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  #1  
Old 27 Feb 2010
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Hercules Supra 3D restoration

My first-born son (aka the first two-wheeled motorized vehicle I've ever owned) has returned back home



I picked up my 1988 Hercules Supra 3D moped (49cc 2 kW / 2.7 HP two-stroke 3-gear manual transmission Sachs engine, type 505/3 DK) last thursday. It's been hidden away behind a shed exposed to all elements this planet has to offer since 2003. I cleaned it today (almost no rust on a 22 year old moped is what I call real good quality!), changed the spark plug and gear oil, haven't found an air filter yet so had to clean the original 1988 air filter. Four kicks later the engine started and runs pretty well once it's warm. Terrible when cold though - when it dies it's really hard to start again, and it sounds like it suffers from a really terrible cough. It gets better after the first hundred meters or so, although I had to readjust the clutch and throttle cable. I'm having trouble with 2nd gear which makes a really horrible clunking sound - my guess is that the gear wheel is loose on the drive shaft. I can maintain speed in 2nd gear but as soon as I accelerate it makes that sounds and doesn't get any faster at all. First and third gear work perfectly fine.

Anybody ever had one of those and know what the problem with the gearbox could be? Also, any ideas how I could improve its cold run? I'll replace the almost ancient air filter ASAP, still looking for a replacement. Spares are a bit hard to find since the engine and moped were only built for a few months in 1988. Any ideas what else besides replacing the 1994 tires I should do?
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Old 28 Feb 2010
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As for poor running - first replace the air filter - then if still bad, the carb will probably be gunked up - modern fuel goes off and varnishes up carb inners within months, let alone YEARS !!!!
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Old 1 Mar 2010
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I found some proper air filters on eBay and will replace the old one this week. Just need to make sure which one to get - there are air filters with 16, 22, and 27mm diameter for this engine. The carb looks pretty good, I was surprised myself. I kinda expected it to be all solid at this point. After some fine tuning the engine runs a bit better when cold, although I feel like there still might be room for improvement. Still looking for tires - anyone know what the difference between 2.50x17 and 2 1/2 x 17 is? The latter I need according to the operating license but it's really hard to find. I found tons of 2.50x17 tires though - is there a difference?
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Old 1 Mar 2010
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I found some proper air filters on eBay and will replace the old one this week. Just need to make sure which one to get - there are air filters with 16, 22, and 27mm diameter for this engine. The carb looks pretty good, I was surprised myself. I kinda expected it to be all solid at this point. After some fine tuning the engine runs a bit better when cold, although I feel like there still might be room for improvement. Still looking for tires - anyone know what the difference between 2.50x17 and 2 1/2 x 17 is? The latter I need according to the operating license but it's really hard to find. I found tons of 2.50x17 tires though - is there a difference?
I don't know this particular model, but a lot of mopeds had a choke lever directly on the carburetor.

There are clubs for people who restore old mopeds (and use as much time as it would take to restore a proper motorcycle ;-)), they might be able to help.
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Old 1 Mar 2010
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There's a choke lever sorta thing right next to the throttle. It sorta looks like a decompression lever but it's supposed to be the choke. Also, there's some sort of button on the carb but I was not yet able to find out what it's for. And I actually found a club for old Hercules motorcycles and mopeds and tried to join their forums, but they want my full name, address, and phone number before they let me in. Go figure

I've also made progress on the air filter front and have purchased the 22mm version. The original is 20mm and I had to chose between 16, 22, and 27mm with no 20mm air filters in sight. I've managed to get Heidenau on the phone and inquire about their tires, but the woman I was talking to didn't seem too competent. According to her the only difference between the 2 1/2 x 17 and 2.50-17 is the max speed. Didn't quite convince me so I'll keep my eyes and ears open.

