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Picked up a 2003 Suzuki LTA50 for my Granddaughter.
She's not as ready as she thinks she is so I have the Winter to tinker with it. Seems well built like our LT80's. Tiny little thing, perfect for a 3+yr old. Rolled right into the back of our SUV. Came with a set of brand new Skat Traks. Apparently it still had the long nubs on the paddles cuz it didn't have the power to drive them. The engine is a piston port design from the late 70's. Reliable and adequate for a tiny tyke to safely learn the basics like brake, brake and brake. CT Racing says the hp is around 1.2 stock and with their milled head, air filter, jetting and really beautiful pipe it will produce 2.6 hp. Double the hp seems like a real good improvement. I couldn't justify buying that kit on my cheapskate budget. After applying most of the simple online mods and a couple of my own it will carry our LT80 riders around on our more casual trails. I've read that it's not worth the time & cost to try to significantly improve the power. Looking inside says this thing will never be able to breathe well. That said, I can't seem to leave well enough alone. My goal is for it to carry a 50 lb child around most of our dunes for under $100. Sand eats power so it may be a unreasonable quest. So here's the Winter plan. Install a reed valve
A buncha reworked cheap China stuff. Reed cage manifold, LT80 carb, rework the piston, head & cylinder kit. Build a matching pipe. * New faux Top end kit. $30 * New faux LT80 carb. $15 (btw, this is the cheapest way I could find to buy a replacment float for a LT80 carb) * New china Reed cage. $10 * Chunk of alum $17 ( this really hurt as I didn't have a scrap around and it's the only quality part used) * New Air Filter. $14 * New Reeds. $18 > over my $ limit, didn't want the steel reeds that came with the cage. Got carbon fiber reeds. Pipe materials = salvaged sides from old file cabinet.
_______ Fab _______ * Reed cage manifold. (done) * Reed cage stuffer. (done) * Plastic reed cage to manifold adapter. (done) * Carburetor to Air filter adapter (1" to 1 1/2") (done) * Expansion chamber * Spark arrestor/ muffler
DIY reed valve assembly _____Tinker_____ * Mill head * Expand & add a few things on the cylinder. (Haven't decided on exhaust port timing) * Cut piston window (done)
* Inspect clutch for mod possibilities (drill shoes?).
Found something that bugs me. The exhaust & transfers are still partialy covered at BDC by about 2.5 mm. Seems a pretty big chunk of a port. Same on stock cylinder/piston and 2 aftermarket kits. I can space it up and machine the deck but don't know what raising the top of the ports will do on this old piston port. The port timing looks pretty sad in the exhaust calcs. Don't understand piston port engines, is this normal? ? Maybe a production change, doesn't make any sense. ? Is this something common in piston port engines? ? why block 20% of the port size? Maybe a simple way to increase volume and be better at low rpm?
Made a .080" spacer & .020" gasket. Decked cylinder .100". Top of piston now aligns with bottom of ports at BDC. Going to put it back together with oem pipe to see how that compares to stock. No noticeable improvment. Now I have port & timing specs to build a pipe and compare that to stock. That will give me a base line to compare the next stage to. Fabricating a pipe has been kinda fun. Motor research with a degree wheel and some patience. Plug the results into the software and play for a couple weeks hoping to learn something. When you finally come up with something that might suit your needs it's a series of pieces in a line that might result in a tuned pipe. All the dimensions needed to cut the pieces. I used an old vinyl cutter & junk vinyl to plot the parts and transfer to the sheet metal for cutting. After cutting, you roll them into cylinders & cones. Another learning curve : ) (you will also need a flange to bolt to the cylinder and a muffler/spark arrestor) These parts line up into a straight pipe. I can't imagine anything that could use a straight pipe .. so .. you need to cut up your nice pieces and weld them back together in a way that fits your project, has smooth bends and maintains the tuned lengths. Yikes, don't forget to compensate for material removed when you cut. Need to do that before plotting your parts. Need to know how many cuts needed to make your bends. Watch out, things tend to shrink, twist & get weird as you weld thin sheet metal. Need experience to know these things. Get lotsa experience making mistakes! I am now an embarrassed amateur pipe weaver .. whatta mess! If you're short on patience & have a short fuse this won't be a relaxing hobby. I think home brewing helped stabilize my welding hand. I'd planned 2 practice pipes for the LT50. A fat high rpm type and a low angle wide band to compare to stock. The fat one looked kinda cool, was very loud but didn't seem to produce more power or rpm. The skinny one was an improvement over stock. No re-jetting. Both produced light brown plug color on the uphill return run. I have no dyno and my test drivers are very young, biased and aren't around at the moment. That means the results are just my opinion and mostly bs. Hoping to use what I learned from this to build a functional pipe for the reed cage mod. Need to take a break for awhile, then come up with a final pipe plan. Much different exhaust port & header pipe diameter. Should be fun.
Got the pipe for the reed engine welded up minus mounting brackets. Building the practice pipes paid off. Learning how much material I lost cutting each bend let me figure that into the cone patterns. The distance from the flange to the belly involving all the bends was only .055" off the calculated length. That's 26 cuts, sanded true, rotated & welded. I be Mr lucky. You can see the difference at the flange. Stock exhaust port ID is only about 1/2". Spent more time getting a better fit so it won't melt the plastics. I'll play with the stinger after it's running. That's if it does run. That's next. Put it all together. Set squish & compression. Hope it will start.
