XS400 ATV

[79xs]

Some of you may recall this crazy little device I put together a few years ago:

Well it was fun to ride, but not really safe or all usable. Due to sprocket alignment the rear tires were not centered with the frame. This caused almost zero tracking. It always wanted to turn.




So I started to do an inventory of all my motorcycle/atv parts. It turns out I have enough Yamaha Blaster ATV parts to make a rolling chassis. Mostly parts left over from this build:

So I rolled the trike up to the garage and had a look.

This isn't a question of how or if it can be done.. just wondering what you guys think.

 

[manuel sena]

I think it would be a fun one of a kind project.very interesting

 

[rshutchinson]

Cool trike. Go for the ATV build, much more useful and practical.


Funny though, I too am in the middle of a blaster build but haven't shared it on here. Though I shoved an FZR600 streetbike engine into it, had to lengthen the frame 4" and redo top frame tubes to fit the carbs. Thought of using the spare xs400 motor I have laying around but I wanted something with a little better sound and power.

From my experience, the biggest issue you'll have is with the lower frame rail width of the blaster and the distance from the sprocket to the bottom of the oil pan on the engine. You'll need to really widen the lower frame rails to drop the oil pan through to line the sprocket up with the swingarm pivot, which means you'll lose a lot of ground clearance OR you can keep the engine above the frame rails and have the sprocket on the engine quite a ways above the plane of the pivot and rear sprocket. The problem with that is coming up with a way to keep chain slack at bay so you're not constantly knocking the chain off a sprocket.

Also, it seems like it should fit fairly easy if you cut the front suspension downtubes where they intersect the upper a-arm tube, reweld them at a steeper angle, gusset them and reinforce the front end with some more tubing.

 

[79xs]

Well this is what we have so far.

 

[BBS360]

Looks good! Just needs some mounting tabs and wires.

 

[rshutchinson]

Do you have plans for a longer rear shock now that the swing-arm is higher?

 

[79xs]

Do you have plans for a longer rear shock now that the swing-arm is higher?

I'm not sure yet. Too much lift in the rear can make the seat lean forward.

 

[rshutchinson]

Yes but effectively you've already done that with where you've cut it. Or you've lost that much ground clearance in the back end of the frame.

If you go with the longer shock to compensate for that you could cut the the lower subframe rails and bend it down to level out the seat.

Just throwing my two cents where it doesn't belong. Keep going and ignore me.

 

[79xs]

You know.. I was just thinking about that with the seat frame.

It's hard to see from the picture, but the frame is notched on the bottom right where the oil filter would be on the 400 motor. This allowed me to bend the frame down in the rear. So for now it's only lower to the ground without anything changing with the seat height or angle. I was also thinking of lifting the shock mount on the swingarm

 

[rshutchinson]

Any updates?

 

[79xs]

Fixed the gap in the rear frame tubes. Welded in the stock XS400 upper rear motor mount. Made lower rear mounts.

 

[rshutchinson]

I'm curious to see how the suspension geometry is going to be once you set it down on the ground.

 

[79xs]

I'm curious to see how the suspension geometry is going to be once you set it down on the ground.

I looked your build posts. Very nice work. I'm slowly trying to build up my fab skills. I don't yet trust myself to build something for the road. I value any input I get.


I need to work on the following issues:

-I am going to need to relocate (or I should say extend) the rear lower shock mount to re-level the frame.

I knew it had to be done, I just didn't know by how much until now. Using a aftermarket cross reference I have found a few shocks that are longer, but I'm not sure if I want to spend $100+ on a used shock just to find out it causes another issue. For example, it might require bushings or need to be re-worked ..who knows. I know the shock I have now works correctly and is in good shape. They puts up with the extra weight of the 4 cylinder build so It should work here if I get the angles correct.


-Depending how brave I am... I may also slot and roll the front half of the frame backwards to get some of my caster back in the a-arms. That caster was removed by the combination of me leveling the frame then raising the ride height of the swing arm. I might also keep this issue in the back of the head and proceed with everything else. As long as I factor in the roll I should be able to correct the frame even after a few test rides.

