Wednesday, May 21, 2014

Peugeot stock variator tuning - a story in pictures

I did this about 3 years ago. After making some modifications to my stock Peugeot 103 to give it more top end (pipe, porting, SHA, reeds), I spent a couple hours removing, drilling, and re-installing the weights to tune it for better acceleration.
Stock cylinder ported, very minimal

My brother at the time was running an Airsal 70 on his, with a PHBG, and was happy with 2 M6 nuts on the swingarms, I tried that and my engine didn't rev high enough to stay in the powerband.

So this is, in pictures, how I ended up tuning my stock 45 mph peugeot 103.










In the end, I ended up going back to a smaller hole (I had a small pile of these weights laying around to play with) for my very conservative engine. I tuned the clutch with 3 balls and 1 star spring.  Having a super high clutch stall and ripping high rpms before you variate sure sounds impressive, but for a stock setup like this, all that sound and fury doesn't get you going much faster. 

The lesson here is that variating too slowly and revving out of your power band is just as bad for a stock setup like this... well maybe not just as bad, but not nearly as effective.. as variating too soon. 

I'm not sure if i ever did measure the small hole + rounded ears, but i'm going to guess the weight was somewhere in the neighborhood of 20.5 grams.  On a higher revving setup the 2x 5/16" hole may be the ticket coming in right around 18 grams.  The numbers listed on there are cumulative meaning that each mod removed weight further resulting in the posted number.

The breakdown is like this: 
Stock Weight   ...... 23.8g
1/4" Hole         ...... -.8g
3/8" Hole         ...... -2.5g
Round ears      ...... -2.25g  (obviously dependent on how much you grind off)
5/16" hole (est) ..... -1.75g

Obviously there is going to be some variation in where you drill the holes and how much effect they have, the ears seem like they would make the biggest difference as they are farthest from the pivot point, the hole in the base probably not so much. 

Also, dont forget to check and adjust your stop to make sure you are variating fully. You don't want to stress the arms, pivots and other parts by letting the slinging weights apply constant tension (this will smash the plastic guides by the way) but you do want to let the arms push up to almost completely closing the variator. In fact push up just a hair away from fully closing the variator. I didn't take pictures of this, but as i mod my stock vario on my TSM i'll be sure to snap a few pics of this adjustment. It is super important to getting full top speed. In fact, on the TSM i'm actually thinking about modifying the cheeks for an 'overdrive' function and letting the belt actually ride up to the full limit. 

The other take-away is that the stock arms are about 1/2 gram imbalanced from each other. If you don't end up using them, you shouldn't have to worry about it, but on a ripper 10k rpm setup, that 1/2 gram could be enough to shake a carb loose, crack a bracket, or even contribute to crank failure. Get out your dope scale and dial these puppies in. 



DONT FORGET THE RED LOCTITE WHEN YOU PUT THE SCREWS BACK IN. 

IF THE SCREWS ARE KINDA STRIPPED OUT MAYBE GO AHEAD AND REPLACE THEM WITH SOME ALLEN HEADS, OK?

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