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Post by zan on Aug 2, 2014 19:42:24 GMT -5
I moved the needle clip up by one notch, turned the air (fuel?) screw all the way in since it gave the highest idle, and switched the jet to 78. The next size up I have available is 82. Here are the results, with the engine warmed up. The point where the cuts happen has moved up a few hundred revs. Also, that puddle on the ground is gasoline from when I cleaned my air filter, not a leak.  |
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Post by zan on Jul 26, 2014 8:42:18 GMT -5
Well, I removed the fuel primer entirely and ran the pump directly to the carb. The cuts are less frequent now, but still happen sometimes. Could the pump be running out of flow?
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Post by zan on Jul 20, 2014 4:44:51 GMT -5
The China-made carbs marked 21mm will be at best a true 18mm, and the Dellorto is a true 16mm. Others in Finland have even run 90cc kits on a 16mm PHBG. As for the fuel system, that's not what my bike has, here's the 'cup' the fuel runs into from the pump.  And the pump itself.  The main jet is a 75, any bigger and she starts bogging and spewing black smoke on full throttle. The sparkplug is the stock C7HSA. I recently took out the head for another, failed project, and the valves were a nice, healthy brown color. I looked up pictures on how a lean running head looks and that's not it. I'm going to drill the holes of the fuel primer bigger today, there's nothing to lose really. If I were to take the primer cup out completely, wouldn't there be lots of overflow through the carb from the pump pushing in more and more fuel even when I'm engine braking and such? |
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Post by zan on Jul 19, 2014 22:09:46 GMT -5
She still does it with the enricher turned on, and with the gas cap off. I got an idea however. The vacuum pump runs into a small cup with a run-off tube back into the tank and a gravity feed to the carburator, and the holes on the cup are tiny, maybe a millimeter in diameter. As I can pinpoint the exact points on certain runs where she cuts out, for example right before a certain curve on a certain road, I'm pretty sure that's the problem. The cup simply runs out of flow and the carb runs out of fuel. That theory also works on the bad cuts, where I'll have to slow down to 20ish kmh, or stop completely and crank the engine for several moments to get fuel from the pump, to the cup, to the float bowl, to the engine. I think I'll take the cup out and drill the fuel hose holes a millimeter or two larger to see if it works, and I'm fairly confident it will.
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Post by zan on Jul 17, 2014 7:36:10 GMT -5
Here I am coming for help again. So I've got my 72cc bike with a 16mm Dellorto PHBG. Occasionally at full speed, after several minutes of riding at top speed, she will cut out, almost as if the ignition has been cut. Pumping the throttle once or twice gets her back running and up to speed, but just one time she cut out completely and I had to stop and wait some moments until she would start back up, then she ran just fine for another hour of riding. I've got a long ride home coming up this weekend to help my mother move, so quick help would be appreciated. One more thing, she gets fuel from a vacuum pump. |
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Post by zan on Jul 17, 2014 7:25:52 GMT -5
Here's what I did to fix the speedometer. Tore out the guts, gutted a 17-euro Sigma, cut a hole in the speedo face and attached the sensor to the fork and a magnet to the brake disk.  |
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Post by zan on Jun 26, 2014 9:03:29 GMT -5
Well guys, I gave up. I took the engine off again and it turned out the timing was off by one tooth, but I decided not to take the risk of wasting another four hours of work. Installed the stock head with the performance camshaft and she runs great now, very rev-happy with the cam. Let's face it, the 69mm valves probably give around the same power as 64mm big valves. Also, one time I took off the pipe coming from the valve cover into a small filter, not the breather, and she popped massive flames out the rear every time I let off the throttle! It's a really good bike, the ride is comfortable and stylish, the exhaust is nice and open from the factory and the fuel tank is located where the engine would go on a "real" motorcycle, so they made the fake fuel tank a storage box. I got her after my vintage moped failed, and she's really useful for a young guy living on his own. The tank fits half a week's groceries and the CVT makes her easy to ride in winter. |
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Post by zan on Jun 26, 2014 4:45:00 GMT -5
I doubt that would give an accurate reading though, considering she's constantly backfiring?
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Post by zan on Jun 25, 2014 18:50:38 GMT -5
Someone help! It's been two weeks since I was last on the road... I checked the spark plug, it's pitch black with dry soot.
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Post by zan on Jun 25, 2014 9:10:12 GMT -5
Installed a size 82 jet, revs to ~5500rpm now before spluttering. Also, when she cuts out, I can feel some air puffing out of the carb. I swapped out the winter tires with the car guys at my vocational school, of course they put it on backwards. |
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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.
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