Bogging after new oil pump

[jcal]

I have a bennelli Andretti with 40qmb 50cc and mikuno style carb. Ran great but leaked oil. Ordered new marinelli oil pump that looked correct and installed which resolved the oil leak. Still sTarts and idles great. Now when cold or hot and under load, engine bogs down after more than 1/4 throttle. Replaced plug. Cleaned carb. Moved needle clip to lowest setting.  It was already on slot two so moved it to first one.   Does smoke a little at start up. Any ideas on what to check next?

oh yeah I lost the m clip on needle. Any idea where to order that?  Just stuck a small washer in there for now. 

[jcal]

Anyone run into this problem before? Is it surprising that the issues with greater than 1/4 throttle coincide with an oil pump change? Today I pulled the fuel line and filter and carb bowl float/seat/needle and cleaned everything out with no difference in performance. Also adjusted the oil pump volume to the max and min with no difference observed.

[190mech]

Perhaps the new oil pump isnt working and the engine is trying to seize up..Did you bleed the pump?

[jcal]

I will premix some fuel and see if that helps.

[jcal]

I bleed the pump and see no air in the oil lines but can do that again as well.

[matlock]

try a smaller jet and you can also premix for now till new pump comes

[jcal]

Pump is definitely bled. I pulled fly wheel and stator and it looked like the plastic drive gear may have a bad spot on it. Ordered anew one for next week. Willpremix tomorrow and see if the bogging is soft seizing. Maybe I never got the pump gear seated in the drive gear or burned a dead spot in the grooves. . I’ve done dumber things for sure.

[190mech]

Dump the pump and PREMIX!You will need to rejet a bit,but lubrication will always be there!!

[jcal]

Premixed at 32:1 and bled all fuel lines as well as emptied carb bowl. Same issue. Idles sweet but greater than quarter seems to need more fuel. Rejet as a next step?

[Mech Warrior]

Yes exactly.Try a smaller jet.The scoot may bog due to too much fuel.

[aeroxbud]

That's is a lot of oil at 32:1. I'm mixing 50:1 on my sport build, and only did 40:1 on a stage 6 racing.
You will actually run lean using that much oil, as the bike is getting less fuel. You should change the jetting to allow for the extra oil displacing the fuel.
A rough guide is 50:1 need a 2% bigger jet. And 40:1 is 2.5% bigger.

[jcal]

Thanks will go to the leaner mix and rejet.

Is it possible my new oil pump was delivering too much oil causing oil mix to be too high at more open throttle?

Either way i need to rejet and see what happens. Down or up with a steady fuel mix and see what happens.

[Mech Warrior]

Sounds good.

[ThaiGyro]

jcal...190 mech said it best. Dump the pump. With only premix, you will know what your mix is at any throttle position. As he said: 50:1 is a good place to start. You should find it much easier to tune.

In my years, the premix ratio going heavier, (like 40:1 for example) was only needed with more timing advance and/or higher rpm's. If you are stock or near stock, you should have no issues.

[jcal]

Premixed at 50:1. MJ was 75, 90 was best. Tuned idle and FTA. Hit 39 mph on my test stretch which was as good as ever. Dumped pump and scoot has never run better. Thanks for the help.