Sprockets build: Drag scooter

My trip to Twist and Gone last weekend inspired me to put my Ruckus build plan on hold, and start working on a drag scooter for next season.

The fast two-stroke scooters I've seen tend to be very finicky, and I'd rather have something I can haul out, run, and, load back up without too much drama. So, I'm using my Honda Elite 250 as an engine donor. The engine/trans is going to be heavy, but it makes 19 HP, so should run with the mid-level two strokes, without too much trouble, if I can get it in a light enough package. Which brings me to this:

Its a 1989 Honda Elite E Moped/Scooter. It was intended for states that don't require registrations for vehicles with a sub-50cc engine, and a top speed of 30 or so MPH. Unlike most modern scooters, its a direct belt drive, no variator, so it only has one transmission ratio. I took it out for a quick spin in the neighborhood, and it has pretty much no pickup up until about 10-12 MPH, then it starts to move a bit better, and climbs to 30 pretty quickly. Its extremely maneuverable at low speeds, almost too much so. Took pretty much no effort to take a turn and I almost dumped it because I was expecting a bit more resistance. This makes the Ruckus seem like a fat pig. The main reason I bought it, it weighs under 110 lbs. The Elite 250 weighs about 280 lbs.

The plan is to modify the rear frame of the E to accept the bigger engine, and try to stuff it mostly under the bodywork, but I will be stretching the wheelbase some for stability. I'll probably use a lawn mower gas tank for fuel, and the stock radiator may not fit in the nosepiece of the smaller bike, so I may need to hunt for a smaller one. The engine will stay fairly stock, at least in the beginning. I want to make sure I've got the chassis squared away so its safe at speed.

Size comparison for the bikes:

I've ridden a 250 Elite so this looks like it will be fun!

Graefin10 wrote: I've ridden a 250 Elite so this looks like it will be fun!

For a scooter, they have quite a bit of get up and go. I'm hoping the combination of them will be somewhere in the 150 lb range, so that engine should really move something that weighs 130 lbs less than stock

Well this is going to be awesome.

Had some time yesterday to take some measurements on the small scooter. Today, I started tearing bodywork off. Started with this:

And it didn't take long to get to this:

I also pulled some of the bodywork from the big bike, in order to take some measurements of the engine:

In order to fit under the body of the smaller bike, I think I'll have to remove the airbox from the engine.

The wheelbase of the smaller bike is about 43", and the larger bike is about 50", so 50" will probably be my minimum for the drag bike setup. The engine mount to rear axle distance on both bikes is only about an 1" different, although the mounting point is on top of the bigger engine's case, and the bottom of the smaller ones. I'll need to build an adapter mount with at least a 6" stretch, but it might need to be a bit longer. Based on the height of the 250 engine, the cylinder head might bump into the frame if I try to make the ride height reasonable. However, if I stretch it a couple of more inches, it can go up through the hole in the frame where the gas tank sits. With that stretch, about half the rear wheel will be sticking out of the rear bodywork.

The possibility of a long stretched mount also gives me a few more options. I was originally going to put the radiator in the nose, but might be able to tuck it under the bodywork in front of the engine. I'll need to enlarge some of the holes in the side panels for more airflow, and I'll lose some coolant capacity by not having long cooling tubes, but the bike never ran hot at all when I rode it, so I probably have some margin. Not too mention, it'll mainly get exercised an 1/8 mile at a time.

The trunk will get retained, but I will cut out the bottom, and use it for the battery and the new gas tank. If I can find a .25 gallon tank, maybe for a weed wacker or chainsaw, I'll use that. That should give it a 10-15 mile range.

I'm likely going to switch down from a 4X10 tire on the rear to a spare 3.5X10 I have laying around. There's a chance I'll lose a little top speed, but I suspect the Elite 250 was drag-limited on speed, not RPM limited.

At this point, I am tire of trying to measure, and think I need to just pull the engines and start mocking things up. Before that, the garage needs to be cleaned and organized a bit, so half a garage bay is available for both welding, and working on the rallycross car at least partway out of the winter weather.

I also need to figure out what to do with the Elite 250 chassis. Its heavy enough it could be fun to find a wrecked maxiscooter, and put a really big engine in it. Also, there is the issue of the 50 engine. I should probably craigslist it, but its kind of tempting to hold onto it and see if I can build a reverse trike go-kart.

Did some more work today. Drained the gas tanks on both bikes, and the oil tank on the small scooter. Both have vacuum petcocks, so I just hooked up the mityvac to drain them and didn't make too much of a mess.

