Post by zan on Jun 24, 2014 19:35:07 GMT -5
Hi everyone. Young Finnish guy here with a light wallet, a low-quality scooter for his only vehicle and a big problem.
I have a 72cc kit, 16mm Dellorto PHBG carb, 6g slide rollers, free flow exhaust, performance camshaft and a high-power coil. I just installed a head with bigger valves and upjetted the bike from 74 to 78. It revved up fine free-wheeling, but when I rode it, she wouldn't pull me past 35-40 kmh nor accelerate quickly at all.
After some issues with carb tuning and a lost and later replaced float bowl pin, I reinstalled the size 74 jet. She runs fine at idle and up to 3/4 throttle, but at full throttle, she won't rev past 4k and snaps, backfires and splutters. If I try to ride her, she barely goes past 15. Here's a running video.
I've played with the carb settings as I said, the spark seems good if I remember correctly, the exhaust is clear, the Malossi air filter is brand new. If it makes a difference, my original head had the new 69mm valves and the new head has the old 64mm ones, I fitted the correct cam bridge with it. I double-checked the timing on assembly and I'm a bit worried it might be that. With the sportbike styling of this thing, the frame gets in the way of the top end and the only way to get a tool in there is to take the whole engine off, in fact I've taken it on and off three times already in this endeavor due to some irritating circumstances. Even adjusting the valves requires a ratchet wrench and tons of fiddling to get the tools in there, a three-hour job. One more thing, the old valve had the hole running from the edge of the head near the exhaust valve, to a tube on the valve cover running to a small air filter, the new valve lacks this.
However, I'm sure the more seasoned scoot veterans among you will identify this problem, and any suggestions will be greatly appreciated. This thing is my only vehicle and I need her for school, grocery shopping and socializing, I even use her every day in our brutal winters.
PS. If this is in the wrong section, please relocate, I'm completely new here apart from what threads I've seen on Scootdawg about somewhat similar problems.
I have a 72cc kit, 16mm Dellorto PHBG carb, 6g slide rollers, free flow exhaust, performance camshaft and a high-power coil. I just installed a head with bigger valves and upjetted the bike from 74 to 78. It revved up fine free-wheeling, but when I rode it, she wouldn't pull me past 35-40 kmh nor accelerate quickly at all.
After some issues with carb tuning and a lost and later replaced float bowl pin, I reinstalled the size 74 jet. She runs fine at idle and up to 3/4 throttle, but at full throttle, she won't rev past 4k and snaps, backfires and splutters. If I try to ride her, she barely goes past 15. Here's a running video.
I've played with the carb settings as I said, the spark seems good if I remember correctly, the exhaust is clear, the Malossi air filter is brand new. If it makes a difference, my original head had the new 69mm valves and the new head has the old 64mm ones, I fitted the correct cam bridge with it. I double-checked the timing on assembly and I'm a bit worried it might be that. With the sportbike styling of this thing, the frame gets in the way of the top end and the only way to get a tool in there is to take the whole engine off, in fact I've taken it on and off three times already in this endeavor due to some irritating circumstances. Even adjusting the valves requires a ratchet wrench and tons of fiddling to get the tools in there, a three-hour job. One more thing, the old valve had the hole running from the edge of the head near the exhaust valve, to a tube on the valve cover running to a small air filter, the new valve lacks this.
However, I'm sure the more seasoned scoot veterans among you will identify this problem, and any suggestions will be greatly appreciated. This thing is my only vehicle and I need her for school, grocery shopping and socializing, I even use her every day in our brutal winters.
PS. If this is in the wrong section, please relocate, I'm completely new here apart from what threads I've seen on Scootdawg about somewhat similar problems.
