DRZ400 ATC build using '86 ATC 250R parts

[HK1837]

Hi all, been busy with work. Over the summer I've had some time to do some measuring and picked up a few more bits.

I'm on the hunt for an 11" front wheel off an '85-'86 ATC250R, 1987 ATCC200X or any ATC350X. Anyone know anyone in Australia that might have one? As I'm using the whole 1986 ATC250R front axle, brakes etc. I just don't have a wheel. I can buy a new one but they are only available in black, I already have silver rears.

[HK1837]

All, I picked up a front wheel and tyre off an '85 250R on the weekend.
Just want to check, which side the hub face goes, I assume its the side with the scalloped bits on it (first photo) and the washers/nuts go on the side with the insert faces on it (second photo)? That makes the most sense, just ant to double check.

[Red Rider]

Just want to check, which side the hub face goes, I assume its the side with the scalloped bits on it (first photo) and the washers/nuts go on the side with the insert faces on it (second photo)? That makes the most sense, just ant to double check.

You are correct.

[HK1837]

You are correct.

Thank you! Much appreciated.

[Carlson]

Keen to see how this looks mate. You got some bits off me for it.

[HK1837]

Its coming together slowly. Doing bathroom and kitchen renos right now, and I'm busy until early next year with a plant build. But I hope to get the swingarm modified to suit the frame this year, and I want to get hold of a pair of DRZ400 forks, so I can bolt then up to the front axle, hub and wheel to get an exact fork centre. Then I can draw up the triple clamps, and get them laser cut. Will get the perimeter, the steering stalk hole and the holes for the forks cut with laser, maybe get them done a few thou smaller and ream them out to size. I'm going to try and be funky with a cut away from the fork holes towards the steering stalk and pull that cut closed with through bolts front to back.
I've already dummied the 2003 LTZ400/KFX400 subframe onto a DRZ frame, won't take to much to bolt it up, just a bit of bending and welding. I have a NOS KFX400 rear fender, that I hope to swap for a good used or aftermarket yellow LTZ one, then I'll build it as a Suzuki. Otherwise it's going to be a Kawasaki which means a black DRZ tank and green Kawasaki tank shrouds.

[HK1837]

Small update. I found someone locally that can laser cut 25mm billet alloy to an AutoCAD drawing. Been doing some basic measurement off my roadgoing 2024 DRZ400E. It looks like that I need to move the forks forward by at least 50mm further from the steering stalk to avoid the radiators on steering lock, so the triple clamps are going to be triangular from the top rather than basically straight across. No matter what I do they are going to hit the radiator shroud plastics, but that is only plastic and can be cut/welded etc. Plus I can narrow the steering angle a bit if I have to. This is going to obviously push the front axle further forward, which is going to compound the problem that a DRZ400E is leading axle with the caliper behind. It isn't going to be easy to trail the front axle. I'll have to go looking and see what other forks are around with trailing axle and caliper like an ATC250R. Although an ATC350X is the same configuration as the DRZ i.e. leading axle and trailing caliper. Which way does the rake run on 1986 ATC250R clamps compared to 350X?

I've started measuring up the LTR450 rear swingarm to modify it for the DRZ frame and I have plenty of room to move the rear shock mount forward compared to where it is on a DRZ so that will lift the @rse end up a bit which is what I want (I'm 6'5") so hopefully that counter-acts the front tyre sitting 50mm further forward, although with the ATC250R front rake removed it might not be that bad?

[Red Rider]

You are going through a lot of work with this trike. My advice is to do your homework, and know what you're getting yourself into, with the front end geometry. I would hate to see you go through a lot of work, and then have it handle/steer poorly. I made the same mistake, when I had my first set of triple-clamps made for inverted forks. I kept the rake, which was built into the clamps, and then went from trailing-axle forks, to leading-axle forks. I told myself, "Ehhh, it won't make that much of a difference." HUGE MISTAKE! It handled like crap. For the second, and final, set of triple-clamps, that I designed, I did the homework, that I should have done in the first place. For my application, it was fairly easy. Since the new inverted (leading-axle) forks were basically the same length as the oem (trailing-axle) forks they were replacing, I simply designed some triple-clamps, with no rake built into them (fork legs are parallel to steering stem), and then spaced the fork tubes out in front of the steering stem far enough, until the trail measurement was identical to the original oem setup. In simpler terms, the front wheel/tire is in the same location, with respect to the steering stem, and the steering stem is at the same height as it was in the oem configuration. It's almost like I took a "side shot" picture of the stock bike, photoshopped out the trailing-axle forks, and then photoshopped in the leading-axle, inverted forks.

