Suspension changes for a Honda ATC250r flat track trike

[Usmoneylover]

I'm in the beginning stages of starting a purpose built flat track / tight track 250r and was hoping for any help or advice, starting with suspension. I found this video https://youtu.be/3A0RF87ly6E online of someone shortening some conventional bike forks...they look very similar to 250r forks and I thought this might be the way to approach shortening my forks. My plan was to remove the short 3" spring from '85 forks and adding a 3" spacer to the pipe, seat, below the rebound spring, as opposed to cutting a spring as shown in the video. Is this the correct way to go about this?

I already have a Durablue lowering link and considered using it to lower the rear end 3" as well(assuming I should subtract the same 3" to keep the rake the same?), but have also considered having my rear shock internally shortened because it needs to be serviced anyways....I'm just not sure if it would be worth extra expense as opposed to just using the lowering link.
I also want to throw in this tidbit of info regarding the rear end and rake...I'm planning to use a -1" (18.5" ctc) LSR swingarm, will this affect the amount I should lower the rear?

Any info you guys can add would be great, thanks!

[bkm]

What tires are you running? Do you ride up on the tank, neutral, or on the back of the seat? This will have an effect on what length swingarm you will want to run.

[Usmoneylover]

What tires are you running? Do you ride up on the tank, neutral, or on the back of the seat? This will have an effect on what length swingarm you will want to run.

I would say neutral to forward for my riding position. I was thinking that the shorter swingarm would make it turn easier? My tire selection is still up in the air, but I was leaning toward the 15x8-8 hoosier rears with an 18" hoosier front. The main concern I had with running such small rear tires was gearing and the inability to run an upp case saver on the front sprocket because of the needed larger sprocket size.

Again, I'm open to suggestions and advice from more experienced racers/riders...Just looking for something that will perform well.

[bkm]

I ran a plus 2 and hated it. It would launch like a top fuel, but would unload the rear tires and spin too much in the corners. I went back to the stocker and liked it much better. I wanted to try a -1 but stopped racing before I could try it out. I'd go with the -1 if it's short course flat track.

I had a Selvy rear shock that was internally lowered so I could run the oem linkage. I've ran the lowering link, but it drops the linkage down low and reduces ground clearance. The downside to a lowered shock is it's always lowered.

I ran kart tires for circle track racing. It truly felt like it was on rails.

You're in the right track with the front forks. The 85 forks can be internally lowered by just swapping the top spring with the bottom out spring on the dampener rod, or spacers for the dampener. I had mine pushed up in the fork tubes, but didn't care for it.

Mike Coe ran a 350x front end on his 250r for flat track because of the leading axle and faster steering.

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[bkm]

This was the plus 2 calfab. I preferred the stock arm way more.

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[Usmoneylover]

Thanks for the input, your trike looks lean and mean! What sprockets did you run with the short tires? I saw some guys in the Ashtabula race running short tires and I always wondered what gearing they were running...I was under the impression the long straight could take a lot of speed.

[ironchop]

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How do you keep from hooking wheels with the guy next to you? You must have more skill than me cuz I'd have that all tangled up by the third turn

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[bkm]

Thanks for the input, your trike looks lean and mean! What sprockets did you run with the short tires? I saw some guys in the Ashtabula race running short tires and I always wondered what gearing they were running...I was under the impression the long straight could take a lot of speed.

I ran 14 front and 38 rear, but I also ran on a tight indoor bull ring circle track, so I left in 3rd gear and immediately shifted to 4th and ran the whole track in 4th. When I ran the TT track I used a stock front tire and 16" H-Track rear tires. Several guys have had custom sprockets made for the rear to run the Kart tires on the larger tracks.

[bkm]

How do you keep from hooking wheels with the guy next to you? You must have more skill than me cuz I'd have that all tangled up by the third turn

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Nothing but the wind to tangle with when you're out in front of everyone! LOL In all seriousness, I raced with some really clean racers who didn't do a lot of rubbing, plus those small tight tracks get single file after the first few laps. I only raced one season, but miss it every year right around this time. Responsibilities suck!

[Billy Golightly]

I ran the 85 spring setup in mine and just took the 3inch spring sections out and put them under the dampening rods (basically a 3in shorten internally without making anything permanent). Then slide the forks up inthe clamps maybe another inch, inch and a quarter.

On the rear I just always ran an adjustable link from Durablue. It does soften up the rear suspension from the linkage ratio change, so you get more squat in the starts than necessary and its not advisable for TT, but for circle track I had good luck with it.

I ran stock length arm on the clay ovals I raced one. I could see a -1 being useful, but never got to that point with mine.

[Usmoneylover]

I ran the 85 spring setup in mine and just took the 3inch spring sections out and put them under the dampening rods (basically a 3in shorten internally without making anything permanent). Then slide the forks up inthe clamps maybe another inch, inch and a quarter.

On the rear I just always ran an adjustable link from Durablue. It does soften up the rear suspension from the linkage ratio change, so you get more squat in the starts than necessary and its not advisable for TT, but for circle track I had good luck with it.

I ran stock length arm on the clay ovals I raced one. I could see a -1 being useful, but never got to that point with mine.

Thanks for your Input...My suspension knowledge is limited, do you know what the effect of putting the 3" spring under the dampening rod VS. removing it completely and putting a 3" steel spacer under the dampening rod instead?
In theory, the shorter swingarm should give less leverage to the shock, so maybe that would help some with the linkage ration change?

[bkm]

Thanks for your Input...My suspension knowledge is limited, do you know what the effect of putting the 3" spring under the dampening rod VS. removing it completely and putting a 3" steel spacer under the dampening rod instead?
In theory, the shorter swingarm should give less leverage to the shock, so maybe that would help some with the linkage ration change?

The spring on the dampener is for rebound. Without it there would be steel on steel hitting upon rebound. You can do the spacer, but you still have to have a spring under it.

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[Dirtcrasher]

I'm running a 450R swingarm so that's a plus 2.25 for 04/05 swingarm, and plus 3 for 2006 to 2014 TRX450R swingarm.

It's on my 350X and that's where your base measurementd are from.

It turned HORRIBLE, tossed it back in the Toy Hauler and raced my 200X instead.

I would like a minus 3, so I'll probably build my own....



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[Usmoneylover]

A little update on this project...ended up having a rear shock rebuilt and shortened internally. Picked up some tires as well: t30 16" Hoosier rears and 18x5.5x10 rd20 front. I have a freshly rebuilt front hub and rear dual row carrier ready to go.
I'm close to having it up on tires...I have the parts to rebuild the front forks and looking at spacer material to go under the rebound spring. Any opinion on using PVC, aluminum or steel?

[86T3]

Those t-30s will suit you well, i ran them for the last year and a half on my 450. If you feel you need more forward bite while you are sliding you can cut 45 degree angles on the outside blocks. That front is a good choice too. I can answer your fork question, sorry. Where are you planning on racing?