surging engine

christianava12 · #1 12-31-2008, 06:01 PM

I have a 80cc RAW engine that is on it's 3rd tank of gas and surges a lot at WOT. My first tank of gas was at the manufacturers recommendation of 16:1 and now at 32:1. I cleaned out the air filter thinking that maybe the filter was clogged from the rich mix but there seems to be no difference. When I say surging I mean it will be going and then suddenly almost completely stop pulling and just coast for about 5 seconds or so then pull strong for 5 or 10 seconds and then stop pulling and coast again, the engine never actually shuts off just not pulling very hard.

any idea's, anyone??

jasonh · #2 12-31-2008, 06:23 PM

It sounds like you're having trouble getting enough fuel at WOT.

Do you have the screen in place on the petcock inside the tank? There is probably junk caught in it. These tanks have a lot of crap in them from the factory. I'd get a see-through inline filter and ditch the screen, after cleaning out the tank.

Also, your float could be sticking. Take the bowl off the carb and make sure the little arms move freely, and that the float is in good shape. Hope that helps.

**Dave31** · #3 12-31-2008, 06:32 PM

It also could be fuel foaming in the carb...check your motor mounts that they have not loosened up on you. Any notice of a small vibration?

captainrichhill · #4 12-31-2008, 07:09 PM

I had a problem like this and I adjusted the fuel valve while riding and I need to RESTRICT the flow a little to get maximum performance.

Walter F. · #5 12-31-2008, 07:53 PM

Quote:

Originally Posted by fairracing31

It also could be fuel foaming in the carb...check your motor mounts that they have not loosened up on you. Any notice of a small vibration?

Happy New Year Fair ol' buddy, got me some New Year Cheer goin', I want you to 'splain to me about this "fuel foaming in the carb"-alright I can IMAGINE an engine vibrating and maybe shaking the bowl of the carb, but in the float bowl it is air tight!!! Have you ever seen this happening inside the carb?Right after the float bowl the gas goes to the emulsion tube where it is made to bubble or foam to better atomize it. I just don't buy into this deal of fuel foaming causing "surging". What does it foam and quit, foam and quit?????? Horse Hockey-------------- Walter F.

jasonh · #6 12-31-2008, 08:39 PM

I'm inclined to agree with you Walter. The jet picks up the gas from the bottom of the bowl, so unless the ENTIRE bowl is nothing but foam (doubtful) there shouldn't be a huge issue.

Walter F. · #7 12-31-2008, 09:18 PM

Quote:

Originally Posted by jasonh

I'm inclined to agree with you Walter. The jet picks up the gas from the bottom of the bowl, so unless the ENTIRE bowl is nothing but foam (doubtful) there shouldn't be a huge issue.

See I'm not a stupid as I look Walter F.

**Dave31** · #8 12-31-2008, 10:07 PM

Well I got some video to show other wise...give me some time to get them uploaded.

Foaming in the carb is the best way to describe it. I have had lose motor mounts and the extra vibration causes a fuel delivery problem. Call it what YOU want...I will call it fuel foaming. The vibration can cause air to enter the carb...when you back off the throttle you lessen the vibration and then it runs fine. As soon as you pick the throttle back up you increase the vibration to where air gets in the carb again. Stay tuned for the vids...

Creative Engineering · #9 12-31-2008, 10:54 PM

Quote:

Originally Posted by Walter F.

Happy New Year Fair ol' buddy, got me some New Year Cheer goin', I want you to 'splain to me about this "fuel foaming in the carb"-alright I can IMAGINE an engine vibrating and maybe shaking the bowl of the carb, but in the float bowl it is air tight!!! Have you ever seen this happening inside the carb?Right after the float bowl the gas goes to the emulsion tube where it is made to bubble or foam to better atomize it. I just don't buy into this deal of fuel foaming causing "surging". What does it foam and quit, foam and quit?????? Horse Hockey-------------- Walter F.

I give it to Walter & Jason on this one!!! The fuel isn't actually "Foaming" in the bowl. The carb is unable to disperse it properly at a high harmonic...the reason...the jet needle, and main jet are doing a circle jerk that prevents the fuel from flowing through the needle as it should. Yes I checked this!!!

Jim

**Dave31** · #10 12-31-2008, 11:00 PM

And like I said...I call it fuel foaming...I am not saying that fuel is actually foaming in the carb. I have had the exact same thing happen. And all it was was a lose front motor mount.