Roadrunner linhai 300cc won't rev up By sanid98 (Read 3,711 times)

[sanid98]

Hi there, I hope I can get some expert help with this problem. I bought a Sunny roadrunner 300 reverse trike with only 1000 miles on it. It had no spark. I had to change the CDI and pick up coil. I now have spark and can get the scooter to a nice idle. I am able to get the back tire to move, as soon as I open the throttle it starts bogging down and does not go over 2200 rpm and sometimes stalls. I changed the carb, adjusted the valves, only minor progress. Any ideas? Thanks

[alleyoop]

Do you have the Air filter attached to the carb. You either have a bad air leak or there is the you have a fuel delivery problem.

Can you take pictures of the carb are and hoses. It appears that you bought a scoot not running and most likely someone could not fix it themselves and might have messed it up worse than it was and is why they sold it.
But You at least now have it running which is good and now it should be some minor fixing to get it to rev up.

It could be the Diaphgram that lifts the needle that is ripped and or leaking that is the under the TOP of the carb if you take the two screws holding the cap you will see the diaphgarm. Pulling it all out and spreading the rubber against the light to see if you see any rips and or holes in the runnber diaphgram.

If all good then put it back and adjust the carbs FUEL RATIO mixture screw:
First turn it clockwise until it stops and then turn it out 2 1/2 turns that is a good starting point for just about all the scoot motor for them to run pretty good.
thescooterprofessor.proboards.com/thread/3001/4-stroke-carb-tuning

Alleyoop

[sanid98]

Hi Thanks so much for your help. Yes the air filer is in place. The rubber neck is hard to get into place its almost like its 1/4 inch long, but I am certain the seal is not bad between the carb and air box.

I am on my second carb, because I thought the previous new carb was bad, they all had a good daiphram.

I put in a new Fuel filter and I can clearly see the engine sucking fuel to the carb every few seconds.

I have tried the fuel mix in just about every setting... it does change rpm but at no setting I am able to get it abover 2300 RPM with throttle fully open. it runs better when the fuel mix is 4-5 turns open. I don't think its fuel.

I can tell the CDI that I installed just couple of weeks ago is starting to go bad! it is buldging on one side, but there is good spark and the engine idles.

I have taken a picture that shows the vacuum lines that connects to the pump and carb, do you see anything wrong there?
i42.photobucket.com/albums/e348/sanid98/photo_zpsa4c10e45.jpg

in the morning I will open up the air box, see if I notice anything wrong?

[alleyoop]

Everything looks good, where is the tank Up in front lower than the carb or in back of the set higher than the carb?

I would change the "Y" connector to have the SINGLE part of the"Y" connected to the INTAKE MANIFOLD Vacuum hose and then the Top of the "Y" one going to the pump and the other to the ACV valve that way GOOD suction goes to both VACUUM needed parts. Right now you have it so the ACV valve gets the most suction and NOT the PUMP.
Alleyoop

[sanid98]

That's true, I actually had it the way you said, but I changed for this picture to show how it was when I got it. I will change it back to give the fuel pump more of the suction. The fuel tank is up front and lower than the Carb.

So today I messed with it some more. I am totally convinced its getting too much fuel. the sparkplug is completely black. they way it bogs down suggests too much fuel. I lowered the carb needle one notch no change at all. I plugged the needle into the main jet! no change. I then noticed that there is always fuel before the throttle plate and the engine intake, its most likely coming from the pilot holes. its a bit more than wet, you can see fuel and I am thinking as soon as i open the throttle slightly that liquid fuel rushes in and it starts to bog down. So the question is why do I have too much fuel coming from the pilot. I went as far as closing the the fuel air mixture all the way.

I thought maybe the carb floater is not working, but I don't have fuel coming out of the overflow port nor is it coming out of the main jet.... just the pilot.

Any ideas?

Thanks

[alleyoop]

Well in your post you said it runs best 4-5 turns out(that is a lot by the way) Normally that indicates the Pilot Jet is actually to small. Now your saying the plug is sooty and you believe it is getting to much fuel.
Check the VACUUM HOSE it may be pulling fuel through the vacuum hose from the pump if so the pump is bad.

Also don't forget when you first start the motor the ENRICHER is also feeding it fuel for cold starts.

Now to test the PILOT start it up and then turn the fuel mixture screw clockwise and see if it kills the motor IT SHOULD kill the motor about 1 turn before it is completely bottomed out.

[sanid98]

An update. Today I found out that the choke was not wired right and thus not working ( on a brand new carb!) Fixed that then did several things to lean the mixture. Unfortunately even after the mixture was leaner on start up, it idles but as soon as I open up the throttle any amount, it starts to bog down and sometime back fire into carb or stalls

I am not sure what it is. The air box is connected and filter in place. There are two breather tubes going to the air box aside from the main carb intake. I wonder if anyone has a roadrunner and has taken pics of the inside of the air box. Only thing I can think of, is that previous owner took something out of the airbox that changed the air flow.

I also checked the fuel pump no fuel is coming thru the vacuum connection.

Any other ideas of what would cause it to bog down as you open throttle?

Thanks

[sanid98]

HI I wanted to leave here a note about the solution, Hopefully it will help someone else. I had convinced myself that this was a too rich fuel mixture problem (black sooty Sparkplug) and worked on the carb endless hours. I then went back and said to myself I need to eliminate each and every posibility. I started with the Airbox modified the amount of air coming in, but that didnt help. I then went to the transmission and removed the CVT assembly and what do you know the rollers in the CVT Assembly (sorry not sure what you call that) were stuck due to dirt and were not allowing the engine to rev up at all. So I took it apart, cleaned everything and now the engine revs and drives to 3800 rpm where previously I couldnt get past idling. I now have backfiring through exhaust at 3800 rpm, so its not yet at full power and I think it is a carb adjustment thing.




Hope this helps.


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