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Post by wrnchbndr on May 15, 2011 12:04:25 GMT -5
Been work on my sons scoot and I'm having a heck of a time getting it to start reliably. It is a JinLun JLQT50-4, it has 12"wheels, a long case 139QMB 49cc all stock at this point. If I adjust the mix so it starts and idles well it is too lean on the topend. I tuned the carb going by plug color, tan after a wot run or two up and down the street, out 2 3/4 turns. Adjusted like this after it sits and cools off alittle it is a very extended crank to get it started back up. If I pull the plug and check it, its wet and black. I had run the needle in to only half turn out and the scoot starts well and it is not too rich at idle, very lean on topend(bonewhite plug).
I hope I explained my problem well enough, any help will be greatly appreciated.
Regards Skip
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Post by 90GTVert on May 15, 2011 12:16:41 GMT -5
Could try one step up on the main jet and adjust the idle for best results maybe. If you are only making quick passes up and down the street, the plug doesn't need a whole lot of color to be in a decent state of tune.
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Post by wrnchbndr on May 15, 2011 12:28:53 GMT -5
After posting I read a little more and came across some thing about the metering needle setting so I went and checked that. It has 4 spaces in it and the clip was next to the lowest position, I moved it up 1 space, put it back together and it started right up.
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Post by jmkjr72 on May 15, 2011 13:46:50 GMT -5
 a great chart to look at so you can see what each part tunes you can see how the needle has an effect on almost the whole range |
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Post by wrnchbndr on May 15, 2011 14:20:04 GMT -5
If I screw the mix screw all the way in the engine speeds up. I have moved the needle clip to the highest position and it still seems very rich at idle. It seems to run very well at part throttle and wot. at idle you can see a little black smoke from the exhaust and smells rich.
Regards Skip
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Post by Fox on May 16, 2011 11:11:09 GMT -5
The mixture screw has little to no effect on the high speed mixture. It's for the idle circuit mixture. Needle clip, air filter and main jet size will have an effect on high speed mixture.
Have you tried adjusting the valves?
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Post by wrnchbndr on May 16, 2011 12:52:55 GMT -5
Yes adjusted valves,(.002 intake, .003 exhaust) Have needle clip in highest position. Idle will be high then blip throttle and it will come down. High speed seems good, at idle it is rich and will flood very easily.
We have a #38 pilot jet and the stage1 ingnition kit coming for it. Just tried to start it and it was extended crank. Finally started after pumping throttle several times. Hopefully the pilot jet will help. Seems down on power gonna move the needle clip back up one space this evening.
I have tried adjusting mixture screw going by procedure on the forum. When I turn the screw to the right the engine never slows. it idles faster. I'm confused :dunno:
Regards Skip
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Post by wrnchbndr on May 19, 2011 21:28:49 GMT -5
I think we got the hard start fixed. We installed a #40 pilot jet, had a#38 and #40 ordered but the 38 was back ordered so we used the 40. Starts fast and idles well, probly a mute point because the bbk will be here tomorrow!
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Post by 90GTVert on May 19, 2011 21:34:29 GMT -5
You might have to readjust, but the bbk will probably like the larger jet too. Let us know how you (or he) like the BBK. ;D
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