20 Year Old Moped Advice- Help


I'm Rob and I have recently become fixated on the moped I found in my garage that once belonged to my father. It is a Puch MKII Sport that I believe is an 1980 model.

My problem is that the gas inside the tank is 20 years old. My dad said that it has most likely gummed up inside, but he does not know whether we should dump it or not. Should we empty the tank?

My second problem is that the moped has a sticker that says something to the effect of "Do not use unleaded gasoline." How do you guys deal with this problem?

This is as far as I have gotten yet, but I do not dare advance in trying to start it until I know the answers to these problems. Any help whatsoever would be appreciated.

-Rob- New owner of a Moped

Re: 20 Year Old Moped Advice- Help


Whatever is left of the gas in that tank is nothing but a liability. You need to get it well cleaned out before you try to do anything else.

If you can get a light in there and inspect things, that will help. Hopefully, it's not all turned to rust and sludge. Either way, you're probably going to have to flush the tank out with some fresh gas before it's ready to supply fuel to the engine.

Re: 20 Year Old Moped Advice- Help

What would this require?

Should I turn the bike over and dump it? And you say to flush the gas out with some new gas.- I don't quite understand what you mean by this. I am sorry for being so needy, but I am almost completely new to the auto part scene.

I moved the bike around, and i could here it move when I stopped so it has become total syrup yet. And there is still the problem with using leaded gasoline. I assume flush means run the bike with some good gas, but I do not know how to get a hold of leaded gasoline.

Sorry for needing so much guidance.

Re: 20 Year Old Moped Advice- Help

What the austrians ment by not using unleaded gas and what you ie: "americans" think of unleaded gas are two different things.What they ment by that warning was not to use "white gas" the kind used in lanterns and camping stoves.You can use Unleaded gas from the gas station no problem.Just remember to mix it with two stroke oil at 50:1 or 2.56 oz of two stroke oil to 1 gallon of gas = 50:1.HTH.jim

Re: 20 Year Old Moped Advice- Help

what you wanna do is just get a crescent wrench and remove the petcock (the thing sticking out from the bottom of the fuel tank) and just tip the bike over on its side; you can drain the fuel quick and easy this way. screw the petcock in a little ways and put a little fresh gas up in the tank and shake the bike around a little bit and repeat; if the stuff draining out is looking brown and rusty you might wanna swish a couple of times and see if if helps. once you feel like the tank is clean put the petcock back in and fill it up for real. you can put regular old unleaded gas in there; the warning is to prevent people from putting kerosene and shit like that in the tank and expecting the bike to run. mix 2-stroke oil in at a 40:1 ratio (approximately 100 mL per gallon of gas) and you should be cool. might wanna pull the carb and give it a good dousing in carb cleaner, and put a new spark plug on it. you can get a little inline fuel filter if you feel that your tank is really sketchy; a little rust or some debris in the gas will foul things a lot less quickly that way

next you say you have a mk II sport which means it is two speed; the two speed gear box is a lot of fun and you want to make sure it treats you right. this means that you should put fresh tranny oil in the gear box. this is the big rectangular thingy on the right side of the bike that says PUCH on it. you can do this two ways.

the way that you really SHOULD do it is, remove the six flat headed screws that secure the transmission cover to the bike and pull the cover. there are a couple washers that might come out with the cover, so keep an eye out for them and the order in which they come. dont want to lose em. account for the washers and then tip the bike, draining out all the tranny fluid that is probably raunchy by now. keep an eye on those washers. once all the fluid is gone wipe up the dregs, put the washers back on the shafts if they happened to come off, and reattach the transmission cover. watch out for the bolts - there are two or three different lengths of bolt, each specific to one hole. make sure you put the right bolt back in the right hole. it is pretty obvious when you are screwing it back together which bolts correspond to which holes. don't force anything. also when you are seperating the transmission cover from the transmission you see there is a little oil paper gasket between the cover and the transmission; try not to mutilate or tear this in taking the cover off or putting it back on. once you have the cover on, grab a jug of TYPE F automatic transmission fluid. you see there is a little drain screw on the face of the transmission (the one smaller screw besides the six that you had to remove. it is around the P in PUCH approximately or so...) remove this screw. then if you look at the top of the transmission there is a little plug, remove this and use a funnel to fill the transmission until fluid starts to leak out of the drain hole when the bike is standing perfectly upright. once you're done, stick the plug and drain screw back in and the transmission should be solid (assuming it works to begin with).

if taking the transmission cover sounds intimidating to you, you could just use take out the drain screw and tip the bike, and try to drain the fluid as much as you can that way, and refill as above, but you will not get rid of a lot of the old dregs that way, so you dont get totally the effects of fresh tranny fluid.. but its probably better than nothing. either way, you should do something about the tranny fluid.

um, check tire pressure against the little metal plate on the bike. you should then be ready to fire it up.. if you have any further problems then something is wrong with the bike.

Re: 20 Year Old Moped Advice- Help

Thanks ALOT guys,

I will surely do this stuff tomorrow. I already filled the tires and I am glad to hear the bike doesn't run on the kind of gas I was thinking.

As for the Transmission, it does sound intimidating, but I want to do this right so I will go with what you say.

Thanks again guys.

Re: 20 Year Old Moped Advice- Help

imho, tomorrow would be better spent downloading, printing and reading THIS MANUAL ..cover to cover..

People who know nothing get a hold of a bike and have a lot of enthusiasm to fix it.. and then things get accidentally broken.. (this forum offers a multitude of examples.)

So I'd recommend you learn all you can about that bike before you dive into it... and if all you own is a hammer and a screwdriver and some pliers, get thee to the tool store asap..

Re: 20 Year Old Moped Advice- Help

Another thing to think about is the mess in the bottom of the carb.

Grey live to ride, Ride to work

Re: 20 Year Old Moped Advice- Help


Ya thanks I now have the manual on my computer. It doesn't seem to have anything pertaining to the fuel tank on my model, even though the manual is for my my model. I will go by "the sean's" advice.

As for the transmission, I think I will do that after I read up a litte on it with the newly aquired manual.

Thanks joew for the link.

Re: 20 Year Old Moped Advice- Help

A bike left with fuel in the tank that's been sitting for decades needs thorough cleaning. The entire fuel pathway from the gastank cap, through the filters and fuel line, through the carburetor and to the engine should be disassembled, cleaned and carefully reassembled. Nothing is as important to assure reliablility and provide good performance as is a sparkling clean fuel system.. no dirt.. no fuel or air or vacuum leaks.. no nothin'.

This forum's Search function should turn up lots of general information that applies.. people are always talking about cleaning tanks, etc.

Re: 20 Year Old Moped Advice- Help


By flushing, I mean that you will need to at least fill the tank with some gas, let it soak for a while, then drain it out. If the tank is really varnished up, then use acetone followed by a gasoline flush.

I'd think twice about removing the fuel petock. If it works, then just leave it as-is. It's likely that (assuming it's not leaking now) if you remove it, you will not get it to seal up again.

But if both the 'on' and 'reserve' positions don't work, then you might as well pull it. You'll probably need a new fuel petcock if it's that loaded up.

Just be gentle with it, and don't disturb anything that doesn't really need it.

The comments on carb cleaning are good. The chances that you'll get away without a cartb clean are slim.

Re: 20 Year Old Moped Advice- Help


Got your email, and wrote a response - but for some reason the email address you used will not accept mails.

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