PHGB 19.5 starting/idling issues on a sachs 505

Mason Campbell /

Hey guys, running an athena 70cc kit on an old colombia. Just having some issues.

Carb and main jets came in today. I checked the float level and preset the idle screws. I left the stock jet in just to see what would happen. It came with a stock 88 jet size. Without the air filter on I could get it to start after some serious pedaling and using the decomp. I don't have the choke hooked up as the lever broke on these old assemblies. However it would not run at all at the low end. Simply won't idle. I tried reducing the jet size to a 74 because it felt like it was choking on fuel, especially since it would only start without the air filter on.

It's also worth mentioning the stock pipe is still on it, as the owner of this bike likes it and doesn't want to upgrade it right now.

I've been reading the PHBG tuning wiki but I just can't figure this shit out.

Re: PHGB 19.5 starting/idling issues on a sachs 505

Mason Campbell /

Update- I put in an 82 main jet. Up on stands the bike runs smoothly once started. However with both idle adjustments screwed all the way in I still can’t get it to idle. Nothing I do is making it idle. I rechecked all the gaskets and there are no leaks that I can tell. Will do a spray test soon.

The only thing I can think of is bad sizing on the idle jet.

Re: PHGB 19.5 starting/idling issues on a sachs 505

theres an idle jet and and idle enrichment screw, your going the wrong way. Little idle screw out to enrichen, in to lean.

The idle speed screw lifts n lowers your throttle slide. in your slide is your needle height, up to enrichen earlier. Lastly the choke makes life easier for cold starts and if buggered would mess up everything. don't run that 72, too small.

Re: PHGB 19.5 starting/idling issues on a sachs 505

Mason Campbell /

> pat splat Wrote:

> -------------------------------------------------------

> theres an idle jet and and idle enrichment screw, your going the wrong

> way. Little idle screw out to enrichen, in to lean.

>

> The idle speed screw lifts n lowers your throttle slide. in your slide

> is your needle height, up to enrichen earlier. Lastly the choke makes

> life easier for cold starts and if buggered would mess up everything.

> don't run that 72, too small.

Is the idle enrichment screw the little golden one next to the idle screw? And I just ordered some new idle jets today as well. I bumped the main jet back to 82. Once started it seems to run well. But it still won't idle. I will take a look at the needle as well and see if maybe I need to back it out some. I'll start with the enrichment screw. And I went lower because on the last two bikes I've done I've had to go lower than expected. I'll keep tinkering. Thank you very much for your input.

Re: PHGB 19.5 starting/idling issues on a sachs 505

Alexander Topazov /

I also have problems on phbg 18 / Athena 70cc

After stopping at a traffic light, he always wants to stall. And during downtime.

He better kept single with sleeve 9655.

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Re: PHGB 19.5 starting/idling issues on a sachs 505

Mason Campbell /

Is that the jet sleeve? Not to familiar with the PHGB setup

Re: PHGB 19.5 starting/idling issues on a sachs 505

Alexander Topazov /

https://www.mopedarmy.com/wiki/How_To_Tune_PHBG_Carburetors

Two stroke AU atomizer

Four stroke AN atomizer

NOTE:If you have reed valves

If you're running the thick stiff reeds you will be fine with running the four stroke AN bushing just by running a richer or leaner AN atomizer, because reed valves reduce the intakes back flow/charge out the carb and back in. The soft reeds will reduce less of the intakes back flow/charge. It is the piston port set ups that will benefit the most by running the two stroke AU atomizer and bushing because the C shaped AU atomizer dam helps prevent the piston ports intake systems, back flow/charge out the carbs bore at low RPM’s from sucking more gas out of the atomizer when exiting out and back in the carb. So the two stroke AU bushing and atomizer will pick up less gas from the AU atomizer system at low RPM’s, on piston port engine's.

moped-army-aeca99065b60952a4c27bb3ac4997609.jpg
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