Pop and Die, in the apex about to exit
  • mframpton
    Posts: 17
    Joined: Sat Nov 25, 2017 10:39 am

    Pop and Die, in the apex about to exit

    by mframpton » Mon Jun 21, 2021 12:15 pm

    2008 CRF450R - Intermittent pop and die in the apex of the corner.
    Hot Cams stage II, Kibblewhite stainless valves,
    Issue stated below after all questions:

    What is your elevation ?? 860 ft, Wisconsin

    What type of riding are you doing ?? MX

    What is your Fuel Screw set at ?? 5/8 turns out from bottom. I can't tell any noticeable change in the full range of turns albeit I can get it to stall when turned closed. I arrived at 5/8 because it's where I could get it to rev slightly at idle with the hot start depressed and the engine hot.

    What jets are in it (Pilot/Main) ?? 42 to a 40 now to a 38 /165 stock main

    What is the Needle Clip Position ?? (IE: 3rd from top , etc.) stock 4.

    Was the bike running fine then just started doing this ?? , or was it like this when you bought it , or after sitting for a extended period ?? I got it with 200 hrs on it, I've put probably 60 hrs on it. It's kind of an intermittent thing so hard to tell.

    Have you actually pulled the carb and cleaned it (removing all the rubber parts like Fuel Screw O-Ring, Slide , Floating Slide Plate O-Ring , gaskets , jets , and flushed everything with carb cleaner and blown out with air) ??? Installed an R&D Racing brass FS. Cleaned carb/jets. Didn't replace anything else but slow jet looking for a solution

    Do you have a Manual ??? (Yes/No) Yes

    Have you lifted the subframe and airbox , and looked down the throat of the carb and twisted the throttle to see if the accelerator pump is squirting ?? , and if it just barely misses the slide and does not hit it ??? Nice squirt under the slide and not on it.

    When/if you took the carb apart , did you note which way the floating plate is on the slide ?? , was the hole at the bottom ?? , or the Top ?? I didn't take it that far apart. Assuming it's right

    Did you drain and flush the tank and put FRESH Premium in ?? Affirmative

    Was the bike sitting for a long time (over 3 months with gas in it , if so see above last 2 questions) ?? No. I drain the bowl every time after a day's riding

    If the bike was recently purchased , was the prior owner up front and explained the issues with the bike ?? I've had this particular bike for 3 years and ride often with the guy I bought if from. *****************Issue below***********************

    No bogs or dead spots anywhere. This only happens like once per an entire day's outing. I get into the apex of the corner and right when I just barely crack the throttle "POP and DIE". Until I went to the 38 pilot, getting it started again would be difficult unless I drained off the bowl some to lean it out. Granted if I didn't have a Rekluse CX installed or weren't in a taller gear, maybe it would automatically bump start itself during the incident. Things I noticed: It will start with the 42 pilot - NO choke and a little erratic idle although not extreme. 40 to a 38 pilot in there now and still erratic with fuel screw set at 5/8 turns from bottom. It will start cold and choked with the 38 Pilot now but needs a little help with the hot start. Sure sounds like it's robbing fuel from somewhere else in the system... Needle Jet wallowed out maybe?
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  • Leardriver
    Posts: 462
    Joined: Wed May 05, 2010 10:33 am

    Re: Pop and Die, in the apex about to exit

    by Leardriver » Mon Jun 21, 2021 3:18 pm

    Very thorough description.

    Here is my first impression. You are painfully lean on the idle circuit. Use a 45 pilot, and the fuel screw turned out 1 3/4 to 1 7/8. Your main jet is fine.

    You can't tell how a bike is jetted from how it runs on the stand under no load. Make that one change and report back. I suspect it will solve the problem unless the carb is also gummed up from sitting.
  • mframpton
    Posts: 17
    Joined: Sat Nov 25, 2017 10:39 am

    Re: Pop and Die, in the apex about to exit

    by mframpton » Tue Jun 22, 2021 1:53 pm

    Interesting. What led me to believe it was too rich with the 42 pilot, I could seat the AF screw while running and it wouldn’t even stall. When I went to the 40 pilot seating the AF would stall it. But what the heck I’ll order a 45 and see what happens.

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