MKII and the Muratic Acid Adventure

Possibly the most beautiful moped Puch ever made, the Brown and Gold MKII Magnum.

This particular model was the 2nd moped I ever purchased, I bought it in a lot of 3 mopeds, including a Columbia Commuter with a Sachs engine, and a 1980 Puch Maxi 2hp. I'm glad to still have it, but one of the few things that was wrong with it when I got it was the tank was rusty. I've used just about every method of tank cleaning known to cheap man. I've tried Vinegar, Coke, and other rinses, but I decided to give a real acid a chance. I bought a jug of muratic acid at Lowes and started my process.
I took the tank off the bike, and drained it. The petcock was so plugged with rust that the reserve didn't work at all, and the on was just a trickle. I rinsed out as much rust as I could with water, plugged the petcock with a rubber stopped, and it was time for the magic. Muratic acid is some nasty stuff, and it sure made the building reek. The fumes were super strong even in a giant shop, so I opened some vents, and left the building. I let the acid sit for 40 minutes and then came back. The tank still looked a bit rusty, but when I drained the acid, any trace of rust left with it. I then corked the tank again and filled it with baking soda and water. I hoped that would neutralize the acid. I shook it all around and got the whole tank coated. I then just put the whole deal in the sink and let water run through it for another 5 minutes. I didn't have any denatured alcohol, so I just sloshed some WD40 around inside, hopefully removing all the water, and then rinsed it with straight gas, followed by a quart of heavy weight oil, to hopefully coat the tank a bit. Finally, after draining the oil and rinsing with gas again, I declared it all clear, and put it all back together. The tank looks very clean, not brand new, but there is no rust at all.

To finish off this project, of course, I was only greeted by more problems, as the luck of my moped adventures usually go. The bike stalled out on the way home, felt like it was running out of gas. I cleaned the carb, assuming a little more rust had found its way past my inline filter, but it was clean. I wondered if the float was sticking, so I put on a new 15mm bing I had sitting around, and it ran with the same problem. It would rev out on the stand, but if the throttle was held open too far, after a few seconds it would stall out from lack of fuel. When I try to drive it, it stalls out at anything more than 1/4 throttle, and if I keep the choke on, I can get it up to about 20mph, but that's it. I'm running a 14mm intake on a ZA50, with a Boss exhaust. I've got a 66 jet in it. Shouldn't be too lean, considering when was all stock with 12mm intake and stock exhaust I was running a 52. It doesn't feel like too rich, so I'm confused. My main guess is that the fuel is contaminated, perhaps some water left over, or condensation from going cold again after being in the shop. I tanked it all the way up, naturally, after cleaning the tank, so I have to drain all that gas and dispose it, I suppose. What a waste. What I need is a small fuel tank that has a fuel valve that I could just put some known good fuel in and hook it up to the carb, so I don't have to waste all my gas, if that is not the problem. Does anyone have a small troubleshooting tank like I've described?

Oh, and for those of you bored with these bikes, I'm getting 3 wonderful frames back from the powder coaters on Tuesday. A Maxi, a Swinger1 and an HS50. Pictures to follow!

Oh, PS, I like comments, even if we have never met, or it is irrelevant to what has been posted. If you find this blog informative or amusing, please comment!