Posts
44
Joined
2/28/2013
Location
Ringgold, GA, USA
Edited Date/Time
9/6/2013 12:38pm
Well heres the things, I recently purchased an 01 CR 250 that needed the cases, purchased the cases and replaced them. All went well as far as the bottom end is concerned. I removed and cleaned the powervalved, polished it along with both the intake and exhaust ports. I've done this on the last 2 2 strokes I've owned, and it's a simple and cheap way to produce a much more predictable and crisp power. The bike had a fresh top end installed by the previous owner, which is believeable as the gaskets were fresh, the piston hadn't been covered in carbon, and the bike has plenty of compression.
Anyways, finished the bike and started it. Rode it around the yard, checked to make all the gears were there.. set up the race sag, clicks, chain tension, etc to make sure it was ready for the track. Took it to a big turn track last weekend, and the power was just a little sluggish on top. It was like the bike had loaded up and isn't clearing out.
BUT, it's not to the extent like the crank seals are gone. The feeling from a mechanics perspective is like the bike is running a little rich. so I went back, reset the Air screw to factory settings. That didn't help, so I went to the gas station, got some fresh 93 and mixed it a little more lean. (started at 40:1, went to 50:1.). That didn't help, so I just kind of put up with it for the day.
Through the week I managed to get a little time to dig into the carb. It wasn't dirty, all passages were clean and so forth.
As far as the Jets are concerned, everything was factory except the Main Jet, which was a 400 (Factory is 420). I'm in the correct elevation for a 400, but I'm about 10 degrees too cold for it on average.
I've checked the jet Needle, it was set as lean as possible, I set it back to factory and it just made it worse.
HERES WHAT CONFUSES ME:
The Main jet is already leaner than what the Service Manual calls for my environment, on top of it being set super lean with the air screw and Jet Needle. YET it still feels rich, its bogging off the bottom and not revving out. My powervalve isn't stuck, I've checked. My Crank seals are good, I'm not losing oil. My gas is fresh along with my oil. My Reeds are good too (check them when I reassembled it.
Anyways, finished the bike and started it. Rode it around the yard, checked to make all the gears were there.. set up the race sag, clicks, chain tension, etc to make sure it was ready for the track. Took it to a big turn track last weekend, and the power was just a little sluggish on top. It was like the bike had loaded up and isn't clearing out.
BUT, it's not to the extent like the crank seals are gone. The feeling from a mechanics perspective is like the bike is running a little rich. so I went back, reset the Air screw to factory settings. That didn't help, so I went to the gas station, got some fresh 93 and mixed it a little more lean. (started at 40:1, went to 50:1.). That didn't help, so I just kind of put up with it for the day.
Through the week I managed to get a little time to dig into the carb. It wasn't dirty, all passages were clean and so forth.
As far as the Jets are concerned, everything was factory except the Main Jet, which was a 400 (Factory is 420). I'm in the correct elevation for a 400, but I'm about 10 degrees too cold for it on average.
I've checked the jet Needle, it was set as lean as possible, I set it back to factory and it just made it worse.
HERES WHAT CONFUSES ME:
The Main jet is already leaner than what the Service Manual calls for my environment, on top of it being set super lean with the air screw and Jet Needle. YET it still feels rich, its bogging off the bottom and not revving out. My powervalve isn't stuck, I've checked. My Crank seals are good, I'm not losing oil. My gas is fresh along with my oil. My Reeds are good too (check them when I reassembled it.
One thing you did not talk about is your spark plug. type color is it wet or dry?? since you had the cases apart you might have a timing issue to where the spark is not advanced enough to allow the engine to rev up and burn the fuel to its max power content.
The Shop
Luxon 4-Post Bar Mounts
$189.95 - $239.95
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
And went back to 32:1, was worse than 50:1.
Make sure the "fork" on the bottom of #14 is around the "pin" on #11 when installing the cylinder, otherwise your PV will not work. Even though the PV slides-moves when you were putting it back together.
Our used YZ 250 ran similar to what you are describing (runs ok down low but at wide open it falls flat, no power) and the PV governer was not working. Tried jetting etc... The Governor was not pushing the PV actuator arm.
Also a quick check is to remove the pipe, remove cover #2. Install pile and start bike. If the PV arm is moving when you rev the bike then it's hooked up right. If not #11 & #14 are not aligned.
Good luck!
.
When you can't figure out a simple problem, look for simple causes first!!
Post a reply to: 2001 CR250 not "opening up". I'm stumped.