[SBG47]

I have an 08 CRF450R. I've been chasing a problem with it starting when cold. I can kick it forever it will not start. Not choked, not with the usual two throttle blips, nothing... It will flood every time and not start. I can't get it to clear our once flooded either. I've tried holding the throttle open full and the hot start on and kicking it 10x's and that doesn't help. I then take the seat and tank off and put a dry plug in and it will start first kick. It will start great the rest of the day. It runs awesome once it's started for the first time.

I'm tired of changing the plug before I ride it. I have rebuilt the engine twice and it's still a problem.
I have installed a new piston/rings, new cylinder, new base and head gaskets, new valve seals, and the problem won't go away.

I just did a leak down test and it holds a 100psi with no air leaking threw the valves or bubbles in the coolant.

Thanks for any help you can offer.

[JimDirt]

Welcome to the site !!

I have a few questions for you

Is this a bike that ran fine before the rebuild ?? , in other words , did it start fine cold before ?? ,

Is this a recent purchase ?? , if so , was it jetted correctly for the altitude your riding at ??

If its flooding that easy , then i would look at Needle position , Float Adjustment , (does it drip gas ??) and jet sizes first

Have you tried adjusting the Fuel Screw (remember its a Fuel Screw not a Air Screw) it should start/run easily within (*1-1/4 - 2-3/4*) turns out from lightly seated , Out is Richer , In is Leaner , idle should be around 1500-1800 and you should be able to turn the fuel screw till the idle raises then starts to drop off , then close the screw till the bike wants to die , counting turns each way , the highest idle should be between the settings i listed (* *) preferably in the middle , this would indicate your jetting is correct , then you need to look at internal parts in the carb if jetting specs out , Floating Valve Seal (on the slide) could be bad , accelerator pump timing (it needs to squirt and just miss the slide , not hit it) , or float level , or needle/seat sticking (you would notice the bike dripping gas when sitting with fuel valve on)

Jetting as follows:

Jetting Guide for Main Jet:(pilot 45) CRF450R/X

Sea level....165
2000 ft.......162
4000 ft.......160
6000 ft.......158
8000 ft.......155


Temperature/Elevation:
One main jet size (up/down) for every 2,000 feet or 25 degrees in temp.


Try this things , and report back with findings , if no positive results , go to the Jetting part of the forum and look for leardriver , find a post with that name , click on the name , it will take you to his Profile , then PM(Private Message) him and he will hopefully be able to figure out your issue , as he is the resident carb guru here .....hope that helped some

[punkrockkiel]

sounds like issue I had on my 07....if everything jim has mentioned is ok or close enough....

put the bike in gear and grab clutch and rock it back and fourth and see if the clutch isn't sticking and causing too much drag and then youll feel it break free and loosen up. don't let up on clutch lever and knock it back into neutral and try to fire it up.

[SBG47]

I am still having trouble. I looked into rolling the bike in gear with the clutch pulled in. It will not roll at all when in gear with the clutch pulled in. I tried adjusting the clutch cable to see if I could get a bigger pull in the lever but it didn't help. The bike will sputter every other kick like it wants to fire up.

So i pulled all the fibers and plates out of the clutch and tried to start it and i still just get the sputter like it wants to start.

[JimDirt]

As far as the clutch goes , did you notice any notching in the basket when you took the plates out ?? , although this wont have anything to do with kick starting it , it will have a effect when your trying to push start it and the clutch drags

As far as the sputtering , you never mentioned , but since you said it was flooding , did you try a new plug ??? , and was your jetting set as per the chart i posted ?? , and what is your Fuel Screw set to , it should be between 1-1/4 - 2-/3/4 out from lightly seated , remember on a 4 stroke its a Fuel Screw , not a Air Mixture Screw like on a 3 stroke , so the more OUT it is the Richer the mixture , but if you have to go less than 1 turn IN then its got too big of jets for your elevation

[SBG47]

The jetting is 180 main 42 pilot and fuel screw is 2 turns out. The clutch basket is notched up pretty good.

Wild thing is... I rode the bike two weeks ago and had the idle and the fuel screw set pretty good. No problems starting, idled fine, no bog on over jumped landings. Then today I randomly try to start it and I'm back to having trouble. My ankle needs a break from kicking.

[JimDirt]

You did not mention your elevation , you must be at around sea level i am, guessing , but #42 on the Pilot is too lean , try a #45 , and you should have the main around where the list shows for your elevation , the bike will still run when its way over rich , but it also then has issues like your having where its finicky because of being too rich .... the notches will definitely prevent you from pushing it with the clutch in , that is why your getting all the drag... your 2 turns out on the fuel screw because your trying to make up for the lean pilot jet , once you get the jetting squared away you will be closer to about 1-3/4 out , which is right in the middle of where you should be

[Leardriver]

Rebuilding the engine has nothing to do with a carburetion problem.
How do you know it is flooding? The wet plug isn't an absolute. it can get wet from the perfect mixture, and kicking it 20 times without lighting off.
You could, however, have a faulty or contaminated needle and seat. People are always asking about setting the float height, and the Honda engineers got it right to start with. Leave the stamped float tang perfectly straight, like it came, and your float height will be fine.
Back to the other issue that could be keeping it from starting. Have you tried getting some speed up on a downhill, shifting to 2nd or 3rd, and bump starting it? If that works, I suspect the binding clutch theory also.

[SBG47]

I have swapped carbs, changed the stater, filed the notches in the clutch basket smooth, and still have this starting cold issue. When the bike starts it will run amazing all day. If it doesn't start you can kick it forever and it will sputter and die over and over. It's like if I could just kick it a tiny bit harder it would start but that's not actually the case. I don't know where else to look. I feel like the carb is good but everyone keeps steering me in that direction. Seems like it would run like crap if I had a carb problem. The valves are shimmed properly as well. It has to be some freak thing not normally looked into.