Sachs prima backfiring out the intake!

Traded my honda a couple weeks ago for a sachs. It wasn't running at first but then I cleaned the carb and it ran ok-ish. It would idle and rev up a little bit back and forth and have zero power going downhill. I took off the jug and whatayaknow it only had one compression ring instead of two lol. Ordered a new ring and put it on but it will continue to backfire out the carb if you go down a hill. Idk what's up thanks

Re: Sachs prima backfiring out the intake!

Check for the air intake. Maybe the reed valve it's crack or not closing prop.

Re: Sachs prima backfiring out the intake!

***Kim Jong illest*** /

timing

Re: Sachs prima backfiring out the intake!

Ademir Cruz there is no reed valve, but I'll check the timing Vanilla thunder thanks

Re: Sachs prima backfiring out the intake!

If timing checks ok look for exhaust clog

Re: Sachs prima backfiring out the intake!

♣Slew Foot♣ /

The Sachs 505 has a square Bing that requires a restrictive airbox.

Peeps also swapped out the a cranks for d cranks. If your flywheel key way is boogered. It is a sign.

Re: Sachs prima backfiring out the intake!

The square bing only requires the restrictive air box because it is jetted for it. Upset a couple numbers and that silly box can go

Re: Sachs prima backfiring out the intake!

I'll check the exhaust yeah but I've got a mikuni vm20 on it now 17.5 idle jet and 60 main

Re: Sachs prima backfiring out the intake!

Checked the timing and the points were touching lol. I tried adjusting it but it was way too tight and the flywheel was in the way and I don't have a puller yet, gonna have to check it out tomorrow and grab a puller

Re: Sachs prima backfiring out the intake!

alotta times i just bump it with an impact just to break it. is all above checks out then, clean grounds under side cover, upjet cuz 60 in a 20 mm carb is small, and delete decomp,theres a wiki on it if it hasnt been done.

Re: Sachs prima backfiring out the intake!

If you broke a ring I wouldn't be surprised if it gouged the cylinder too. then you would still have poor compression and that'd cause the problems you're having

https://www.mopedarmy.com/wiki/Sachs_505/1a_performance

lotta detail in that page including plugging the decomp. bad decomp could cause the mentioned issues too.

Timing i'd agree though is most likely. you should be able to adjust through the windows in the flywheel.

do you have a 20mm Mik on a stock 50cc? I used to have an 18 on my sachs (I didn't set it up that way) you'd definitely be better off with a smaller carb on a stock jug. or go ham porting it up

Re: Sachs prima backfiring out the intake!

Yeah last time it ran downhill I think I may have broken a ring lol. Thanks for the input

Re: Sachs prima backfiring out the intake!

Chöschi21 C.K. /

Wait, what? You run a 20mm Mikuni? What's the rest of the Setup including the geraring, a VM20 on a Stock Setup won't run right ever.

Re: Sachs prima backfiring out the intake!

All stock except the mikuni, didn't run properly with the stock carb though either

Re: Sachs prima backfiring out the intake!

Chöschi21 C.K. /

Then put o the Stock Carb, if you tell me what the Number on the Bing carb is i can tell you the Stock settings, take it back to stock completely and you can start searching for the problem.

Re: Sachs prima backfiring out the intake!

Yes that MikuniI is way too big for it. You will drive yourself crazy trying to tune with a 21. Even an 18 would be difficult on stock 505. They run best with around a 14

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