So I took the 90D driven off to adjust the spring preload. Damn if I just could not get that thing apart. I followed the instructions and I used the largest gear puller I had but that helix did not even budge. What I also realized is that my 90D did not have the multiple holes for the spring adjustment. I'm assuming that is because I bought the version that was designed specifically for the FL250 so it's probably pre-adjusted from the factory. So what I did was drill another hole about 70-degrees counterclockwise from the original hole. Then using flat screwdrivers I was able to carefully pull the spring out of the original hole and let it slip around to the new hole and push it in. It was not that hard to do and really, I could've probably done that without even removing it from the input shaft.

After this latest adjustment, I have to say that this thing rips pretty good now! The CVT starts shifting almost immediately now and once it does you can really feel yourself getting pushed back into the seat. I feel like the CVT could still be adjusted a little more but I'm going to run it like this for a while. It's a blast I couldn't be happier!

Short video of a test run.

Now that I got it running pretty good, I figured it was time to class it up a bit. I used some SEM color coat plastic/fabric paint to refinish the seat. I used my 3d printer to make the Honda logo template. I'd like the logo to be a little brighter but it looks decent in person. I might go over it with something else later on to make it pop better. I didn't bother with the headrest because that'll be coming off -- when wearing a helmet it's in the way...

Got a better video here of my brother taking off on it.

https://www.youtube.com/watch?v=xqFOjA5HJcs

Been crossing more items off my todo list...

Freed up the parking brake
Installed hub spacers in the rear to widen the stance about 7 inches total
Installed tubes in the rear tires
Painted the wheels (so so job)
New tires up front
Gauge panel w/ tach, GPS speedo, voltmeter, and oil temp gauge
Fab'd undercarriage pan to mount battery low and forward for better weight distribution

I don't have pics of everything, but here's the battery pan:
I'll also mount the fuel pump here and anything else that needs to be securely mounted and protected


here is where I mounted it


gauge panel

good job, have fun with it

Thanks! Yes, I'm having tons of fun. This is probably the best project I've gotten into in years. Unlike my car projects, as I cross things off my list, the list actually gets shorter instead of longer! All hail the F250

I picked up a set of rim spacers on ebay. I drilled out the threads on the hubs and tack welded in larger grade-8 bolts for strength. Also mounted the rear fenders with spacers.

Been enjoying this buggy as much as I can with the crappy NE winter weather. I'm really happy with it, it's lots of fun! Once the weather gets a little warmer, I've got some more mods to planned: I bought a spare set of heads and had them ported and milled by performance670.com. I got a set of dual Mikuni 26mm carbs and plan on fabbing long intake runners. And I got a custom gearset that will work better with the 4-cycle's RPM range. I'm hoping the porting, increased compression, and extra CFM will put me over the 30hp mark, but who knows.

Here's a vid of some night riding through the woods. I love the sound of the v-twin https://youtu.be/J5p37VFGVtA

The latest on this project:

I installed the milled and ported heads along with a set of stiffer valve springs. I had to sand down the intake manifold so it would seat correctly to heads. After putting them on, I took it for a ride and the thing sang right up over 5k RPMs and promptly died. I was like, WTF?? It started right up no problem, but upon another WOT (Wide Open Throttle) pull it shut off again. What I eventually determined is that the Engine has a rev limiter somewhere in its very limited electronics. After disconnecting the kill wire, it rev'd just fine.

So the head work and valve springs definitely woke it up and allowed it to produce power out to 5k. Prior to that, you could really tell that after 4k the torque was dropping off. But that wasn't good enough. I really wanted to try something (even more) different -- a long-ram dual carb intake. So I put to use my new-found (and limited) skills of 3D design, 3D printing, and lost-wax aluminum casting. After several resin prototypes, I cast an aluminum two-piece manifold and used Alumiweld to join the tubing. Feeding the intake is a 24mm and a 34mm PWK carb controlled in a primary/secondary arrangement by a cam that I also designed and 3D printed.

It was a LOT of work and I had no idea how the result would be. I was preparing myself for disapointment. Fortunately, it worked! And not only did it work, it did give me a boost in power. So much so that I felt it was time to rebuild the reduction unit and install the alternate gearset. With the new gearset it has a top speed of about 45mph which is plenty fast for this chassis and it pulls hard.

My brother and I did a few drags with it against my mostly-stock FL350 and the FL250 would leave it in the dust from a dead stop because it digs in and just goes while the 350 does a lot of spinning. From a rolling start, they seemed pretty equal.

So I think I finally have this FL250 where I want it. I consider the project complete but not finished. The carbs still have the factory jets and needle adjustment so may benefit from some fine tuning. Overall it needs to be cleaned up and I need to fab some Engine shrouds to help with cooling and maybe a larger oil cooler.

It's kind of a crazy set up I admit, but I (mostly) enjoyed the work and learned some skills along the way that I'll use on future projects -- and that's what it was all about!

Nice!

Here's the intake...not pretty but it works!


Here's why I wanted to try a long ram intake


My intake runners are approximately 26" long

Also, I used thin metal head gaskets instead of the thick stock ones. I run 93 octane fuel to avoid detonation. I didn't actually try 87 since I changed the heads but would rather be safe than sorry.

I wanted to change the rockers to a higher ratio but just couldn't find any that would fit.

Damn! You've taken tunnel ram to new lengths..lol I would be interested in seeing how long you could go before it hurts performance.

hehe...yeah I don't know about that but it'd be fun to experiment on a dyno. I bought a bigger carb (40mm) for the "secondary" to see what kind of difference it makes vs. the 34mm. I figure 64mm total carb bore is more appropriate for the 713cc displacement.

I've offically named this thing the "FLankenstein 250"

I'm noticing a new problem though -- I think the belt is slipping as it shifts out. It seems that once the Engine hits about 4k, it quickly wings up to 5k while the vehicle speed increases more gradually. Hrmph! I'm guessing the slippage is at the driven since I took a bit of tension off the spring to get it to backshift more slowly.

Should be easy enough to test, just put it back the way it was and see if it reacts.

It wouldn't be to easy to put the old intake, carb, and linkage back on...

I think what I need to do is adjust the weights on the primary and the spring on the secondary. I had reduced the tension on the secondary spring quite a bit to get it to help it shift out at a lower RPM and backshift later and I may have went too far.

I may also need to do just a general service on both.

I meant just the tension on the secondary spring.

ooooh hehe ok, my misunderstanding.

I cleaned off the clutch faces with Acetone and replaced the belt and that took care of the slippage. She pulls good now. I don't know if the previous belt got some oil on it or what but the surface feels slick compared to the new one.

One thing I realized was the mount on the steering wheel shaft for the front tie rods was bent, probably from someone hitting a rock or something. This being the only FL250 I've ever seen in person, I had though it was supposed to be curved upward. I heated it up and banged it flat which very much improved the steering.

I'm going to be taking her to an ATV park tomorrow for her maiden voyage so I spent some time getting it all neatened up and adjusted. Here's better pics of the dual carb setup. I'll try and get some vids of it running. It sounds good. It's amazing how cool the runners are after some WOT (Wide Open Throttle) runs from the evaporative cooling of the fuel. I've already seen condensation on them.

Short video of take off

https://www.youtube.com/shorts/5GlX9fTA018