Kreidlers like to stay stock, but a few things can help on the hills.
The first mod - Removing the baffle in the exhaust pipe.
- The end-cap unbolts, a 10 or 12mm, hit it with carb cleaner, and pull it out.
- Drilling a little to weaken it helps if it is stuck.
- It adds a crackly-crack-crack when you let off or hang at like 1/3 throttle. Sounds cool
- Adds 1-3 mph. Improves acccel in your head only.
Second mod - Take off the airbox and using panty-hose as a filter.
This caused my bike to actually hit 41 max downhill with two people, 36-38 down grade flats, and 27-33 sustained on up and down roads. This is with a 64 jet-12mm bing. A 68 improves accel, but limits top speed. I need to try a 66, that might be the trick.
Third mod - Second gear clutch spring mod---coming soon with pics
This mod involves two people and patience.
Remove second gear clutch, disassemble - don't lose your chin, and removing with a belt sander 5-13 or 17 coils of the single spring-it only has one.
What this mod does, is cause a lag until the second gear hits-shifts and lets the motor rev up past 1/4 throtttle before shifting.
Stock is 9-11
I got mine to 13 by taking 5 off.
I am shooting for 17-19 shift-downshift to help keep the revs up on the hills.
CAUTION -- It is very dangerous and requires two people for reassembly because the sping is so much tighter.
Upgrading carb to 14 or 15mm Bing
3. Bore out the intake to desired size! (14, 15mm) I didn't take a picture because why would I? Hit it with a drill, or file, or dremel, or a bunch of sandpaper, etc.
4. Fit your now modified intake with a 1.5mm SHA shim. This part takes measuring because I'm not sure which one I used. MAYBE THIS ONE https://www.treatland.tv/Dellorto-SHA-carburetor-shim-moped-1-5mm-p/dellorto-sha-shim-1.5-tomos.htm ?! Either way, I have full confidence you will figure that out. The shim LOOKS like it is loose in the photo but trust me it fits perfect. My intake's OD was 18. These things are cast so your results may vary.
5. Put everything back on your kreidler and rejet. A 14mm bing (no air filter) along with biturbo pipe clamped onto the stock Kreidler header will get you to 37mph+. Start in the mid 70's when jetting with this setup. It is a snug fit between the carb and engine case but it does fit. Might have to tap it on gently. It sits ever so slightly at an angle but close enough. You will need a sharply curved throttle cable guide in order to fit under the stock Kreidler sidecover.
- Carb upgrade to 15mm Bing: Buy new 15mm Bing from Treats, have somebody modify the stock intake to accept the larger carburetor. Upjet and enjoy! My main Bing jet was 82 last fall with no air filter.
- Exhaust upgrade: Have someone hack your header onto a Proma Circuit for a Vespa. Extreme top speed and acceleration improvements from doing this! Much better investment than the BiTurbo; you just have to figure out how to mount it without zipties.
- Sachs 25mm ID header is an exact fit, but will need cutting as it goes to the "wrong" (left) side.
- My GPS speed after mods was 34 mph top on flats.
- 4hp cylinder port map.