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Post by 180°off on Oct 29, 2015 12:50:45 GMT -5
My friends chinese scoot has trouble starting after it has been warmed up. He needs to put it at full throttle to start it. And then it barley wants to start. When its cold it fires up no problem. I checked valve lash. I cleaned carb. Spark plug looked good. Light brown or greyish color. .004 to tight on exhaust maybe?
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Post by strgazr27 on Oct 29, 2015 13:44:23 GMT -5
.004 is not too tight. Have you done a compression check? Cold engine tolerances are a bit looser. As engine heats up, clearances tighten and compression comes up. What carb is on the scoot? Have you pulled the auto enricher, if it has one and checked its operation? It could be stuck on causing an over rich condition when warm although that should show with a fouled, wet plug.
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Post by Fox on Oct 29, 2015 13:44:59 GMT -5
Mixture screw? Could be a compression issue. Worn rings. Starts good cold when the oil is thick and then loses compression once the oil thins out.
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Post by strgazr27 on Oct 29, 2015 13:47:21 GMT -5
That was my other thought Fox. Soft seize or bad compression.
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Post by Fox on Oct 29, 2015 13:53:53 GMT -5
That was my other thought Fox. Soft seize or bad compression. Yeah. It's a 4 stroke but it would probably smoke some if the rings are bad enough. Could be a burnt valve too. Good call on the enricher. That's a good suspect too.
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Post by 180°off on Oct 29, 2015 15:24:16 GMT -5
Never would of thought to check enricher. This problem started after he put in a performance cam. A8 cam i believe. It still has stock carb with no idle adjustment screw. And the throttle screw is tightened all the way down so that it will stay idleing.
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Post by strgazr27 on Oct 29, 2015 16:58:40 GMT -5
Never would of thought to check enricher. This problem started after he put in a performance cam. A8 cam i believe. It still has stock carb with no idle adjustment screw. And the throttle screw is tightened all the way down so that it will stay idleing. He can probably drill out the idle mixture screw. That would allow you to back Off idle speed screw likely. Did he do a BBK or just the cam? Really won't see any improvement with that can and stock carb and exhaust. Start with the carb adjustment first and checking the enricher. Did the problem start as soon as he swapped cams or a little while after?
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Post by 180°off on Oct 29, 2015 17:31:43 GMT -5
Just as soon as he swapped out cams. No bbk. If i drill out idle mix screw is there a screw behind the plug or do i have to put one in? That would be very helpful to me.Probably solve all his problems.
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Post by strgazr27 on Oct 29, 2015 17:46:10 GMT -5
49ccscoot.proboards.com/thread/5148/unsealing-carbs-mixture-tamper-screwsThe A8 cam is supposed to boost top end. That being said its of little value if that's the case as its trying to pull more air/fuel into the engine but trying to do it with a stock carb. Then its trying to exhaust that extra fuel/air through a stock exhaust, chocking it off again on that side of the combustion process. (I'm assuming that's what he has, I could be wrong). Start by getting to the idle mixture screw. This really should have little impact on starting wether it's hot or cold. We don't adjust mixture every time the engine changes temp but being able to adjust it will be beneficial down the line. That's why I went towards the enricher. If it's stuck open it would allow for a normal cold start but could lead to flooding / over rich condition when the engines hot. Make sure it's connected also. Maybe it was disconnected during the cam swap. Here's a great tutorial on setting both the Idle Mixture and Idle Speed screws. 49ccscoot.proboards.com/thread/429/idle-mixture-adjustment
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Post by sjfishon on Oct 29, 2015 20:40:14 GMT -5
sounds like its set a little lean, when cold the electric choke, will do its job,,but when warm the el ck. will be open,,mine starts perfect when warm,, i am set rich, and have the idle set as high as i can, with out pull. but if you pump the gas, while cranking,, it should start, if it does then either do the adjust, or GO For A RIDE
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Post by sjfishon on Oct 29, 2015 20:47:55 GMT -5
str;;;;; tell me about this enricher, i am confused of its purpose. and where is it located?? thanks
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Post by strgazr27 on Oct 29, 2015 21:31:42 GMT -5
It's purpose is to provide a temporary supply of extra fuel when first starting the scooter. It's an auto choke. There is a needle that rides on a piston. As 12v is applied the unit heats up and the piston extends, drives the needle down closing off this extra supply of fuel. If it's not working than it will not extend to close off the port. On a warm engine this can lead to an over rich condition and hard to no start. You can see it in the pics I've posted and this vid gives an idea of its operation. youtu.be/IVLHaVPf7SIThey can be tested but I would start with getting access to the idle mixture screw first. Once that can be adjusted you can go from there if needed.
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Post by Deleted on Oct 29, 2015 21:36:18 GMT -5
When I first got it, my scoot would start great cold, but not when warmed up. Then, after reading on how to properly tune my carb, I made the adjustments and now, it starts on one kick cold or hot. That is a good place to start.
Bill
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Post by Fox on Oct 29, 2015 21:40:18 GMT -5
As for the enricher, it's a electrical component that has a plunger inside that moves in and out of the enricher body. The default or cold position is plunger retracted. When cold starting, this allows an extra amount of fuel into the combustion chamber via a third jet called the enrichment jet so the engine will idle kind of fast. After the engine has run for a little bit or so the enrichers electrical heating element inside heats up a spring which expands making the plunger extend outward from the enricher body which closes off that extra jet effectively leaning out the mixture and the idle slows down. It's called an auto enricher but it could be called an auto leaner just as easily cause that's what it does when activated. It only gets voltage when the engine is running so when you shut the engine off it will retract slowly as it cools inside. The ambient temperature outside will affect how fast the enricher expands. In arctic winter it will take longer for the idle to slow down than in hot weather. I marked the enrichment jet "choke jet" here: To test it you hook the leads to 12v and watch the plunger. You are correct. There is a screw behind the cap. When you drill the cap don't push too hard as the drill can damage the soft brass screw when the bit breaks through the cap. On this one I drilled one hole off center and then drilled one dead center and the cap stated spinning and came out with the drill bit but you may have to pry it with something sharp.
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Post by Deleted on Oct 29, 2015 21:50:25 GMT -5
What a pain in the A** that some folks have to drill out their carbs to be able to tune them. Thankfully, my stock carb was not like that. I did buy a new carb. and tuned that one as well. It had larger jets installed that I needed and, my old carb had seen better days. For $25, it was easier and cheaper than rebuilding my stock one which had 4,000 miles on it.
Bill
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