zacio
Scoot Junior
Posts: 6
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Post by zacio on May 9, 2012 7:28:53 GMT -5
Hi everyone  I have a problem with my scooter. The problem is that it misfires from idle to mid rpm I think or something like that (I don't have tachometer). I tried everything. My carb is standard Mikuni (16 I guess or maybe 14, don't know), 57.5 main jet, idle jet no idea,choke doesn't work, don't know why, it just stopped working and I have to choke it manually with my finger. Also I have an air restriction on the air box which is 11.5 cm and if I pool it out at full throttle is going WAAA, very lean so I assume main jet is too small. Tried adjusting it, but nothing. Now is running lean (spark plug very white, almost no smoke) but that is the best option, otherwise the misfiring is even worse. I can't start , it struggles. When engine is cold, is ok, but when warms up misfires again .... New spark plug Denso W24ES-U, new air filter ... Does anyone have any idea ? I suspect maybe the ignition coil makes problems, I don't know ... maybe the broken choke does the problems ..... Thank you !!! |
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zacio
Scoot Junior
Posts: 6
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Post by zacio on May 12, 2012 6:26:07 GMT -5
Anyone  Could it be because of wrong timing ? I haven't adjusted it ever ... I am hopeless  |
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Post by 90GTVert on May 12, 2012 9:01:02 GMT -5
:welcome: to the forum. Coulda swore I replied yesterday. :stumped:
Leave the snorkel in the airbox if that's the restrictor you mention. A lot of those are 14mm, so they match the stock carb. If it's 11.5mm it may be restrictive, but with a little 57.5main jet you prob need that restriction to keep from going to lean. If it's removed you'll need a larger main jet for sure, just a ballpark guess would be around 70. You said you tried adjusting it, do you mean the main jet? Only way to adjust the main jet is to swap it out for a different one. What you should be able to adjust is the needle and idle mixture.
The needle has grooves in it and a clip that goes into one of those grooves. Putting the clip in the highest groove lowers the needle and leans the mixture. Putting the clip in the lowest groove raises the needle and richens the mixutre. Wherever it is now, I'd move the clip down a notch and see if anything improves. The needle primarily affects part throttle.
There are 2 adjustment screws on the side of the carb. There should be a large one and a small one that's recessed or flush. The large one is idle speed. The smaller is idle or low speed mixture. Turn the mixture screw all the way in, don't force anything, and count how many full turns you make before it stops. Write that number down so you have some point to go back to just in case. Turn the mixture screw out again to where it was set. Start it and let the scooter warm up to operating temp. Turn the mixture screw 1/4 turn at a time one way or the other. Each time you turn it, give it a few seconds to respond. Turn one way and if you don't get a good response turn the other way. At some point you should notice idle speed either increasing or decreasing. You are looking for the highest idle speed. Once you find it, turn the mixture screw in (clockwise) about 1/8 turn to err on the side of rich. You may wish count the turns out that gave you the best result and write that down for future reference. Once that's done, adjust your idle speed to around 1700-1900RPM. If you have no tach, adjust the idle speed so the engine runs without wanting to stall. If you have a headlight switch instead of the always on kind of headlights, make sure the idle speed is still OK with the lights on. The headlights create a load and can drop RPM.
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Post by 90GTVert on May 12, 2012 9:06:27 GMT -5
I also noticed that Denso plug cross references to an NGK B8ES. You might want to try an NGK BR8HS. The ES is a longer reach plug that has causes problems for some. If you can't get NGK or just prefer Denso the BR8HS cross references to a Denso W24FSR.
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zacio
Scoot Junior
Posts: 6
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Post by zacio on May 12, 2012 10:19:08 GMT -5
2 days ago it started geting worse. I have tried everything but no use. Today I took out the stupid euro 2 Matrix exhaust and my scooter revs like hell, no hesitation, no misfires, it's a pleasure to my ears now. I am going to change the exhaust pipe. Thank you very much 90GTVert for your time, tips and help !!! It is the exhaust that was fooling me around. It must have got clogged or something, and don't know. Thank you again 90GTVert |
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Post by 90GTVert on May 12, 2012 10:51:21 GMT -5
Oh it's got one of those fake expansion chambers on it stock (looks like a race pipe)? Those things suck from what I've heard. I'd just get a regular style stock pipe or if you don't mind doing some tuning to the carb and CVT you might be able to find an aftermarket pipe for a similar price and get a little performance out of it. Will need a larger main jet, probably needle and idle mix adjustment, possibly different roller weights and clutch springs in the CVT though. Whatever you do, make sure you check the plug and aren't still getting white insulators. If you are still getting a white plug after some riding, it's too lean and you are at risk of a soft seize.
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zacio
Scoot Junior
Posts: 6
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Post by zacio on May 12, 2012 12:39:06 GMT -5
It's not even a 'fake expansion chamber', it's a shity stock exhaust like on the photo. Btw, I have 5 gr malossi rollers, I removed weight from the clutch pedals for better start and it works thanks to this forum. Anyway, I was not able to see the spark plug color because I don't have new exhaust yet so I can't run it for too long. But put that aside, carb is adjusted as it should be and the engine works smoothly, throttle response is excelent and so on. I will update my work. I don't have much cash now so I don't know if I am going to put stock or aftermarket pipe. Best regards mate:))) Attachments:
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byte
Scoot Member
Posts: 51
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Post by byte on May 13, 2012 6:43:03 GMT -5
Looks like a 4stroke pipe to me.
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Post by 90GTVert on May 13, 2012 9:16:14 GMT -5
Some of 'em do just use 4T cans with a headpipe that fits up to the 2T. When I tried the 4T style can and the stock exhaust that seems to be designed for a 2T, the one designed for the 2T definitely showed better results.
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zacio
Scoot Junior
Posts: 6
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Post by zacio on May 17, 2012 2:36:25 GMT -5
Hey all Finally got an exhaust mount on. I didn't have money for an aftermarket performance pipe like Giannelly or Tecnigas, but, I got one from my friend for free  . It's a Suzuki pipe, I think from SJ50 scooter. I am very happy with it, it sounds great, and the most important thing is that the engine power is awesome . It has great power band all over the engine revs and excellent throttle response. Great start, great acceleration, top speed according to tacho is around 65-70 km/h, but that is because the variator pulley is not closing fully, but I don't care. I live in a not so big city so acceleration is more important to me. Soon I will post some photos and videos. Best wishes to all |
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Could it be because of wrong timing ? I haven't adjusted it ever ... I am hopeless 
. It's a Suzuki pipe, I think from SJ50 scooter.