Wednesday, May 11, 2011

Peugeot, finally

If you're a compulsive moped tinkerer such as myself (and why would you be reading this blog if you aren't one?) you probably have had periods in your life where you were forced to daily-drive a bike that just isn't right. For me that period was this entire winter. I rely on my bikes for 365-days-a-year transport to school and work, so its pretty frustrating when my daily driver isn't sorted out, and having my workshop way the heck on the north side, without a station wagon or truck to move mopeds in, this winter has been very frustrating indeed. The poor little Pug has spent most of the winter maligned, and limping along way out-of-tune.

Since this little green 103 is my first foray into Peugeot tuning, there have been some speed bumps this winter getting the old girl running just right. Since it is an ongoing project, and pretty much the only thing i'm doing that I can talk about, I've been whining on here about the trials and tribulations encountered while setting it up.

So, it is after a ton of mucking around that I am so happy to report that this bike is finally sorted out and will be receiving a 'cranks' headlight sticker, as it is finally worthy.

About 2 weeks ago, I forced open a hole in my schedule and stopped by Blaze's garage, which is about 1/3 the distance to my workshop, and he has the Pug puller set. I was concerned that the last time i put the flywheel on, i clocked it in the wrong position. I removed the flywheel and reinstalled it, started up the bike, and was very confused by the fact that the pedals were spinning vigorously. D'oh! Put the damn flywheel on backwards, so the engine was running in reverse. Pulled it off again and re-installed it to find that the timing marks i had on there from the first time, and i had lined up to the second time, were still dead-on.

I set the timing at 1.40 mm as accurately as possible, and took off. By the time i got home, i was seeing the same heat fade, loss of torque, etc. as i was before re-clocking the flywheel.

About a week ago I finally got the Peugeot head machining Jig finished and turned an extra stock head I had laying around. I swapped that on later that day, noticing a ton of carbon buildup on the piston face, cylinder head. In my experience, carbon buildup usually means too advanced timing (leading to the heat which cooks oil into carbon) and too-rich mixture (too advanced timing feels like running lean and most people richen up the jetting to try to fix it)

With the hi-comp head, i found that when cold, my torque was through the roof, but the heat fade was getting worse. It seemed pretty crazy, but my timing spec (.1 mm retarded from the stock setting) was apparently still too advanced. I finally backed off the timing to some eyeballed amount around 1.2 mm and couldn't believe the difference. The bike is now pulling hard all the way up to top speed, which still feels a bit lacking, but that could be due to variator tuning, worn-out-after-a-harsh-winter-outdoors wheel and pulley bearings, or the restriction still present in the un-ported intake manifold.

Also, now that the timing is adjusted properly i should be able to dial back at least 5-6 jet sizes in the 14mm bing. It isn't four stroking right now but the plug is dark and sooty. We'll see what that plug looks like after a few miles with the correct tuning, then adjust and hopefully realize some performance gains from the right setup.

I just saw someone had posted the transcription of Jenning's chapter on spark plug selection and timing advice. Great advice and a must-read for any up and coming tuners. Personally I think that Jennings book is pure gold and a a great place to start for anyone who wants to get into 2-stroke tuning, but that chapter is especially good. Its pretty crazy when a long period of trial and error prove exactly what Gordon wrote over 30 years ago, to the letter.

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