Decided to run most of the stinger inside the baffle cone. Still maintains the tuned lengths, fits the bike in stock location and should be a more durable assembly. Muffler/ Spark Arrestor * Outer skin = ss bbq salvage * Baffle screen = microwave window screen * Stainless fine spark screen = brew basket remnant * Alum screen packing = satellite dish salvage * Tubing = salvage lawn awning frame * Cleanout cap assembly = top of dried out PVC glue bottle * 2 Brand new Chevy freeze plugs! ($3.60) * 8 stainless button screws ($2.40) Inspection port, cleanout or open pipe?
Dual pipes & a cutout baby!
Put it all together to test fire. Tight fit everywhere, this thing is tiny. Some pix of the reed assembly. Kinda funky but I'm limited to basic tools. This first test is with the muffler cap on so it's as quiet as it gets. The muffler is working. It's crazy loud as an open pipe with the cap off. This is a new LT80 china carb I've done some work on. The jetting is just my wild first guess. Seems kinda flat at low rpm but really wants to rev .. won't know where it wants to rev to till it goes through afew heat cycles. So happy it even runs!
So it's down to tuning and some clutch work. I broke the training kill tether mounting one of the practice pipes. Replacing it with a wireless relay. Much cheaper and works from the lawn chair. I want to thank the Gentleman that shares his 2-stroke knowledge as AuMechanic on YouTube. This expansion chamber is the result of watching his educational videos and using his expansion chamber design calculator software. I've learned so much and it works. Check out his stuff. Guess I've used up enough of your bandwidth. Just thought I'd share this project while so many of us are home for the Holidays and hiding from Covid. We can do many things with what we already have, a little imagination and no fear of failure. Be safe! Didn't want to melt the plastic or burn little legs. Formed this heat shield from an old highway sign.
Just a little puzzled as to the purpose of your machine, as a standard LT50 is fast enough for the size of child it is meant for. However a superb job, the time and craftsmanship displayed is extremely impressive, particularly using scrap materials, much easier to buy new stuff than to see the potential in an old microwave screen or glue bottle top.
I don't really believe you're puzzled, but I understand your need to express concern. I suspect a large percentage of 50cc forum threads are seeking a bit more power. They're slugs. The purpose of the machine remains the same. Train and entertain the kids. Their skills develop quickly but some aren't physically big enough to move to an LT80. Most 50's and a lot of 80's don't ride the dunes. They stay in the flat sand around the parking area. More fun if they can tag along and explore with the Family conga line. The little screw on the thumb throttle remains. The wireless kill switch allows an adult to lead or follow with the ability to shut it down. Safety is always the primary concern but the safest way to deal with quads & bikes is to stay off them. And, yes, this is kinda an obsession with me but I call it a hobby. I've been tinkering with our Blasters & LT80's for years. Building a alcohol LT80 wasn't necessary but we had some fun with it before it went back to gas. Kids are always interested in what's new and excited to do some testing. I don't just attempt to improve power & brakes. I add lights and horns and stickers that add smiles to the learning process. Thanks for your concern and the nice words. Happy New Year!
A problem I knew I would have to face turned out to be a pain in the # .. the air & idle screws are on the opposite side of the LT80 carb. Impossible to tune with the plastic on and almost as bad with it off. Top engine mounts where in the way. Since I've been welding cones I made up a couple tuning cones & tubes. Now the tuning tool slides through a small hole in the plastic and is guided right onto the screw. Think I have an air leak .. I'll run that down and put a new crank seal on the left side. Drill some holes in the clutch shoes and wait for some kids to stop by for some real testing. The crank seal made a wrong turn with USPS. Tracking says "Mis-sent"
So, I did lighten the clutch shoes. I knew the LT had a damaged swingarm when I got it. Took it off to see about repair. Their welds didn't penetrate and the cracks were now extending past the welds. It was such a mess it had to be replaced. Years ago we had Works shocks on our YZ Blaster. One blew out on my Son at the Winchester Bay dunes. Threw'em in a tub & fit YFZ shocks. Got to thinking if I could find those shocks maybe we could re-purpose one for the LT and build a swingarm to match it. While searching for the shocks I came across aTrail Tech Vapor. We Used it on the Blaster when we where testing things like timing, pipes, carbs, gearing, methanol & such. It senses RPM, temp & MPH with memory which gave us a bit of a base line. Was good fun. Took another couple days to find the sensors that connect to it. Anyway, thought it would be interesting to hook it up on the LT so we can see what kinda rpm it's turning.. The shock got some internal changes, slowed the rebound a bit, the stroke shortened, fresh oil and 250 lbs of nitrogen. Took it apart a few times playing with the valving and tried some different spring combinations. Settled on a LT80 rear spring and made a spacer instead of a second spring. The LT80 & 50 springs appear to be the same rate with the 50 having a smaller coil diameter on the bottom seat. I think it's a good setup with room to adjust the preload up or down. The results are double the stroke of the OEM shock. Should be good for 50 to 90 lb riders. This is not a pit bike for adults. LT50 compared to LT80 sprung Works with spacer.
The new swingarm is extended 1 1/2" with the shock mount relocated to work with the new shock. Larger tubing and heavier gauge. It's a little crude but it's true & stout. I didn't get a chain guard with the bike so I didn't weld on the mounts. The LT50 key switch just grounds the ignition circuit so I changed it for a LT80 switch that also has a 12v circuit. That might save the battery pack from discharging all day. Also added a on/off switch & LED for the remote kill switch so we can see when it's active. Finally got the crank seal so I'll start putting this thing back together and see what we got. If this thing is functional I might have to splurge on a graphics pkg and call it done. Just waiting for new graphics.
Good point. None on any of my real ones either. Cheap china knock offs have one. Came in handy in this case to see if it was rich or lean at low rpm. Maybe? If it fails I'll steal the float I need for a real carb.
Nov 26, 2020 | 11:57 PM
LT50 to reed valve (rambling)
