that has to be one of the coolest looking 4 stroke builds Ive seen I like the way you did the jack shaft
Chassis for 2nd bike
- Thread starter Buzzerbiker
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Crap! My reply died, got to retype it all! Just correcting my gear ratios. It matters to understand this little engine if anyone else is considering using one.I calculated my belt ratio based on pulley diameter, wrong! My overall primary ratio is 22:1, which is my 4th gear. 16T to 16T, BB to cassette. 1st is 44:1, and 5th is 18:1 in round numbers. So, this engine will rev over 8000RPM in 1st. Max HP is achieved at 7000RPM, Max torque is at 5000RPM. In 3rd gear, it'll pull 7000. In 4th, 6600, in 5th, it tops out at 6400 on level ground. I need to pull 7000RPM in 5th if I want to hit 30 MPH, which would be nice on the country roads. I have massaged the jetting, intake, and exhaust to no avail. Don't think I am unhappy though, it is a wonderful little engine. The one thing I found in some research though is the carburetor, a Walbro WYB is rated for 4 strokes less than 30ccs. Since the GX35 is for a rototiller, that is fine. Walbro makes a WYK in many variants for up to 50ccs, so I am researching these models, there are some large WYKs, but I would only want about 20% larger. Just can't leave well enough alone, right? In spite of our schizophrenic weather, I have managed about 130 miles of riding, and still have a couple tank fulls left in my first gallon jug of fuel! Have fun, will keep on tuning.
I bought a Walbro WYK-57-1 off ebay, It is 1mm larger than my OE, 11mm, vs 10mm is significant volume wise, but was a very easy install with minimum porting. This was awhile ago, and while waiting I was scheming how I might dyno the motor instead of running up and down the road a couple miles at a time in wildly varying conditions. Then the lights came on! Remembered my Minoura rim trainer on my basement bike. Gosh that was too easy! My new carb has adjustable HI and LO screws. So I set the rim trainer up for max resistance, and tuned it according to MPH, and exhaust temp. I actually put over 20 miles on the trainer in third, fourth, and fifth gears. Being able to focus 100% on the engine allowed me to see the error of my top gearing as well, so I swapped out 4th and 5th cogs the following week to tighten the 4th and 5th shifts. Went from 16T/13T, to 17T/15T, quite a drop in 5th. But, with the larger carb and closer ratios on top, I'm getting near 8000 RPM, and 30MPH, plus it pulls headwinds and rollers much better now. Finished off my first gallon of fuel at 160 miles, but that is all testing, time will tell, but commuting should easy on gas. Spring is in the air!
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I like your methodical engineering approach, you sound like a man who knows how to accomplish great things. 
Keep it up, and thanks for the rim trainer idea, that's a great idea!
Being able to tune a carb and change gearing stationary and record things is something I hadn't thought of doing on a bicycle. Its almost like a dyno, you might also be able to do it with a generator and a large load high power variable load resistor is such a thing exists surplus for cheap.
I bet one could find the spec sheet from generator motor and monitor the power it outputs minus losses to find the numerical HP at the wheel quite easily. The load resistor would be difficult to find unless you had fixed value shunts you change out or made your own switch.
See, thinking is contagious, thank you!
Keep it up, and thanks for the rim trainer idea, that's a great idea!
Being able to tune a carb and change gearing stationary and record things is something I hadn't thought of doing on a bicycle. Its almost like a dyno, you might also be able to do it with a generator and a large load high power variable load resistor is such a thing exists surplus for cheap.
I bet one could find the spec sheet from generator motor and monitor the power it outputs minus losses to find the numerical HP at the wheel quite easily. The load resistor would be difficult to find unless you had fixed value shunts you change out or made your own switch.
See, thinking is contagious, thank you!
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Thanks 16! I got that rim trainer new for $120 7 yrs ago during my rehab period. You may find one cheap on ebay, and take some real techno leaps with those thoughts of yours. The Minoura is so smooth, there is little friction loss, so adapting a generator and working out the "watts" would make you a true low power dyno quite reasonably. Retirement has turned me into a more methodical man than before. As a second generation Master Tech, gears and fuel run in my veins. LOL! My disability keeps me out of big stuff, so bicycles and RC have become my outlet for gearheaditis; havin fun. Thanks for the encouragement, I have more pics next week of the 99.9% finished product. And BTW, I really dig your bikes too! Am the racer at heart, you are an artist!
Hey again"16", After signing off last nite, I remembered selling a Leece Neville 250AMP alternator last year too cheap. Dang, that would've have potential for a 4.5 HP capacity! Oh well, here are my 99.9% complete photos. Nothin's ever 100%, right? I got that giant handle bar bag for 75 cents at a thrift store and it is perfect on the seat. The fenders came off a Huffy I took on trade. Don't usually use fenders, but I think they look right on this build. Am also 99.9% satisfied with this as a pleasure cruiser, soooo smooth and Quiet! I have however been studying the volumetrics of this engine as compared to bigger single 4 strokes I've rodded. So, I can get another cam for less than $20. Am seriously thinking a regrind with .020-.030 more lift, no change in duration. You can change the cam and set lash in 5 minutes! The regrind however is hours! HMMMMMMMMM? Anyhoo, have fun all, I certainly am!
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Hey gang. Just an update now that test and tune is pretty much history, and I've been enjoying the scenery and waving at the rubberneckers on the road. My idea of regrinding a cam is off my mind after a few weeks of nice riding. The roads here are just to rough to cruise over 25MPH in most places on a bicycle. Buzzer II has been a blast, have a lot of gear heads here, so always get to stop and do a show and tell almost every time out. And how about 220 MPG guys? Ya, it's awesome, 21 miles on 12oz of regular fuel every time! If I blast down a county road WOT for an hour it uses more, but on urban rides it just "SNIFFS" the fumes. LOL I did add a forced air intake like what modern chainsaws use off the flywheel fan. In reality it is a very small boost effect, but it now pulls the 6% grade west into town in 2nd gear at 15MPH without pedaling, vs 1st gear prior. WAY fun, and I just don't have a desire (yet) to try to top this, at least as a practical ride! Have a great summer all, and pray for Boston! 