Hi all,

I just picked up a 1978 mkII moped for 80 bucks. I got it running, but with TONS OF WHITE SMOKE. Im premixing, since i dont trust a 20 year old oil injection setup.

Its a 2 speed with new atf fluid, but the trans shift like crap. I have a maxi 2 speed, and it shifts MUCH BETTER. The clutch is reluctant to engage, and when it does, it rides first gear, and then after playing with the throttle, i can push it into second.


Anyways, the fuel tank is starting to loosen up with LOTS of rust. It turns the gas in it brown and rusty, and when i take off the fuel valve, big CHUNKS of rust come out. How can i clean this


Sorry for the long post


Mike (MA) /

HI Anthony,

I just posted the same "shift adjustment" question this weekend. My 2 speed shifts too early. One fella said if the ATF level is wrong, this would affect it. Mine's ok however. It's supposed to be up to the side-plug level. So I still don't know what I can do to adjust mine.

Concerning the tank rust, there are lots of posts in the archive. They cover the spectrum of advice on this. I've used the Kreem kit of acid/acetone/sealer-paint on a motorcycle tank, and it worked very well. But it was alot of work, and I clogged the 2 ports at the bottom lobes of the tank w/ the paint, which was a hassle. On my Puch tank, I wanted to forgoe the effort and cost of the Kreem kit, so I tried Naval jelly (any hardware store) diluted w/ 25% water. I left it in for 2 hours, and it did almost nothing. If you go that route, plan on overnight-2-3 days. If I was going to do it all again, I'd spend the $30 on the Kreem Kit and do it right.



The cream kit is the way to go but I used to have to clean old tanks with a bunch of rust and crap in them. The cream I have never used but have seen it and have heard great things about it.

A half good fix is to take the tank off and put some rocks in it, then put a little kaerosene in. Take the whole thong and slosh it around and around and around. You will have to drain and refill it several times depending on the amount of rust. Use nickel sized rocks. The ones made of quartz in the street will do. You can shake, rock and jiggle the thing around making sure that the abrasive (thats the rocks) are rubbing against the walls of the tank all over.

Once you are finnished, you need to make sure that you put something over the surface of the inside of the tank to clean out the karoseen. I used the keroseen because it will help to break down any oil goop from having the gas just sit in the tank. Make sure that you put some gas treatment in the first tank to get any water out that may have stayed in the tank.



Take your tank off the bike. Put about 3-4cups of pea gravel in your tank with like a whole can of carb cleaner and another can of engine degreaser. I have used a little black sand blasting sand too. Shake the hell out of it numerous times. Keep shaking for 15-20 minutes. Your arms will get tired and you will have to stop and start again. This will be a good workout too. This will loosen all the crap up that is stuck to the inside. Empty all this stuff out and then rinse it thoughly with soap and water. Keep rinsing until ALL particles are out. Then blow it dry with an air hose or a hair dryer. Then take the petcock off and take it apart and clean it too. I have used this technique with 100% success on every cycle tank that needed a good cleaning including my Magnum. It won't work on step through models though. Unless your a gorilla and can shake the whole bike. If done correctly, your tank will sparkle inside. And, you will not have to keep cleaning the rust out of your petcock. The other thing you can do is install a clear in-line filter to monitor your success. It may seem a little radical but it works and it costs very little. Good Luck


Mike (MA) /

Beware of the Magnum petcock. I took mine apart, and I swear I didn't loose any peices, but it leaks, no gushes, now. If you still do it, know that it's spring-loaded, so don't shoot your peices into the neighbor's yard.



Ron Brown /


Take the sugestion to search the forum using words like tank, acid, rust.

I have used the gravel and solvent method, the Kreem kit, muriatic and phosphoric acid, you will find details on all of these if you search..

My favorite is phosphoric acid. I have had no problems with re-rusting, especially if you use pre-mix. The oil seems to be a good enough protector. The in-line fuel filter is also a good idea.


Re: Transmission

Are you using F type transmission fluid ? If it was used for any length of time with Dexron the clutch plates will be shot and will need an overhaul. If it just sat for a long time you may be able to make it work by just riding it a lot and changing the transmission fluid often, if it still won't work you'll have to open it up.

Thanks Everyone!!

I appreciate everyones responses, im currently taking the tank off.

Also, the rear mag has a flat spot in it, is there a way to fix it?Brian wrote:

Re: Thanks Everyone!!

Anthony , I have a friend who runs a bike shop , he had a bike with a flat spot and called one of those places that does mobile dent repairs and they fixed the wheel very well..

Bending the rim

Do you know the number to it? Mag wheels are expensive, so a repair seems feasable. THANKS

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