Lightening a '75 250MX

[Tahitian_Red]

If you wanted to shave a few pounds off a 75 KTM 250mx where would be a good place to start?  The rims look a little heavy to me, but I haven't weighed them.  Thanks for any help!


Jay

Racing the "FaltaNator" in 2010

[gooddirt]

Not much you can do, the power of the motor takes care of it. Will your bike see the track for 2010 ? I have just about got a 1974.5 har sram done I stared a few months back and should be done sooner or later.

[joe novak]

Any weight that is removed from the part of the front and rear suspension which moves (ie. up and down) will make the motorcycle handle better.  I believe it is called "unsprung weight".  I have read that a rule of thumb is that for every one pound of unsprung weight removed, it makes the vehicle handle like it was ten pounds lighter. Google the topic.  These items include: wheel assemblies, hubs, swingarm, the lower part of the shock absorber, fork legs, sprockets, chain, tires, tubes, rim locks, and MUD.  If you ride in mud, rims which do not collect the mud and trap it in the rim are an advantage in handling.  Those rims with the high shoulders are notorious for collecting mud.   A lighter wheel assembly also takes less HP to accelerate.  Sort of like pushing an empty merry-go-round on the playground V.S. pushing it with half the class sitting on it.  Other items are: Titanium bolt replacement, trimming off excess threads of bolts, removing lock washers, using LOC-TITE, less fuel in the gas tank (you do not need a full tank to run a short motocross race), replacing steel rear axle spacers with aluminum, removing small brackets and tabs, et.al.  If you do not use the FMS position, the entire lower bracket can be removed.

[Tahitian_Red]

Larry,

I should be on the track sometime this season.  

Racing the "FaltaNator" in 2010

[jeff greenberg]

Joe-  Some very good weight saving info. On another subject, we you ever able to confirm if that Berkie ever really did belong to Jon Leak?  Thanks and Happy New Year!
Jeff

[Tahitian_Red]

quote:Originally posted by joe novak

....Other items are: Titanium bolt replacement, trimming off excess threads of bolts, removing lock washers, using LOC-TITE, less fuel in the gas tank (you do not need a full tank to run a short motocross race), replacing steel rear axle spacers with aluminum, removing small brackets and tabs, et.al.  If you do not use the FMS position, the entire lower bracket can be removed.

Joe,

You said the "T" word.  I was afraid that's what it might take. LOL

Basically lighter wheels and bolts($) and removing excess frame metal are about my only option.  Thanks for the advice!

Racing the "FaltaNator" in 2010

[sixdazed]

You could swap to a first year jackpiner frame and build from there keeping weight in mind.
                                   Ric

ric emmal

[gooddirt]

Joe, yes all of that is true ; but my feedback was based on using the stock components and what Jay has to work with;). He needs to just get the bike out on the track as he is a year behind:D.

[joe novak]

Jeff,  The Penton Berkshire which I had previously mentioned was purchased by my cousin.  He did buy it from Jon Leak.  I saw it over a year ago sitting in a barn.  Same old story... stopped running, then sat there.   It would be a memorable Penton to "recover".   I think Jon won a few races on it.  Did he win an Ohio State Championship on it?   Joe                                        p.s. I should try to track it down again....

[jeff greenberg]

Joe- That would be cool if that's the one he has. No hurry but you'll have to see what you can find out. If memory serves me right I think Jon won the 125 state championship on a Sixdays. I think in 1973 when we were both racing our Berkies that he fell or had a mechanical. Regg Raider may have won and I think I got 2nd or 3rd. If it was his bike I'm thinking that his sister Lorri may be interested in it. Would be very cool if you could snap a picture of it. Thanks again Joe and happy new year to you and all POGers!
Jeff

[rob w]

1974 Ohio State Champions

100cc
1- Mark Weidner
2- William Rosko Jr.
3- Lee Godby
4- Robert Shoup
5- Brian Tignor

125cc
1- Jon Leak
2- Mark Tracy
3- Jeff Greenberg
4- Dave Glenn
5- Denny Ashworth

175cc
1- Clint Fannin
2- Bruce Sanderson
3- Don Gunter
4- Rex Erskine
5- Brian Cater

250cc
1- Duane Dreyer
2- Robert Johnson Jr.
3- Herbert Miller
4- Dirk Walton
5- James Rhea

500cc
1- Gary Slater
2- Rick Hawthorne
3- Bill Wise
4- Ron Ruble
5- Jim Greenfield

[jeff greenberg]

Rob-  Thanks so much for taking the time to dig out those results! At least my memory wasn't too far off the mark. It was all so long ago but such great memories.
I really wish I would have held on to those Cycle News East articles and results from back in the day. The only one I have is 1976. Maybe someone has the results from '73 as I'm pretty sure we were both on our Berkies. Jon was so smooth and fast.
Joe- I tell ya, Jon won so many races on that Berkie that your cousin may have in his shed. When Jon was "on" we were lucky to just keep him in sight. The boy could fly! My good friend (to this day) Mark Tracy was the only one of those top 5 125 riders listed that did not go pro and earn an AMA national #.
Jeff

[garrettccovington]

I have a friend of mine take his old YZ125 and change out just about every nut and bolt from steel to Titanium, Drilled everything he could possibly think of, even if it was just to put a little dimple, removed the petcock, weighed tires, blah, blah.  He spent alot of money trying to lighten up the bike and IT WAS Light.  We suggested he cut down on the double cheeseburgers and the bike would get alot lighter faster, and cheaper that way.  He's 6'5'' about 250 lbs.  He now rides a KX500.  The YZ is still pretty trick though.G

72 six-day

[joe novak]

Jeff, After I saw Jon ride off the track at Mid-Ohio (the original MX track) with his front wheel hobbling with broken spokes and bent rim, I always brought an extra front wheel to races.  He finished the race that way, too.  I never needed mine, though.  That track usually had a very hard packed surface.  joe

[jeff greenberg]

Rob- Hey, I did some digging and actually found results from the 1973 Ohio State Champ race. You don't happen to have the 75,76 or 77 laying around covered in dust somewhere???
Thanks.
Jeff