Sophomore Rider
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Post by 4950cycle on Apr 21, 2013 12:00:14 GMT -5
Hi folks, I have had to keep a 2007 JCL MP 250 A running for my girlfriend. I have had more issues than I should have with this bike. But, what seems to be a reoccurring issue with these 257cc Linhia powerplants is chronic stalling do to the exhaust valves persistant loss of clearance more often than should be. That being said, I just had to find an easier /quicker way to alieviate this bugaboo. The prescribed procedure is just to time consuming and tedious for this ADHD guy to have to do so often. So, I use these shortcuts to get her back on the road without tons of fuss and muss. First, I focus on the exhaust valve only instead of both valves. Its the main culprit for the stalling between the two of them. Its the one that gets SUPER heated over & over again on every hot exhaust stroke and distorts (gets longer). THE hottest part of an ICE (internal combustion engine) is the exhaust valve. Its a wonder they don't fail so much more actually. Anyway, First I cut the belly pan about an inch and a half or so in front of the rear vents in said belly pan. Right behind a little devider you will see on the inside of it. I also drill a hole in each side at the very bottom of the bodywork to get to the rear belly pan bolts.If you make this area of the belly pan removable this will give you access to the exhaust valve cover, the exhaust pipe bolts, the vaccum fuel pump and maybe even the ever elusive spark plug ? (can't remember) . This is a lot of gain for this hard to work on model. I also gambled and tried something that I was a little leery to do. I lay the scooter down right on the earth (not slab or asphalt) with a big peace of cardbaurd to protect the paint. With something a foot and a half or so off the ground to lay the handle bar on to help support the weight of the scooter. Hey, when you don't have a $1500 lift this gives you much easier bottom access. Scoot didn't seem to leak any fuel or oil to speak of. And also ran fine upon the completion of the task. With ZERO stalling. ;D I will post some pics shortly. Sorry for TMI. Just trying to give back.  |
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Post by woowilly on Apr 21, 2013 13:43:40 GMT -5
If it's lean the exhaust valve and seat will run hot and burn and wear and reduce valve lash clearance quicker than if it's jetted a hair rich. Jetting a hair rich will drop combustion temperature with a minimum of power loss. When lean, there's a surplus of oxygen left over after the power stroke that gets blown out the exhaust. Essentually the same thing happens as a cutting torch, heat the steel real hot then blow oxygen on it to make the metal go away...
( for the exhaust valve and seat it's far better to have a lower temperature and blow CO, CO2 and a minimum of O2 over 'em than have a higher temp and a greater percentage of O2 blown over 'em..)
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Sophomore Rider
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Post by 4950cycle on Apr 21, 2013 15:38:46 GMT -5
I agree, I had 78 Kaw 750 B model air cooled twin that would lean pop here and there, Did'nt run right when it was cold, Run Hot. Could not fix this problem with those twin Mikunis (no air leaks) till I drilled the main jet one number drill bigger than stock hole in jet. It drew just a pinch more fuel from the float bowls and the bike ran great from then on. I need to get those pics of Scoot belly pan up.
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Sophomore Rider
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Post by 4950cycle on Apr 21, 2013 22:20:03 GMT -5
Here are some before and after pictures of my panel installment project. This is picture of the final product. Attachments:
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Sophomore Rider
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Post by 4950cycle on Apr 21, 2013 22:24:50 GMT -5
Here is the trap door that I created out of the piece I cut from the bellypan. See the 2 little sheetmettle tabs I screwed to the belly pan . The tabs slide into two slots that help keep it in place. the two existing bolts fasten the door in the rear. Attachments:
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Sophomore Rider
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Post by 4950cycle on Apr 21, 2013 22:25:58 GMT -5
This is the belly pan after being cut and forward part fastened .See that screw securing the forward bellypan to that silver lower bodypanel ? The screw in each side is not absolutely necessary. It just keeps things from rattling when riding. Now, When my girlfriend comes to me and says her scooter is stalling when she comes to a stoplight I no longer get a sick feeling in my stomach !  I know I will most likely be able to go in and adjust the exhaust valve with as little effort as can be expected And the scoot will idle fine again. Translation , Does'nt turn into an all week project. ;D I know, I know. Some of you claim you do this job, adjustment in 38 seconds or so. I'm just saying this guy can't. Attachments:
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