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Post by sifu on Dec 29, 2009 18:05:40 GMT -5
Hi guys, was wondering if you knowledgeable people can help me out here?!
I've got a chinese branded scooter used of an auction site (too cheap to let go!) which is a clone of a honda ruckus type scooter, its running the gy6 50cc engine.
Anyways Im having a few problems with it at the moment and would like to eliminate it if possible.
Firstly the scooter is pretty darn hard to start, theres a electric start but it seems like all it does is turn and doesnt seem to have enough juice to start the motor? Once in a while (say 2/10) it will start with the electric start.
Secondly once in a while the scooter will not start at all even if I use the kick start, the only way around this is to take the damn air snorkel off and spray some carb cleaner into the carb. After this it will start?
I've also had instances where it has started but doesnt idle very well and I would have to adjust the idle speed up just to make it idle properly. Occasionally it still dies off right away though.
Thirdly and probably my biggest concern is that sometimes when riding the scooter the engine will just cut out and die on me which often can be quite dangerous! From my experience it usually dies out in one of the following situations:
1. When I let go off the throttle for a sec and then jump back on it again, it would "bounce" then the engine would cut out.
2. When going down a hill (but this may be the same as above as I let go of the throttle when Im going fast down a hill).
Anyone able to give me their feedbacks on these problems? I pulled the spark plug out aswell and its black like its running rich?
For a standard 50cc gy6, what kind of jet sizes should I be using in the carb? And is there a way to measure what kind of jet size you have? The numbers on them doesnt seem to make much sense.
Could it be possible that the fuel pump is busted and its time for a new one? bear in mind that the gas tank is where you place you feet and its operated via a vacuum pump not like a standard petcock setup.
Any feedback or help at all will be appreciated!!!
Thanks in advance Smile
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Post by jimh on Dec 29, 2009 21:23:57 GMT -5
Sounds like a valve adjustment would be the first order of business. If that isn't it at least you can eliminate that from your list.
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Post by sifu on Dec 29, 2009 21:27:06 GMT -5
Valve adjusted to 0.05mm so I dont think that is the problem.
Out of curiosity, what kind of tubing size is everyone running? Im running 4mm ID for vacuum and fuel.
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Post by ILLGotti on Dec 29, 2009 22:58:56 GMT -5
whoa buddy. I hope thats a typo. I set mine at .004 INCH, which is .1 mm
some people like a .003 INCH, but a .05 mm is only what? .002 INCH? I think that would be a little too tight.
Might wanna check for vacuum leaks, maybe double check the carb. The top cap should be on there tight, if not, thats a good as a vacuum leak.
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Post by erictheviking666 on Dec 30, 2009 3:57:38 GMT -5
No he's about right. My manual (that came from Scootdawg I believe) says it should be 0.06mm intake (0.0025in), and 0.08mm exhaust (0.003in). I know most people use 0.004in but, I have always used those specs on mine, and it runs great.
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Post by sifu on Dec 30, 2009 5:42:54 GMT -5
Well I've just changed it to be about .1mm and the problem hasnt gone away.
Do you guys think it might be a fuel pump issue? Taking into account that the tank is where the feet area is and has to pump UPWARDS instead of the usually gravity fed downwards of usual scoots.
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Post by "Big Guy" on Dec 30, 2009 7:37:19 GMT -5
If your plug is black you will have a hard time starting the scooter. This combined with the fact that that scooter comes from Shenke, Jonway/JMStar and they are using the coating that turns gas to root beer in the tank is probably your problem.
First, take out your plug and get the tip of the electrode and the grounding strap cleaned up with some carb cleaner and mild sandpaper. Next pull your carb out and do a good carb cleaning. Your symptoms sound like a clogged pilot jet in the carb, combined with a weak spark.
Once you've got these two steps done, it's probably going to start and run fine. Run it for a day or so and then pull your plug again when the engine is hot to look at it. If the plug starts looking dark again, check your air/fuel adjustment and turn it clockwise a 1/2 turn and try again.
These scooters are pretty good runners, but we have to make sure the coating is removed from the tank. If not, the carbs get gummed up 100% of the time and have the exact symptoms you're talking about. Run out that tank of gas as soon as possible and refill it with fresh premium gas and a chaser of injector cleaner as well.
