First issue with sever bogging/cutting out at WOT

[JDubya381]

SEVERE*

 

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 a little 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.

Edited May 1, 2014 by JDubya381

[Curt026]

I'd say cleaning the carb is the first thing I would personally do. It may be something as simple as a plugged up main jet. I've never messed around with the jd needles in the keihin carb, but your jetting sounds good from my experience.

[JDubya381]

I'd say cleaning the carb is the first thing I would personally do. It may be something as simple as a plugged up main jet. I've never messed around with the jd needles in the keihin carb, but your jetting sounds good from my experience.

I was thinking between cleaning the carb, a fresh plug, and a silencer re-pack it should be alright. Probably lean out the jetting for the drastically warmer temps. Hopefully I didn't fry a ring or something..

[Curt026]

You know your bike than I ever could, but at near sea level it your jetting looks pretty good to me. I wouldn't lean it out anymore until you find the cause of the bog. A bog is a lean condition so if your problem isn't being caused by a clogged jet then a smaller jet will only make it worse.

Edited May 1, 2014 by Curt026

[JDubya381]

You know your bike than I ever could, but at near sea level it your jetting looks pretty good to me. I wouldn't lean it out anymore until you find the cause of the bog. A bog is a lean condition so if your problem isn't being caused by a clogged jet then a smaller jet will only make it worse.

That is true, but I'm almost entirely sure it was running rich. I'll check the plug and post some pics. Last October I experimented with the 2nd clip position and that really woke the bike up. Then winter came so I moved it back down. I'm thinking it's time to go back to the second clip position. How do you get half clip positions? I feel like that would be butter.

[Curt026]

Don't quote me but I believe the red needle is for half clip changes. I think if you take the jd red needle and put it on the 3rd clip that you would effectively be running half a clip leaner. I've never had a jd kit so I don't know that for a certainty.

[Hans Schmid]

I'm betting your too lean.... Bike needs more fuel! Go up two on the main and raise the needle/lower the clip...

[JDubya381]

I'm betting your too lean.... Bike needs more fuel! Go up two on the main and raise the needle/lower the clip...

I appreciate the answers, I know it's hard to diagnose someone else's problem on the internet.

This problem kinda came out of nowhere though. The only change I made was a half turn out on the A/S. That's why I think it has to be something else other than lean jetting. Because the temps were hotter than ever, so it was running richer than the last time I rode it from the second I started it up. I have a small dent I BBC the bottom "bowl" of my left radiator, could it be starving for water and over heating? I also wonder if I somehow got an air leak, causing a sudden lean condition. Gonna start with the basics and move from there.

What about electrical? Anyone have any possible advice there?

[Hans Schmid]

Air leak was my next thought. Build a pressure tester and check it before digging into anything else...

[JDubya381]

Will do. Saturday is when I'll have time to start checking shit out so I'll let you all know.

[JDubya381]

Shitting bricks right now. Opened up my airbox and my filter must have rattled off? Not sure how that happened but I'm pretty pissed, god knows what kinda shit got sucked up into my motor. &%$#@!...

[JDubya381]

What do you guys think? I read an older thread on here where someone was riding in the desert and found some dust/sand in their air boot and carb, but sounds like everything was okay. Sounds like you have to ingest quite a bit of dirt or sand to foul up a crank. I'm pretty nervous right now, but I pulled the exhaust off and took a peak thru the port and everything looked pretty good. What does blow by look like? I honestly will probably just end up doing a top-end for the hell of it. It's probably about time anyway, and this whole incident just makes me nervous enough to put a fresh piston and rings in it, and break it in more properly than last time.

[frdbtr]

Don't quote me but I believe the red needle is for half clip changes. I think if you take the jd red needle and put it on the 3rd clip that you would effectively be running half a clip leaner. I've never had a jd kit so I don't know that for a certainty.

 

JD's needles are identical with the exception of 0-1/4 throttle ranges where the red needle is leaner.  They are not half clips off.  My bet would be on a lean condition like an air leak.  Of course his air filter being off could have sand blasted the piston too.

[frdbtr]

What do you guys think? I read an older thread on here where someone was riding in the desert and found some dust/sand in their air boot and carb, but sounds like everything was okay. Sounds like you have to ingest quite a bit of dirt or sand to foul up a crank. I'm pretty nervous right now, but I pulled the exhaust off and took a peak thru the port and everything looked pretty good. What does blow by look like? I honestly will probably just end up doing a top-end for the hell of it. It's probably about time anyway, and this whole incident just makes me nervous enough to put a fresh piston and rings in it, and break it in more properly than last time.

 

One thing I learned with my 06 is with the metal base gasket, it is really important to use hondabond/yamabond on the seams of the crankcase to seal up the cylinder base with the bottom end.  Mine had a massive air leak there on my last top end when I pressure tested it after torqueing everything down.  Had to run and get some yamabond and pull the base to get some on there and it sealed right up.

[JDubya381]

One thing I learned with my 06 is with the metal base gasket, it is really important to use hondabond/yamabond on the seams of the crankcase to seal up the cylinder base with the bottom end. Mine had a massive air leak there on my last top end when I pressure tested it after torqueing everything down. Had to run and get some yamabond and pull the base to get some on there and it sealed right up.

I have Hondabond on there with the metal gasket. The piston really doesn't look bad, just haven't had a chance to dig deeper yet. There's some spring cleaning going on around me that's really F'ing up my groove..

keeping my fingers crossed that there's not too much damage..

[frdbtr]

I have Hondabond on there with the metal gasket. The piston really doesn't look bad, just haven't had a chance to dig deeper yet. There's some spring cleaning going on around me that's really F'ing up my groove..

keeping my fingers crossed that there's not too much damage..

 

Well, if you used hondabond on your base gasket, I would assume you don't have an air leak there.  Without a pressure test we don't know for sure though.  Still might also have a crankshaft seal leak.

[JDubya381]

Well, if you used hondabond on your base gasket, I would assume you don't have an air leak there. Without a pressure test we don't know for sure though. Still might also have a crankshaft seal leak.

I don't have a real way to perform a leak down test. Tried the homemade one that's stickied here and would not work no matter what I tried.