Sachs 505/1D Low End Bog Saga (after warm) - need help

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")

Condenser: New

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.

POSSIBLE PROBLEMS/SOLUTIONS:

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!!

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

If it performs worse when warm that to me means you're running slightly rich. Have you tried dropping the throttle needle?

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

Hey Nick:

That's what I thought too, seemed logical.

But when I drop the needle, the power actually would decrease, like it was starving. So, tried raising the needle, then 4 stroking. That's why I've settled on 2nd slot from the top. It's definitely worth trying again though.

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

I kinda wanna suspect the clutch, that's something you could feel tho, does it engage like right away? Sometimes if theyre not all sliding, you wind up engaging early. or is there any drag on it, drag on the wheel or brakes?

you say timing is dead on, but dead on what? Stock they can be as high as 30deg BTDC, and even on the D's they restricted perfromance by obnoxiously advancing timing. 17deg is a lot closer to where you should be.

Or compression seems like a problem, your numbers look great but it's not an easy one to measure compression. Also is your decomp plug bottomed out in the port?

try a different carb maybe too

80wt gear oil is actually lighter than 30 weight engine oil. theyre different scales

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

Hey Willd, thanks for the info.

The clutch engagement seems to be somewhat variable at times, though i was thinking it may have to do with the pads being so new. Not sure. When it's idling on the stand and settles a bit after warming up, the rear wheel spins only slightly, but, once I do take it off the stand, I do notice the RPMs of the engine lower a bit, as if there is still some drag/engagement. For the most part as soon as I hit the gas, even a little it wants to start pulling. And then, randomly, there are other times, when it hit the gas, the engine revs up super quick, and suddenly the clutch engages and lurches forward. Not really a super repeatable occurrence. I did not replace any components in the clutch besides the two pads. Would worn plates an/or donut spring possibly be a culprit?

When I say timing is dead on, I'm referring to the markings on the flywheel. Though, you are right, that is a pretty large gap between the firing mark and TDC mark. I did experiment with retarding the timing, but I did not measure the exact degree marking. I'll give 17 degrees a shot though.

In terms of the Decomp, yes, I bought a bolt long enough that it seals up at the bottom, rather than the bolt head on top. I tested it for air leaks, and it seems pretty sealed up. Plus, I don't see anything dripping out of the bottom decomp exit hole.

I'll see if I can source an alt carb option and give that a try. Also, for reference, the stock square bing 85/12/104A, was a total dog on this bike. Still had a similar problem though. Seemed fine for about 3 minutes, then take off was lame after warming up.

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

Ah, Willd, one other thing.

Re: the Gear Oil, that makes sense, and that chart is awesome.

Do you have an idea of how that compares to ATF type F? I'll start looking that up too.

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

the rev surge I have come to believe is from the plates catching on the splined piece. filing the splines might help, or rearranging the order of the pads so they dont line up with divots or wear spots in the splines. Like it's thin thick thin, but doesn't need to be.

the other helpful tip on timing, the flywheel has almost exactly a 360mm circumference, so measuring 17mm on the circumference is 17 degrees.

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

Thanks Willd.

Great tip on the flywheel.

Not totally sure by what you mean by "splined piece". Are you referring to the oil channels in the pads?

In terms of the plate arrangement, I have the 1.7mm piece first (closest to inner engine), then the other two plates are 2.5mm. So it's Thin, Thick, Thick. Is that considered a changeable order?

Both pads between are new performance pads from treats with only about 20 miles on them. But I could try moving those around if it changes some sort of orientation/interaction.

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

splined piece the little toothed shaft that all the clutch bits sit on

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

Got it. That makes sense.

I'll double check all of that and clean it up.

Thanks Willd!

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

Ok, adding one more question/variable into the mix. My condenser has 2 wires connected to the top solder, and of course is grounded through the base. But, when looking at this wiring diagram, it shows only having 1 wire connection...possible issue? https://www.mopedarmy.com/w/images/5/5f/Gen3.gif

(That's the eagle wiring diagram on MA) (edited)

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

Doesnt matter on 2 vs 1 wire. Did you try a new condenser they act funny after warm up as well. External mount for the win.

Cracks on coil...

Clean grounds to frame... (edited)

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

yea there can be 2 wires on th econdenser, really the difference with the diagram winds up being where the split is to #2. Right, so that wire condenser to points then out to plug connector that Y's off the top of the points, it sounds like for you that Y is on the condenser top, no diffrerence in function. all in contact, just varying where they tocuh

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

Thanks Pat and Willd. Good to know for sure. I'll double check it follows that same path you described.

And yeah, the condenser was installed new last summer.

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

I have wasted way too much time fiddling with a 505 1C, just as an experiment ya know.

There are some great suggestions here already but I'd focus on:

Timing 17°-19° I used the no flywheel key method

Lean the carb a bit, but my biggest suggestion would be to lose the foam air filter. Go with either the Puch rubber and mesh filter or experiment with the jbot shampoo air box method.

I tried the Puch MLM velocity stack filter and it didn't seem to like the restrictive foam element. I might try some fiberglass window screen.

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

I also had problems with old exterior coils. I had a few that worked, never failed, but when swapped out with new it affected the jetting. Drove me crazy learning to tune a clone phbg on a non Sachs ped.

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

♣Slew Foot♣ /

It's the backscavenging the carb always needs a little restriction.

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

Thanks Frank and Slew Foot.

I'm currently running the bing hi-flow foam filter

https://www.treatland.tv/bing-air-filter-p/puch-bing-black-foam-filter.htm

Seems everyone is in agreement about the timing needing to be 17 deg.

I'll definitely go for that.

Also noticing consistent blow by on the piston, so I'm going to swap that out for a new Meteor Single Ring piston (and ring).

Didn't think about the coil, figured that would just fail if it was malfunctioning. I'll take a look into that too.

Thanks guys!

Re: Sachs 505/1D Low End Bog Saga (after warm) - need help

♣Slew Foot♣ /

Shits and giggles...

Run 3/4 marvel mystery oil to 1/4 synthetic atf. Blaster oil.

It might be glazing of the clutch the mmo will make it slip to higher rpms before engagement w/o glazing.

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