JMSTAR 150cc problems :-(
 

Hi everybody,

I have a new (August 2008) JMSTAR 150cc "Sunny Princess" and it's got issues. I want to know if other people have had these issues, what they did, and if it's even worth it to fix them if everything else is likely to fall apart too. It was a graduation present and I don't want to have to pay to fix a lemon!

Ok, so first problem - after about 50 miles, it stopped starting with the electric start - the battery wasn't charging, or wasn't holding a charge. i got a new battery for it and it started working again.

i've now gone about 200 miles, speeds up to 70 but mostly around 45-55. It now only starts with the electric if I *also* give it some throttle, which the owner's manual says isn't necessary and shouldn't be done. Also, it's started stalling just about every time I stop, so I have to keep gas on it to keep it from failing. I imagine this is bad for it.

i've never owned a scooter before, so I'm not sure if this is a problem, but the engine sometimes makes noise like something's scratching on the inside. this usually happens when accelerating, but sometimes it makes that noise when I'm at a constant speed.

also, about 2/3 of the time when I start the scoot, one of the blinkers is on. i'm pretty sure I turn the blinkers off before I park the scooter, but if this is a known electrical issue it might be helpful to know.

Thanks for any help!

The stalling/starting is likely carb related. I think it may help to turn the idle speed up slightly and richen the fuel mixture.

Electrical problems I am not much help with. The scratching noise?

Visit the website in the sticky posted at the top of the scooter forum. It has alot of repair help for scooters.

With alittle bit of effort you should have it up and riding reliably.

Allen

k.. I'll see if I can figure out how to do those things.

I went outside after posting and tried to start it to take it to the shop, and it is leaking something... oil, I think. It didn't smell like gas, anyway... and now it doesn't start at all. I'm no good with the kickstarter so I didn't even try it.

:-(

Re: JMSTAR 150cc problems :-(
 

Does anybody break-in their engines anymore?. Do you still have that excuse for engine oil these bikes come with. The consensus is that it's just a preserving oil, not really up to going 70 MPH so early in the engine's life. My geared-up and uprated Qingqi 200 struggles to get to 70 mph so you must be wringing the neck off that 150 cc machine something awful.

Early battery problems are endemic on Chinese machines, so no surprise there.

Re: JMSTAR 150cc problems :-(
 

I agree with you on proper break-in procedures, including changing the oil before riding for the first time.

That said, I'm inclined to believe that our new friend is referencing km, not miles per hour.

Re: JMSTAR 150cc problems :-(
 

He quotes distances of "miles" twice in his post, so I just assumed that being in the US, (I don't think the the JM Star is sold in Europe), he meant MPH.

BTW The importers only claim 65 MPH as the top speed. The makers site claim less than 10 BHP and 130 kg dry. I don't think it could reach 70 MPH.

70 on a 125 is crazy good if it is mph, Probably has a KPH speedo and on it.

update
 

ok, update time I guess. I did mean up to 70mph, though I wasn't the one who took it that high, so I don't know if it actually got there. Normally I don't take it higher than 45.

I changed the oils and adjusted the idle, and put some "fuel system cleaner" stuff in the gas tank on my step-dad's advice, and it worked pretty well for a few days, and then it stopped starting again except in the morning, and just a few days ago it was slowing down when I added throttle. I found a guy who works on scooters here in town, and even though he'd never seen a JMSTAR before he was able to fix the not-starting problem (and the slowing down problem) by adjusting the idle again. not sure if I had it too high or what.

He said the slowing was something to do with the fuel mix being too rich, (another person said it might be flooding the engine) but he isn't familiar with electric chokes, so he wasn't sure how to fix that. It seems to be running okay now, aside from still being somewhat difficult to start, but I won't be surprised if tomorrow it fails again.

Any ideas about the slowing?

thanks again everybody.

I strongly recommend visiting http://www.oregonvintage.com/Scooter.html and at least downloading the GY6 engine manual, (right-hand column, about 3/4 of the way down the list). Even if it's the 50 cc model the general procedures still apply.

This manual contains very detailed step by step diagnostic procedures to deal with lots of problems.

These scooters are fitted with a relatively sophisticated CV carburettor blessed(?) with a couple of devices that are a constant source of problems: the automatic choke or "by-starter" and the ACV (air cut-off valve).

Before doing anything else, check to see what make the spark plug is. If it's an unknown Chinese brand like "TORCH", change it for an NGK C7HSA or CR7HSA and even if it doesn't solve the problem, it'll be an improvement, in starting, idling and general behaviour, also the Chinese one WILL give trouble sooner rather than later. If your funds run to it, fit an NGK Iridium C7HIX or CR7HIX. Expensive, but a worthwhile performance improvement.

It's a long shot, but the correct valve clearances are vital to ensure reliable starting and correct running. It shouldn't need them adjusted this early, but one of the characteristics of Chinese engines is that their valves tend to close up their clearance early in their life. I believe this is due to "valve seat recession", where the soft alloy in the heads causes the valve seats to sink in during the engine's early life and close-up the clearances.

There's a video here http://www.youtube.com/watch?v=eaKyYpdYmjQ where it details the valve adjustment procedure together with comments about how if affects cold starting.

Where would I get these replacement parts, like the spark plug? (I haven't checked yet, but it's good to know)

Are they commonly sold at places like yamaha dealerships/shops, or do I have to order it online..?

The standard plug, C7HSA or CR7HSA is very common and used on thousands of different scooters. Most scooter and bike shops will have them. They're so popular that even AMAZON have them:

http://www.amazon.com/NGK-C7HSA-Stan.../dp/B000CSGX5G

The iridium ones will only be stocked by performance parts dealers, as they're expensive to keep in stock, around $12-$15 .

Check the following to see if there is a defective part that could cause this to happen. Is your brake light coming on when you apply the brake to engage the start button? If not this is the problem. Recharging issues are usually caused by rectifier/regulator or a stator. You should check all the connections for the stator and regulator. Make sure your battery lines are connected completely.

Taillight is out
 

So, the last couple of nights I've had people yelling at me from their cars that I have no taillight. At first I was just confused, and then realized that they meant my taillight is not working.

Is there an easy way to replace the bulb? The manuals the main link goes to seem to show that I have to basically disassemble the entire body. That seems like it shouldn't be the only way. Help?

If there are no visible fasteners on the lens part, the bulb might be accessible after lifting the seat, from behind.

Thanks for the suggestion... unfortunately, it seems that I really do have to disassemble it to get to the bulb. I called the dealer, and I have to remove the seat, the side panels, the bumper panel, the back-top panel, the sissy bar, and the gas tank to get to it. I tried to do this earlier, but the stupid Chinese parts are made of crappy metal, so trying to undo the bolts with the provided wrench just strips them.

I'm going to call the guy in town who got it running last time, to see if he'll replace these crappy Chinese parts with good ones for some price I can handle. Until then I'm borrowing a truck.

Blah. Maybe I should just get a car after all.