Also pulled the tanks and the engine from the small scooter:

Also, I found there is a separate engine mount between the engine and the frame:

This should be a great base to fab up a new mount for the bigger engine. I can mock it up, and possibly tack weld it together on the scooter, then pull it off to fully weld it.

Not sure how much work I'll get done in the next week. I need to get back to working on the Neon soon.

I'm finding myself drawn more and more to scooter projects. I picked up a cheap 50cc chinese scoot to keep down in Pensacola to run around when Im there but I'd like to get a project to play with up at home eventually.

Watching with great interest.

I am enjoying the build as well. Cheap, readily available, and small so you can have more than 1

I like this!

Having fooled around with scooter modification, I'd suggest that you're going to want larger diameter wheels (at least a larger front wheel) and a significantly stiffer front fork.

In reply to JThw8:

The hot ticket for a modded street scoot seems to be the 94-01 Honda Elite SR. The AF18 engine in them shares most of its parts with the AF16 used in the rest of the world. 90cc is possible without having to crack the case and grind out some clearances.

Of course, if you're happy with 50-55 MPH on a small two stroke, a Yamaha Zuma or a Genuine Buddy 50 with a 70cc kit and some other work is probably the easiest option. The Minarelli engine in them just tends to get a lot more expensive than the Honda once you start pushing the boundaries.

In reply to Billy_Bottle_Caps:

You're telling me, I'm up to 4 of them at this point

In reply to Woody:

I think you are right about the front fork being stiffer. I may see if I can install some spacers and just cut the stock springs. I'd like to stay with the stock front wheel, as its nice and light, heck the brake drum is actually part of the wheel. Fortunately, this one won't get much street time, except for a little testing, so it just needs to be stable enough to track straight on the dragstrip.

Talked with one of the other racers to get some ideas, and got some motivation tonight. The Elite 250 has undergone a significant weight loss:

Took a bit more time than I expected, and at first, I disconnected the wrong bolts to remove the engine, but eventually got it done. Hefted it up on to the trailer to do a quick mockup:

I'm probably going to go with closer to a 9" stretch in order to get it fitted the way I want. It looks like it will create quite a bit of leverage to do this with just the stock mounting location, so I may triangulate it into the stamped steel part of the frame. If so, on the opposite side of the triangulation, I'll run a brace up to the front fork, preferably at the same angle.

The electrical bits related to the bigger engine also take up significantly more space, so if they go under the bodywork, there won't be room for the radiator, so I am back to having it up front. If so, there are two possibilities. One, cut open the front panel, and mount the radiator into the hole. Two, run the radiator behind the front panel, and try to duct air from the fender. Either way, I'll be cutting vents in the leg shield to let the hot air out. I'm also not sure there's room to run the radiator the second way, which would be nice, though, to keep the bike clean looking.

Also, looking at the photo above, the suspension mounting points are going to be at a fairly extreme angle. I'm going to run hollow tubing with threaded rod ends in order to allow minor adjustments in rear rider height. They are going to mount to the tubing that makes up the area that held the gas tank. My compatriot mentioned that its probably too weak to use to mount the suspension to without some reinforcement, and I tend to agree with him. Not sure if I'll use some gusseting around the bottom of it, or if I'll try to tie something into the reinforced engine mount. I have some time to figure that one out.

And lastly, I think the trailer is too short to be building this on. After the Neon is squared away for the winter, I think I'll build a longer table to work on the bike. It'll make mockup a lot easier when I'm not worried the engine is going to slide off.

eastsidemav wrote: In reply to Woody: I think you are right about the front fork being stiffer. I may see if I can install some spacers and just cut the stock springs. I'd like to stay with the stock front wheel, as its nice and light, heck the brake drum is actually part of the wheel. Fortunately, this one won't get much street time, except for a little testing, so it just needs to be stable enough to track straight on the dragstrip.

What I meant was that you need to control the fore and aft flex. Going fast on a scooter can be a frightening preposition.

In reply to Woody:

Most of the fast scooters use a brace between the front fork and the rear upright area to stiffen them up to reduce flex. I'll be doing that for certain.

Also, it turns out that the guy I talked to just removes the springs inside the front fork, and runs no suspension up front. I'm not sure I'll go that far, but I'm tempted to cut one of the front springs in half and use one piece each to lower and stiffen the front suspension. Another possibility may be to remove the springs and see if i can use somethong like poly bushings from early mountain bike forks to still have a small bit of front suspension travel.

