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Hi all Primavera 125 fundis,

I am a newbie and my first post.

My wife's '78 125 Primavera has the following symptoms and problems;

Cold start is normally easy, choke on, closed throttle and away we go. There is however a lot of white smoke which takes quite some time to abate once out on the road.
1) Fuel consumption is high at around 20 litres per km at 65 to 70 km/h. And she is not heavy, less than 60 kg (130 lbs).
2) Plug is mostly pretty black and sooted up. After a longish ride the electrodes show some sort of dark brown reddish cleaner burn.
3) Hot start very difficult, requires full throttle and she then after the 4th or 5th kick starts running, very slowly at first then finally gets going.
4) It appears that over the last six odd months she is slowly loosing power.
5) In my mind she appears to be RICH bogged down. Very slow acceleration.
6) A new first over size piston and rings have recently been fitted. I have replaced the coil. Carb is standard and Jets are standard. We live at sea level.

Could the problem be due to the main bearing oil seal and loss of crankcase pressure?

Any help and ideas would be appreciated.

Thank you,

Roger Brink, Mossel Bay, South Africa
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"1) Fuel consumption is high at around 20 litres per km at 65 to 70 km/h. And she is not heavy, less than 60 kg (130 lbs)."

at that sort of fuel consumption you are DEFINITELY over rich
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Indeed Gravelrash, my thoughts as well.
Something I forgot to add in my earlier post.
If I turn the mixture screw fully in, engine continues to run, which of course it should not! So the question is where is the engine getting fuel from at idle when the mixture screw is fully in and tight?
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Johnny Two Tone
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I'd also consider your exhaust may be getting full, which would have similar symptoms.
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Not to hijack a thread with stupid questions but what does it mean that the "exhaust may be getting full"?

Hal
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That's not a hijack - the exhaust fills up with 2 stroke residue bit by bit until the engine can no longer breathe. You put a new one on and it's like a whole new engine!
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Exhaust can be cleared out, usually using some nasty chemicals.
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Yeah if you are game you can go that route but I'm not a fan of nasty chemicals
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burnup
Heat can be used instead, but then all downwind of the bonfire get a lungful instead...
If it burns completely it's only the CO2 that would have been released had the carbon in the fuel oil mix combusted completely, but there will be incomplete combustion too and oxides of elements, other than carbon too....
Otherwise it's poking and scraping from each end of a removed exhaust, but I'm not sure how effective that would be.
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I have built a fire in my backyard and put the exhaust system in the fire and let it get really hot. This will slightly disform the metal and break the soot and creosote-like off from it. Once it cooks for a while, take it out and let it cool and then the black stuff pours out.
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The exhaust was cleaned not to long ago, so I am thinking not really a clogged exhaust issue.

Some feedback, I have redone the packing of grease around the felt ring.
Also, and here is the weird thing, I have turned IN the mixture screw to the stop and now she idles like she has never idled before. In the past with the mixture screw out say 1 and 1/2 turns, the throttle would have to be blipped every couple of seconds to prevent a "bogged" down stoppage. I surmise far too rich at the idle and low throttle setting?

As to how this will affect the fuel consumption as well as the rest of the performance, well time and a long run will tell.

Cheers
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have you checked compression yet? losing power over time could be poor ring sealing, and it will behave a lot like you described - poor warm starting, loss of performance, etc. bad sealing rings feel like a very rich engine.
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