How do i get more air to the engine?

[Jsquared]

Let me give you a brief history of what I have done to this bike in the last three weeks.
 new carb and fuel filter replaced lines to petcock new gear oil and new motor oil. Thought I had bad gas treated it with heet. I have checked all vaccuum lines and they seem to be fine. The one comming from the crank shaft side that is goes directly in the crank case looks like it could use a little help but it is not leaking as of yet unnless it is too small for me to notice.
Symptoms now. Bike bogs down a little when I go from 0 to full throttle. It was bogging down alot before I took the air filter out. It is still bogging down a little now though . How can I get more air to the motor?



I got the bike running and it was bogging down it seems to be getting fuel so I took the air filter off less bogging but I also put heet in the fuel tank because I thought I had bad gas. Oh ya hard to start to unless bike is warm already. Tonight I changed the petcock airline and tightened some other lines and decided I would put the air filter back in. The bike would bore down horribly. II took it out and it wasn't so bad it is still bogging a little but not even a 1/4 as bad as it was with the air filter. Easy enough I need a new air filter but ... it is still bogging with the air filter off not a lot but enough for me to notice so? I am thinking the bike needs more air how do I accomplish this

[reg]

Hi, what size is the new carb? is it same as old one? what size is the jet? Your engine is running very rich, too much fuel going in. If you cant supply the engine with more air then you must fit a smaller main jet, i am guessing but when i had this i started with 5 sizes smaller and then went from there. It sounds like the new carb came fitted with a large jet not suitable for your set up.

[claynine]

You can't get more air to the engine with out changing to a bigger carb but you can lean out the mixture by changing the jets and/or needle position of the existing carb.  You need to be able to run with the air cleaner.  Odd that is is hard to start cold if the mixture is too rich though...An engine can bog down if the mixture is too lean also...But then the air cleaner removal should have made it worse.  I had a snowmobile that had a mouse nest in the muffler that plugged it up and so that one acted weird too. I would try to pinch off the fuel line to the carb and see if the engine starts to perform better when the carb bowl gets low on fuel.  If it runs good for the few seconds before the bowl runs out of fuel then you are getting too rich of a fuel mixture.  That would simulate smaller jets.  What scoot are you working on?  Good luck.

[Jsquared]

It is an agility 50 cc 2007 the new carb I put on is a 19mm the old was 17mm the crazy thing about the carb is I have no idea what size jets they are being that the guy guy I bought it from works at a scooter shop putting together scooters and had two left over. He said it was the same as the one in my bike just a little bigger 2mm I am not that crazy about changing the jets I will if I have to, But I am a little squeemish sees being the last carb I worked on I had to replace completley because I had not a clue what I was doing I leaned alot though lol.I actually just sent him a text asking what kind of bike model year ect the carb was made for hopefully with a little research I can figure it out.

You can't get more air to the engine with out changing to a bigger carb but you can lean out the mixture by changing the jets and/or needle position of the existing carb.  You need to be able to run with the air cleaner.  Odd that is is hard to start cold if the mixture is too rich though...An engine can bog down if the mixture is too lean also...But then the air cleaner removal should have made it worse.  I had a snowmobile that had a mouse nest in the muffler that plugged it up and so that one acted weird too. I would try to pinch off the fuel line to the carb and see if the engine starts to perform better when the carb bowl gets low on fuel.  If it runs good for the few seconds before the bowl runs out of fuel then you are getting too rich of a fuel mixture.  That would simulate smaller jets.  What scoot are you working on?  Good luck.

[Jsquared]

Oh ya just a little info that might help anyone trying to help me figure this out. The guy I bought the cab from  has a 70cc and a 100cc bore kit if my engine is running to lean would putting one of those on maybe help?

[Jsquared]

We took the bike to the beach today when trying to go over the bridge which is a pretty good hill for being on the beach in NC the bike barely made it to the top it kept losing more and more power when it got to the top and crested the hill it ran better which gave me an idea put the bike on its stand so it is leaning forward and see if it makes a difference and sure enough if my bike is on a decline it runs better. I have no clue what that means anyone???

[reg]

Okay, so your engine is running very rich for sure because when you remove the air filter it runs better. The carb is an oversized replacement with unknown jets. At one point the engine wasn't getting any fuel at all. The engine is sensitive to being inclined or declined. I am just typing these things out to keep me on track!!

So it seems that the engine switches from being flooded with fuel to being starved of fuel basically when it feels like it. It kinda looks like the  float in the carb is defective. The float should ensure that there is always a steady constant level of fuel in the carb float bowl. If the level isnt right then the jet sizes dont really matter because they are either being swamped with fuel or nopt getting enough. This business about the engine performing differently according to its angle also suggest that the float is 1) sticking on its hinge, 2) leaking so that it becomes heavier and floods the engine 3) the replacement carb has been configured and jetted for a very different engine probably a much bigger one.

I wouldn't think about installing a new bbk until you have it running correctly as it is. More new parts would only mean more dead ends to go down in your investigations. It would be good if you could get your hands on the correct carb for a good price. I have a feeling the scoot would be fine then.

reg

[blue]

I have a scoot that I took a 20 mm carb and the opening that gos to the motor I took and made the carb a few mm bigger the take off is great...............so its more like a 22mm carb now.And I went with a 85 jet I drilled out to 88.