250r/500r mod question

[3WheelHouston]

I posted this in the other forums, but apparrently it didn't make it over. I decided to build my dream trike from scratch, and I'm going to use a 250r chassis for suspension and handling. My next questions are these: which powerplant and what kind of axle/suspension/swingarm mods to use. My riding style is motorcross and woods, with not much dragging. I've heard alot of people talk about the 500r conversion but I don't know how heavy that would be or if it would compromise track performance due to weight. Also, I don't know how far to extend the swingarm and axle for this style of riding either, or any suspension mods I will need to do. I'm asking all of this so that I end up doing it right the first time and not buying something only to find that I'm dissatisfied and have to ebay it. Any takers?

[Kilborg]

The 500 motor isnt significantly heavier then the 250. You might gain 20lbs tops, so thats not really as much a concern.

As far as the swingarm goes, im running mine with a stock arm for awile. If your jumping, your not going to want any more then a 4 inch longer then stock. Take a spin on a 500 bike, and you quickly realize that your going to need a conservative wrist either way. The 4 inch arm is still going to let the machine come up at will. Basically, the idea behind the longer arm is for improved handling so you can use the power. You could put a +10 on there and still be able to bring up the frontend.

[3WheelHouston]

Well since it's only a 20lb gain, and I'm pretty light (155 lbs) I think I'll do that, however, I still need some more info about the swing arm and extended axle. I'm gonna go at least +2, but would it be better for that style to go for it at +4? I'm also concerned about turning radius on woody trails and fitting between those narrow spots.

[Kilborg]

If you ride really tight woods, a +2 arm might be in your best intrest. For mx, a +2 or +4 axle would suit your needs perfectly. I would personally use a +4, more for when your riding fast your gonna have the rear end swapping alot more and the longer arm helps this a ton. a +4 arm isnt all that much longer (hey its only 4 inches), so it would take some REALLY tight riding. Also, Your turning is still going to be sharper then most quads. If you use proper body english and such, you should have no problem. Your turning radius will only change a little bit.

[3WheelHouston]

Wow, thanks man. You've got your stuff straight. I appreciate your input. Anyone conflict with this opinion or has he just got it perfect?

[Jeb]

I think Mr. Blaze hit that nail right on the head.

Those super long swingarms are the ticket for drag racing, sand drags, hills, basically anything you're gonna go full power in a straight line.

For MX 3 wheelers, back in the day Team Green used a +2 swingarm on the Tecate 250s. Some Honda guys ran a -1 on their 250Rs for better cornering.

I would go +4 because, like you, I would be riding in woods, trails, and tracks. The only open bike I've ridden for long periods of time was a YZ490. With the CR500s being more powerful, I'd definately want as much as possible. On the axle, go with the plus 4, but pick your lines through the woods carefully. I have a +4 axle on my 84 Tecate and a +2 swingarm. and the wider rear end does make a difference. You might try hub spacers for a quick change from stock width for woods to wider for tracks.

Good Luck

[MR ATC]

there are severall things to consider with the 500R conversion 1 the frame it needs to be gusseted or the noncounterbalenced 500R motor will vibrate it apart. 2. motor mounting. the exhaust pipe manifold and frame tube do not line up so to cure this situation there are 2 popular methods to do this one is easy but will not withstand hard MX use this involves cutting away the lower inside frame rails this alows the motor to sit lower in the frame this is fine for sand dragging or causual play. the second and stronger but more complicated way is to "raise the Y joint on the frame downtube more work is involved but it is the best way for MX this is also the way HONDA did it with there prototype factory 500 conversion racers. as far as swingarms Jeb (sorry buddy but) is wrong team Honda extended there swingarms on the 250 anywhere from +1 1/2" to +2" for MX. it was the 86/87 TRX 250R's that were shortened 1". for the 500's HONDA ran +3" to +4" anything over that will compromise cornering. gearing is also a issue seldom taken into consideration with these conversions the stock CR runs a 13/50 (give or take 1or 2 teeth on rear i can't exacty remember right now) most ATC'S run 36 to 40 combo's for the 500R you can get away with a 34 to 36 and have PLENTY of power yet not have a machine that will not flip over backwords every time you touch the throttle. also HONDA offers a wide ratio transmissin for the 500 it keeps 1-3 the same (the only gears you need for woods/MX ) but changes 4-5 for eye watering top speed (over 100mph). also if you want to run lights you will need a aftermarket stator to run them (not to hard to get) as for suspension heavier forks springs and a revalved rear shock would also be recomended. axel width should not go over 6" for MX and 2-4" for woods. also if you run a lot of tight woods with slow speeds larger radiators may be needed. the pipe can easily be modified your best bet is to get a newer model pipe they are low slung pipes unlike the earlier high routed ones.

[3WheelHouston]

Okay, so what do I do about the radiator problem, if I encounter it? Is it possible to use the radiator from the cr? Also, Billy once mentioned something about cr500 or xr500 (I don't remember which) forks on his conversion that he's working on. What is that possibility? thanks for your help. -Aaron

exactly what is gusseted?