Post by: redrider611 on January 02, 2013, 08:20:24 AM
2004 CR250. Bike runs great (crisp and clean) for several laps (5-10) and then all of a sudden it has a random bog for a split second.
It will usually happen in the whoops or on landings.
Things that have been checked already:
PV is working fine (even eliminated it) and it still does the same random bog
Float level at different settings
reeds are new and sealing fine
no air leaks found
kill switch removed
CDI changed
the bike ran great before and all of a sudden it started this. I am lost.
I hope someone has the answer for it.
Thanks
Post by: arnego2 on January 02, 2013, 11:30:46 AM
Post by: eprovenzano on January 02, 2013, 02:30:51 PM
Post by: SachsGS on January 02, 2013, 04:15:01 PM
Post by: _X_ on January 02, 2013, 09:05:26 PM
Post by: redrider611 on January 03, 2013, 02:45:19 AM
I have also ran 3 different carbs with no luck.
I have also changed the coil and again no luck.
It is an absolute random bog.
I am going to be spiting the cases tomorrow to check for cracks internally causing a random lean issue.
Starting to think it needs holy water in the rads....
Post by: Stusmoke on January 03, 2013, 05:19:12 AM
Also check the fuel shut off valve filter thats on the tank. If thats filthy dirty there could be dirt getting into your fuel and therefore, into your jets. Hence the random bog. If its filthy dirty, clean it (duh) and leave your bike to idle for about 10 minutes then come back and pull it off. If its disgusting again, you sound experienced enough to know the rest.
The force you take on when you plow through whoops or take big landings could be enough to force some of the dirt that might be in that filter through it.
Good luck. Exhaust ALL of the simple options you or anyone can possibly conceive before you start splitting anything
Post by: 2T Institute on January 03, 2013, 11:13:31 AM
could be caused by fuel splashing around (fuel starvation) in the float bowl. i think that is a reason boyesen made the super bowl http://boyesen.com/super-bowl.html
My thoughts as well also set the float height to be just before fuel comes out the overflow. Save yourself the grief of splitting the cases.
Post by: SachsGS on January 03, 2013, 04:18:52 PM
Post by: redrider611 on January 04, 2013, 03:54:11 AM
I have used 3 different carbs with float levels set and it still does it.
All vent tubes breath fine, no holes in float, etc.
coolant is not getting into the combustion chamber either.
It is really strange. On average I build 1-2 motors a week and I have never seen anything like this before.
It bugs the crap out of me too.
Post by: Stusmoke on January 04, 2013, 04:39:35 AM
Post by: 2T Institute on January 04, 2013, 11:31:29 AM
All things have been checked and rechecked.
I have used 3 different carbs with float levels set and it still does it.
All vent tubes breath fine, no holes in float, etc.
coolant is not getting into the combustion chamber either.
It is really strange. On average I build 1-2 motors a week and I have never seen anything like this before.
It bugs the crap out of me too.
Is your pilot jet a bit rich or lean, as this seems to be a heat related issue. Could it be once heat soak occurs your jetting is to rich off the bottom?
Post by: evo550 on January 04, 2013, 02:41:01 PM
My sons YZ 85 had a similar problem, turned out after much investigation that there was a small crack in the float that would slowly fill up with fuel causing the level to change, creating a bog you described.
Post by: SachsGS on January 04, 2013, 04:58:51 PM
Recently I repaired a neighbour's YZ 125 that has, if I am not mistaken, a Mikuni TMX carb that is similar to what you have on your CR. The YZ had a similar "bog", but more pronounced, than your CR. The bog went away if I left the choke on but it was obviously too rich and couldn't be ridden that way.So fatten up the pilot and all will be fine? Nope. I didn't want to waste a lot of time jetting the bike (time I didn't have) but something was not right. A freind had a similar problem with his TMX equipped Husky WR250 and he ended up putting a Keihin on the bike after wasting a lot of money trying to jet the Mikuni to no avail.
Post by: TMKIWI on January 04, 2013, 11:06:17 PM
Reason I ask is I have had problems with some outboards having a random missfire and after countless hours of wasted time went out with them and found it only happened at 1 spot on the water.
It turned out to be electrical interference from an under water cable.
Strange but it does happen. That is why you see all the different electrical standards on CDI's.
Radio and/or electrical interference is so rare these days it can take awhile to diagnose it.
But it does happen..
If it happens at any track , disregard the above.
Post by: Stusmoke on January 05, 2013, 04:24:56 AM
Does it happen at only 1 track , or does it happen everywhere.?
Reason I ask is I have had problems with some outboards having a random missfire and after countless hours of wasted time went out with them and found it only happened at 1 spot on the water.
It turned out to be electrical interference from an under water cable.
Strange but it does happen. That is why you see all the different electrical standards on CDI's.
Radio and/or electrical interference is so rare these days it can take awhile to diagnose it.
But it does happen..
If it happens at any track , disregard the above.
THats trippy shit. You must've been like WTFFFFFFFF!!!! A miniature and electrical bemuda triangle
Post by: SachsGS on January 05, 2013, 04:35:44 PM
Post by: moto867 on January 05, 2013, 04:49:18 PM
Post by: Stusmoke on January 05, 2013, 09:25:53 PM
Strange things happen in NZ.
I know right. Especially when they inspect all their fat lambs, with their pulverized rectums. ONLY IN NZ!
Post by: redrider611 on January 06, 2013, 03:07:41 AM
It does it randomly at every track no matter if it is on the first lap or 10th lap. It is completely random.
Post by: redrider611 on January 06, 2013, 05:44:10 AM
I have never seen this before but there is a first time for everything.
Thanks to everyone for the input.
Post by: 2T Institute on January 06, 2013, 05:51:32 AM
Post by: TMKIWI on January 06, 2013, 08:17:15 AM
I know right. Especially when they inspect all their fat lambs, with their pulverized rectums. ONLY IN NZ!
Enough of the sheep jokes stu.
They weren't funny 20 years ago and still not funny.
An intelligent man wouldn't throw out the same joke every 5 minutes. It gets old.
Post by: redrider611 on January 06, 2013, 02:57:37 PM
Where was the crack?
On the bottom (crank web area).
Post by: Stusmoke on January 06, 2013, 09:51:49 PM
I know right. Especially when they inspect all their fat lambs, with their pulverized rectums. ONLY IN NZ!
Enough of the sheep jokes stu.
They weren't funny 20 years ago and still not funny.
An intelligent man wouldn't throw out the same joke every 5 minutes. It gets old.
Sorry mate. I'm not taking the piss either, being serious.
Where was the crack?
On the bottom (crank web area).
Thats really crap. Are you gonna buy a new case?
Post by: SachsGS on January 07, 2013, 12:17:59 AM
Post by: redrider611 on January 07, 2013, 06:02:30 AM
Post by: cnrcpla on January 07, 2013, 12:30:13 PM
Post by: redrider611 on January 07, 2013, 05:06:17 PM
Post by: Stusmoke on January 08, 2013, 03:21:59 AM
Post by: eprovenzano on January 08, 2013, 05:37:48 PM
That's a new one for me.I agree... Just glad you found the problem.
Post by: SachsGS on January 09, 2013, 12:12:42 AM
Post by: cnrcpla on January 09, 2013, 01:09:25 PM
Post by: SachsGS on January 09, 2013, 03:06:11 PM
