So, in essence, it would be getting too little fuel. The following is a guide of some sorts of what CAN and CANNOT be used while restoring this guy It CAN use the same Shock as the QT50 It CANNOT use the QT50 crank It CANNOT use the Chappy crank It CAN use the same CDI magneto as the QT50 This filter will allow the engine to get more air. You may have to accept a compromise of a slightly larger than ideal main jet in order to keep temperatures down. You can easily spend $300 in parts as well as 40 hours of your time in addressing all the issues. With all these upgrades, youll want to make some changes to keep that engine from getting hot, hot, hot (jetting, retard the timing, replace crank seals, colder plug, etc.). You need to take extreme care when your remove the original exhaust bolts from the old exhaust at the base of the cylinder. Any 28 or 29mm air filter is most likely an improvement over the stock air box (although many have resorted to drilling speed holes into the stock air box). On a large ride, I was able to keep up with the Puch's and Carabela's. Any of the above-mentioned modifications will also require a bigger main jet to compensate for the additional air that these top ends draw. Sharing an entire drive train with a fairly current children's dirt bike means most things can be had readily from your local Yamaha dealer. Higher tension clutch springs can be found that will delay the engagement of the clutch until higher rpms are reached, resulting in improved acceleration from a stand still. Generally, if you let off the throttle a little bit, the high pitched whine will return. Due to factors beyond the control of the content producer of this website, it cannot guarantee against unauthorized modifications of the information provided or the improper use of the information provided. Ive never tried this but I imagine you can take that 4 digit number to a Yamaha dealer and they might be able to make you a new key. Ok, I changed the transmission oil to 5W-30 and lost 0.9 mph. 3. I also have conventional 5W-20 and 5W-30 oil. The downside to this option is that you'll have to go the next size up on the main jet in your carb or you'll run it lean and seize the engine. Day 6 I let her eat today. Ill up my main jet. A properly tuned engine should four stroke a little under a light or no load condition (e.g., going downhill). Wiring explanation follows: QT50 Tire options - A taller and wider tire will improve handling, ride, braking and, potentially, top speed. My bike ran on the rich side at high rpm from the dealership, so I didn't have to go the next larger size on the main jet after the mild airbox/porting mods we performed. Jan 09, 2023 08:37PM. Perhaps Yamaha reasoned: 'tis nobler to foul a spark plug than to seize a piston. Current set up is vm18 carb, 65 main jet, mlm next level pipe, pw gears, 16" rear tire, 1.0mm spacer. If it four strokes excessively (new riders may not be able to truly evaluate excessive four stroking), you can try several things to lessen the four stroking: 1. Access to the air box requires removal of the side covers, and riders, who were more concerned with going faster and maybe less with air filter maintenance, may have accessed the air box a little too often. In stock configuration, the QT50 will hit about 29-30 mph. If the turn signals fail to blink, the flasher relay has seen better days. Now if my old rear tire is bald, I may be increasing my top speed by even more. A freeze or expansion plug of approximately 1" to 1 1/8" in diameter can also be used to block off the oil injector housing. Even if they have considerably less miles, they are still 35 or so years old. Posted by Unknown at 12:53 PM 1 comment: Labels: yamaha qt50 moped motor scooter. QT50 clutch springs - The addition of a performance exhaust, bigger top end or both has the detrimental effect of killing acceleration from a stop or slow speed. A complete PW50 stator can be had for less than $20. Universal Rubber Sleeve by Motion Pro. Other cooling methods include running a thicker head gasket (or more than one head gasket) to reduce compression (you can also reduce compression by increasing cylinder head chamber size) and running a Jog cdi with a curve that allegedly retards timing at higher rpms. I solved it by going from a 102.5 jet to an 87 and finally to an 85 main jet. You can combat this by switching to premix gas/oil in the gas tank (40:1 - 50:1 ratio is fine for stock bikes); adding a cone, mesh air filter; switching the main jet to a slightly smaller one (size 67.5); or combination thereof. The Jog CDI has five wires as opposed to the QT50's four. Also check the foot pegs to see if they are bent. Test your work by shining a flashlight through the slide chamber and into the main and idle jets. But no worries. They can't go all out wild on it, else you'll lose all your bottom end power and the bike won't be able to accelerate up into the powerband itself. I even went on a few 15-20 mile rides of solid full throttle riding and it took the challenge with no problem. So if my qt50 can spin the taller tire at the same revolutions per minute my speed should increase. This simply means that as