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Stuck Rings

by Bitter, October 25, 2006 in Performance, Engines, Engine Swaps, Cornering

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my GF always wears her helmet and gloves, she'll be getting a full face and some leather this spring.

psst i dont ride it, she doesnt drive MY car and i dont ride HER moped, but we do work on each others things.


my GF always wears her helmet and gloves, she'll be getting a full face and some leather this spring.

psst i dont ride it, she doesnt drive MY car and i dont ride HER moped, but we do work on each others things.

Not even to test it?

nope! i like 4 wheels on the ground!

just thought that i'd update.

the carb was bored to a full 14.2mm all the way through and the intake elbow bored to match as well. the carb used to be 14mm engine side and 12mm choke side. the new stock exhaust is on as well as a brand new topend which increases the engine size to 75CC. the moped now goes 35mph and with the addition of a chambered exhaust which is tuned it should be able to hit speeds in the 40's without re-gearing, possibly touch 50 with less reduction of the engine rpm.

the 75cc kit not only increases displacement but it also raises compression to 12.1:1 and i'm getting a compression reading of 185-190 psi now that the kit is broken in. its noticeably harder to pedal start, infact its less of a pedal start and more of a kicking of the pedal whjen its on the stand.

i bid on and won on ebay a larger carb with 2 stage jetting, idle and a high speed jetting (more control) and also a high compression head with much larger cooling fin area so overheating wont be a problem with a higher power output. the more power the more heat!


The problem with scooters, mopeds and even motorcycles is that they are more vulnerable to the outside elements such as weather, road surfaces, bad drivers, etc. They don't have as much protection from the environment and they are also less visible.

They sure are good on gas and fun to ride!!

I might have suggested Seafoam, Yamaha Ring Free or Mercury QuickKleen (QuickSilver) if the engine were still running. I believe these products were designed for 2 stroke marine engines to relieve the combustion chamber from excessive carbon buildup incurred during low speed operation.

Hey, i have a piston with some stuck rings and I'm wondering what i can do to get them unstuck. i've tried some mechanical methods, picks, tapping with a hammer, rolling against a cast iron table while tapping with a hammer. nothing! so now I'm soaking it in ATF, i let it sit overnight in the cold (freezing up here now) and then i microwaved it for 3 minutes till it was very hot and its still soaking. if this doesn't work, what else should i try?

when i was searching i found some WEIRD home remedies for rust, such as a dilution of water and molasses to remove rust. i may try it on the crankshaft of this engine since theres some hard to reach areas of it.

if you're wondering, the engine is a 1977/78 Minarelli V1. the stuck rings and rusty crank are the parts engine which I've split and setup for testing

I'd like to try to save this piston since its in good shape. I've been working the cylinders lip down to raise compression, and with this mock up and a few more bolts and nuts and a aluminum head gasket i can check cold compression off the engine to see how much I've raised the compression.

nah, there was no way that engine would have ran at all. there was engine coolant in the gasoline which was rotten, the bore was rusted, the piston totally seized, etc. even the magneto side of the case was cracked! it had been abused and broke but i only paid $10 for the whole moped. as spare parts.

The problem with scooters, mopeds and even motorcycles is that they are more vulnerable to the outside elements such as weather, road surfaces, bad drivers, etc. They don't have as much protection from the environment and they are also less visible.They sure are good on gas and fun to ride!!
yea, she loves it. its going 35mph now. i paced her in my car to verify her mechanical speedo and its as inaccurate as the speedo in my car default_tongue its reaching topspeed in about 1/2 the distance it used to take to reach its old lower topspeed. i can not wait to slap on the high comp head!



changed to a plug one step warmer and increased the gap to .040". new topspeed is 38mph!


well her moped put the needle just past 40mph today before she ran out of room on her street, all i did was make a 3/8th inch hole in part of the exhaust!

the stock pipe has 3 baffles with a tube connecting each chamber and then holes which pass the exhaust back through, sort of in a circle… the stinger reaches into the last chamber where that happens, so i drilled a 3/8th inch hole to connect the stinger to the chamber before it. its not really any louder, the hesitation from a stop seems much less, the exhaust is coming out of the tip with ALOT more force behind it (is coming out faster), and it seems to have picked up a decent amount of power in the mid range.

