Ooooo this was the thread I should have been looking for.
http://picasaweb.google.com/srinath.the.man/SavageChopperBuild#53768675803138...
That is my chopper built ~3 years ago.
Ooooo this was the thread I should have been looking for.
This was my observation after doing the chopper mod the way I did.
The front wheel is 21" aluminum. So @ the same road speed, that wheel spins about 25% less. It also is about 1/2 the weight of the steel wheel. Therefore with the rotational kinetic energy only takes into account the effort required to turn its direction is of the order of 50% less.
Now the offset in the savage triples are 2.5". The custom triples I made didn't touch that, else I'd clobber the tank ... so 2.5 it was. However the wheel has an offset axle. I flipped the legs left to right and ended up with 1.5" taken out of the offset effectively. The bike was a lot lighter to steer as a result. Its a demostrable effect I will gladly show anyone who wants to stop by my house in charlotte NC. I have a maxim FE in a savage I should finish out in the next few weeks.
Here is the other cool factors with this mod.
The stock FE out of most 80's dirt bikes - DR250, 350, 650, KX125, 250, 500, rm 125-500, and more, I just tried these, typically yamaha used 28X28 mm stems and honda used 26X30 and suzuki and kawi used 25X30. So kawi and suzuki FE's are drop in to the savage which uses 25X30. 26X30 is useable too, just get the complete upper bearing with it - you have to pull the outer race from the frame - usually damaging it. So get a new one ... I did for that bike.
So a whole FE 9"-11" longer just drops in ... triples and all. So what's the problem ... yea the tank. These FE's all have 1"-1.5" offset, we need 2.5 minimum.
So you make upper triples ... Or cut and weld the frame.
Do triples if you have a good machinist - Make them to be spaced as in the triple you are using the offset needed to clear the tank on the savage and the extra rake you need to get it looking right. I'd do no less than 7 degrees, no more than 12. But to each his own. That bike was a 9.
What you have to do is to cut a wedge with the rake you want out of metal or even wood. That will be used to block up the triples in the mill. I used 1" plate for the top and 1.25 for the bottom 6061 aluminum. The distance from upper to lower triple i na savage is ~6.3" if I recall. Measure it. You need it for your calculations.
Now in the Upper triple is 2.5 from the center of the stem to the forks, lower triple is 2.5"+ [6.3" X cosine (rake ange)].
Center punch those spots in the aluminum plate and take to the machinist. Done in under 1 hr.
Now the weldup method - I have only theorised this not done 1 myself.
Find a welder who has experience chopping a bike.
Get thin walled steel channel section of 6" or 3 2"X2" box section square tubing. Weld it to make a 2"X6" section and cut 1 end straight and the other mitered to your rake. Put it in and weld it up. Why the 2" stretch on top - the dirt bike FE you would use has a 1" offset or so ... without 2" on top, you'd clobber the tank ...
After that its simply bolting everything together.
In a way that dirt bike FE turned backwards makes all the difference for handling so I will just say leaveyourself that option if you do this.
The frame or triple clamp job should cost you under 400 labor and materials. The forks off a dirt bike - whatever your local junkyard charges for them. I paid around 20 for the few FE's I got ... 3-4 ... but they were all missing parts. I dont see a complete one going for over 100. $500 and other misc like bearings tires, tubes etc cos no dirt bike gonna have street tires on it ... so 600-700 depending ... for one delicious little very very easy and streetableas well as reliable and freaking one of a kind chopper ...
Cool.
Srinath.
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