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Post by ilovenxstage on Jun 4, 2013 20:20:19 GMT -5
I traded a Fuji road bicycle for an old qt50 "moped" (looks like a moped, but has the "mo" and not the "ped"). It runs, but not well. It's missing the air filter, so I have only run it a little bit. It's VERY hard to start, and when it does start, I have to keep the RPMs high or it will stall. I tried riding it around the parking lot, but it barely had enough power to move with me on it. Also, the front brake wont work. The cable is adjusted properly, but it must be a problem inside the drum itself. There is very low compression on the engine, and I'm sure I'm gonna need to do a full top end rebuild. Does anyone know a good source of parts for these little bikes? The thing is basically a piece of junk, but I want to resurrect it. Here are some pics of my new toy. Attachments:
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Post by ilovenxstage on Jun 4, 2013 20:23:52 GMT -5
No air filter Attachments:
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Post by ilovenxstage on Jun 4, 2013 20:24:58 GMT -5
Broken/missing kill switch Attachments:
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Post by ilovenxstage on Jun 4, 2013 20:27:07 GMT -5
Odometer Attachments:
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Post by kingkaymo on Jun 4, 2013 22:36:47 GMT -5
i had one of these for a short time. never got to ride it, but it had great compression.
there are actually lots of parts to make these go faster. the yamaha PW50 has the same motor, only it has gears. it also has a higher geared rear end. PW50 racers actually swap the moped rear end in for off the line power, so you can go the other way on the moped for top end speed. mine had boyensen reeds and a new top end. all that stuff can be found on ebay. dont mess with the exhaust unless you rejet the carb, you will lose power even drilling an extra hole in the exhaust (according to PO and the welded hole in the stock muffler) and of course dont run too much without a filter.
personally id try to find a pw50 or even yt60 engine because it has semi auto gears. it would make a really neat mini cafe racer IMO and thats what i had planned on doing with mine. sadly someone had stretched it 4 inches to make it comfortable to ride (my knees would have been in the handlebars and im only 5 10) and had failed to line the wheels up straight. I sold it as it was to a younger kid who wanted a project.
personally if the motor wasnt any good id just swap some larger motor on to it and not even worry about keeping it a yamaha unless you just like original. one pitfall of a swap is it being shaft drive, you must choose a swap that either has a rear wheel integrated like a moped, or build a swingarm and do a sprocket.
ive noticed that many 2 stroke 50cc mopeds have top engine mounts, as well as 150ccs. i would imagine a 150cc swap on one of these would be pretty sick. a 4 stroke 50 wouldnt be hard either but im an overkill kind of guy.
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Post by skuttadawg on Jun 4, 2013 23:11:24 GMT -5
Reminds me of my youth as a couple of buddies had one as I was riding a Honda Urban Express and later a ton of pedal types as my father and I bought up all of a local shops surplus as he wanted to get out mopeds and focus more on Husvarna TT racers . No air filter it will be too lean to run , bog beyond usable , and get dirt into the carb . Finding an original airbox may be hard to do and you might opt for a Uni or K&N style or other after market one . Remove the jets and see if they are listed on the chart www.jetsrus.com/FAQs/FAQ_identify_that_jet.htm as you surely want to go up a bit larger but just lil bit . I tried a larger main jet on a Tomos Golden Bullet and it actually went slower as it was stock . These type do not have a CVT and most are slow on take off but have better performance at midrange and get killer MPG as you can run WOT all day long , but go slow up hill . Make sure to use decent 2T oil instead of weed eater junk . I like Maxxima 2T synthetic blend as its around 10 a quart and barely smokes when you do a cold start , where when I ran weedeater stuff as a pup it would leave a com trail and foul out the plug . A simple remove and hit with carb spray and wipe clean and check the gap was under 5 minutes as most are in the open with no cover or panel to remove . I would inspect the chain and cogs for wear . May get lucky and find OEM parts and unsure if you can get choices in teeth amounts on these unlike MX motorcycles have plenty . The frame is light and ok for a light rider but may need tweaking for hot rod mods and a heavy rider . What is the engine stamp code ? These are great for around the block or short trip rides , as well as on college campuses , way more reliable than a Chinese scooter , but limited on power and speed . If you could find a pipe with an expansion chamber and maybe do custom porting with a Dremel and CF or FG reeds and again more upjetting might be able to get more RPMs out of it . Here is more links www.sip-scootershop.com/en/main/base/home.aspx www.mopedarmy.com/ www.mhr-usa.com/What would be cool if you could find and more so if it would fit with no or little mods , Tomos made a 2 speed auto tranny that shifted like a Chevy Powerglide . I had 3 of em and take off and uphill was better except a not so steep hill it would shift up and down more than it should . Hope you get it going and post with happy news
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Post by domindart on Jun 4, 2013 23:29:26 GMT -5
Looks like a fun lil' project
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Post by ilovenxstage on Jun 5, 2013 13:23:30 GMT -5
I know nothing about 2 strokes. Since there are no valves to come out of adjustment, what could cause low compression, besides bad rings? I read where you could put a small amount of oil down the spark plug hole and the oil would temporarily seal the bad rings and briefly restore compression. I tried that and it still has very weak compression. I'll let it cool, find my ancient compression tester and check what the compression is. Also, does anyone know if there are any high flow air filters available for these bikes? I know it has a Mikuni carb, but I don't know what aftermarket parts are available. I also need a new kill switch. I accidentally gave myself a nasty shock when I touched where the exposed wire goes into the brake lever. Also, how do you take apart the brake drums to get to the shoes? And one more question, There is a spot for a battery, but what does it power? There is no electric starter and all the lights are powered off the magneto (unless that was a mod that one of the previous owners did). By the way, this is a 1980 model.
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Post by ilovenxstage on Jun 5, 2013 13:52:58 GMT -5
Compression is only 90psi.
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Post by bdog on Sept 4, 2014 4:15:29 GMT -5
psi should fire up just fine you need a battery for it to start the battery helps give it the initial spark google the type you need. Make sure you are getting spark take the spark plug out and hold it well it's connected to the spark plug lead to the side of the engine if your not getting spark check the kill switch on the break leaver. If your getting spark screw it in and kick it over for a bit then pull the plug out and see if its wet if it's not find why it's not getting fuel. Could be the peat cock or a blocked jet if it's a blocked jet youtube how to clean it then if your getting fuel and spark it's just a matter of tuning the carb screw the mixture screw and idol screw all the way in then screw the mixture screw 1 full turn out and the idol screw 1 and a half turns out that should get you running if not let me know
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