That's pretty sweet default_biggrin Need to put a meaner exhaust to make it sound a bit tougher - maybe modding a Supertrap muffler or similar.

i dont care if it sounds like an elton john song, as long as it goes fast and gets to fast in a hurry.


that what you had in mind fish? :-p i added one 3/8th inch hole to the exhaust in a certain way to alter the path of the exhaust past the baffles. picked up a little more topend (and killed the speedo drive!), but mostly a broader powerband....and it sounds like a small CC dirtbike now.

Now that's what I'm talking about!! That is awesome default_biggrin Really does sound like a dirtbike - pretty cool.

Killed the speedo drive - DOH! That's sweet. Bet the manufacturer didn't expent people to play with them that much.

i'll get her a new one when we bring it upto the shop and get some other new complete new wheel assemblies, back axle, chain, etc. then i'll fab an intake and mate the 19mm carb to it, jet that right, and wait for the pipe i want to come back in stock.


you can see how hard it is to start now against the compression. shes no weakling and she has to stand on the pedal, pedaling it with the starter cluch engaged is pretty hard. compression is 180-190 psi, the CR is about 12:1. i dont think shes really gone full throttle since we modd'd the pipe since the chain is wonky.

getting a stronger 6V coil to help fire a larger gap at higher compression. car coil should put out 30-40KV and the stock does 15-20KV. should let the bigger gap idle smoothly and let us run a higher CR without putting the spark out.

we had put a 75cc topend kit with a big 70cc motor head on it, but we dont have the supporting carb and exhaust to make it sing like it should, so for now we're going back to the 50cc cylinder with the regular head but increasing the compression more. with an expected CR above 12:1 i really feel the need for a stronger spark so that we dont get high rpm misfires due to the spark being put out. also i feel that the current exhaust and carb are holding the 75cc kit back, and that with the 50cc topend we'd actually be able to go faster because the exhaust and carb sizes are better matched. well it all makes sense to me atleast!

The story and videos about your moped are making me go "hmmm." Oddly enough, while stationed in England 20 years ago, my British GF also had a moped, and I got quite addicted to riding it. Actually, it had more than enough power for us to ride double, though we usually didn't. Most of the time, I'd be riding my regular pedal bike alongside her on her moped. I forget the make, it was some Italian make if I recall, but not the same as yours. I'm going to have to dig for old photos, but I lost a couple of boxes of photos in many of my Air Force moves, I think they may be among that number.

What would be a good make of moped available new or used today? Can those things be ridden on the street without a motorcycle license? In the U.K. they had to be licensed and registered.

liscensing varies from state to state

tomos models seem to be readily available, have lots of parts available, and can be bought new with a warranty. the engine on my gf's ped is a minarelli V1 which is about the simplest motor you can get. plain ole piston port 2 stroke with a single jet carb. other models are reed inducted, have multiple jet carbs, etc etc. is a good place to start, but the general chat section is down at the moment. just make a post in the repair section asking about which make/model is easy to work on and cheap to maintain. there are 4 stroke mopeds around, but those are harder to find and harder to get parts for unless they share their engine with something else like a scooter or power equipment.

coil is on, flippin awesome spark! in open air its 2x longer and much fatter and totally blue. gapped the plug to about .035-.040 and it hauls ######. no more snotty drone, its crisp and clear each ignition. idle is strong, like theres real power in there now! the flatspot when snapping throttle wide is gone, it just runs soo much better. its amazing.


Nice pictures.

All you need now is a custom paint job!!

theres a couple videos too, i'll repost them here when i have one of her zipping down the street so i can show a before and after.

a while back the lowbeam in her sealed beam headlight burned out. i got another one that had neither filaments working (was an auction lot). so i cut its lens off and its a direct fit to a 6v 55w halogen spot light. just got done putting the thing together here, tomorrow i'll install it and test it. hoping its a little brighter. how do i convert CP to lumens?

Converting Candle-Power to Lumens is non-trival. Nearly impossible unless you know exactly how the beam is being focused. Easiest way is to measure it directly with a lightmeter.

Basically you are comparing units of illuminance and irradiance. First assume a light is producing one candela. Candela is the base unit in light measurement, and is defined as follows: a 1 candela light source emits 1 lumen per steradian in all directions isotropically. A steradian is defined as the solid angle which, having its vertex at the center of the sphere, cuts off an area equal to the square of its radius. This means that the one candela light produces one lumen/square foot at a distance of one foot = foot candle. Problem is that the original definition calls for the radiation "isotropically" distributed - that is, radiation is equal in all directions. Once you fit the lamp into a projector or sit it behind a lens - then the definition breaks down. Comparing apples and oranges at this point.

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