When you have a hard start issue, cover the inlet to the airbox with your hand to cut off the air while you're cranking it. You'll feel the suction and it'll start up quicker this way. Chances are you just have a dirty jet and plug right now.
Once you've done this and resolved the problem, put in a good new plug, like the NGK.
-Rich
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Post by sifu on Dec 30, 2009 8:39:56 GMT -5
Not too sure if it makes a difference but my scooter is a futong branded one which looks something like this: www.fancyscooters.com/images/DSCN0222Moped824_500.jpgI've cleaned the carb already numerous times and im pretty sure its not blocked at all as before and after cleaning the jets, the"hole" through them looks the same. Also im not too sure how you would "measure" the hole in the jets but one of it says 1.35?? seems a bit large??
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Post by "Big Guy" on Dec 30, 2009 9:09:50 GMT -5
Have you cleaned the spark plug?? And yes, a 135 jet is the wrong size... no wonder. Why in the world did you get that jet? 107 or 108 is stock (1.07mm, 1.08mm) for a 150cc, 115 seems to work best.
-Rich
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Post by tank50 on Dec 30, 2009 10:59:12 GMT -5
what brand plug u runnin?
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Post by "Big Guy" on Dec 30, 2009 14:28:21 GMT -5
It makes no difference what plug it is as long as it fits the scooter, his problem is the 135 main. Once he gets the problem resolved, then he can switch to a new NGK.
-Rich
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Post by sifu on Dec 30, 2009 17:17:03 GMT -5
The scooter including the carb and jet was bought as is, seems like the previous owner may have swapped out the carb from the OEM one?
From my understanding different manufacturers mark their jets differently? hence why I wanted to ask is there a way to "measure" them besides reading the number on the side.
BTW this is a 50cc so what size should I be running? Both main and pilot jet that is. Recommended stock size? if I run a free flowing filter??
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Post by tank50 on Dec 30, 2009 20:49:25 GMT -5
85/88 if runnin 50cc. idk rich i think if his plug is bunk it wont start at all. if his plug was correct at least it would start and still run like crap.
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Post by "Big Guy" on Dec 30, 2009 20:50:00 GMT -5
The scooter including the carb and jet was bought as is, seems like the previous owner may have swapped out the carb from the OEM one? Okay, so let's start over then. We'll assume you have the wrong carb. The OEM carburetor Jet size for the main is #72 - #85 for the 50cc 4-stroke QMB139 engine, and 30mm for the pilot jet. You can measure the carb and it should read: Inner Diameter (intake/engine side): 20mm Outer Diameter (airbox/ air filter side): 40mm My guess would be that you have a 150cc carb on there right now. As long as you see the number, it should be right. Almost all China scooters use the same carb body. Start stock, #72 - 85 for the main and 30mm for the pilot, but you have to have the right carb as well. Measure it as I said above - it sounds like someone wanted to try and mod it and used the wrong part. This would account for the black spark plug and rich running condition as well. -Rich
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Post by "Big Guy" on Dec 30, 2009 21:01:54 GMT -5
85/88 if runnin 50cc. idk rich i think if his plug is bunk it wont start at all. if his plug was correct at least it would start and still run like crap. I was assuming he has the right size plug, and that's why I said to just clean it for now and replace it when he's done and has it running right. If the plug is just badly fouled, a cleaning will work for now. -Rich
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Post by sifu on Dec 30, 2009 21:12:08 GMT -5
Ok just went out and measured the carb outside, the 20mm ID and 40mm OD seems to add up right so that means I have a 50cc CARB
HOWEVER
On closer inspection of the jets i found out the following:
Pilot jet : 35 (It says L35 hence why I got it mixed up thinking it said 1.35)
Main Jet : 120!! Still definitely oversized!
Seems like the carb had been replaced with 125/150 jets??
Im assuming the 5+ on the pilot jet is for the bigger displacement?
Would it be alright to run say 35/80 ? That way I will only have to buy a new main jet. Im thinking 80'ish so that I can run the bigger free flowing filter??
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Post by erictheviking666 on Dec 31, 2009 0:33:02 GMT -5
That may not be the actual jet size. When I pulled my stock jet out of mine it was stamped #103. However it was way smaller than the #85 I was putting in it. After getting some actual measurements it was more like a 79 or 80.
