Roketa 150 gy6 motor dies at speed By cruisethescoot (Read 9,978 times)

[cruisethescoot]

Ok, so I have had a Roketa 150cc scooter for about 3 years now. I have had no problems, until recently. What happens is it will normally start fine, and I can ride several miles before the motor start chugging and stalling, and will eventually quit. Sometimes it will start right back up, and sometimes I will have to wait. I replaced the fuel petcock/valve under the tank, which didn't help. I have also run into times where the spark plug would not fire, but after charging the battery (when it doesn't start, I run the battery down trying to troubleshoot) that problem went away. Also, I have checked the following: fuel flow, vacuum lines, carburetor, air intake, fuel filter, stator, pickup, CDI, ignition coil, and spark plug. Because the problem is so intermittent, and only happens after riding for a while, I am having a difficult time determining the cause. I am open to any suggestions, and will (hopefully) be able to answer any questions. Thanks.

[Cruiser]

Welcome to Scooter Doc, cruisethescoot. This sounds like a possible valve adjustment problem. When is the last time the valves were adjusted?

[sprocket]

I agree with cruiser.. classic tight valves...set the intake to .004 INCH and the exhaust to .005 INCH.

[cruisethescoot]

Valves have never been adjusted. I have seen several articles on how to do this, but I am wondering how long it will take? Can I get the valve adjustment strips at any automotive store?

Oh, and by the way, the scooter has about 1800 miles on it, should I be using fully synthetic oil? Would that make any difference?

[sprocket]

Oil makes NO difference... yes your valves are probably very tight... you go to an automotive store and ask for a 'feeler gauge' but make certain they have both .004 inch and .005 inch gauges...

Then check YouTube there are several videos that show how to set the valve gaps...


You can do it with the engine in the scooter but you may need to remove some plastic..

[cruisethescoot]

Ok, thanks. I actually just watched that video a bit ago before I read your post. I'm not a mechanic, but it seems pretty straightforward. Do you guys have any idea about what the stock valve setting is?

[sprocket]

It really varies.. most use .004 INCH intake (top) valve and .005 INCH (exhaust) bottom valve...

I set mine to .003 and .004...

Just the way my engine likes them...

[cruisethescoot]

So, my valves are tighter than .004 and .005 is your guess, which is causing the problem?

[Cruiser]

At least one of the valves is too tight. The synthetic oil may be the reason you have gone so long without adjusting the valves. A valve adjustment is usually done with the PDI.

[cruisethescoot]

PDI? Sorry, I'm new to this world, and don't know the acronyms.

How often do you adjust the valves?

[Alleyoop]

Prep Dealer Inspection(PDI), in other words, go over your scooter for loose bolts, panels,mufflers checking that all hoses are connected etc..

As far a valves are concerned it really depends on the quality of the metal of Head and Valves.
The Valve that usually tightens up is the Exhaust Bottom Valve due to the extreme heat it has to take. The Intake Valve Top not so much because the Gas and Air cool it down as it comes in. Normally after a scoot is broken in around 1500 or so miles the valves usually can go anywhere from 1000 and up without adjusting.

But you will know when they need to be adjusted, the scoot will be harder to start, maybe start dieing out when coming to a stop, loss of power.
Alleyoop

[Cruiser]

PDI is also known as Post Delivery Inspection. This is done when you first receive your scoot. Here's a link which breaks it down:

chinesescooterreference.com/pdi.htm

Valve adjustment at this point is considered optional, but it only makes sense to do it now since the scooter is already all apart. Check out our library listings on the home page. There are many useful entries for maintaining your scoot.

[cruisethescoot]

Thanks, I have no idea if my dealer did this or not. I am just confused since it ran without a problem for 1800 miles. I'll adjust them and advise on the progress.

[Alleyoop]

What they really do , is the crate comes off the ship they pick them up and stack them in their warehouse. Then someone orders a scoot, and they go and get it to be shipped out and they LOOK AT THE CRATE and say DUH YUP LOOKS GOOD TO ME VERN WHAT DO YOU THINK BUBBA and stamp it that is was PDI'ed...lol
What I am trying to convey is that when they say they PDI the scoot do not expect a hell of a lot if anything at all checked.
You must check it all out before you ride it.
Alleyoop

[cruisethescoot]

Ok, so I got a feeler gauge and set the valves (intake was pretty close, exhaust was tight) and she started right up. I rode around the block a few times and was getting excited about maybe having solved the problem......until it died. It was parked in my garage and just idling when it just struggled and stopped. I have yet to be able to get it going again.

On the bright side, the valves are now adjusted right....

The way in which it stops I find interesting, in that it only seems to have problems with the engine is warm, and it doesn't seem to be a mechanical problem, since it will run (when it works, it actually runs pretty well), but I am completely stumped.