Posts
10642
Joined
7/21/2009
Location
Harrisburg, OR
US
Edited Date/Time
5/5/2014 4:05pm
Had my first bogging issues today.
2004 CR250 w/ 2000 CR kehin carb. 45 pilot, blue jd needle 3rd clip, 178 main. Temps were mid 80's today (record for Oregon), elevation about 500'. Bel-ray H1R @ 32:1 with 50/50 110 leaded Sunoco and 93 premium non-ethanol.
Things were fine first practice but I needed some more spunk so I moved the A/S from about 1 1/4 turn out to 1 3/4 out. Throttle response was better, but they had put a good amount of sand on the track, so in the sand at WOT it was falling flat and not really revving out. Before I could raise the clip or go down on the main, I ran into problems.
Thank God I was tired and was about to take a breather lap when I pulled up to the biggest jump on the track because my bike completely cut out and almost bogged to the point of dying. I pulled off, still couldn't' get it to rev out. This was after about 5 laps, so it was up to temp. I shut it off for about a minute then it seemed to come back to life. Went out for the next practice after giving it a little check over, and while it didn't completely cut away, it was still a little boggy in the deeper stuff.
So this weekend I'm gonna clean the carb, check the reeds, pull the exhaust and check for bad signs thru the exhaust port and pull the head if I have to. I think I was just too rich for the higher temps and the deeper sections, but I've never had this bike completely cut away like that. Any suggestions? Oh, also gonna check the RC butterfly for cable tension and full opening.
2004 CR250 w/ 2000 CR kehin carb. 45 pilot, blue jd needle 3rd clip, 178 main. Temps were mid 80's today (record for Oregon), elevation about 500'. Bel-ray H1R @ 32:1 with 50/50 110 leaded Sunoco and 93 premium non-ethanol.
Things were fine first practice but I needed some more spunk so I moved the A/S from about 1 1/4 turn out to 1 3/4 out. Throttle response was better, but they had put a good amount of sand on the track, so in the sand at WOT it was falling flat and not really revving out. Before I could raise the clip or go down on the main, I ran into problems.
Thank God I was tired and was about to take a breather lap when I pulled up to the biggest jump on the track because my bike completely cut out and almost bogged to the point of dying. I pulled off, still couldn't' get it to rev out. This was after about 5 laps, so it was up to temp. I shut it off for about a minute then it seemed to come back to life. Went out for the next practice after giving it a little check over, and while it didn't completely cut away, it was still a little boggy in the deeper stuff.
So this weekend I'm gonna clean the carb, check the reeds, pull the exhaust and check for bad signs thru the exhaust port and pull the head if I have to. I think I was just too rich for the higher temps and the deeper sections, but I've never had this bike completely cut away like that. Any suggestions? Oh, also gonna check the RC butterfly for cable tension and full opening.
You'll need to know elevation where you're at, and go to weather .com for current conditions air temp, barometer, and dew point are what is needed for the above calculations. Just plug those into the app at this website.
Oh and definitely look at the plug to confirm. Always a good idea to check compression once in awhile a tired motor will start to go fat also.
Something else to check is the squish, a wider squish can get you in trouble with detonation. Tighter squish with higher msv keeps the heat out from around the edge of the piston. It forces the hot gases back into the middle of the chamber for a better burn. Essentially a proper squish provides a cooling ring affect in the cylinder.
The Shop
Can someone try to clarify the relationship between the A/S and pilot jet, as well as the pilot and main jets compared to clip position? So for example I lean the air screw and turn the idle down? And if I raise the clip, should I run bigger main and pilots if necessary?
forget all the bullshit about how many millimeters your floats should be set at.
pull off your carb. pull the floatbowl off. put a 14-14inch piece of hose on the fuel orifice. with one hand, hold the carb level, and now make certain that you hold the floats so that the seam on the floats is perfectly 100% parallel with the bottom of the carb body.
hook up that piece of fuel hose. now blow into it. when the seam on the side of the black float (toward the top) is 100% parallel you should not be able to blow into it at all. its sealed off. when you drop the float downward toward the ground just a hair, about 1mm, you will be able to blow. moving it back up 1mm, it will cut you off and you wont be able to blow.
that's a properly calibrated float. ignore hard settings like "15mm" because over the years, float tangs get bent into funny shapes, and float needle valves come from different buildings in china, so a hard setting like "15mm" means jack shit.
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