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Post by sifu on Dec 31, 2009 6:15:41 GMT -5
^^ Yup i read a similar thing somewhere hence why I wanted to ask is there a way to measure the jets???
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Post by rapidjim on Dec 31, 2009 9:54:35 GMT -5
I did some measuring this morning on some main jets using indexed drills.
#85 Jet #66 bit #88 Jet #65 bit I didn't have a 120 jet but did have a 122 jet, #58 bit.
Hope this helps
Jim
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Post by sifu on Dec 31, 2009 15:40:15 GMT -5
thanks alot rapidjim, I'll have a look at it later and see what i have! BTW now it seems like my scoot doesnt want to start at all! I definitely know its a fuel/vacuum issue because the scoot will not start at if I leave everything as is, however if i put the tank up high and connected it directly to the tank so that its gravity fed it starts up and runs! Gas just floods right out of the carb though! is this normal? or should the carb be a fully sealed unit? I was under the assumption that the only way for the gas to flow out is if I opened up the drain tube??
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Post by ILLGotti on Dec 31, 2009 23:27:20 GMT -5
sounds like your float might be stuck open. Without the petcock, the float is the last line of defense against a constant fuel flow...
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Post by sifu on Jan 2, 2010 5:16:34 GMT -5
ok found my problem guys!
Small imperfection in the casting caused one of the gasket to not sit fully flush and leak vacuum ever so slightly on the carb!
Really had to examine the carb to see that defect!
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Post by Bluefront on Jan 2, 2010 5:41:31 GMT -5
^^^^^Are you talking about the large float bowl gasket? And what did you do to fix the problem? FWIW.....Both my Chinese 50s had no size markings on the jets. Makes tuning somewhat of a problem if you don't have small drill bits. Nice to see you kept at it till the issue was solved. Some people here would have sold the scoot......
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Post by sifu on Jan 2, 2010 18:26:28 GMT -5
Yes thats correct, im talking about the bowl gasket area. What I did was use my dremel and ground away the defect area and got a new gasket. Running alot smoother now No more "hiccups" when letting go of the throttle on hills and what not.
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Post by sifu on Jan 13, 2010 7:04:44 GMT -5
Ok guys running into some problem again the damn thing wont start on me! It takes a good 2-3 mins of spraying carb cleaner into the carb and kickstarting it before the damn thing will start. Once its running though I dont have any problem at all and even if I turn if off and let it rest a bit then try to start it, it will start up first go. The problem comes when I let it sit for a few hours, the thing wont start at all and I have to redo the carb cleaner kickstarting thing?! My guest is that its got something to do with the gas not staying the the bowl, although I cant seem to find any leaks anymore now?? That or maybe I dont have any vacuum? Will this make it harder for it to start? Im thinking that I might be low in the compression area therefore not creating enough vacuum and thus making it hard to start? is this a possibility? I have changed the plugs, engine oil, gear oil, checked for spark, set valves, changed to the correct jets (as per problem earlier) etc... , im kinda stumped now why this keeps happening???
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Post by sifu on Jan 13, 2010 7:21:34 GMT -5
BTW I installed one of these pumps/valve: s.ecrater.com/stores/72289/49832ab2c2ad6_72289b.jpgWhen I hooked it all up (but left the fuel out line dangling) and tried to crank the engine, the "vacuum" doesnt seem to pull any fuel out of the fuel out line, is this normal??
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Post by tortoise on Jan 13, 2010 12:38:37 GMT -5
the gas tank is where you place you feet and its operated via a vacuum pump not like a standard petcock setup. So why did you install the vacuum fuel valve referenced in the previous post?
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Post by sifu on Jan 13, 2010 17:24:38 GMT -5
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Post by ILLGotti on Jan 13, 2010 18:25:52 GMT -5
Sounds like you didn't prime the fuel system. Hook up the petcock to your carb, then fill your carb by sucking on the intake vaccuum line. you should hear a faint sound of gas coming into the carb. The motor has to be running to pull vaccuum. Just cranking it may not be enough. You can test the petcock by itself by sucking air through the top inlet. You should hear the diaphram opening when you pull vaccuum on the petcock.
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Post by tortoise on Jan 13, 2010 18:30:13 GMT -5
This is a vacuum operated petcock valve for gravity fuel supply . . NOT a pump.
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