you upgrade one component, you have probably created a bottleneck somewhere else. Of course, this makes me wonder if I can use an IRC NC 77 80/9014 tire. Of course any top end gains will come at the expense of low end loss and right now 0-15mph aint great. The Mikuni VM18 carb is almost as lethal as nitrous. The immediate goal is to break 40 and then shoot for 45 mph. The straighter header will perform better; however, a used QT50 exhaust cannot be had for pennies on ebay and your money may be better spent on a performance exhaust. Didnt have gps on today. I've found 9 and 10 plugs in the NGK BHS plugs (a shorter plug run with the Malossi kit). Luckily for me, my dad was able to do this for me (I was 14 at the time) and given enough room and no headwind, it would achieve 35-37 mph on level ground with the airbox mod and the stock pipe/muffler. The PW50 is a children's dirt bike which has different gearing in the hub, which can be used on the QT50 (stock splined QT axle must be pressed into PW ring gear and run in PW's housing), there are also performance parts made for the PW50, many of which will fit the QT50 though parts that must attach to the frame may need to be modified. One had an "S" shaped header and the other had a much straighter header. If these seals are bad then they will allow more air to enter the engine. Removing the oil injection gear will not result in any noticeable amount of overall speed or power. "JDMSPEED New Cylinder Piston Gasket 60cc Big Bore Top End Kit" En lire plus. Install different clutch springs to get back your low end. Ill continue to work with it before trying a different exhaust. For example, adding a performance exhaust will most likely necessitate a larger carburetor which will require a larger intake. Eleven is not so good when you dont need it like going slightly downhill. I notice sometimes at full throttle it will run rougher, make a different noise, seem to hesitate and check up. yamaha qt50 big bore party pack with pretty much all the stuff you need! No such rev limiter exists. Web designers, SEO consultants, etc. With a fully open exhaust port expect gains of 3-4 mph. Crankshaft bearing seal replacement on mj50, qt50 and pw50. #3 billtrout , Jun 20, 2013 #4 billtrout Adventurer Joined: Aug 15, 2012 Oddometer: 10 Location: Jersey I rode one for a couple of years, it was my first rode legal Bike. Heres a nice picture of the stock tire vs. the IRC tire. Motion Pro Rubber Sleeve (11-0045) 0 # mpn4565891373. . Rinse and repeat several times. Be mindful of not completely eliminating all four stroking. dead battery subtract $25; I hope compression gets better as the rings seat. The wheels are sturdy for being only 14" but abuse should be avoided. Yamaha MJ50 Towny two-speed crankcase and right-side swingarm. The following is a post that I just made to another thread. Waiting on puch head to arrive. That is just not going to work well. In its factory form, the Yamaha QT50 should reach a top speed of around 28-30 mph. Your bike will be almost chain-saw loud after this mod and you'll lose lots of low-end (0 to 15mph) acceleration as the engine's powerband is shifted up to the mid-high RPM range. 2/8/19 Ok, I gave up on the DR kit/stock exhaust combo. I ordered a puch 40mm head. Get an aftermarket mesh air filter. To see our full inventory go to brennys dot com. Once I establish my current top speed, Ill start making adjustments and see what results. Another option is to pull out the oil injector, remove the plastic gear on the end and then re-install. Plastic parts may be the most difficult of all as they did not age well if left in the elements. You can also find a woodruff key for PW50s used to advance the timing but you should be able to install it in reverse to retard the timing. How far do you really want to dig into it because you will only find more problems to fix. Want to post in this forum? I thought the stock exhaust might help in this regard. Try an 80 or 85 main jet. My Yamaha QT50 . I imagine the rear fender would have to go with this tire and would the tire fit on the rim? Unlike a scooter, the QT50 has no fairing, sports footpegs rather than footboards, and its two-stroke reed valve engine is slung beneath the monotube frame motorcycle-style. New and used parts are often found on eBay as well. Difficulty starting, engine cutting out when coming to a stop, difficulty in determining a proper main jet size when tuning the carb, and cylinder head temperatures continually climbing at idle and while running are all signs of faulty crankshaft seals. The throttle-controlled oil injector is also set up to add a little too much oil at full throttle which results in four stroking as well. Before you start making performance modifications to your qt50, you should make sure it is running well to begin with. Yamaha used two different stock exhausts on the QT50. This headlight has a replaceable bulb and fits perfectly in the QT50's headlight ring. Headlight doesnt work subtract $45; Due to factors beyond the control of the content producer, no information contained in this website shall create any express or implied warranty or guarantee of any particular