Well after a long while the bike rides again and better than ever!
Worked with Fred Koehnke and he was very helpful, spending many phone calls with me working out the problems.
Part 1
- Sent Fred Cylinder, crank, rod and piston. My cylinder was already bored out to 0.030
- Received replacement rebuilt crank+rod, modern piston and mated replacement vintage cylinder.
- Rebuilt motor with new parts, started up and ran for a mile or so and then started locking up.
- Call Fred, gets some solutions to check.
- Mess with carburetor, break off high speed adjustment needle. Curse.
- Test piston spacing, crank/crank bearing is seated correctly and centered.
- Open side cover, find damage to edge of needle bearing.
Solution: Replacement crank was slightly wider than original or crank shaft spacing washer was oversized/matched to old crankshaft. This made the crankshaft too tight against the needle bearing/side plate and shoulder of crankshaft would seize against needle bearing/side plate.
Flat ground washer down and pushed out needle bearing about 0.08" Fred said he runs them sticking out of the side plate like this to reduce chances of contact with shoulder or end of crankshaft.
Part 2
- Purchased new needle bearing and replacment Carter needle and seat kit from Fred
- Rebuilt side cover with needle bearing
- Set bike up on stationary stand.
- Couldn't get bike to idle low, motor would run up RPMs or die. (This was kind of how the bike acted before, but now it was worse with all the carb adjustments off now)
- Called Fred. Fussed with adjustments with no improvement.
- Sent whole carb to Fred.
Part 3
- This carb I bought off ebay ~10 years ago to replace original which was rotted out by moisture. It is a Carter Model N, but it is not a whizzer version, but rather has the gas inlet in the side and a throttle pull direction 45 degrees off of the whizzer style. I modified the gas inlet position and swapped parts from the Whizzer carb. Always ran rich and thus I ran with a modified air filter made from fine brass wire mesh. (Fred informed me that this carburetor is for a slightly larger engine but is identical aside from a slightly larger venturi, causing issues with gas flow when paired with this engine.)
- Fred rebuilt with better condition throttle butterfly axle to remove slop, new butterfly plate and did some "trade secret" modifications to it to make it work better with the "smaller" whizzer motor. As well as bench tested it and adjusted hi-speed and idle air needles correctly.
- Received carb, installed and on bike, put bike on stand, opened fuel petcock and gas started to pour out overflow port.
- Called Fred. (I ran into this issue when I first bought the motor 16 years ago due to a hole in the fuel float, but had forgotten how that had caused this problem) Fuel bowl was stuck down from the assembly being dry. Fred advised starting the motor with petcock off and letting the vibrations and fuel flow out of the bowl reset the float assembly. Tried this and then opened to petcock with no more overflow.
- Dialed in idle adjustment on stand and runs like a top! No runaway RPM can idle way down maybe at 700 rpm, but set to 1000
Bike went for its first full on-road test ride of 12 miles and performed perfectly, probably the best it has ever ridden since the original carb had issues as well, and the crankshaft end washer was probably too thick as well.
Three Hurahs to Fred, and hope he can pass on his "trade secret" carb fix.
Bike is always a hit where ever it goes. Got two admirers at the sandwich shop in 5 minutes and kept a half dozen friends entertained for some time at a party when I rolled u
