just picked up a 07 YFZ 450 (it was a repo) so i dont have any info from the past owner. It does not like to start up at all and when it does you can only ride it with the choke all the way out. Also it will just shut off when riding. I have been riding for many years myself (bikes) and this is my first quad (actually it is for the son). It is also running extremely hot, the exhaust coming off the engine glows red about 30 secs after start up. Also i have yet to see the fan kick on. What do you all think i shoulkd start looking at first?

It does run great with the choke out when it is running but dont wont to run it to long because of the overheating.
I would think the starting problem is carb related but what would cause it to get so hot?

 

Sounds way lean... You need to get it checked quick like... If you keep running it like this, you surely have engine damage... Pull the spark plug and check the color. Dark = too rich, Brown = good, light to white = lean.... Does it have any after market parts on it? Is the airbox lid on or off?

 

the airbox lid is on, i opened it to see that the filter was clean and it was. I was thinking the same thing (running lean). thanks for the input i will check it out

 

what is the stock jetting?

 

carb need a good cleaning

 

i removed the carb for cleaning and have done many watercraft carbs before but this is the first atv. I am told this has a throttle sensor in it so i want to avoid messing with that if at all possible. What side or bottom of the carb can i safely open to take a look without distrubing the sensors?

 

i think it is running way to lean since the plug glows red even in the day. what should i check for? how can i correct the problem?

 

The sensor connection is on the left side of the carb. It is able to be unplugged. (At least on an '06 it is) Be careful not to let it hang by the sensor, it can break easily. $180 to replace.

See this thread for links to good Jetting Info. I'm on the second page.

The link has videos on how to reomove the carb too.

I would agree you are very lean!

 

thanks alot that is great and lots of help

 

It sounds like you just need to take it to a atv shop and let them service it for you asfar as the glowing pipe thats normal my stock 2008 did that when i got it maybe they ran cheap gas or just never took care of it but good luck on it.