Hey everyone,
Just got my yfz thursday, and I noticed that when I hit the throttle real hard it would sputter and almost die. When doing this in neutral it does completely die. I talked to the yamaha dealership and they said it could be because they filled the gas tank with 87 octane unleaded gas instead of 91 octane. So I drained my tank and filled it with the 91 octane, but unfortunately it did'nt help. Do you have any suggestions for me, or should I just demand that the dealer fix the problem. I mean that isn't normal is it? I should hope not.
Thanks for the replies in advance,
Tim[img]i/expressions/face-icon-small-confused.gif[/img]

 

Did you remove the baffle from the end cap, or remove the airbox lid? It sounds to me like its running lean on the pilot jet and/or fuel screw. When your free reving the quad and stab the throttle real quick it bogs/or dies right? If thats the case then your pilot jet/and or fuel screw is lean. My buddys Yfz did this when he removed the exhaust baffle. If it does this and you havent touched anything, take it back to them and tell them they need to rejet it. Or if you know how to rejet you can do it yourself. I can tell you know its not supposed to do that,and a properly jetted motor will not hesitate like that. Make them fix it. And don't let them give you any crap about it. Part of their "Set-up fee" is adjusting the carbs so that they will run right for the enviroment/location they're in.

 

I'm going to try and get them to do it. Will I have to get a jet kit to do it myself?

 

Grr my yfz does the same exact thing When u hit the throtle quickly it will bog or even try to back fire. Told my dealer where I bought the quad at and they told me that I had been riding two strokes to long and there were no jetting problems just the nature of the four stroke engine. Needless to say I was PI$$ed off but what can you do?

 

its because this machine does not have a CV carb like almost all 4 strokes, the slide is directly operated by the throttle cable, where as a CV carb relies on vacuum to open the slide up. What happens when you slam the throttle open from an idle is you get too much flow through the big carb into the engine, and the flow actually reverses. Don't believe me, go smell all the gas in your air filter. The solution is to 2 stage the throttle from an idle. At all other engine RPM's there is enough flow through the engine that this doesnt happen.

 

If your filter is over oiled it could be a bit rich but it sounds like a lean problem. Have you tried to richen up the idle mix. screw a little? Might help if it's lean.

 

I havent tried any thing yet but I dont belive I should Have to start re jetting and tinkering with the carb.The reason for buying the 450 was that I could have a decent running quad that I didn't have to Mess around with jetting and all that other stuff. Belive me the banshee is more than enough to keep up with.The thing pops when letting off the throtle so it's lean but like I said the dealer wouldn't admit that any thing was wrong. I guess I could try adjusting the screw but as for taking the float bowls off or adjusting the needles Definatly not gona happen call me lazy but Like I said earlier on a bone stock quad that I paid set up fees on I shouldn't have to jet the thing.

 

I dont care what the Dealership says, a new bike should not sputter or stall when you hit the throttle. Would you accept a new car that stalled when you punched the gas? Make em fix it and let us know what the problem was, I was looking to buy a 450 in the next couple of weeks, but if there is a cronic problem with the bikes I may lean on over to the new Honda coming out in a few months.

 

If it pops on decell. your lean and richening up the idle mix should help quite a bit. I wouldn't be concerned about a thing like a lean idle, the factories need to set them up to pass emissions and if a turn of a screw solves most of the problem I wouldn't complain.

 

And your dealer is full of it..... Just like I told the other fella on here, its lean!!! You need to adjust your pilot jet and/or fuel screw. It should run cleanly. And if it is poping excessively on decel its the pilot jet being to lean. This is the jet that supplies the motor fuel during closed throttle operation such as decel coming into corners.