50cc bogging under load By wheezy (Read 1,240 times)

[wheezy]

So I pulled my generic 50cc out of the corner of the garage after almost two years in storage. The new battery I bought back then won't keep a charge. Sucks cause the bike has only about 400 miles.I have a couple other 12v batteries that have spade lugs rather than posts. So I at least can crank it.

At first, it wouldn't start. It had been out of gas, so I assumed maybe junk in the tank or water. Managed to eliminate both of those. Then thought fuel wasn't flowing (again maybe junk in the tank or petcock not getting vacuum), turns out the float bowl was full, so no flow. I took of the carb and cleaned everything. The diaphragm is in great shape. Figured it would be a good time to do my own PDI, since I bought it off Craigslist. The valves were close, but I set them both to about .004 inches. The vacuum and fuel lines are in decent condition. Replaced all the zip ties with new ones, and verified the wires are good and spark is sparking blue.

I got everything back together. Still no start at first. I remembered the float was full, but maybe not primed. So I put a spoonful of gas into the diaphragm cover, and it pretty much fired up with some coaxing. The A/F was way off, don't know how it got that way as it ran great back in GA. I adjusted that and the idle speed. The back idles now better than it ever did. Throttle response is instant.

Took it for a test ride and that's were my new problem arises. I live on a slight incline. Downhill and at low rpm's (less than 4k), the bike is fine. I turn around and go uphill, and it bogs heavy until I goose the throttle, then it's only good again for a couple more seconds before I have to goose it. Now, even uphill at 4k rpm, it runs well but I only get 10mph, well below the performance before it sat. Downhill again and it's fine through the whole throttle.

So at first I thought main jet, but I cleaned that. But here is where it gets real weird. Back on the stand, without the load from the rear tire, the throttle is great through at least 6k rpm. No bogging, no sputtering, nothing but great response.

I will be pulling off the clutch and variator to check and clean. But, other than that, anyone have any ideas as to what causes the bogging under load?

[alleyoop]

If it bogs your carb is not adjusted right, on the center stand let it warm up and then adjust the Mixture.
What you want is to get the HIGHEST IDLE on the center stand and after you find that setting and the idle is high causing the rear wheel to spin lower the idle using the IDLE SPEED SCREW on the carb to where the rear wheel stops spinning or just wants to turn slowly.

Your rpms on the center stand should crank up to 7-8k.
Alleyoop

[wheezy]

Thanks Alley. On the center stand, the rear wheel begins to engage at ~3500 or so. I got it to that point, adjusted the mix slightly, and I am now up to 5k before it bogs on the hill. That's an improvement. I'll continue fine tuning in the morning.

Question: You said 7-8k? On my tach, my redline is at 8k.

[alleyoop]

Once you get it NOT to bog or hesitate when you give the throttle a quick full blip the RPMS should climb quick and drop back down to idle quick. If it only is reaching 5-6K rpms your weights are to heavy. To climb hills you need more rpms so lighter weights will get you more RPMS. The 4 strokes red line is 8K like you said, but the RPMS where the motor makes it's MAX horsepower is around 7500rpms. So you want to get the rpms to at least 7000-73000 rpms at least.
Alleyoop

[wheezy]

Thanks again Alley. It's about 90% there after 30 minutes of adjusting. On level road, I'm running about 6k @35mph. There is silicone gasket around the cover, so the previous owner may have changed the weights. I get real good acceleration, but lose 5-10mph up the hills of GA before I moved to FL.

It will be some time before I put any money into this bike. I just found out that there is a way to register pre-2004 50cc's in FL with no title, so I am just trying to keep her running til next year when we move, then I will register it. As of now, this scoot is a toy around the neighborhood.

[fflintstone]

If the bike is still bogging a little,think about restricted fuel lines and filters--maybe some thing you haven't looked at yet--always a little simple thing will be a problem--good luck,fflintstone