rollmyown

I made a couple of prop hubs and ran a single bbl and a 2 bbl Toro, both with a Master Airscrew Classic prop. I used this same prop to test the 21 and 25cc engines I have done. The 2 bbl toro gave 7300 to 7400 RPM. I use a ACE Tachmaster that I modified and added 3 extra scales to along with a 2 or 3 blade selector switch. As long as the Sun is out, I have a 5k, 10k, 15k, 20k, and the 25k RPM range. I still have the article to do this somewhere, if anyone is interested in the modifications. OK so the 2 bbl put out around 7300 to 7500 RPM and I could see it was not going to go much higher so I concentrated on adjusting the idle, THE ONLY ADJUSTMENT, and it would idle nicely around 2200 RPM or so. These are still new engines with very little time. The throttle response is very quick. The single bbl engine idled great, but sagged above 3/4 throttle and I was running out of time today for this. It was obvious that the single bbl carb has problems. I will take it apart out of curiosity to see if I can find the problem. The way these carbs are designed, they are Walbros by the way, it is very difficult to "bore" them bigger. There is wire that moves into out of a plastic tube, when the barrel rotates. The wire doesn't look like it can easily be removed to work on the bbl. I would try this if possible because of the excellent throttle response. I now am going to make a carb spacer adapter and try a 13mm Zama (9/16") to replace the single bbl. I haven't given up on the 2bbl engine. I am going to look at the ports on both engines also to see if they can be opened. I think an aluminum plate adapter is possible for the existing 2bbl carb spacer to adapt a 13mm carb to it also. I am going to modify the existing 2 bbl carb spacer/manifold also. I think the main intake port can be opened some and I am going to leave the secondary Reed ports in place and in operation to see how this works. I think there could be some potential with using the Reed ports, after all there are already there, and before I defeat them, I want to satisfy my curiosity. One other point about these engines, I think a aluminum plate mount bolted to the rear of the engine is well worth the trouble. 1/8" is thick enough, and this gives you a larger footprint for mounting along with strengthing the rear of the case, in my opinion, for not that much weight. I use a 3" x 4" plate with the engine centered. I counter sink for the 10-32 mounting screws, but not all the way flush. If you leave them a bit high, your firewall will keep the screws from backing out. Another small point is that the muffler on the engine can work out very well for a side mounted engine. The screen "spark arrestor" (I guess that is what it is for) is easy to pry off and then an exhaust hose could be used. I tested with the original mufflers and they are pretty quiet. When you examine them, it doesn't look as though they would restrict the engine too much and they are not overly heavy. Until the next chapter of the Toro saga.