare the two. Have work to do outside now though.

Another interesting point about this drawing is we gained 4.1866mm up in the bore by adding the +4 rod. That's effectively .1866mm higher the piston is at the same 90 degree crank angle. Its a good illustration of how much slower the piston is moving off TDC when compared to the shorter rod. The cam and crank are still doing the same thing they always did, only the piston is in a different spot when compared to stock (for a given crank angle). Neat!

 

<div class="FTQUOTE"><begin quote>Originally posted by: BigMc

J.R. your right. I was talking out my azz last night I guess. (to much southern coke i guess) If you move toward the cnter line of the crank, your not gaining a thing. Your hurten yourself.

But, if the big end center line moves away from center, say 2mm, you would gain a full 4mm in stroke. 2mm on botttom, 2 on the top. This of course gives you more CC.



Sorry. Ill try and put my brain in gear before runen my mouth next time. Booze and a keyboard, not a good mix.</end quote></div>


Ahhh, no worries! I know you know,,, its just hard to get out in words. [img]i/expressions/face-icon-small-happy.gif[/img]

Btw, there was 101 turkeys over here last night.... n I think 5 or 6 is still running around my head. [img]i/expressions/face-icon-small-sad.gif[/img]

 

<div class="FTQUOTE"><begin quote>Originally posted by: BigMc

J.R. I swear he told me that stroking the motor would affedt the revver adversley. But maybe Vince ment the total revs possible before it just, comes apart? Idunno. Thats why I like this place, no matter how much youve been around these things, you learn something new all the time.



P.G. Thanks for checking on that 250r case man. I guess i need to check out the bay again. Glad to hear your back in action.



keep-em-alive</end quote></div>

Yeah, I remember you posting that a long time ago. I also remember thinking I wasn't sure what he was talking about. Just figured maybe there's something I dont know. We'll get to the bottom of it though. [img]i/expressions/face-icon-small-wink.gif[/img]

 

<div class="FTQUOTE"><begin quote>Originally posted by: BigMc

gforce, what is that finish on the swinger and axle carrier? I like. Ive been considering a tear down to repaint the frame and arms. I need someting that will cover the weld seams on the swingarm. That would work great I think.</end quote></div>



It's Herculiner. About 2 months ago I completely disassembled the quad and ended up using two 1 quart cans total, that's with 2 coats at a cost of $60.00 compared to powder coating which obviously would have been much more expensive. It's held up to this point with no problems and makes it easier to clean and easier on the eyes from it's previous state.[img]i/expressions/face-icon-small-wink.gif[/img]

 

<div class="FTQUOTE"><begin quote>Originally posted by: JustRandy







Here's the first drawing. You can see the angle of wrist pin movement decreased by 1.25 degrees when using a +4 rod. That means less piston slap or chatter. Latter on I'll compute the forces on the cyclinder for a given downward force and compare the two. Have work to do outside now though.



Another interesting point about this drawing is we gained 4.1866mm up in the bore by adding the +4 rod. That's effectively .1866mm higher the piston is at the same 90 degree crank angle. Its a good illustration of how much slower the piston is moving off TDC when compared to the shorter rod. The cam and crank are still doing the same thing they always did, only the piston is in a different spot when compared to stock (for a given crank angle). Neat!</end quote></div>


So because of the added length the piston tends to "linger" for a bit longer then the stock rod/piston would? Which increases the rev limit if you will. Sorry just trying to get my head around this. Also decreasing the angle which reduces friction of the piston inside the sleeve?

 

<div class="FTQUOTE"><begin quote>Originally posted by: gforce34

So because of the added length the piston tends to "linger" for a bit longer then the stock rod/piston would? Which increases the rev limit if you will. Sorry just trying to get my head around this. Also decreasing the angle which reduces friction of the piston inside the sleeve?</end quote></div>

Yep, sounds right to me.

 

Here's a stock 230 rod n stroke on the left and a stock TRX250x on the right. The 250 will easily out rev the 230.

 

ATC250R on the right.

 

Damn, I hate when I don't get email notifications! Got 3 pages of homework now![img]i/expressions/face-icon-small-happy.gif[/img]

 

HI GUYS, NEW HERE JUST WONDERING IF ANYONE HAS DONE THE TM28 ON A 230. I SEARCHED AND REALLY DID NOT COME UP WITH ANY INFO. JUST WONDERING WHAT JETTING EVERYONE IS USING.