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My 2005 Cr250 is running rich and I have no idea where to start with jetting. The bike runs fairly good until WOT and starts to feel flat on the top.
Has it suddenly started running rich?
Is the clutch side crank seal leaking?
What carb are you running?
What jets are you using?
The guy I bought the bike from ran Maxima K2 at 40:1, but the engine was sent off to Pro Circuit where they jetted the bike for 32:1.
How would I know if the crank seal is leaking?
Mikuni
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I'm thinking about putting a new spark plug and air filter on it then switching to some fresh gas mixed 32:1 instead of 40:1. I'm thinking the 40:1 is making the bike run too rich fuel wise since the bike was jetted for 32:1. The bike starts 1st or 2nd kick but once goes "flat" on the top end almost feels like I'm at the end of the gear or hitting a "rev limiter". It goes from continuing building power and rpms to feeling like it "flattens" out and I shift because it just doesn't sound like it's good for the engine. I'm thinking it's running rich but I don't know the sound that I should be listening for. Would you agree that the bike is running rich from the looks of the spark plug being that it's black and oily?
Hitting a "rev limiter" is more likely to be the power valve not opening fully, check the cables.
The spark plug being black and oily can be a number of things...
- Oil leak between the gearbox and crankcase, caused by a leaking crank seal or center case gasket.
- Bike being ridden at low rpm for extended periods.
- Jetting too rich.
Changing from 40:1 to 32:1 is less than one increment in main jet size.
Replace the jet block gasket.
You can get one from JD Jetting.
Check the powervalve cables for slack, then check the plastic gear that operates the powervalves, they break off/ wear out, that has to be eliminated as a potential cause. Definitely new plug also….
Been meaning to get around to that just haven't had time to pull the tank. The previous owner told me that he never adjusted the rc valve cables.
Grab the cable outer between your fingers and try moving up and down, if it moves there is slack in the cables.
I think I found my problem
LOL, somebody didn't like to rev it!
I'm excited to see how the bike rides now that I fixed it. It bolt isn't even an uncommon bolt they could have use a bolt from the shroud on the tank instead of what they used. This was definitely why I felt like it was flat on top, correct?
That fixed the lack of top end I was feeling, but ohh my gosh it really unlocked the bike.
The servo motor would have been straining it's guts out pulling against that bolt and also stressing the plastic gear. The motor and the gear are already weak links and yours got an extra beating. Might as well start sourcing replacements as they are a little tricky to find.
There's a good video on YT demonstrating how to properly adjust the cables. Forget the instructions in the manual -- they are useless.
Essentially, you want to make sure you adjust the cables so the exhaust flap is fully closed at low Rs, but fully clear (above) of the exhaust port at higher revs. Remove the pipe when you are adjusting the cables so you can check the position of the flap valve against the exhaust port.
Getting this right is one of the real keys to making sure these bikes run the way they should.
That’s the way I adjusted the cables, the way this bike rides I think they got a bad rep from the cables not being adjusted correctly at dealerships.
100% agree with you. Cables properly adjusted and clean up the OEM jetting and the bikes rip. Mine's an '05 too. My only complaint is that the Mikuni is more sensitive to temp/pressure/humidity changes than the Keihin carbs I've had (usually just air screw adjustments), and it also seems more susceptible to ethanol fouling from pump gas. (No reliable source of ethanol free pump gas near us).
Pit Row
My bike is running a lot better since replacing that bolt and adjusting the cables. It's definitely still running rich because I'm having spooge coming from the spark plug hole. exhaust, and exhaust flange. The bike doesn't feel like it has a bog to me, buy maybe I just don't know what I'm looking for. I've had a Yz250 before and I prefer this bike over it for sure. I haven't been in the mood to pull the carb to see what jets are actually in the bike. What's the easiest way to pull the carb so I'm not removing anything extra. I thought about getting some race fuel to mix with some ethanol fee 93 since the bike is already running rich to see if that fixes my spooge. What premix are you running in your CR? I'm currently running 40:1 with Maxima K2.
I have notice a leak from my countershaft seal could that cause my bike to run rich? I bought this bike about a month ago and I'm pretty sure the bike was sitting for 2 years before I bought it.
I actually found out you can use the servo internals from a CBR600RR exhaust servo. All CBR600RR gears, cable pulley shaft, motor and potentiometer and cable swapped over from my understanding.
Yes, it will suck gearbox oil and appear to run rich, there will be oil on the rear fender.
While you replace the crank seal, check the Drive Gear Collar PN-13617ML3000 the crank seal runs on for wear...
The last gen CR is also susceptible to leaks between the crankcases, under the intake...
The servo's motor can be replaced with a Mabuchi RS-365SH-2080, or equivalent, there are lots of options.
Just to make sure we are talking about the same seal. the seal behind the front sprocket, correct? I guess if I have a leak between the cases I would have to spilt the cases and replace the gasket? I've been thinking about eventually doing a full rebuild with a OEM piston and an OEM crank. I think I'll rebuild the top end at least once before I do a full rebuild unless I find some play in the rod when I do a top end. I'm honestly not entirely sure about all the tools that I would need for a bottom end rebuild.
The right side crank seal #28...
The only way to confirm it the seal or the center case gasket is leaking is a leak down test...
I also recommend buying a service manual...
https://www.helminc.com/helm/product2.asp?Make=AHC&Model=CR04&Year=2005&Category=&class%5F2=AHC&mk=Honda+Powersports&yr=2005&md=CR250R&dt=&module=&from=result&Style=helm&Sku=61KSK52&itemtype=N
I'm pretty sure that seal was replace at some point on my bike as it came with a pack of seals, and that was the only one that was used. The leak I noticed was from 32. I do have a service manual.
Seal #32 won't effect how the engine runs, but it will lubricate the chain and drain the gearbox!
I switched my Mikuni to a JD Jetting kit not long after getting the bike. Using the suggested jetting, including red needle on middle clip. I run 40:1 BelRay HR 1 mixed with VP C12/93 pump at a 50/50 ratio.
I'd suggest removing and cleaning the carb at regular intervals. Easiest way is to remove the subframe and then remove top shock bolt to get the carb out of the frame more easily. When you're cleaning the carb, pull the needle valve seat (part no. 3 on the OEM parts fiche) and make sure the small o-ring at its base is pliant and in good shape. (Ethanol kills these o-rings).
If you're still not completely satisfied with how it runs with these steps, try replacing the jet block gasket as suggested above. JD Jetting has a kit that includes a new gasket, a torx wrench to remove the jet block, instructions and a new needle valve seat o-ring.
And, of course, inspect the reeds and do a leak-down test.
I'll eventually get a JD jetting kit to really dial in the bike. I went ahead and switched from 40:1 to 32:1 because I suspected that's what the bike was actually jetted for. I plan to ride some over the weekend to tell how much of a difference it really made, but from just putting around in my backyard it seemed like it prefers 32:1 plus I didn't see any spooge from the exhaust.
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