Rare case - Chinese XY50QT

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Rare case - Chinese XY50QT

Postby rac421 » Wed Jun 13, 2012 6:57 am

Just purchased two brand new 2008 of this model (yes, cheap) that had been sitting in a barn since bought by the original owner, who fell seriously ill before getting these going. One has 2 miles on it and the other 8 miles. They had a small amount of fuel left in them but have set for four years. I have them all cleaned up (mint) and batteries (had water) seem to take a charge, but starter button does nothing (turn signals and tail light, and horn work but nothing else).

Kick starting does nothing (as expected). Where should I start? I'm a pretty good shade tree mechanic but have no experience with scooters. Please get me headed in the right direction.
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Re: Rare case - Chinese XY50QT

Postby tortoise » Wed Jun 13, 2012 10:36 am

2-stroke or 4-stroke?

Information resource.
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re: Rare case - Chinese XY50QT

Postby rac421 » Wed Jun 13, 2012 2:31 pm

Four stroke, took the carb, tank, petcock off and flushed and cleaned them all. Put it back together and it fired up and ran for ten or fifteen seconds and then died. Still acts like it's not getting enough fuel. Replaced two bad lines vacuum lines that had obvious cracks even though the scooter has never been run. Ran smooth and idled down nice while it was running. Starter solenoid not making contact from starter button but can jump the power cables on the solenoid and it works. At least I know it's getting spark and the timing is good etc. I'm not crazy about the auto-electric choke - is there any way to bypass it?

Thanks for the help - any advice appreciated!
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re: Rare case - Chinese XY50QT

Postby John » Wed Jun 13, 2012 9:19 pm

Take starter switch apart, probably corroded and needs cleaned up.
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re: Rare case - Chinese XY50QT

Postby rac421 » Wed Jun 13, 2012 10:47 pm

Update:

I didn't realize I had to hold the left brake lever down for the electric start button to work. Unit starts fine now, when cold, but dies as it warms up (which is not long as it's 98 degrees here).

If, after starting, I accelerate and keep the rpms up it will run - I expect this puts it past the electric choke control zone and allows it to keep running.

Sooo, I expect it must be the electric choke that's screwing up. I'll order one in the morning ...or maybe two, as it's brother will probably have the same problem. Keep in mind these are brand new bikes that were never started - though the original owner did try, and put a small amount of gas in them.

Does all this sound reasonable? What I'm wondering now is how you can kick start them if the battery is dead and there is no power to the electric choke ...and if there is an after market carb with a manual choke that can be grafted on to these scooters.
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Re: re: Rare case - Chinese XY50QT

Postby tortoise » Wed Jun 13, 2012 11:22 pm

rac421 wrote:starts fine now, when cold, but dies as it warms up

That would seem to indicate that the enricher (choke) fuel passageway is clear, but the low-speed (pilot) jet/passageway may be obstructed.

Video link.

Image
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re: Rare case - Chinese XY50QT

Postby rac421 » Sat Jun 16, 2012 8:51 am

Thanks for the carb flow chart. Re-cleaned the jets and all is well - both bikes are now starting and running perfectly! Wife and I took them out for a little night-spin and put seven or eight miles on them (she thought it was great fun) and even though I know the rings can't be seated yet they easily reached 30mph - which was maintained for only for a few seconds as I would like to put a few more miles on them before using full rpm.

I know about the new theory of running them hard from the get go, but am old school and have a hard time buying into it. I've built a lot of race engines (I have seen this used on full on racing engines, but these were engines that were meant to be rebuilt every few races). The most important thing I have found is to make sure to constantly vary the rpm range and allow a cool down period every fifteen minutes or so, especially in the first 50 miles .

Another thing I will do this morning is to change the Chinese oil in these scoots to Valvoline 10/40 and replace the tranny oil with a quality lube. (even though the scooters only have about 10 and 15 miles respectively at this point. I have very little confidence in the oil these come with and think a lot of break in problems (and future durability) stem from this poor quality Chinese oil during the break-in peiod.

One problem I discovered after last nights ride was that the headlights get so warm they are causing some distortion in the headlight itself and in the fairing above it - has anyone else found this to be happening? I was really disappointed to see this as the bikes are pristine otherwise. Has anyone taken steps to vent these ...or? I may install a cut-off switch in the headlamp circuit so I can keep them off when not needed - right now they are on all the time the scooter is running. Any thoughts appreciated.
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Re: re: Rare case - Chinese XY50QT

Postby tortoise » Sat Jun 16, 2012 10:58 am

rac421 wrote:I may install a cut-off switch in the headlamp circuit so I can keep them off when not needed - right now they are on all the time the scooter is running.

Related topic.

Periodically check for .002 inches valve lash on a cold 139QMB engine . . German video.

Noting your "Rocky Mountains" location . . depending on your elevation, up-jetting the carb may actually be detrimental (too rich fuel mixture). Might want to experiment with some 5 or 6 gram variator weights to maintain a little higher engine RPM on hills and into headwinds . . resource.
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re: Rare case - Chinese XY50QT

Postby rac421 » Sat Jun 16, 2012 7:18 pm

That was an excellent video - one of the best I've seen on setting valves ...leave it to the Germans :)
I will reset these valves at about fifty hours as long as they continue to run as well as they are now.

I'm going to run these in for about fifty hours and then change oil again. I have a friend who works for a Chinese small-tractor importer and he was telling me they had cut their engine warranty returns by nearly fifty percent in the first year by changing to a high quality oil and tranny lube before selling them. He said they lost some warranty work but gained word of mouth sales.

I did make ventilation holes in the headlight housing above the bulb - 35 watt halogen - and it appears to be working as there is no further distortion in the one bike and none at all in the one with even more hours. I did keep the distorted one idling for some time while ran cleaner through the carb and mad adjustments - this was on a hot day - and I think the lack of air flow contributed to the problem - in any case I would like to keep the 35w lamps as they are impressive at night. I'll try to add a picture - I dismantled the headlight and drilled it out on a drill press. As I have said, it seems to be working very well.
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re: Rare case - Chinese XY50QT

Postby wardie » Thu Jun 21, 2012 11:38 am

Two things I would check; first make sure your gas cap is vented. Sounds like you're pulling a vaccuum which is causing fuel flow problems. Second check that no mouse has made a nest in the air box or in the exhaust pipe. Seen both. Wardie
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re: Rare case - Chinese XY50QT

Postby rac421 » Mon Jul 02, 2012 7:50 pm

Scoots are running beautifully now - They have about 35 miles on them as of this morning. Both of the original filters were clogged, though they looked good. Installed two new ones. Also switched the cheezy fuse holders and Chinese fuses for higher quality automotive type setups (though these are made in China as well :^) )

I did install a cutoff switch for the headlights and also a 12v receptacle for the trickle chargers - opening the battery compartment every time you want to charge the batteries gets old fast.


I'm amazed the old original batteries are operating as well as they are. Have two new ones on the way along with ignition wire caps and NGK plugs. Seems to me a lot of problems folks are having down the line are brought on by just a few poor quality original parts and lubricants out of the box.

Of course these may both fall apart tomorrow.
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