yfz 450 hesitation

[busafantic]

i got a hmf slip on pipe and when u pat dat gas it starts to bog alittle then once it gets going its fine on top.how would i adjust the air/fuel screw.what jettibg size should be used

[yfzrider310]

Its a common yfz problem the only thing that helps is doing the zip tie mod (search it im not explaining it). Also along with the zip tie mod you get a small leak jet but I'm not sure about the leak jet size. Someone correct me if I'm wrong. Also proper jetting helps if you did not rejet for the exhaust.

[pitsrule]

I have a Honda and with most FCR carbs this hesitation off of the bottom is a problem. To fix mine I ordered a smaller leak jet as yfzrider310 suggested. This fixed my hesitation problem completely on my 450r. My friend just bought a YFZ 450 and he has the same problem. I just happen to have another leak jet that is smaller than his stock so I am going to try it and see if it fixes his hesitation problem too. Ill report back.

This leak jet is confusing too...smaller is correct...what it does is allows fuel to leak back into the bowl from the accelerator pump...the smaller the jet the less fuel that can leak back into the bowl thus allowing more fuel to remain on tap for the accelerator pump, as a result...when you stab the throttle you have more fuel initially to rev the engine, instead of it stalling until the carb can catch up.

By the way I went from a 70 stock leak jet to a 50...

[yfzrider310]

Well I did some more research because I want to finish mine up. The yfz's have a 50 stock leak jet and thats to big so most people are buying 35 leak jets and that seems to do the trick. So put in a 35 leak jet and do the zip tie mod and you should be golden. Thats what every website I went on said. Now if anyone knows where to buy a leak jet let me know. I know magic racing sells them but they don't go down to 35 sizes. I think just 45.

So my question is where do you buy leak jets?

[myersracing41]

Leak Jet
I ordered mine from Yamaha. Seems like it was around $10 bucks or so. Problem is you need to search for one on a bike, the guys I ordered mine from didnt even know what it was. I found a site that sold yammy parts and looked through their engine diagrams to find it, but that was over a year ago and a different computer, basically I lost the site I was using to search for it.

Mine is completely gone now, but thats with AP mod and rejetting for full HMF exhaust and K&N settup with no lid.
Main jet 168
Pilot 45
4th clip on needle
2 1/2 turns on pilot screw
#35 leak jet

In GA.