Got a little work done on this project today. I've been taking measurements, and started working on a jig for welding up the engine mount:

Need to take it apart to take a few more measurements. After that, I'd like to wait until weather is a bit better so I can do grinding and metal cutting outside, but I'm not sure there'll be a good time for a while, so I may just have to set up shop inside the garage.

eastsidemav wrote: Fortunately, this one won't get much street time, except for a little testing, so it just needs to be stable enough to track straight on the dragstrip.

It's pretty awesome that you can safely test your "race vehicle" on the street without much fear of harm to the general public, or anyone actually thinking you're racing, for that matter.

petegossett wrote:

eastsidemav wrote: Fortunately, this one won't get much street time, except for a little testing, so it just needs to be stable enough to track straight on the dragstrip.

It's pretty awesome that you can safely test your "race vehicle" on the street without much fear of harm to the general public, or anyone actually thinking you're racing, for that matter.

Well, it'll be fast, for a scooter. However, a V6 Camry would be able to annihlate it in a drag race...

In reply to eastsidemav:

Unless that V6 Camry kept blowing up motors!

In reply to sethmeister4:

Ouch..too soon?

BBC

I was thinking about something similar, but when the words "radio flyer tricycle" and "chain saw engine" were mentioned in the same sentence, the wife got pissed.

N Sperlo wrote: I was thinking about something similar, but when the words "radio flyer tricycle" and "chain saw engine" were mentioned in the same sentence, the wife got pissed.

You could always build a drift trike. I'm thinking of making that my next welding project after this is all together.

Got an above freezing day yesterday, and Ashyukun came up to help, so I was able to open up the garage door, and run the grinder, chop saw, cut off tool, and welder.

Got the main part of the engine mount made, unfortunately not after cutting one piece wrong and having to start over.

Everything still seems to line up properly, so next time the weather warms up enough, I'll be able to finish the mount, and move on to the shock mounts. Really hoping to get some more fab time in soon, I figure once its done, the rest of the work will be easy to do in a closed up garage, so my space heater might actually have an effect.

Finished the engine mount tonight, with help from wae. Tomorrow, I'll reassemble everything and make sure it all still lines up. At least this weekend is going to be warm, so I should also be able to paint it, instead of waiting until spring.

Next step is to build something to replace the shocks. I've got a rough idea, and just need to figure out if it'll work and be strong enough:

Managed to get some work done on the rear suspension links today. Most of my time was spent making the 4 U-shaped brackets that will be welded to the frame and used on the link to mount to the shock mounts on the engine. Between having a weak, cheap drill press, and having to cut with an abrasive saw and an angle grinder, it's not all pretty, but it should work. If I do much more stuff like this, I think it'll be time to look for a metal-cutting bandsaw.

Would have gotten more done, but the police showed up across the street about halfway through my work, and since I'm friends with those neighbors, I decided to be nice and not run loud power tools while they were talking to the officer in their driveway. With any luck, I should be able to weld things together this weekend.

Finished up the rear suspension links and brackets, and welded the brackets to the scooter today. The links are slightly different than my original design, but pretty close.

Getting the brackets lined up evenly on the scooter's frame was a bit of a task, but in the end using a piece of 3/8" allthread and some nuts to space them out properly, then very carefully measuring and adjusting the brackets' locations before clamping them in place to weld worked out well.

After everything cooled off, it was time to reattach the engine and the frame for the umpteenth time, but at least everything went relatively smoothly. I may need to shorten the links a bit, but I'll wait until I'm closer to done to be sure.

Judging by how high I ended up having to set the welder to get a good weld on the frame, the tubing is pretty thick and strong. However, I am thinking of doing a little bit of bracing. Here's pieces of 3/4" and 1" square tubing to give a general idea of what I'm thinking of doing. I'm leaning towards going with some L-shaped steel, though, so it'll be easier to build a battery tray on top of it.

Other than the bracing for the rear suspension, and a brace between the front fork and the rear frame of the scooter, major fabrication is finished. It'll just be a matter of stuffing a battery, radiator, radiator fan, radiator overflow tank, ignition circuitry, and a small gas tank under the bodywork. Should be easy, right?

Spent a little time in the garage before the big freeze hits here, and welded up some bracing on the rear frame to beef it up where the rear suspension connects. I don't think its needed, but it can't hurt, and should make a good base for a battery tray.

Not sure when I'll get more work done, but at this point, I can work with the garage door closed, so I don't have to wait for the weather to cooperate.