I apologize up front for the long description. I recently purchased an 07' YFZ450. Beautiful shape and seems to run well around the yard. Will be used primarily on the dunes. Has K&N filter but otherwise stock. Starts right up everytime. Guy had it as a spare quad and has seen very little time. Said it sat around without use so much he recently had to have the carb cleaned due to the gas sitting in it for long periods of time.

So heres my issue, it seems to have a hasitation at times when cracking the throttle open. I heard this was common on these quads, is this so and are there any fixes?

Also, if I crack the throttle open 1/2 to 3/4, while parked not in motion, I start hearing this high-pitched cracking sound coming from the muffler and an ever so slight amount of vapor I believe to be unburned fuel based on the looks & smell of it. Its not loud, but is obvious. Any ideas what this might be?

Only other thing I can provide is the guy I purchased it from said he trusted his bike mechanic for years and 'the mechanic' said he believed the YFZ's were always on the 'rich' side from the factory. I dont know if any adjustments were made while he had the carb off.

Thanks for any info.

 

Well, something was lost in the translation on YFZs being rich from the factory. Mine actually like a little bigger pilot when stock at least.

The hesitation is normal for the FCR carb. There are quite a few aftermarket solutions out there to fix it. Boyeson has the Quickshot that has now evolved to the Quickshot2 I believe. A few companies have copied that design. There is a whole float bowl out also but I can't remember who makes it. personally, I have an original Quickshot, works well. My bro has a knockoff that also solved the issue. Truthfully, I never noticed the hesitation when trail riding where it is rare for me to go from idle to wot quickly enough to bring that out.