sachs tuning...running rich?

my newly scored sachs with a 505 is behaving funky. am i running too rich, and need to down-jet?

here's what i know:

1) after maybe ~1-2 minutes at full throttle, i lose power, i.e. it's like i've totally backed off the gas, even though my hand has not moved. if i'm running at half throttle, maybe 15-20 mph, it seems to do ok

2) it's stalling at full stop, sometimes hard to restart, and keep idling - idle screw hasn't been checked yet

3) noticed a little pool of gas forming at the bottom of the carb/top of the case, carb is a bing from a puch (probably not related? but it certainly ain't a good sign)

4) there is basically no air filter on it, just a piece 3-4 inch tubing clamped on the carb - no screen, paper filter, pantyhose, no nothin', etc.

5) exhaust is a biturbo

6) i don't know what jet is on it right now (i just bought the moped) but former owner says it's around a #80 or #74

7) seems to have good compression

8) haven't checked the plug yet.

any help would be appreciated.

thank you, my babies.

Re: sachs tuning...running rich?

you are probably running lean. but do not jut put in a bigger jet. you probably have airleaks. is your engine all dirty and oily?? if so, it probably has leaks. check the decomp valve. check your intake to cylinder. check carb to intake. use carb cleaner and spray it on the motor where you suspect a leak and if there is one, your motor will die. carb cleaner is a great way to check air leaks. make sure your petcock (fuel valve) is not clogged. check inside the carb where the fuel line goes (called the banjo) and throw away the tiny shitty little filter that is the cause of most bing-fitted moped problem. good luck.

Re: sachs tuning...running rich?


decomp valve is bypassed (which probably explains the hard to start part). the engine is pretty clean. fuel filter, lines and petcock (new) check out.

intake to cylinder, carb to intake, and banjo will be checked next.

anyone else feel free to throw in their 2 cents.

will post here if i run into any more stumbling blocks.

Re: sachs tuning...running rich?

Check the rubber at the tip of your float needle And the banjo mentioned earlier. Thats where mine was clogged. Could be your bowl isnt staying full enough for WOT. If its leaking gas out of the little hole by the air screw thats your float needle also. Wipe it all clean and see where the leak comes from. Mine is leaking from the hose at the carb and petcock. Is it a Bing 85/12/101A? Let me know cuz Im trouble shooting the same carb.

Re: sachs tuning...running rich?

if it has a stock square bing, it has that stupid plastic float which is prone to failure. the float is working intermittently and not shutting off fuel and not turning on fuel. take it apart and make sure the needle moves freely.. i dunno what to say, we've got one in the gang that wont work no matta what.

Re: sachs tuning...running rich?

Damn I didnt want to hear that. I just bought a second one because I broke the first one trying to clean that float needle.

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