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Post by ultrasuede on Jul 23, 2020 21:05:33 GMT -5
G'day gents,
I have a 125 GY6 thats been a thorn in my side for the past 2 years.
She's got a cheap chinesium 150cc big bore kit on her, toughened springs, racing valves, port and polish, A9 cam, ebay exhaust and a valve lap job.
Naraku variator w/10gram weights and stronger springs in the clutch.
I had another thread about her where I tried to change her to EFI. After much stuffing around I got her working, only to have the regulator die and send 30v straight into the ECU frying it. It's been thrown to the back of my shed since.
I've recently revived her using a 30mm carb. I have a wide band hooked up and have tuned her to sit at 12.9 at WOT (6800 RPM) with a 110 main jet.
The thing only hits a top speed of 70kmh which is alot less than I expected.
I have a new Jinlong 150cc engine on it's way and I was hoping to build that up to get a better result.
Any ideas on why she's slow?
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Post by 90GTVert on Jul 26, 2020 12:56:32 GMT -5
Have you checked compression?
Inspected the CVT?
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Post by rocketdogiv on Jul 30, 2020 21:04:51 GMT -5
The Carb. is too big for the size of your engine. Go back to the 24mm or a 26mm at the most. Maybe try 11 grams, that's what I'm using for a 38 tooth rear gear with a 13 inch rear wheel. I get more than 65 mph out of my 172cc with a 24mm pwk clone.
Oh, and pull the plug out and have a look. I bet it's coal black. I bet you smell raw gas when it's running as well.
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Post by ultrasuede on Jul 31, 2020 1:37:13 GMT -5
Have you checked compression? Inspected the CVT? Compression and CVT is all good scooter senpai  |
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Post by ultrasuede on Jul 31, 2020 1:46:43 GMT -5
The Carb. is too big for the size of your engine. Go back to the 24mm or a 26mm at the most. Maybe try 11 grams, that's what I'm using for a 38 tooth rear gear with a 13 inch rear wheel. I get more than 65 mph out of my 172cc with a 24mm pwk clone.
Oh, and pull the plug out and have a look. I bet it's coal black. I bet you smell raw gas when it's running as well.
You might be onto something. I discovered something odd about it. It's a 30mm diaphragm carb. I have a wide band hooked up, so I've been cheating with the tune. 110 main jet was giving me readings of 11.00 - 11.50. Quite rich and odd for this carb as it was fitted with a 120 main jet stock. This was fitted with a foam uni filter straight to the carb. Today I put a length of hose between the carb and the filter in order to get the filter out of the way of any rain. The thing leaned out at WOT and stalled. LEANED out. How can restricting the air flow lean the engine out if it was running rich with less restriction?!? Changed to a 120 main jet. WOT at 16.00 - 17.00 WTF?? Changed to a 135 main jet. WOT now at a nice 12.10 - 12.50 nice. Much more low end torque too. So what was happening is that the open air filter directly on the carb wasn't creating any back pressure, reducing vacuum, which was not allowing the plunger to lift.. Adding a little restriction to the filter is now allowing the plunger to lift fully, thus opening the airway fully. This took me days to work out. crazy. |
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Post by rocketdogiv on Aug 1, 2020 21:18:11 GMT -5
I'm happy you are getting a handle on it Ultra. I've been through that type of situation more than once. I have an AFR oxygen sensor too. Don't trust it explicitly. It can get you close. At least that's what I've discovered.
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Post by cypher1982 on Aug 4, 2020 21:26:24 GMT -5
The Carb. is too big for the size of your engine. Go back to the 24mm or a 26mm at the most. Maybe try 11 grams, that's what I'm using for a 38 tooth rear gear with a 13 inch rear wheel. I get more than 65 mph out of my 172cc with a 24mm pwk clone.
Oh, and pull the plug out and have a look. I bet it's coal black. I bet you smell raw gas when it's running as well.
You might be onto something. I discovered something odd about it. It's a 30mm diaphragm carb. I have a wide band hooked up, so I've been cheating with the tune. 110 main jet was giving me readings of 11.00 - 11.50. Quite rich and odd for this carb as it was fitted with a 120 main jet stock. This was fitted with a foam uni filter straight to the carb. Today I put a length of hose between the carb and the filter in order to get the filter out of the way of any rain. The thing leaned out at WOT and stalled. LEANED out. How can restricting the air flow lean the engine out if it was running rich with less restriction?!? Changed to a 120 main jet. WOT at 16.00 - 17.00 WTF?? Changed to a 135 main jet. WOT now at a nice 12.10 - 12.50 nice. Much more low end torque too. So what was happening is that the open air filter directly on the carb wasn't creating any back pressure, reducing vacuum, which was not allowing the plunger to lift.. Adding a little restriction to the filter is now allowing the plunger to lift fully, thus opening the airway fully. This took me days to work out. crazy. From what I've seen, the restriction is only half the key, the other is direction of airflow. Im sure some of it has to do with pressure differential before and after the piston. But them needing to draw in the air causes its velocity to increase, you need that speed to push the carb piston up. With the cone on the carb, the air has no track to really get moving through....but maybe I'm wrong |
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Post by guyfromeurope on Aug 5, 2020 7:39:36 GMT -5
G'day gents, I have a 125 GY6 thats been a thorn in my side for the past 2 years. She's got a cheap chinesium 150cc big bore kit on her, toughened springs, racing valves, port and polish, A9 cam, ebay exhaust and a valve lap job. Naraku variator w/10gram weights and stronger springs in the clutch. I had another thread about her where I tried to change her to EFI. After much stuffing around I got her working, only to have the regulator die and send 30v straight into the ECU frying it. It's been thrown to the back of my shed since. I've recently revived her using a 30mm carb. I have a wide band hooked up and have tuned her to sit at 12.9 at WOT (6800 RPM) with a 110 main jet. The thing only hits a top speed of 70kmh which is alot less than I expected. I have a new Jinlong 150cc engine on it's way and I was hoping to build that up to get a better result. Any ideas on why she's slow? Hi, Did you do all the mods at once? I will be also instaling a 163cc big Bore kit on my Kymco agility 125cc and does the A9 cam change something? |
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Post by ultrasuede on Aug 8, 2020 6:06:47 GMT -5
I don't know. It's still pretty gutless even with the AFR sorted out. I picked up a brand new 150cc engine off eBay on special, so I'm swapping that in tomorrow to see a comparison.
If it's still gutless, I'm buying a CT110 and giving up on 4 stroke scooters.
I have a 70cc water-cooled malossi rep project that needs attention anyway.
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Post by aeroxbud on Aug 8, 2020 7:18:44 GMT -5
It's so easy to make the two strokes faster. Even up to four of five times what they are stock. The four strokes suffer by comparison.
Hopefully the new motor will be enough.
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