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Smoker's Custom Motard

415K views 2K replies 180 participants last post by  crazypj 
#1 ·
Been thinking A LOT about building a custom two-stroke motard. :D

I've got a nice 1987 RZ350, completely bone stock. I REALLY hate to strip it down to build a custom, but it's probably the best thing to do. It's already registered and plated here in California, so that will avoid a lot of future hassles.

So, now is the time for planning the build. Any ideas you guys may have would be much appreciated. I'll post up my ideas, and will get the work started when I feel comfortable with the design.

I want to use the existing RZ350 frame and engine, beyond that - it's wide open!! Soon, I'll post pics of the bike as it is now.

Here is a custom motard built with the same engine and frame:









 
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#73 ·
Well, I stand corrected then. If you're getting the main frame for that cheap and it's new, or damn close enough, Then trying to shoe horn the RZ motor in there seems a little more practical after all...
Practical? When the hell do we build anything practical, LOL.

Anway, Sounds like you have some big decisions to make. And I now see your deleima with the front motor mount. Looks like you moght have to have a couple of tubes welded up in a drop down fasion to meet the engine. Similar to a Spondon GSXR frame. It can still be stress member, it's just gona take some extra large mounts made to accomplish it.

You've got my gears turning with this one bud. Curious to see how this works out.
 
#75 ·
I couldn't figure out why the ad for the Aprilia SXV frame said:

Only sold to a legitimate person who honestly needs a frame. This will not not be shipped without a conference with the racing staff.

You will need to demonstrate legitimate proof of need before this transaction is finalized.


So, I looked up the parts fiches, which said that only the '06-'07 SXV frame is available. The price I saw was $1,930.66 USD plus shipping from England. I haven't spoken to anyone to verify the info, though.
 
#76 ·
I know you guys like monster engines- but it makes sense to build the RZ engine to have about the same HP as the SXV engine, that way the components won't be overstressed.

I was just watching this video to get juiced up for the build:

http://www.youtube.com/watch?v=Lmb2k-qGQ8Y&feature=related

It would be crazy if I could get this 12 liter SXV tank and cover it with carbon fiber. Maybe if the plastic is firm enough? I'll have to find out about that - wouldn't want delamination problems or cracking. The tank shape is so sick! I think it looks better WITHOUT the plastic radiator shrouds attached. :knucks:

The tank would need some work, though. It comes with a fuel pump, but the RZ carbs run on vacuum feed.

I've seen a small carbon fiber cover for the top of the standard tank - not sure if it also fits this oversize tank. If it's not good to wrap this tank, it might be possible to make some carbon side covers for it.

 
#78 ·
You can weld to cast but this can present problems. While it can be done im not sure that i would want to do this for a frame(personally). Ive welded cast aluminum before and depending on the casting methods used, you can end up with weak welds. I would like to assume since Aprilia cast these frame sections to be welded to other parts that their process is/was suited for it.

For me the choice would be simple. Id modify the RZ frame to suit the style swing arm and bodywork I wanted. You've ridden a stock rz, you know its a little on the flexy side so it would be a good project to stiffen up while modding. A nice back bone out or large diameter tubing would let you drop an mx tank off anything pre twin spar. Heck you could probably find a pre 97 CR, Pre 04 yz etc and weld parts of that frame to your rz frame. You can pick up 125s for next to nothing pre 2000. If you find a rolling chassis that will give you brakes, a set of hubs to lace some 17s onto. suspension(would need to stiffen up) and bodywork for a few hundred bucks. Not to mention a full set of new plastics and tank would be cheap if you wanted new stuff.

Thats how i would go with the project.
 
#143 ·
You can weld to cast but this can present problems. While it can be done im not sure that i would want to do this for a frame(personally). Ive welded cast aluminum before and depending on the casting methods used, you can end up with weak welds. I would like to assume since Aprilia cast these frame sections to be welded to other parts that their process is/was suited for it.
Here's a cast R6 swingarm that RGV Steve welded for me. There's a new plate on the top and botom to seal the original shock hole, and the new billet shock mounts on the bottom. The pivot is also modified, so it will bolt right onto the OEM RZV500 frame. Just wanted to show some of Steve's work, he does good welding and fabrication.



 
#83 ·
I think you can build something cool like that on a low budget. There are tons of old 2 stroke engines out there looking for a second life. A lot of cheap dirt bikes and enduros, too.


Well, the Aprilia parts order is in.
$2,300 for 15 pieces...I probably only need about 200 more pieces!! :doh:
I don't know why I do these things without thinking them through, but who cares...

THE PROJECT IS ON!!! :drinks:

I'm guessing these parts will arrive next week.
 
#86 ·
Got a pic from someone who did a test, and who probably knows more than me about bikes. He recommended to use the RZ frame instead if the Aprilia frame. That seems to be the opinion of some of the knowledgeable guys I know.



I still want to try to make the Aprilia frame work. If it doesn't - it'll cost me the $550 USD for the frame and whatever work I put into it, but I think it's worth taking a chance. Hopefully, I can still use all the other Aprilia parts with the RZ frame, if I have to go that route.
 
#89 ·
The drop-down bracket on the Aprilia frame for the RZ front engine mount will look a lot like the front of the frame on the RZ.



The main drop-down brackets can be straight bars with a crossbar at the bottom for the front engine mounts and the torque bar mounts. The radiator mounts will be up above the exhaust pipes.



 
#108 ·
I guess you mean - will the Aprilia frame work? It has to. I'm going to sacrifice the original RZ350 frame to legalize the Aprilia frame.

There is a bigger clearance problem than I thought, because I forgot that the carb mounts are 1/4 inch wider on each side, than the intake manifolds. Somehow, I'll find a way to make it work. Also have problems with swingarm pivot/countershaft sprocket alignment vs down pipes clearance, and where/how to relocate the kickstand, so that the left side pipe can come up on the same side ( not GP style).

I'm not sure if I can modify the Aprilia fuel tank for use with the RZ engine. Not much confidence modifying plastic fuel tanks.
 
#111 ·
Worked 24 hours, and now been up all day reading about anti-squat, squat, pro-squat, chain torque, and other rear suspension design stuff. Just trying to understand what could go wrong with the engine swap.

Also starting to look at how to run the custom pipes. The pipe in the pic is from a different project. I'd like to relocate the kickstand and have the left pipe stay on the left side, intstead of crossing over to the right side. The pipes should probably cross over in the front, to get extra length.

 
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