Part 1:
I went to ride the spree to work Friday and she wouldn't start. Turned over 'till the battery died, but never fired. It was like she wanted to fire, but just wouldn't. I had just ridden her 3 days prior with no problems. I hooked up the battery charger and kept going. Nothing. I ran out of time so I took another motorcycle to work.
Came home and tried again. Same result. Pulled the plug to see if I had spark. Check. I unplugged the auto choke, no difference. I took off airbox side of the carb and I thought that I would manually choke the carb with my fingers and I noticed that there wasn't much vacuum. Didn't think about it much because I'm not really familiar with 50cc 2 strokes, but my chainsaw has more vacuum than that. next, took off the carb. cleaned it all out. thought maybe there was something that had clogged a jet or something, but found nothing.
Next I took off the exhaust to have a look in the exhaust port and I also wanted to check out the header to see if there was a restrictor that I could remove anyway. Just for fun, I hit the starter and she fired up. I quickly shut it down because I think itÔÇÖs bad for a motor to run without any back pressure. Finally, I looked down the tailpipe and found this:
I stuck a screwdriver in there and some kind of * off black bee or thin fly flew out and there was what looked like dried mustard all over my screwdriver. The amount of nasty yellow grime that came out was amazing. It must have been 6ÔÇØ deep. I started the bike and revved it up and jabbed my screwdriver up there until I didnÔÇÖt get any more crap coming out.
Part 2:
Now, as I was doing all this, I was taking notes on the jetting (68 main, needle 4th down), and looking for some free mods I could do to get just a little more performance out of her. I had heard of a restrictor washer in the exhaust header, but maybe it was another model. I also heard of drilling extra holes in the airbox. While I was doing this I noticed that someone had drilled one hole, so I drilled 2 more. Thinking more air = more power.
Now I took her out for a test run and she would fall on her face over ┬¢ throttle or 20mph. went back to the garage and did some bench testing and all the problems went away when I put my finger over the 3 holes in the airbox. I put some tape over the holes and she was better than before. I think the one hole was leaning it out just a little. The point of the story is: Tiny little adjustments on this bit of kit make huge differences. I was amazed. But what it also means to me is that thereÔÇÖs some power to be had with a larger jet and maybe even more holes.
Next:
I'm going to buy an assortment of jets 70-80 and see how many holes I can drill and match to the jetting. I would imagine that at some point I'll hit the limits of flow for the exhaust or carb.
-Kevin
these dam bugs
