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Post by tansen on Nov 26, 2013 16:24:25 GMT -5
I hear ya, GT. AC fired CDI wiring looks pretty basic. So basically what we're looking at is and engine that, when the slider begins to lift a little bit, receives too much fuel in the cylinder as shown by the smoky exhaust couples with sooty plug. So what's happening? Carburation would be the obvious fault and that's the route I will be taking. But in your experience, is there anything other than carburation that could cause a mid range rich stall? I've heard of worn ring/cylinders not having enough pressure to pull in mixture at higher throttle openings and I've also heard of aging reed valves allowing too much mixture to flood the crankcase. Thanks again GT for checking in so frequently. Once this is solved it will be a cool puzzle to look back on
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Post by 90GTVert on Nov 26, 2013 16:48:00 GMT -5
Now I'm sorta confused. I have been reading the issue as it idles well, but you can't give it gas without it dying. It sounded to me as if you can't ride it because it stalls out under throttle. So am I wrong? Can you ride it or rev it but it's just a section of part throttle that acts up?
The fact that you say even removing the air box doesn't cure it, plus other carbs/jets don't cure it, really makes me think it's not in the carb. To give you an idea of how sensitive these can be, sometimes just removing the snorkel from the stock airbox without rejetting/tuning can make the scooter unable to move. For that reason I would expect removing the airbox totally or covering the inlet, if it were simply a matter of carb tuning, should have some noticeable effect... but I believe you said it didn't.
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Post by tansen on Nov 26, 2013 18:56:35 GMT -5
Ok Guys, nothing speaks better than a short video It doesn't seem to die now unless I really hold the throttle pulled for a while as it's missing and bogging. youtu.be/6R2VDBqSD9MGT! Nothing seems to have any effect whatsoever. Different turns on the mixture screw, airbox on or off, spraying carb cleaner or starting fluid in the intake, removing all transmission parts accept for kicker to get it started, removing exhaust, the works!! Do you think it sounds like the spark is just cutting out at higher revs? My friend says he put a new cdi in it...
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vaporz
Scoot Enthusiast
IF YA AINT FIRST..... YOUR LAST SUCKA!!!!!!!!
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Post by vaporz on Nov 26, 2013 22:39:24 GMT -5
....and the mystery gets deeper...
First question....What does your manual tell you to set your idle speed at? Unmodified stock Zumas are 1750 rpm. Your idle sounds low to me.
Second....This is the first time I have ever heard somebody use a pilot jet on a stock 49cc bike smaller than a 32...maybe a 30 every so often. What is the stock carb jetting from the manufacturer listed as in the manual? I'm sorry but I'm not sold on how a 49cc 2 Stroke engine can heatwise OR can benefit performance wise from a pilot anywhere below a 32 and that's even questionable. A 15??? 17.5 to 22.5 like GT said. I just don't get it, along with half size jets for two strokes. This is educating me too in different bikes so drop your knowledge....
Third.....your video sounds as if it could put blame on that pipe which also sounds like a four stroking condition at too low an rpm. What can also mimic a four stroking condition is to low of idle speed. Where are your rpms at during idle?
Fourth....Where is your idle speed screw....position? Do you set your idle higher than target rpm before tuning the carb?
Also, you stated you replaced the CDI. You tested all electrical for continuity? I have also read many places including here that the wiring for replacement CDI's might need some adjusting in different bikes.
It doesn't sound like a spark or timing issue and you sure aren't twisting the throttle hard enough to even pass 5k rpms from what I heard....if that. If you needed a timing adjustment I would know after the ordeal I just went through with my bike.
What makes you think the bike is getting to much fuel? Cause you saw the atomized fuel mix with the airbox off? I highly doubt this is an over rich carb condition. The reason you can see that is because without your airbox, the vacuum is not as strong so you can visually can see the atomized fuel mix as it gets sucked into the engine.
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Rune 75
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Posts: 441
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Post by Rune 75 on Nov 27, 2013 2:04:10 GMT -5
Ok Guys, nothing speaks better than a short video It doesn't seem to die now unless I really hold the throttle pulled for a while as it's missing and bogging. youtu.be/6R2VDBqSD9MGT! Nothing seems to have any effect whatsoever. Different turns on the mixture screw, airbox on or off, spraying carb cleaner or starting fluid in the intake, removing all transmission parts accept for kicker to get it started, removing exhaust, the works!! Do you think it sounds like the spark is just cutting out at higher revs? My friend says he put a new cdi in it... For me this sounds like an ignition problem. It idles really hard, sounds like the timeing is way off. Does the engine sometimes kick back when you fire it up ?
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Post by stepthrutuner on Nov 27, 2013 4:28:34 GMT -5
I think you should substitute another carb in just to see if anything changes. I'm wondering if there is a missing part or if the float is heavy, etc. Subbing for the cdi and coil may also reveal the problem. Maybe you should try replacing the spark components first.
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vaporz
Scoot Enthusiast
IF YA AINT FIRST..... YOUR LAST SUCKA!!!!!!!!
