I saw the thread "how fast is your ped" and thought I had this to say about that... My stock 1977 Pacer P-78 Sport maxes out at about 37-39 mph on a flat road with no head wind. The TomTom and the speedo seemed to be in perfect sync on this. I'm working on the other '77 Pacer to get it up to par with this one.
Previous to a couple changes on the P-78, it was maxing out at about 33-35 mph. I pulled the BOSCH plug, sandblasted it, regapped it and reinstalled it. Then I took off the 31 year old spark plug wire (oh yeah, the plug is 31 years old as well) and replaced it with a length of spiral-wound, carbon core-low-resistance spark plug wire that I scabbed off of my 1989 Mazda 323 before I donated it to Goodwill. The difference in the performance was immediate and very noticeable. It sounds ten times better and runs much smoother. I also attribute the way it runs to the oil I use, nothing but Castrol Two-Stroke and remain faithful to the 32:1 mix recommended in the M-1 service manual. I sure there’ll be some feedback on the oil and mix, but I’ve tried all sorts of different oils including synthetics. The Castrol was the last oil I tried yet not the last oil by choice. I looked for it everywhere but couldn’t find it, then finally located it at Pep Boys.
I’m old school when it comes to two strokes, particularly when it comes older technology. I’m not a luddite and sure, I know there are a lot of great lubricants out there, however I tend to err on the side of caution when dealing with old machines, particularly old machines made of magnesium.
The P-78 wouldn’t run for shit with a clean properly gapped plug with synthetics mixed at 32:1. Had to choke it longer, the plug fouled and the power band arced downward. With the fuel at a 40:1 or 50:1 ratio it ran considerably better, the trade off though was heat. I don’t have an infrared thermometer gun, nor any means of getting an accurate gauge of temperature off the head, but I’d venture to guess the cylinder and head were a good 75 degrees warmer burning synthetics. The low friction of the synthetic oil changed the way it ran and I didn’t like it. Throttle response changed, choke/warm-up time changed, and again, the heat it threw – none of it really for the better, not if I want to keep our peds running. And it didn’t sound right either.
If these 31 year old engines were made of aluminum I wouldn’t be so concerned, I’d tinker with synthetics and find something I could live with, but they’re not – they’re made of magnesium. While magnesium is an extremely durable material in a well maintained state, it is easily compromised and weakened by moisture. There is nothing that will kill a two stroke engine made of magnesium quicker than water and/or moisture. I’ve seen where exposure to rain seeped down head bolts and oxidized where the bolts threaded into the casings. This initially led to blow-by at the base gasket and then complete failure of the head bolts. Thankfully there was enough beef on the cases to drill them out and helicoil them.
Most folks don’t bring their newly found ped home and commence to taking it apart, i.e. pulling the side covers off and having a look-see. Then again, sometimes you wish you didn’t have to see! If there is some unseen oxidation lurking within the introduction and stress of more heat is only going to worsen matters. In an engine so compromised, the vibration and mere revs of the engine itself could cause its own demise.
In an ideal world, if I had a cure for pain, and if I had all the tools, I’d bust the cases apart and send the whole thing out to have it dipped and plated (cadmium) or painted. (Proper preparation of magnesium for plating or paint is some really nasty shit, neither are for the do-it-yourselfer. It involves some highly toxic and flammable chemicals that will cause you to grow breasts on your back and a penis on your forehead. Besides, I doubt most of us could get our hands on any of these chemicals anyway. Just as well!) Dipped and heat plated cases, jug and head is the best. Dipped and painted cases is second best. Both are just as good and will probably set you back in the area of $75 – 100. Again, I speak of an ideal world, cost and time prohibit me from doing this.
Our two Pacers have low, low miles and have been kept dry/indoors and have overall been well maintained for 31 years. If they were in poor repair I’d consider the expense and do as much of a rebuild as I could with parts available, and of course, have the cases done. For the sake of the bolts that haven’t seen a torque wrench for 31+ years and the tired gaskets, I think sticking with manufacturer recommendations on the type of oil used in the oil bath clutch (no detergent!) as well as fuel/oil ratios. I’ll run it till the wheels fall off like this. On a resurrected ped this just seems to be the best practice for me, besides the P-78 sounds pissa!