You may have already found this, but here's a thread discussing rake/trail: https://www.3wheelerworld.com/showth...il-for-dummies

[legacy51]

I agree that you need to understand your front-end geometry before going further. I am not sure what the axle offset is on DRZ forks, but I am pretty sure that pushing your forks very far forward is not good. BVC pushes their forks forward to make that triangle shape you talked about and they aren't known for great handling. Maybe they do that to reduce trail with their chopper like rake?? For your rake, which looks to be 26° or 27°, you can tip the dirt bike frame forward slightly or you can chop and weld your frame. There is a third alternative that I have ridden and it felt great, but it goes against the theory that you just need to get the trail correct. That would be "negative rake" triple clamps, where you pull the front tire back with rake built into the triple clamps. That would give you a huge trail number, but maybe the wheelbase is better, and that counteracts the large trail?

Anyways, if it was me, I would stick to a setup that is simple and known to work. Draw up your tire size, fork offset, triple offset, and head tube angle (rake) to get your trail number using a leading axle setup and then adjust rake or fork offset to get the desired trail. Keep the trail in the 40mm area. Stock trail numbers of the old trikes listed below.

84,85, & 86 Tecate - 40mm trail
84 250r - 45mm trail
85 250r - 37mm trail
86 250r - 38mm trail

This is my sketch of my trail figurin for a yz426 conversion


Post some pictures as you go, it sounds like a sweet trike! I am only 6' 2" so I can't imagine how you feel, but I am not a fan of the old Honda trike cockpits and think that the modern trikes are great. The taller seat height that most complain about makes them so much better for us taller guys. Obviously, it makes them tippier, but everything is a compromise. I also think that the dirt bikes have the footpegs in the right location for proper riding position, or the KFX400, for that matter. The 250r and 350x footpegs and fenders are so far forward that you can't stand and ride on the balls of your feet very well.

[HK1837]

Thanks guys. I'll digest and will be back with some questions.

[Dirtcrasher]

Australia?? Poor fella, will you even be able to ride it? That country seems to be treating it's people pretty lousy these days, but pampering immigrants with all your tax dollars; Coming soon to the USA I imagine (Kalergi Plan). I guess kids there can't use the internet under the age of 16 now? Not a bad thing other than it seems to be a method of forcing a digital ID on the people. Best of luck to you, hopefully you're far away from the major areas.

[HK1837]

Australia?? Poor fella, will you even be able to ride it? That country seems to be treating it's people pretty lousy these days, but pampering immigrants with all your tax dollars; Coming soon to the USA I imagine (Kalergi Plan). I guess kids there can't use the internet under the age of 16 now? Not a bad thing other than it seems to be a method of forcing a digital ID on the people. Best of luck to you, hopefully you're far away from the major areas.

Plenty of places to ride it! I think Aussies are pretty well off. I think what you are seeing is BS from right wing media. Kids under 16 are free to use the 'web, they've just banned them from accessing harmful social media like Foolbook etc. Bullying on it is bad enough but pedos are reported to be using it for grooming.

[HK1837]

I tried to do some measuring on my DRZ400E bike but its too hard to estimate what the front end angles will be until I have the swingarm sorted. So I think I'll change track a bit and get the LTR450 swingarm modified and bolted up, then get the axle and rear wheel on and see what it looks like.

My current plan is as follows. In the images below you can see the brace at the front of the black (steel) LTR swingarm (both are upside down in the image), I'll cut it out and make up another brace to go across the arm that replicates the DRZ lower shock linkage point. I think I'll move it forward maybe 20mm which will push the swingarm further away from the frame. If I have to make adjustments to the height I can get two of the DRZ linkage arms laser cut shorter or longer to suit. I can buy these off the shelf for a DRZ but only longer ones which lower the bike.

All I have to do to make the LTR pivot fit is to machine 5-6mm off each end (on the outside only) - the distance across the engine in the middle is the same, and the ID and OD of the bushes are the same, just the OD of the alloy on the DRZ arm is bigger than the steel of the DRZ but that makes no difference. The LTR uses cups for seals but the DRZ are sealed internally. You can see the 6mm machining off the ends of the LTR arm will go into the weld but I don't think that will affect it. I'll use the DRZ bushes, washers and swingarm pivot bolt.

I haven't looked closely yet what the relationship between the engine sprocket and the LTR rear end sprocket looks like, if its close I will leave the LTR chain rubbers where they are. If it has to move across right by 6mm (which I think it does) I'll modify the steel of the LTR swingarm to take the DRZ chain rubber - it is only held in place by 3 x cups and screws (you can see one on the alloy DRZ arm to the right of the shock linkage mount). If it has to move right I'll just put a spacer ring between the axle mount and the sprocket to move it right by the same amount - plenty of room for that.