Carby Zeda Dio Reed Tuning, Backfiring

Jag

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Oct 6, 2018
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138
I have a 66cc BikeBerry bottom end and a Zeda DioReed top end, ported W/ high compression head and expansion chamber. (Just Rebuilt)
Can only get it running for a few minutes before it dies, hardly any throttle response and won't really rev, and lots of oil spitting out the exhaust. Its also is always backfiring out the exhaust, idle and all other rpm's.
has a #105 main jet & a #38 idle Needle clip in the middle 20/1ish fuel mix
I'm almost certain it's running rich, I was also wondering if these symptoms could be caused by failing reed valves.
The pictures shown are about 5 minutes running w/ choke on and off.
 

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Timbone

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Apr 20, 2014
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20:1 oil ratio is too much. Drop back to between 25:1 and 32:1.

Chinese 2 strokes have a main jet of around 70. Usually that is dropped down to lean out for good top end. Are you running big 4 stroke carb on your 2 stroke engine?
 

MacZulu

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Jul 8, 2015
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can you take your air filter off? if you do, does it run better? if not trying choking the air of abit, although with a 105 mj I doubt your lean. but I dont know your carb. does it have an air/fiel screw, and an idle screw? the best way to read a spark plug is when it's well warmed up and been WOT for a a little bit. I think you need to get it close before plug reading.

I would try tune your carb leaner any way you can, preferably by increasing air. but even if it starts running awesome, you still have to check the plug. these small engines seam to love running lean, which is bad. high heat and piston damage/failure.

edit, and I agree with Timbone 20:1 too lean on fuel. so if you change that you will be even richer on air/fuel mix.
 

Jag

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Oct 6, 2018
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Air filter won’t do anything if I take it off. Very oversized. Only a idle screw, and a powerjet that I have “deactivated” can’t really run the engine because it dosnet really want to. And I know all about these engines, just wanting a confirmation from someone else that it’s running rich before I lean it out.
 

MacZulu

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Jul 8, 2015
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that look like it has an air/fuel screw, and an idle screw. so it's a very tuneable carb.

I'm no pro, but I have played with my honda ruckus carb alot. I would first get the engine running, use the idle screw to keep it running (screwing out as engine warms and idle climbs) when warm you can try tuning thr a/f screw. if you gun the throttle and let go your idle should drop down fairly quick and settle out, it shouldn't linger and slowly decrease. if you can do that and get it rideable, then you can plug chop to figure out rich/lean. if you still bog out and cant ride I would suggest going down in jet size in as small increments as your jet collection allows.

you also mention a needle clip, your carb has adjustment for full throttle range. you just need to tweak the idle, mid range and top end. once you get it set up to your current intake/exhaust you should be good
 

Jag

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Oct 6, 2018
Messages
138
No fuel/air mix screw. But I will Downjet idle and adjust needle clip. Still wondering if failed reeds cause this problem. And when carb is mounted it sits on angle (by design) should I worry about float adjustment in my state, fuel does not leak out when bike is level.
 

MacZulu

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Jul 8, 2015
Messages
93
I googled 21mm carb tuning zeda, and found some good advice. More specific than mine.

On the engine side of the carb you can see a small hole in the plenum, and it looks like there is a screw in line with the bigger hole. Pilot screw, or a/f or something, it looks like a steady air/fuel circuit regardless of throttle position.

There are no adjustment screws other than the idle screw?

When I googled it I did see reference to float height being an issue, if your running the engine angle as it was designed you should be ok
 

Street Ryderz

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Joined
Oct 14, 2016
Messages
2,951
I have a 66cc BikeBerry bottom end and a Zeda DioReed top end, ported W/ high compression head and expansion chamber. (Just Rebuilt)
Can only get it running for a few minutes before it dies, hardly any throttle response and won't really rev, and lots of oil spitting out the exhaust. Its also is always backfiring out the exhaust, idle and all other rpm's.
has a #105 main jet & a #38 idle Needle clip in the middle 20/1ish fuel mix
I'm almost certain it's running rich, I was also wondering if these symptoms could be caused by failing reed valves.
The pictures shown are about 5 minutes running w/ choke on and off.
The first pic of plug is decieving for a oil rich mix it should show signs of it,that plug looks etheir washed or way lean and tbh I'd be betting lean.Most folks with this setup start at 45/115 and go down some to fine tune,generaly over rich will run and lean will not.The reeds failing as in not sealing and losing charge is possible and you can check that and that they open for that matter.That carb does have an air screw but it's effect is only on the idle circuit and first transition and when the pilot is way off their will be little to no effect from this screw.When the pilot is correct the air screw will be between 1-2 turns out from closed,then it's affect can be seen.
 
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