I took it out for a spin today and was surprised how well it runs. I easily squeezed out 55 km/h and more without any engine modifications whatsoever. It's so light and small - the perfect city vehicle. I need to readjust the drum brakes though, they're terrible. And fix the gearbox because 2nd gear is completely gone.
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Old 5 Mar 2010
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I wonder if the little button on the carb is a "prime", to tickle the carb & flood the carb to aid cold starting???? Like me old Triumph.
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Old 6 Mar 2010
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Possible. I'll give it a shot next time, although I have no troubles cold starting - keep the choke pulled, kick 2-3 times and it runs.
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Old 28 Mar 2010
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Pigford, that is exactly what it is. Without flooding the carb I need ten or more kicks when it's been standing for a few days. When opening the fuel gauge in time and flooding the carb, either with or without the prime, it usually starts after the third, fourth kick.

FYI, I've made some progress with the bike. The gearbox is fixed now - turns out it simply needed readjustment to get 2nd gear back. I need to get the clutch adjusted, too. Unfortunately I need to open the gearbox side panel and drain the gearbox oil to get that fixed so it might be a while until I find time to do it.

Edit:
Some more pics (click for bigger version)


So tiny compared to my GSA


5,200 original kilometers






49cc goodness


I've replaced the single mirror with two new ones and am now looking for a 6V horn.

Hard to imagine that this used to be every 16 year old's dream back in the 80s. Today it's all about the Playstation while mopeds/mokicks are laughed at. I've been riding it for a month now all around town and interestingly enough many kids6 seem to mock me and laugh while most 30+ year olds seem to ogle me in awe.
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Last edited by mj; 28 Mar 2010 at 16:12. Reason: Added photos
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Old 22 Sep 2010
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New owner

finally!! i have been googling like crazy over the past 2 months trying to find a thread relating to the bike i just bought. i recently purchased a (i believe) 1984 sachs moped that looks exactly like yours. and while i love riding around on, it seems to run great one day and then poorly the next. when its having troubles it sounds like the engine is struggling to even rev and i can barely putt around at 10 mph. but then the next day i can fly at about 35mph. any ideas? it was in pretty bad shape when i bought it but i have since cleaned the carb, fixed the clutch, ran it with the air filter both on and off, and changed the spark plug. just can't figure out for the life of me why it will run so great and rev just fine but then the next time i start it no matter how much throttle i give it, it just won't budge...

but i do agree, it is VERY fun to zip around on. i'm in college and live about 10 blocks from campus but with the moped (when its running ) the commute it very enjoyable
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Old 23 Sep 2010
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I would put a new engine in, they only cost $150 for a new 125cc that will probably fit straight in.
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Old 23 Sep 2010
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I would put a new engine in, they only cost $150 for a new 125cc that will probably fit straight in.
it would fit a 49cc bike?
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Old 23 Sep 2010
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It wouldn't fit. It's an old German 1980s Sachs 49cc engine and can only be replaced by another 1980s Sachs 49cc engine. Not even every Sachs engine, there are differences. The Supra 3D's engine should be a 505/3 DK. Too bad they've stopped making those in 1991 when they went bankrupt.

Regarding your problems: it sounds like you've pretty much done anything that can be done. It's a two-stroke so there isn't really much maintenance and nothing that can really break. I have two ideas: a) the magneto-generator or spark coil or b) water in the system somewhere. I'm guessing a), maybe you can try replacing those. If we weren't too far apart I'd lend you mine but there seems to be an ocean in the way

Btw, I have managed to find some technical documentation (engine specs, wiring scheme) which I can email you if you're interested. Oh, and congratulations on the bike.
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Old 23 Sep 2010
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ya the engine stuff and wiring diagrams would be fantastic. so how would go about checking the magneto generator, spark coil and all that good stuff?

go ahead and pm me and i'll give you my email address that you can send it too.

thanks soo much!!! this is great!
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Old 26 Sep 2010
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You've got mail! Hopefully

Frankly, I have no idea how one would go about checking the magneto generator or the spark coil. Never had to do something like that yet so I never really looked into it. My guess would be to find someone who has a similar bike and replace it, but that might prove impossible.
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Old 2 Oct 2010
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it would fit a 49cc bike?
Yup, perhaps with a few minor adjustments though. The reason being is that all of these horizontal motors were based on the motor from the Honda CT110 and therefore they're all pretty much the same, the head will be a little bigger of course but if you have clearance behind the front wheel then I think it will work.

Edit: I didn't realise this bike was a 2-stroke but I would still check it out.
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