Results 1–30 of 39
Geoff L — 3 years ago
Excellent advice. Thanks
Geoff L — 3 years ago
1981 Yamaha QT50, with just 700 miles on it. I recently took ownership of it and got it running. New top 60cc top end and new carb (fuel issues with original).Runs great now and I took it for spin the other day and noticed the front wheel dragging. The hub was getting hot. I suspected bearings and pulled the wheel off. It turns out that one of the brake shoes actually de-laminated and the loo
Geoff L — 3 years ago
Can you tell me the size of the bearings for the front wheel?
Geoff L — 3 years ago
Nice! I need that lol.
Geoff L — 3 years ago
Is the clone the Miniky? Looks just like the Minuki? If so, you probably need to go down on the main jet. I have a thread on here where I received some good advice and part of my issues were that it ran rich and I resolved it by dropping down to a 68 main jet. I have a 60cc top end kit, Miniky clone (from Amazon), oem exhaust and oem air filter/box.
Geoff L — 4 years ago
I bought a PW50 stator on Amazon and transferred the charge coil to my original stator plate. This may be different than the ones that Jack R has discussed. I would say the quality is questionable as it arrived somewhat broken. Nevertheless, I installed it and it definitely improved my spark. For $14 it was a simple troubleshooting maneuver that I am happy with.https://www.amazon.com/dp/B01MTX
Geoff L — 4 years ago
Based on searches that I have done in the past in here - I've seen compression numbers ranging from 105 psi to 145 psi. I wouldn't trust my Harbor Freight gauge for accuracy, but anything north of 100 psi would normally be a motor that can be at least started. With my QT I ended up replacing the original top end out of precaution because the bike is almost 40 years old. $40 and 20 min
Geoff L — 4 years ago
The exhaust is clear - no real carbon. I soaked it in carb/parts cleaner for two days as a precaution.I think I have everything squared away. I am running a 66 main jet with this Miniky clone carb and 60cc Niche kit, stock filter. It takes a minute or two to warm up/clear out. Once it is warmed up, top speed is just beyond 30 mph (speedo pegged) and it has a slight bog at the very top depending
Geoff L — 4 years ago
I think that I discovered something else... The float needle/valve sticks. When I have the bowl apart it won't fall out of its seat unless I blow into the fuel inlet. This might explain some of the shutdowns I was having. Unless I'm mistaken, the needle should fall out on its own? loose....?
Geoff L — 4 years ago
I didn't have a 67 but tried a 66 and it improved further. It slightly bogs at the very extreme top of the rpms where, frankly, the motor is screaming. I misstated my top speed earlier. It's closer to 30mph.I did try it without the air filter and did not notice any difference.How do I determine if the exhaust is blocked? The bike only had 700 miles on it when I received it so would it
Geoff L — 4 years ago
More follow up.... Today I had ridden the QT for about 5-10 minutes. The "dying" issue has been resolved. Victory!It was still bogging WOT so for giggles I took it for another very short test ride with the air filter off, no change. I dropped the jetting from whatever is stock in this Miniky clone carb (probably 70+) down to 68. It seems to have cleared up the bog WOT except for at
Geoff L — 4 years ago
Jack, understood about the air filter and oiling. I have a set of SHA jets on the way to me. I will jet lower and see what, if anything, improves.Again, thanks for the advice on the coil. That seems to have resolved the initial issues (dying out after brief ride). I remembered someone on a forum in the past saying that your problems are "always electrical 90% of the time.....". I sh
Geoff L — 4 years ago
Roger that
Geoff L — 4 years ago
Jack, or anyone who has used Miniky (clone) carburetor: Can you point me to a source for correct main jets that work on Miniky? I think that the oem Mikuni jets that I have are actually a different thread pitch, which I think is strange. Thanks in advance.
