Hey all you Sachs guys and gals,
I could really use some opinions on a power issue that I can't seem to pin down.
Basically, my Eagle III with a 505/1D seems to lose low end power at take off after everything warms up. Mid range power is amazing (anything past 10 mph really). But once I hit that stop sign, and give it some gas after a full stop, BOG CITY for a few seconds until it passes 10 mph. But, before everything warms up, I seem to have better take off. Just for reference, I weigh about 165.
I've done a lot of reading, tweaking, and upgrading, and every step seems to improve overall performance, but the take off issue seems to always be there.
Here are the stats of the current setup:
Engine: 505/1D with 3000 miles on it (original cylinder and piston from what I can tell).
Carb: Bing 15mm round with 68 jet, needle position 2nd from the top (4 total options) running high flow foam air filter. (i upgraded this from the stock square bing). This setup seems to be the sweet spot for this bike. Plug looks nice. Any leaner, I lose more power, and richer, I start 4 stroking a bit.
Timing: dead on. checked it with with strobe timing light to verify. I've also experimented with retarding the timing a bit, seems to help, but marginally.
Points: New, replaced with NOS Bosch points. gap in spec (.016")
Plug: NGK BH6S
Pipe: MLM G3 Peoples Pipe (clean). Also installed springs at the header to force pressure upward and keep the pipe on there!
Compression: 155 PSI cold, 140 PSI warm
Clutch: replaced old pads with new treats performance pads and cleaned up the plates. Experimented with shims for preload, and am now running with only the stock setup, no additional shims added beyond the thick single one required.
Tranny Fluid: Had been running O'Reilly's Type F tranny fluid, changed it out for Royal Purple Max ATF and engagement seems more smooth. Was hoping it would allow the engine to hit a higher RPM before engagement, but it's marginal.
Air Leaks: Decomp removed and plugged up with appropriate bolt, and RTV. No leaks there. Intake, no leaks. Carb, no leaks. The only leak that still seems slightly there is at the base gasket, on the top. I replaced the gasket, and don't think I can tweak down the nuts anymore without stripping the stud. When I spray carb cleaner, the RPM drops a tiny bit, but not much. Should I try using two gaskets? Would that effect the port timing? Also, suspecting a slight exhaust leak at the flange. Details below.
Gearning: 11T Front 46T Rear
Top Speed: Seem to keep maxing out at 32mph. It's funny though, I can hit that holding 3/4 throttle, then if I go to WOT, I can hear the engine working harder, but the speed doesn't seem to increase...not sure if this is also a sign of something related.
1. Piston Blow By: When I pulled the cylinder off, I noticed a bit of carbon blow by on the piston. Also, a small amount of vertical hash marks on the piston skirt. Maybe it's time for a new piston and ring? If so, which option is preferred, the treats dual ring stock piston https://www.treatland.tv/sachs-stock-piston-p/sachs-stock-piston.htm, or the Meteor single ring piston https://www.mopeddivision.com/moped-make/sachs/sachs-504-505-engine-38mm-single-ring-piston-kit-meteor/ (my current piston is a single ring)
2. Exhaust Port Leak: The flange coming out of the exhaust port is definitely loose and black carbon fluid leaks out a bit around the flange. The pipe is attached very tight, and as I mentioned above, I installed springs to force the pressure upward. Not sure if this is fixable beyond what I have done.
3. Gear Fluid?: I'm trying to figure out if 80W gear oil would help the engine reach a higher RPM before engagement. After a lot of reading, I don't think this will solve my problem, but wondering if you have any thoughts.
4. Replace Cylinder and Piston?: Since I have an issue with a small air leak at the top base gasket, plus the exhaust flange leak, do I just need to bite the bullet and buy the Athena 50cc kit? https://www.treatland.tv/Sachs-Athena-50cc-cylinder-kit-p/sachs-athena-50cc-kit-073900.htm. I'm not really looking to put a 70cc kit on there as I don't want to tear up the clutch. If I could just get better takeoff, I would be happy.
5. Unrealistic expectations?: Well, this is pretty self explanatory. I don't have any other experience with Sachs bikes, so it's possible I'm expecting too much, but it just doesn't feel right to me.
Anyway, I know this is a ton of info, and if you're still reading, you are awesome! I tried to solve this on my own before plugging into the collective Army brain, but I'm hitting a brick wall. Any and all feedback/opinions would be MUCH appreciated. THANKS!!