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- I'm going to also roll/lower the rear sub frame like rshutchinson brought up. Its a simple fix for seat angle. Lucky enough all the fender mounts are part of this sub frame.

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Fuel System: I know its early in the build, but due to space I need to plan ahead for this. The stock fuel tank will not fit. The motor is a lot taller than the stock motor. I don't have access to an A/C tig welder so I can't make a custom aluminum tank. I'm not 100% sure what I'm going to do yet, but here are some brainstorms.

This is a 2.5 gallon tank:

7.75" L x 12.75" W x 7.75" H

Not counting the angle area of the tank, this is a cardboard mockup of the tank:

Of course I would need to make a steel box to protect and support the tank.


Kind of a beast, but 2.5 gallon would be nice.

 

[rshutchinson]

Here is my Blaster build thread too if you want to take a look.

http://www.blasterforum.com/threads/yzf600-engine-stuffed-into-a-90-blaster.62650/

You're probably waiting until the end to add gussets to everything but I just want to make sure and suggest adding gussets between the lower frame rails and the pieces you added in to move the swing arm pivot up.

As for the front caster, what if you just cut out a few inches of the top tubes, bend the front end back up (where you previously bent the lower rails) and weld them back up? Then you've only got one frame cut rather than two? Just an idea.

A good cheap upgrade for the rear shock is a 400ex shock which I'm using as well but it requires bushings for the top mount. However, I don't think it's much if any longer than stock. I do have a shock that was longer than stock and adjustable but also requires bushings, I'll try to find out what it is off of because it really raised the rear up on my bike.


Does that tank fit in that area as is? I'll have to measure next time I'm out working on it. 2.5 gallons would be perfect for my build. I have space where your carbs will be and I thought of using that space as well. My engine uses a fuel pump as well which helps. You could probably just use some steel straps to hold the tank up rather than a full box.

Coming along nicely!

 

[79xs]

Slick, I am going to check it out. Here is my build from a few years ago http://www.blasterforum.com/threads/xj550-blaster.29934/


Quick note about the tank: You will notice the Blaster frame has an odd setup where the sub frame tubes on one side curve in and the other side curves out. This will need a bit of tweaking to fit the tank. Also the cap sticks up a bit.

Here is a PDF of the Fuel safe tank: http://www.usplastic.com/catalog/files/drawings/13885%20103114.pdf

Odd enough the same tank, but not fuel safe, has a better drawing:

http://www.usplastic.com/catalog/files/drawings/8665.pdf

 

[79xs]

So what's everyone's view on the rear lift? Do I just make a block that simulates extending the shock and weld that into the swing arm?

 

[rshutchinson]

Here is what someone had done to the swingarm that came on my bike when I got it. Someone used this in conjunction with a longer shock. If you want to raise it you could do the same just on the other side of the mount to raise it up with a stock length shock.

However, I think just going with a longer shock and making some bushings for the top mount would be safer.

 

[rshutchinson]

progress?

 

[79xs]

I haven't decided where I want to set the pivot height yet.

The main issue is that the motor can not really be put between the frame rails without looking odd. With the larger four cylinder XJ550 I was able to drop the oil pan between wider frame rails. The XS400 motor is pretty much flat all the way across. The frame would need would need to be wider than the pegs on the left, but only a bit wider on the right. In short, just starting with a larger frame from a Warrior or Raptor would have been 100 times better, but that's not fun. That darn pivot height is just so low for the stock Blaster motor.

Right now, the chain is pretty happy and so is the ride height. The chain is tight enough when the swing arm/shock is fully uncompressed, but only slightly looser when the shock is compressed. The problem is that the chain could start to hit the pivot when coming off the power, but I believe I'll just need to use a chain guide over the pivot. Also, the angle of the swing-arm is required to keep the correct ride height.

 

[rshutchinson]

Looks to be just where you want it to be IMO. How is the angle of the seat?

I'm thinking of cutting out the factory swingarm mounts and moving them up on my build just so I don't have to come up with something for my chain routing since I didn't drop the engine through the frame and the engine sprocket is way above the pivot.