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Post by kirah65 on Jun 17, 2024 16:39:40 GMT -5
Hi so I have this issue with my Kymco ZX Fever, it starts right up, runs flawlessly. Until I have driven it a lot in WOT and I let go of the gas to slow down. Then I try and re apply gas, then it bogs down horribly with no throttle response at all and dies.
Sometimes it starts right back up and is fine for a while longer until it happens again. Sometimes it just will not start no matter what and I need to let it sit for 5–10 minutes. Then it starts back up, and I have no idea what's causing it.
I used to take it to a what turned out to be a whack mechanic who did everything badly. So I took it to a proper mechanic, got it done right, the whole engine was pretty much gone through. Crap ton of gasket maker replaced with actual gaskets, full top and bottom end was redone. And we still have this one issue that we just can't figure out anyone got any ideas I'm stumped here
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Post by oldgeek on Jun 17, 2024 19:35:26 GMT -5
The stock CDI gets weird sometimes, I have had a couple go bad on me. Replacement from Ebay did not last long either. A standard 4T CDI will work fine if you can get it wired correctly. I cut the plugs off of one of the bad stock CDI units and spliced them into the new CDI
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Post by kirah65 on Jun 17, 2024 22:01:26 GMT -5
The stock CDI gets weird sometimes, I have had a couple go bad on me. Replacement from Ebay did not last long either. A standard 4T CDI will work fine if you can get it wired correctly. I cut the plugs off of one of the bad stock CDI units and spliced them into the new CDI I have already replaced the cdi as well with proper ones no cheap China specials sadly no luck |
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Post by kirah65 on Jun 19, 2024 11:55:41 GMT -5
Tried replacing the CDI just in case as it's a relatively cheap part, and It's still doing it full throttle for maybe 5 minutes lets go of gas to slow down and while still rolling i re apply gas to get going again, and it just makes baa sounds with 0 actual acceleration, and it rolls to a full stop and dies its so weird it starts up and gets going just fine and then it dies
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Post by oldgeek on Jun 19, 2024 16:14:21 GMT -5
It may be you are slightly lean at WOT after a bit. The motor may be soft seizing just barely. Do you have a cylinder head temperature gauge? It would tell you for sure.
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Post by repherence2 on Jun 19, 2024 16:22:34 GMT -5
It may be you are slightly lean at WOT after a bit. The motor may be soft seizing just barely. Do you have a cylinder head temperature gauge? It would tell you for sure.
i agree with oldgeek.
other than that, try and switch to transparent fuel lines so that you can check for air bubbles/pockets in the the fuel line. sometimes running at WOT can result in less fuel being delivered if you have a vacuum operated petcock. sometimes at WOT there's not enough vacuum to hold the diaphram valve open in the petcock.
other than that, it seems like you are soft seizing. maybe you have to rejet. but like Oldgeek mentioned, get a cylinder head temp gauge. it makes tuning jets so much easier. i tune by temperature at WOT. i keep changing main jets and going on WOT runs until i get stable temps around 350 degrees F. if you tune to 350F, you can run WOT all day long.
try check your plug too, maybe wrong heat range.
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Post by thach2264 on Jun 19, 2024 17:01:31 GMT -5
I’ve the the exact problem!!! Tried 3 cdi already, when first installed it ram great for 5-10min, then it’ll died, cut power and sometimes can’t even start back up. Once it’s like that, letting sit over night is not helping the CDI, it’s like it killed the cdi but not completely.
It’s the CDI problem for sure. I’ve tried scooter assassins, TZR50 and the chinese Minarelli.
I don’t think it’s the gas liner or anything, if that’s the case the scooter should have start back up with full power.
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Post by repherence2 on Jun 19, 2024 17:20:33 GMT -5
I’ve the the exact problem!!! Tried 3 cdi already, when first installed it ram great for 5-10min, then it’ll died, cut power and sometimes can’t even start back up. Once it’s like that, letting sit over night is not helping the CDI, it’s like it killed the cdi but not completely. It’s the CDI problem for sure. I’ve tried scooter assassins, TZR50 and the chinese Minarelli. I don’t think it’s the gas liner or anything, if that’s the case the scooter should have start back up with full power.
...just a thought, could it be the rectifier?
