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Post by pazuzu on Sept 6, 2016 12:03:19 GMT -6
I fixed the problem. This time when setting the engine to TDC, I rotated the engine until I saw the TDC markings on the gear, but instead of lining the markings up exactly, I let it naturally fall into place. If you've ever done this, you'll know what I mean. As you rotate the flywheel, there are periods of resistance followed by a quick release. As I let mine naturally fall into place, the markings were off by a few degrees. At this point the exhaust valve was very loose. After adjusting both to .004, the scooter runs great and is much quieter.
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Post by pazuzu on Aug 31, 2016 11:54:26 GMT -6
I adjusted my valves about a month ago to .005. I noticed that my previous problems of stalling under WOT were gone. However, I noticed a considerable ticking noise. So the other night, I adjusted them again to .004 and the ticket got worse. I adjusted them again to .003 and the ticking was just as bad. I put the cover on with the valves at .003.
I drove it to work today and the performance is crap now. Doesn't stall under WOT but generally runs poorly especially after stopping at a stop sign and then starting off again. The problem didn't get better or worse through the 15 minute drive.
When I adjusted the valves the other night, the scooter was cold (2 days sitting). I Thought I had it at TDC based on the markings on the fly wheel and the holes on the gear (big hole at the top, two small holes on the sides). I did notice that the bottom valve (exhaust) was really tight. No clearance. I had to work pretty hard to loosen it. Not the nut, but the valve itself.
Considering it ran well before this last adjustment, the fact that the exhaust valve was really tight, and the fact that it runs worse and ticks a lot at .003, it makes me wonder if I really wasn't at TDC. But I can't see how that's possible since I had the holes in the right place on the gear.
Any ideas what it could be? I'm going to adjust them back to .005 and see if it runs better, but I can't imagine that would help with the ticking.
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Post by pazuzu on Aug 3, 2016 23:34:23 GMT -6
Hooray! I just took my scooter out for a test drive and I was able to make it up and down main street quite a ways with no problems! Sounds like the initial problem was caused by the tight valves. The secondary problem of the scooter not starting at all was likely a leaky/faulty fuel filter.
I did notice a bit of a "clackity" sound from the engine, so I'm guessing the valves are now a little too loose. I'm dreading opening it back up from the placement of the gas tank. I may just have to drop the tank and go buy a wrench in the right size (I as using sockets before). How long is it OK to run the scooter with loose valves?
Thanks everyone for your suggestions!
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Post by pazuzu on Jul 25, 2016 11:16:18 GMT -6
An update for you guys:
I adjusted the valves. I must say, that was a much bigger pain that I'd hoped. On my scooter, there are two things preventing easy access to the valve cover. First, the floor tank is about 1.5 inches from the bottom two bolts. Second, there is a part of the frame that goes over the cover to bolt the seat onto. Regardless, I eventually got it off and got the valves adjusted.
I got it started up and it sounds like it's running great, but it was running great at idle before. But then, out of nowhere, it just died and wouldn't start. Once again, the fuel wasn't making it up the fuel line to the pump. After trying several fixes, I ultimately bypassed the fuel filter and plugged the hose straight into the pump from the tank and suddenly I had no problem getting fuel up the hose. So, bad/leaky fuel filter. I ordered a new one that should be here today. I think that's a separate issue from the WOT issue, but may be the reason I could not get it started on the street a couple weeks ago. I'm out of town for a week, but I'll give it another test drive when I get back.
Thanks for your help so far.
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Post by pazuzu on Jul 21, 2016 20:46:49 GMT -6
Thanks guys. To answer some of your questions:
- No, there are no emissions hoses or canisters. Just the one port out of the manifold.
- Like jct842 said, no vacuum petcock, if that's what you meant. Just the pump.
I'm about to adjust the valves now. I've never done this, so I need to watch a couple videos first. Hopefully I can get it all done tonight and give it a test drive.
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Post by pazuzu on Jul 20, 2016 16:20:29 GMT -6
All gy6 engines need adjusting of the valves especially when new and periodically after that. Valves can effect vacuum. Fuel delivery depends on vacuum which as the engine reaches high speed gets less and less normally. If you should have a slight vacuum leak in the manifold it may never show until you open the throttle and keep it there for a period of time. Routing of the fuel line can and will cause problems too. If fuel stops at high speed the engine will still run until the carb bowl runs out of fuel. I've ordered a set of gauges, so I'll be adjusting the valves this weekend. I'll also remove the manifold and inspect it and the o-rings. I'm still not sure what caused it to not start until the next morning the last time I killed it. I guess I need to take it out a few more times and try to reproduce the problem. Thanks for your help. I'll update after I get valves adjusted. |
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Post by pazuzu on Jul 20, 2016 16:18:43 GMT -6
What do you mean by a manual valve? Are you referring to the petcock? I have a pump, so I wouldn't have that issue.