Posts: 117
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Post by vaporz on Nov 27, 2013 13:13:38 GMT -5
....here's what I would do based on all the info submitted.....
Before trying to play with timing....
A) Remove exhaust and completely disassemble. Remove silencer(if possible). If you can remove silencer take a garden hose and run water thru the pipe. To ensure no clogs. Water will not hurt anything. Disassemble silencer and rebuild.
B) A CDI and Magneto swap is an excellent way to test for faulty operation. YOU MUST also do electrical testing on all wires checking output, resistance and continuity. This is a must!!!!
C) Pull ignition coil and test for proper operation. Check manual for target specs.
D) The magnetos are drilled for specific spark ignition. Most 49cc scoots are setup STOCK between 13* and 14* BTDC. Unless there is faulty wiring OR the magneto screw slots have been drilled I find it hard to believe that timing will be off unless one of the above with wiring is to blame.
E) Do what GT and STEPTHRUTUNER have suggested. You got 3 carbs. Inspect em all. Use the good parts and build one good one if need be. Check float height, float needle.
F) I know you said you've checked your reeds but check em again......
HAPPY ALMOST THANKSGIVING!!!!!
There is also a chance your ring or rings on your piston aren't making a complete seal anymore...Put a new plug in gapped at .028 inches.
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Post by JEGZ on Nov 29, 2013 4:06:41 GMT -5
I have never heard quite that sound before. maybe similar but quicker on the taping. scary man. sounds really retarded. try setting your idleat about 1600 rpm.
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Post by moofus02 on Nov 29, 2013 9:24:13 GMT -5
Might want to check your Flywheel make sure the key is there and not sheared
Sent from my SPH-L720 using proboards
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vaporz
Scoot Enthusiast
IF YA AINT FIRST..... YOUR LAST SUCKA!!!!!!!!
Posts: 117
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Post by vaporz on Nov 29, 2013 23:19:33 GMT -5
Good point Moofus!!!! If your flywheel was removed with the improper puller, chances are your Flywheel will have a slight concaveness to it. Outer edge will be raised slightly and the center is dipped inward. What happens next is that the 3 rivets that hold the Flywheel outer shell and inner together begin wearing down the holes they go through due to high rpms. This is because, once you bend the flywheel as minute as you think it might be, you actually bend the rivets holes also. This can lead to a clicking noise. The rivets can be reset but I would only do that if the Flywheel IS NOT BENT. If it is bent you should get a new one.
So, check your Flywheel and if there is any play between the inner and outer shell this COULD be a cause of ticking or clicking sounds. This is not a guarantee but a good possibility when a strange noise appears to be coming from the Flywheel/Magneto area.
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Post by stepthrutuner on Dec 2, 2013 2:21:05 GMT -5
I'm with moofus. Sounds like iggy timing issue.
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vaporz
Scoot Enthusiast
IF YA AINT FIRST..... YOUR LAST SUCKA!!!!!!!!
Posts: 117
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Post by vaporz on Dec 2, 2013 5:08:20 GMT -5
Strange sound.....Hold on a second...Where did Tansen go? Dude disappeared....lol
Anyway....The idle sounds way to low for me which would cause improper spark ignition sounds. Bad ring or rings could cause this too. If nobody has tampered with the magneto and the new supposedly correct cdi was installed...How can the timing be off? Jegz said raise idle to 1600 and that's low guys.....He needs to bump that idle up to 1800 and retune that carb. Then he can move on from there IMO.
Am I missing something in that video guys? Which bad sound? At what time in the clip are you referring too?
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Post by olescoot on Dec 26, 2013 20:13:10 GMT -5
for info my 2t stock 75 main 17.5 pilot
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rupert
Scoot Enthusiast
Posts: 236
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Post by rupert on Dec 31, 2013 9:58:14 GMT -5
If it was me: I would return to the scene of the crime. Pull the flywheel, paying attention to the key, and remove the stator and check the crank seal underneath. Then if that stuff all seems good I would look real hard at the cylinder base gasket and the other crank seal.
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Post by skuttadawg on Jan 1, 2014 22:57:18 GMT -5
I think you a large pilot as mine came with a 40 . t has always started and idled fine . I have a 19mm TK carb that came with a 68 MJ . I put on a BBK and had to give it a sip of throttle at start up . It would idle fine for a bit but I would have to give it throttle after a minute or it would stall . Even after letting it warm up and raise the idle speed . I put in a 45 pilot and tada it starts with no throttle and idles perfect . I would check the float valve as it may be over filling the bowl . I took off the airbox lid for laughs when it was stock just to hear how it sounded . It was louder and started up fine but it would bog when I gave it throttle . When I later put on a BBK I started out with too large of a main jet and it would sputter and get the Uni wet with gas . I had to try a few more until I had it just right with a 120 MJ . I use NGK BRP8HIX the iridium when it is warm and the 7 version in the winter . Running without the pipe can cause excessive heat around the head . With the pipe it allows the heat to flow away . Here is a jet guide as some have been known to have the wrong size stamped on em www.jetsrus.com/FAQs/FAQ_identify_that_jet.htm
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