New Idle Problem

Posts: 10

Hi everyone. I have tried using the search feature with several different search criteria but cannot find my specific model/mods/problem. If it has been addressed, I apologize.

Here is my issue. I have a Yerf GX150 Model 4209. Stock, it ran and idled great.

This afternoon I installed a UNI Filter, a high output coil, High Performance CDI and an NGK Iridium spark plug. I now have GREAT throttle response and much faster acceleration. However, my idle has gone in the dumper. I am now getting a lot of RPM variation. Higher RPMs for 20 seconds or so then RPMs drop for 15-20 seconds then back up. It will continue to do this in idle for 1-2 minutes or so but eventually during a low RPM cycle it will stall.

I left the air lines hang from the motor that originally attached to the stock air box. I was actually told by a gentleman at Buggy Depot (where I purchased the upgrade kit) to do so. I have stock exhaust and stock carb and jet.

With the mods that I made today, do I need to

a. Rejet my carb?

b. Replace or gut out my exhaust?

c. Do something different with the extra motor air lines?

Thanks in advance for your input!

Todd

Posts: 1893

Since you removed the restrictive air box, you are getting much more air into the engine and it is running lean. With a stock exhaust, you need a 120-125 main jet in your carburetor.

Posts: 10

So either rejet or gut the stock exhaust not both? Which is more effective? I don't really care for the look of the "Eastside" aftermarket exhaust. Kind of like the look of the stock. Would like to replace the exhaust at a later time I find one that I think is aesthetically pleasing, but would rather spend that kind of money on more, less expensive mods first. More bang for the buck kind of thing. Figured gutting the stock would be far cheaper for now and allow me to do most if not all of the others things I want to do.

Thanks for your input. I love it when I find an online community for an interest of mine that is both friendly and helpful!

Todd

Posts: 1893

If you replace or gut your exhaust, it will require an even bigger jet (130-135). No matter what you do, when you increase air flow in or out of the engine, you have to add more fuel by using a larger jet.

Posts: 2583

Northern Virginia, cool. Another Y'Dog that's not too far away. Gut your exhuast and go with a 130 jet. That's where I'd start out at. You should buy a set of jets to play with. 126-128-130-132-134-136-138. Chances are you won't need anything more than that.

Tom over at KidNMe Karts is close by (He's KidNMe on here) and can sell you the jets.

We have a few people from your neck of the woods come up to our Northeast Bash's.

You've got a good start...

Posts: 10

pgh & Hog-

Thanks so much guys! I just ordered a whole bunch of jets (probably don't need them all but I figured at $4-5 a piece, why not!) I got a 125, 130, 132.5, 135, 137.5 and 140. Who knows, I might need them depending on what I do to the Dog in the next couple of months. This is addicting!

I checked out KidNMeKarts.com but he doesn't have online ordering and I'm an instant gratification kind of guy and couldn't wait till tomorrow to order so I got 'em at both BD and BladePerformance. (BD only carries a couple I guess and Blade was out of stock of some.) I couldn't find a 120 at either place. Hope I don't need that one. Wink

Since he's close though, I do plan to take a ride up to KidnMe's place soon and check out his shop. Guess I better take a trailer with me just in case!

Todd

Posts: 74

Posts: 74

Did you adjust the Fuel screw?

Posts: 1013

Posts: 10

garider, I have not tried adjusting the fuel screw yet. To be honest, I don't even know where it is but I will find it and try it. I used to fly rc planes quite a bit. I assume it is kind of the same principle as the needle valve on a rc engine?

eggy, you mention a possible vacuum leak. Could it be because I left the hoses from the factory airbox just hanging? I actually called the BuggyDepot Technical help line and asked what to do with them and was told to just leave them hanging and that I didn't need to remove them from the motor and seal the holes or anything.

Thanks for the input guys!

P.S. - I know this is kinda the wrong forum but can someone tell me how (procedure, tools, etc.) to go about "gutting" the factory exhaust? I will be getting an aftermarket at some point but I haven't found one I like the look of yet and am not ready to spend that chunk of change till I get a bunch of other things done to the bug first.