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Stator cover gasket causing air leak?

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Hey guys I was just cleaning underneath my bike and noticed the very bottom back side of my stator cover. The gasket was hanging down below where it should in 1 little section and there was a tiny hole letting air into the stator area...I've been having a surging idle once my 98 cr250 is warmed up and many members have thought it could be due to an air leak, so I was wondering if this could somehow be causing it?

I'm not sure if you'll really be able to tell in these pics. The main black part is the gasket...Once again this is me looking from UNDER the bike from the opposite side of the bike, so this is the bottom back side of my stator cover...Please tell me what you think.

IMAG0555.jpg

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To my understanding that gasket it to keep dirt and mud out of the stator it is not to seal the engine that is what your crank seals do. Ive seen intake and base gaskets cause a surging idle/hard starting ect. You could spray wd-40 around your gaskets with the engine running and listen for the idle to change, or a more accurate way of checking is to leakdown test the engine.

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My favorite way of testing for air leaks is to get a propane torch that is not lit open the valve and point it at various parts of the intake until you find a spot where the idle gets better. its been very effective on my four strokes.

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Thanks for the tips fellas I already tried starting the bike and spraying everything down with carb cleaner. No change in idle or anything and I also consulted a knowledgeable mechanic friend about that gap and he said it's designed to be there so any condensation will dry out!

I am not even sure at all that I have an air leak...I had the bike stick to WFO throttle 2 times randomly, but I had throttle hardware tube, housing, and cable on the bike that were literally like 7 years old. Not only that, the cable was routed wrong. All of that has been replaced and it has been running great, but originally I started a thread and everyone just said I have an air leak, but it was clear they hadn't even read all of the info I provided so I don't know. Only time will tell. The matter of it being a gasket or anything doesn't matter this motor is being rebuilt later this week.

The only other thing is once my bike gets warmed up it has a surging idle, which I'm pretty sure is a lean condition. I am at exactly what the manual calls for, but I am going to just bump my pilot jet up 1 size, as my air screw is running at only 1 turn out (the minimum) and will run most of the way in, so I need the next biggest pilot and hopefully that will cure it up. Then it won't be EXACTLY what the manual calls for, but then again, I've been told every bike is different and I'm sure it's normal to go a little off the exact manuals specs some times.

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yeah that seal is just ther to keep foriegn debri out. sounds as if its lean surge. possible air leak? sounds like ur on top of it. u'll get it sorted im sure.

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Yea I hope. I just hate that it could be a "mystery leak"

I mean is bumping up 1 size on the pilot from the service manuals recommendation ridiculous? Isn't that normal? The manuals spec is a 55 pilot (which is what I have) but it covers about a 30 degree swing in temperature...Also, another clue is it does it once the bike gets warm..Don't know what to take from it, but the reason I ask if it is un-reasonable, is some guy was like your just trying to jet out your air leak, but I just don't see why everyone is so quick to diagnose the air leak. I didn't think 1 size bigger pilot was a big deal. I could see if I was like 3 sizes bigger, like really rich or something. I keep getting told every bike is different and requires something a little different. It's getting colder and bikes go lean, so you've got to richen them up. I already richened up the main 1 size, seems normal to me? But I'm new to all this still, so I just try to do everything I can. I just really don't want the throttle going WFO on me again in the middle of a stand up wheelie because of some mystery air leak. However, I really believe that was due to 7 year old throttle assembly and misrouted cable...

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True. I guess I never thought of it like that. Well I did, but I quickly decided I need to get it right. The thing is how do I know what to have it on the warm up period? Definitely don't want it too lean then. I guess I'll go with my bigger for sure richer jetting. 58 pilot from 55 like planned and my current 178 main from 175.

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Trying to jet a worn out engine is a waste of time. The same goes for reeds that don’t seal properly. Ive heard that worn reeds will mimic rich jetting, and worn rings will mimic lean jetting. Once everything is in good condition I think I would go with what the manual suggests for your altitude and temperature for break in and fine tune from there.

