G3 505/D SLOW

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Picked up my first Sachs the other day and am experiencing a big lack of power/speed now that I’ve got it running. It’s a 79 G3, 9,500 miles with a 505/D and a bing 85/12/104.

What I’ve done so far:

1. Cleaned and rebuilt carb, fuel lines, in-line fuel filter.

2. Added new stock air filter.

3. Changed transmission fluid.

4. Checked wheel bearings.

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Problem:

Moped idles smoothly, and starts on a quarter kick. First test ride, accelerated quickly on flat ground, no issues.

Second ride, accelerated well at first and felt a noticeable shake/skip in the acceleration. Immediately stopped and brought back to garage. 3rd ride attempted to reach maximum speed, no “skips” or “shakes” but only managed to reach a top speed of 20mph on full throttle. Moped smokes like hell running and at idle. New to this motor and couldn’t find any clear answers after searching.

Re: G3 505/D SLOW

aside from the usual fred's guide stuff?

i just dealt with a leaky decomp (removed and plugged it) and it ran like a raped ape but now the crank seals are pissing oil so i just ordered bearings and seals from treats

not sure if yours sat for a long time or not but a rebuild is only slightly more involved than an e50 and there are more than a few tutorials and vids so if you got the time it may not be a bad idea

Re: G3 505/D SLOW

oooh baby, looks like you got some fresh earl on that pedal crank

wipe both sides down completely with shop rags, warm it up and take it for a spin

check for leakage(edited)

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Re: G3 505/D SLOW

Blukas Lukas /

Could be a clogged muffler with years of buildup, check that, since it is smokey it might be burning it off.

Re: G3 505/D SLOW

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Pulled the decomp valve, and it appears that the person before me cross threaded the port. Motor runs and idles but it appears that it was half-ass helicoiled as a fix. Although the decomp valve was locked shut. When starting fluid was sprayed on the decomp, motor died instantly. How do I proceed?

Re: G3 505/D SLOW

use the search function for the long form but get:

One (x1) M10x1.5 socket cap screw (i forget the exact length just make sure it doesnt stick out inside the cylinder)

I used JB Weld and a socket cap and let it set overnight. Perfecto.

you can either remove the decomp plug, shorten your starter cable, and be good to go

or of youre in a rush, just zip tie the decomp clip closed and tighten your starter cable at the grip if you can. janky but it'll work

Keep in mind, when you do this compression will look for another path of least resistance so you'll find out pretty quickly if you need seals and gaskets or not.

but def take apart that exhaust while your waiting for the JB Weld to set

ive had decent luck with letting Gunk Gel soak in it for awhile then blast it out at the local diy auto wash. Although sometimes a BBQ followed by a can of high temp paint is the most thorough and clean looking way to go

Re: G3 505/D SLOW

The amount of carbon across the decomp certainly suggests to me that the exhause needs to be decoked.

Re: G3 505/D SLOW

Cleaned up some of the wiring last night and looked at the pipe and intake. Filthy. Will give a thorough cleaning as per everyone’s advice and will update with results. Not sure if you can see it in the picture but there was chunks of thread coming loose in the decomp port after I removed the valve. Threads on the actual valve are in good condition, but has me wondering if it’s crossthreaded/heli coiled. Should I be concerned, or just send it?

Re: G3 505/D SLOW

get the socket cap i mentioned and blow out the metal shavings

if there are still any threads inside the hole, SLOWLY and GENTLY screw in the bolt you bought (put a couple drops of oil to make sure you dont force anything) and make sure its fully in but dont torque it

just give it a slight tug and see if theres any movement to the bolt

if not, take out the bolt, clean up all the the oil and jb weld it back in

if the bolt moves you may have to rethread it and get a bigger bolt or just close the hole completely with jb weld

Re: G3 505/D SLOW

Also with 9,000 miles (wow someone really loved that bike!) you may want to toss in some fresh rings! I bet those things have seen better days.

Re: G3 505/D SLOW

take a look on the right side of the motor on the cylinder side fin, should be number on the casting 30km 40km or 50km. If it is 30km then 20mph is all you going to get stock, 40km and you will be hitting 25mph and 50km is a 30mph rated cylinder... porting will fix that issue, but them you will have to fool around with the carb.

Re: G3 505/D SLOW

> Rebel Moby Wrote:

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

> take a look on the right side of the motor on the cylinder side fin,

> should be number on the casting 30km 40km or 50km. If it is 30km then

> 20mph is all you going to get stock, 40km and you will be hitting 25mph

> and 50km is a 30mph rated cylinder... porting will fix that issue, but

> them you will have to fool around with the carb.

that square jug is the 50 every time.

Everything above is pretty much what I would've said too, from the 1st post my immediate thoughts were definitely leaky decomp and very likely clogged exhaust.

seems like you're addressing those. my approach would be to clean the hell outta that port with brake cleaner and try to thread in a plug (not the valve - see the 505/1a performance wiki page - section on plugging decomp) maybe using some epoxy sealer to help.

after that other issues maybe leaky crank seals, Other sachsy type issues are they slip timing pretty regularly and generic attention to points etc is key as ever.

Re: G3 505/D SLOW

Clean the exhaust port on the jug and clean the exhaust pipe. Also replace the rings. And use the right oil gas mixture. You might also need to change the transmission fluid and add new type f fluid in and make sure you dont overfill.(edited)

Re: G3 505/D SLOW

Get some brake cleaner and clean the outside of the engine too.

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