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Post by pazuzu on Jul 19, 2016 12:03:55 GMT -6
I believe it probably is a fuel delivery issue, so my first thought was a vacuum leak. After replacing the pump and all the vacuum lines and inspecting the intake manifold and spraying carb cleaner around it to check for leaks, I can't see how it could be the vacuum. Is there another spot in the vacuum I need to be checking?
The other weird thing is that the vacuum is able to easily pump gas up through the fuel line when the bike is cold/warm, but after the long, fast runs, when I crank the engine, the gas doesn't seem to want to make it more than half way up from the tank to the pump. Until I let it cool, then it works just fine.
I will try adjusting the valves, but do you think that could still be a factor if it's running fine most of the time?
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Post by pazuzu on Jul 18, 2016 15:12:36 GMT -6
Hey, everyone. I'm new to this forum. I've notice most scooter forums are mostly dead nowadays, but it looks like you guys are still alive and kicking, so I thought I'd join the fold. I’m sorry this is so long, but I like to be thorough when asking for help. I have a 2007 150cc generic Chinese scooter with about 3000 miles on it. It's most similar to the Roketa Capri 150cc. I live in Utah, about 4,500 ft above sea level. My scooter runs really well in pretty much every way. By that I mean: - The auto choke works like it should and the scooter starts very easily. I believe the choke is shutting off after the engine warms up as it should.
- It idles just fine.
- It accelerates off the line with no hesitation or sputtering.
- It gets to top speed of about 45mph with no initial problems, which is about the top speed when it was brand new.
The problem happens when I try to run it at full throttle for 10 - 20 seconds. When I do this, the engine suddenly stalls and I coast to a stop. Even if I let off the gas before it has a chance to stall (after 10 or so seconds of full throttle), it sputters and inevitably stalls anyway after another 5 seconds or so. After waiting for about 20 seconds, I'm usually able to start it back up after cranking it a few times (until now. More on that in a bit.) Before I go on, I should say that the scooter was stored for about 6 years up until this spring. I cleaned the carb, drained/refilled the gas tank and added octane booster, and have ridden it about 100 miles since. This problem started before I stored it (part of the reason I stored it) so I believe it's unrelated to storage issues. Things I've tried to alleviate the problem:- Replaced the fuel and vacuum lines with 3/16 and 1/8 (respectively) Tygon lines.
- Replaced the fuel pump with a Mikuni rectangular pump (I have a floor-level tank).
- Replaced the manifold-to-carb clamp (the old one was stripped and loose).
- Replaced the spark plug.
- Drilled a few new holes in the gas cap to eliminate potential vapor lock.
- Checked the air filter, which seems to be clean enough.
- Tested all the electric system and replaced the CDI (as a fix for a failed CDI, which appears to be unrelated) with a performance CDI.
After the above upgrades, the scooter appears to start, idle, and run even better than before. Enough so that I was confident I could go out onto a faster road and try extended full speed again, but found the problem persisting. The difference is that this last time I could not get the scooter to start after it died. I had to walk it home. Here's a timeline of what I did after I got it back home: - I watched the clear gas lines as I cranked it and saw the gas making it about half way up to the pump, but no further.
- I sprayed carb cleaner into the air intake and cranked it. Got it to fire up for about 1 second.
- Opened the top of the carb and poured a little gas in. The scooter started and ran for about a minute, probably long enough to burn off the gas in the carb.
- I’m sorry to say that I have yet to actually open the bottom of the carb to see if there is any gas in the float after it dies. I will test that tonight if I take it out again and stall it.
- I gave up and let it sit overnight. The next morning, it start up just fine like nothing happened.
- After it was warm, I spraying carb leaner around manifold and other areas to listen for RPM change to see if there is an air leak. No RPM change.
- I tried to replicate the problem with the scooter on the kickstand but I was afraid I was going to throw a rod, so I stopped.
It sounds like a vacuum problem, but the fact that it runs so well at normal speeds and I replaced all the hoses makes me think that’s not it. I thought maybe I need to re-jet it, but being that I’m so high above sea-level, I’d think I’d be a lot more likely to be running rich than lean, which doesn’t seem to explain my problem. Any thoughts on what I can try next? I’m so stumped. Thanks in advance! Edit: I should note that I am normally able to drive it 5 miles to work as long as I keep it below 35ish mph. I haven't tried the drive since my last stall where I had to walk it home. |
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