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Like I said before, once you get your engine rebuilt and jetted to where you think it should be check that your idle speed is set correctly. Too high of an idle will cause a surge at idle. Look in your service manual to see what it should be set to. If your throttle valve is open too much at idle the pilot circuit cannot supply enough fuel and the needle jet and main jet aren't supplying fuel yet so you get a lean condition.

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Okay great THANKS a ton guys for letting me know. I definitely could have worn rings, but this bike runs great! It's just time...It's lost compression, harder to start, etc. etc. but when it's running it's great, and it has the recommended jets in it now and runs great except for the surge.

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Doesn't matter for me as both of mine are worn I'm sure :bonk:

I would think the worn reeds would be lean and worn rings would be rich, but do not listen to me on that.

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Okay thanks for the tip. I checked my intake boot when we took it off tonight and no cracks. My reed gasket is broken, but my mechanic friend said it's not causing a leak because it's not completely broken into 2 pieces. I'm still iffy on it though, so I ordered a new reed gasket. Obviously the head and base gaskets will be brand new, along with exhaust Orings and silencer repacking, I also got boyesen dual stage power reeds, with a few other OEM bolts and things along with new white plastics.

Here's tonight's progress: My piston and cylinder look surprisingly well. Well enough that I will not need it re-honed. That's $75 saved...

IMAG0556.jpg

IMAG0557.jpg

I also took my choke knob off tonight to check it for obvious possibilities of leaking air. I thought it might have an o ring or something in it, but it doesn't...So I just cleaned it up.

The only other possibility for an air leak is my crank seals. Hopefully there is an easy way to determine if they are leaking or not...

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The only other possibility for an air leak is my crank seals. Hopefully there is an easy way to determine if they are leaking or not...

left side Crank Seal will leak if RPM changes with propane as said earlier. Right side crank seal will leak if you notice there's transmission fluid missing. Measure how much goes in and comes out at next change.

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ist it the other way around?

Maybe I did get it backwards,but either way it was only stated to help make my point that your engine needs to be in sound condition before you spend too much time trying to perfect your jetting. Trying to jet for worn parts is like herding cats-you'll always be chasing something. :bonk:

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left side Crank Seal will leak if RPM changes with propane as said earlier. Right side crank seal will leak if you notice there's transmission fluid missing. Measure how much goes in and comes out at next change.

Okay excellent. I have been leaking a tiny amount of tranny fluid but that's because my check bolt won't tighten down all the way. I ordered a new check bolt and washer and we're just going to seal it up BUT you meant the right side crank seal will USE tranny fluid i.e. not leaking but burning it into the motor...I will have to check for that.

How much of a PITA are both crank seals to replace? Would I have to split the cases?

Maybe I did get it backwards,but either way it was only stated to help make my point that your engine needs to be in sound condition before you spend too much time trying to perfect your jetting. Trying to jet for worn parts is like herding cats-you'll always be chasing something. :bonk:

Herding cats :smirk:

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Okay excellent. I have been leaking a tiny amount of tranny fluid but that's because my check bolt won't tighten down all the way. I ordered a new check bolt and washer and we're just going to seal it up BUT you meant the right side crank seal will USE tranny fluid i.e. not leaking but burning it into the motor...I will have to check for that.

How much of a PITA are both crank seals to replace? Would I have to split the cases?

Herding cats :bonk:

Changing your seals is a piece of cake and you don't have to split the cases to do it. The flywheel side crank seal is behind your flywheel and stator. You need a flywheel puller to get to that. the other one is a bit more work since you have pull the clutch cover and the clutch side of the case. I believe that you have to pull the clutch to get to it too. pop them out with a seal puller or screw driver and then press the new ones in.

As far as your gap on your flywheel cover, you need to get that fixed and use a new gasket and make sure it seals up good. Too much dirt in there will blow your flywheel side crankshaft seal and will cause air leaks.

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Well actually that tiny gap at the bottom is supposed to be there to allow any condensation build up inside there dry out, and also allow the drain of anything....This is what I've been told by my real experienced and respected older mechanic friend that is doing my rebuild....It doesn't make sense that the gasket would hang a little below it though.

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