[Yoshi]

2009 CFR450X Seattle WA

I am pulling my hair out trying to figure out why this bike does not like full throttle!!!
I have so far:
Air box mod (top and sides).
New plug
New air filter
JD Jetting kit as per their specs (165 main, red needle 4th clip from top, 50 leak, air screw 1 3/4 out).
Tokyo Mods smog block off kit.

Have checked:
New 92 gas
Fuel filter supply/breather not blocked
Carb stripped and cleaned

Left to check:
Swap around main jet sizes and needle position
Valve specs
Valve timing not jumped
Check grounds on electrics
Change plug out.

It pulls very strong from low down to mid 3/4 throttle - but then holds back, not really misfiring, more of a drastic reduction in power and just not running good. I started off with a 165 main jet (As per JD Jetting recommendation) went up to 170, down to 160 and couldn't notice any difference???
I would appreciate any help tying to figure this out as i am on a bit of a learning curve with these four strokes.

[Swim_fan02]

Have you tried doing a plug chop? That's going to be a really good way to check and see if your jetting is good. I would try that first and then go from there. To me it sounds like you need to bump up the main. It is also quite possible that a piece of dirt could've gotten jammed up in there somewhere. All it takes for these carbs is just a little dirt and they won't perform like you want them to.

[JimDirt]

I was in Pasco Washington for almost a year (2011) i went up for the Seattle SX and brought my bikes and ended up staying at my buddies house and we just went all over the state riding tracks , and when i went there , trying to ride any track , , i had a hard time getting my bikes to run without a 180 main and 48 pilot with the fuel screw at 2 3/4 , Pasco is at 500 ft , i rode in Spokane (1,843 ft)with the same jetting , my friend that lives there also had the same issue when he bought his 2011 KTM 450SX-F and struggled with the stock jetting , and went with a 180 with a 48 pilot to get the bike to run good ...makes no sense

I came back to Idaho (2,300 ft where i live) , and am at 160/45 where its always been , when in Washington , my bikes would not even start , let alone run with that jetting

Your at 65 ft , so i would go richer than 170 , try a 175 and see if it gets better , if it does try a 180 you may even have to swap the 45 pilot with a 48 pilot , i don't know what it is about Washington , but for some reason it needs richer jetting than that elevation should need anywhere else , it makes no sense , but going even richer should help , everyone i talked to there had way richer jetting then what would be the norm for the elevations

It makes no sense at all , but it won't hurt to try it , all your out is the cost of the jets and a few minutes of time

[Yoshi]

Thanks for your input.
I finally resorted to starting rich on the main and trying to come down from a (probably over-sized) bigger main jet, and pulling plug in relation to throttle position - adjusting as necessary. I went i little nuts and put in a 178, knowing i would be reducing. Trouble was the bike was running pretty nice and i just stayed playing all day! So next time out i will devote the first hour to bike set up (honestly).
I also completely cleaned the carb and gave it a complete make over with a rebuild kit- including middle body gasket which was a little scary but am confident this went in as good as it possibly could have using 3M Scotch Weld 847.
Checked the valves & timing - all good there.
Swapped out the plug.
Checked fuel supply and breather- no problems.
So at this stage i am putting it down to jetting.
Good news is bottom end is just about perfect, i have zero delay on throttle response - which is really nice and smooth as was slowly picking my way through the forests.

[JimDirt]

LOL i was editing when you posted , so re-read my post , basically what i put about going to 180 is about where you ended up , this jetting worked for my 450R and 450X

[Yoshi]

Well i gotta say its sounds like we are both thinking alike as far as going bigger on the main, and end up going with what "feels" best, instead of going with is supposed to be in there.
I will pull the plug next time out, just to take a peak and make sure its not black sooty off the chart rich. Then try and dial the mid throttle to wot for a smooth transition...all in all i am now much happier with what this bike is capable of. This is my first time on a four stroke having always had CR250,s....i knew it was running right on my fist ride.
What is an eye opener is how many four strokes you hear popping and backfiring because they are not running right.