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Post by kirah65 on Jun 19, 2024 19:41:10 GMT -5
I’ve the the exact problem!!! Tried 3 cdi already, when first installed it ram great for 5-10min, then it’ll died, cut power and sometimes can’t even start back up. Once it’s like that, letting sit over night is not helping the CDI, it’s like it killed the cdi but not completely. It’s the CDI problem for sure. I’ve tried scooter assassins, TZR50 and the chinese Minarelli. I don’t think it’s the gas liner or anything, if that’s the case the scooter should have start back up with full power.
...just a thought, could it be the rectifier?
Could this be the issue for me as well? I have also put in an order for a temp gauge and some clear fuel lines, as well as a new vacuum petcock just in case, tho I dread having to do possible carb / jetting work carbs are a god dam enigma I might just have to take it some place or just count my losses and sell it and get something different, but the dam market is flooded by cheap Chinese 4 strokers so i would not even know where to look |
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Post by oldgeek on Jun 19, 2024 20:15:25 GMT -5
If it is a main jet issue going up a size or two should fix it. How is it at idle and part throttle?
Tell us some more about your scoot. Stock or upgraded cylinder? Stock carb? Stock airbox?
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Post by kirah65 on Jun 19, 2024 20:33:40 GMT -5
If it is a main jet issue going up a size or two should fix it. How is it at idle and part throttle? Tell us some more about your scoot. Stock or upgraded cylinder? Stock carb? Stock airbox? Stock Cylinder/piston, air box and stock carb (I think I got it used so it could be different, but it's stock sized for sure might be a Gurtner clone?) CDI is an unrestricted version of the stock one
Malossi Multivar variator and a Malossi MHR Delta clutch and Tecnigas Silent-Pro exhaust
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Post by oldgeek on Jun 19, 2024 20:39:18 GMT -5
If it is a main jet issue going up a size or two should fix it. How is it at idle and part throttle? Tell us some more about your scoot. Stock or upgraded cylinder? Stock carb? Stock airbox? Stock Cylinder/piston, air box and stock carb (I think I got it used so it could be different, but it's stock sized for sure might be a Gurtner clone?) CDI is an unrestricted version of the stock one
Malossi Multivar variator and a Malossi MHR Delta clutch and Tecnigas Silent-Pro exhaust
Do you know if your mech upped the main jet in the carb? are the cooling shrouds on the motor? Post a picture of the carb and airbox setup if possible. 49ccscoot.proboards.com/post/7984 |
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Post by kirah65 on Jun 19, 2024 20:54:43 GMT -5
Stock Cylinder/piston, air box and stock carb (I think I got it used so it could be different, but it's stock sized for sure might be a Gurtner clone?) CDI is an unrestricted version of the stock one
Malossi Multivar variator and a Malossi MHR Delta clutch and Tecnigas Silent-Pro exhaust
Do you know if your mech upped the main jet in the carb? are the cooling shrouds on the motor? Post a picture of the carb and airbox setup if possible. 49ccscoot.proboards.com/post/7984I don't think, so I will ask him in the morning and take a picture once it's light out its degen hours the cooling shrouds around the cylinder are in place you also asked how it responds on low / half throttle it's fine It's slow as molasses during take off especially when cold and smokes quite a bit (clears once warmed up) which is why try to avoid coming to a full stop at all times
I found a picture of my carb setup on my phone
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Post by repherence2 on Jun 19, 2024 22:46:10 GMT -5
...just a thought, could it be the rectifier?
Could this be the issue for me as well? I have also put in an order for a temp gauge and some clear fuel lines, as well as a new vacuum petcock just in case, tho I dread having to do possible carb / jetting work carbs are a god dam enigma I might just have to take it some place or just count my losses and sell it and get something different, but the dam market is flooded by cheap Chinese 4 strokers so i would not even know where to look
dont dread carb tuning. once you get a temp gauge, it makes tuning through the whole throttle range so much easier. a tachometer makes transmission/CVT tuning a lot easier too.
i would not sell that bike. you don't realize the potential of that type of engine. go on youtube and search "oahu moped cruise", you will see a shit ton of DIO type engine scoots.
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Post by thach2264 on Jun 19, 2024 23:06:37 GMT -5
Mine is 💯 % stock, first kick and run perfect every times with a new cdi for the first 5-10min and reach top speed around 45mph. Then it’s just down hill, unless put in a new cdi.
After that:
A few kicks with a bit of throttle and sometimes dont even start.
You can see the spark is weak when testing for spark afterward.
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