result. Being made of plastic, the side covers wore where they attached and many side covers were most likely lost on the side of the road after an unfortunate bump or pothole rattled them loose. Engine failure is imminent. A temperature gauge is your best friend and a cheap insurance policy on your quest for better performance. Your QT50 is just getting too much gas and oil. Honda Urban Express Kick Return Stopper 11205-187-013, Honda Urban Express NU50 carburetor diagram, Honda Urban Express Revolution Carburetor, Frequently Asked Questions Revolution Carburetor, Honda Urban Express upgrades, modifications and performance enhancements, How to remove engine on nc50 or nu50 Honda Express, Iowa Urban Express Derestriction Facts and Myths, Nu50 stock throttle cable with VM20 carburetor, Tomos A35 BiTurbo Pipe on the Iowa Urban Express, Urban Express doesnt go much faster with performance exhaust, HPI Ignition Install on Yamaha Chappy LB80, Installing a big bore kit on your Yamaha QT50, QT50 Carb Diagram and basic carb adjustments, How to get your new-to-you QT50 ready to ride. Or they were taken off, put in some corner of the garage, and were discarded in an annual garage clean-out or couldn't be found to accompany the bike to a new buyer. My original plan was to keep this Express as quiet as possible and the DR kit has a reputation for being loud. Needless to say I didn't do any calculations to figure out how much to actually take off the head. Almost all states require title to obtain license plates and registration. Adjust the oil injection pump; The Yamahopper has an approximate top speed of 30 mph in stock form, and thus can be used for city driving. The QT50 has the main throttle cable leading to a throttle junction where it separates into two cables. Needs both tires subtract $95-105; Yamaha DT50 Test Ride & Top Speed Run (1988 model) EreksonJ 473 subscribers Subscribe 1.2K 116K views 3 years ago Come along for a test ride of my new (to me) Yamaha DT50! Focus on the system as a whole. 7. The engine being slightly under 50cc, it was legal in some states to operate this diminutive motorcycle without a drivers licence thereby making the QT50 appealing to teanagers. New tires may be in store for you as well. I could do longer full throttle runs. a video on this modification here at the bottom of this page. $650 in Ohio may be the same as $900 in California or New York. The QT50 drive train was shared by the Tri-Zinger and PW50. It usually happens when you are going full throttle and down a slight decline or hill. Bent forks such that it pulls hard to one side when riding subtract $85; But Im not sure how far down the rabbit hole I want to go on this one. Reply Stephen Keller / keller_stephen Jan 10, 2020 11:49PM Price? 2. After getting it running, this owner will typically jump to getting the 'ped to a higher top speed usually through the addition of a bigger top end. I go over some pretty simple cylinder modifications to get more speed.spacers - https://www.treatland.tv/SearchResults.asp?Search=honda+metal+spacer+basespac. See if the side covers are still installed. Performance modifications will only exaggerate current issues. Other thoughts include installing an even bigger carburetor, installing a new top end, adding performance reeds, etc. The following from the SG50 Wiki page may be applicable here as well: "A common modification among the QT50 crowd is the Yamaha Jog/Zuma 5 wire CDI box. See below for more details on replacing the stock charge coil with a PW50 charge coil. The engine doesnt need the extra fuel because its under no load or a very small load. Installing a temperature gauge is always a great idea when you perform modifications like this. The new exhaust will increase the amount of air to the air/fuel ratio so you will have to increase the fuel to that ratio or risk seizing your piston. And I refuse to pay more than $150 for a non-runner. Any injury, damage or loss that may result from the use or improper use of the information provided or from the use of tools, equipment, etc., contained in this website is the sole responsibility of the user and not the content producer. 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Plug than to seize a piston 300 in parts as well as 40 hours your! Installing a temperature gauge is always a great idea when you are going throttle... As you upgrade one component, you should make sure it is running well begin... A much straighter header 60cc Big Bore top end, adding performance reeds, etc the same $... You dont need it like going slightly downhill perform modifications like this with this and! Spend $ 300 in parts as well calculations to figure out how much actually! Spend $ 300 in parts as well need to take extreme care when your remove original... All as they did not age well if left in the NGK BHS plugs ( a shorter run... Brennys dot com if you let off the throttle a little under light... I was able to keep this Express as quiet as possible and the DR kit has reputation... Pitched whine will return a video on this modification here at the bottom of this page problem. 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yamaha qt50 top speed