Geoff L — 4 years ago
I put a new filter and oiled it with a K&N spray. Is it possible that it maybe over oiled and its acting like a dirty filter, causing a rich mixture? I'm still going to try a 68 jet, down from 70 to see if this resolves the WOT bog. I'm also going to put the needle jet clip back to stock (clone carb) because while my acceleration picked up, I think I have created a hesitation.
Geoff L — 4 years ago
Thank you for that confirmation PD.
Geoff L — 4 years ago
This is my quasi-plug chop. I rode for about 1/2 mile, then WOT for last 200 yards and then kill switch. There was a slight bit of wet oil/fuel on the threads/washer.The dying out problem was definitely solved!!! Thanks for your guidance Jack Rutherford.
Geoff L — 4 years ago
This is a photo of my spark plug with about 15-20 minutes of run time on it and trying jets 70, 77.5, 75 and back to 70. Does it look like a rich mixture?I cleaned it and will do a quasi-plug chop this evening.
Geoff L — 4 years ago
Sorry.... first attachments didn't work for me
Geoff L — 4 years ago
I'm making good progress. The noise from the stator/flywheel was self inflicted: I neglected to fully tighten the stator plate screws. I normally use a touch of impact driver on these and for whatever reason, forgot...With the noise solved, I put a lower jet (75) in and although it improved it still suffered the bogs at WOT. I then changed back to the unmarked jet that came with the car
Geoff L — 4 years ago
Just a 60cc kit (niche) and miniky clone carb. Thanks for the tip on the 5 pack. I do have a 75 and will try that first. I notice that the Mikuni jets are a little higher than the one pulled out of the clone. I'm sure that has an effect.It can't be the stator wire because I actually was able to use the stock wire and it is a pretty tight fit. I de-soldered it from the original coil
Geoff L — 4 years ago
Jack, I think I am solving it..... I put the PW50 charge coil on the stator using your Youtube video instructions. While things were apart, I also upjetted the clone carburetor with a 77.5.The spark must have improved tremendously because it only took 1/2 a kick and it fired right up. Before it would take several kicks. I took it for a brief ride but two things are now happening and I didn�
Geoff L — 4 years ago
It's good advice and I did try it early on. I purchased the PW50 stator and will change out the charge coil. Should be easy since I was just in there to change the crank seal. I'll update when I get to it this week.Thanks!
Geoff L — 4 years ago
I was initially concerned with fuel delivery but have ruled it out. The gas tank had horrible varnish which I thoroughly cleand. I replaced the petcock.....twice. I replaced with the original carb with miniky clone (I didn't even bother with the original carb because of the varnish situation and couldn't find a complete rebuild kit at the time). In fact, I tried two different miniky
Geoff L — 4 years ago
I was saying that the stator coils are low mileage - because I believe them to be original to the bike that has only 700 miles.
Geoff L — 4 years ago
A picture of the stator charge coil? I'm 99.9% certain its the stock coil but I will take a picture of it and upload it. Sorry, I may have made this confusing, but I'm asking if there is history of QT50 charge coils going bad? And could a symptom be intermittent failure at certain temperatures?
Geoff L — 4 years ago
I honestly don't know. I would assume that they are OEM. They looked OEM and all else is stock on this QT (700 original miles on the bike itself)
Geoff L — 4 years ago
Another question for the group: How can I rule out an electrical issue caused by temperature? This may not be a soft seize issue at all. The bike fires up and cruises great for five minutes or so and then starts the routine of dying out until it cools down. I'm a points and condenser guy so I immediately think about a failing condenser. This is a CDI, something somewhat foreign to me. I
Geoff L — 4 years ago
I found that site... but thanks anyway! It will be my likely route.
Geoff L — 4 years ago
Thanks live evil. That makes sense. I think my injection is working. I've replaced the crank seals today and will take it for a ride tomorrow to see if any changes. If its still dying, I'll revert back to a new 49cc setup.I'm looking all around the internet for decently priced round main jets. It seems that I could buy 10 sizes that I don't need for about $8 or I can buy o