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Pressure testing '01 CR250???

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OK. I'm running through a general health check and decided to pressure test the engine. While testing, I found that air is escaping from the power valve area into the tranny area. The pressurized air is passing around the pinion shaft (the shaft that passes into the tranny area and engages behind the water pump) and passing out the tranny vent tube. BTW, the power valve is in the "L" position. The leak made me think there was a crank seal leak, but the crank seal appears to be tight as a drum.

During a pressure test is an air leak around the pinion shaft into the tranny area normal?

BTW, the pressure in the crankcase leaks down immediately.

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the bushing that the shaft sits on might be worn, or not there at all...is the engine new, or has it had some time and/ or overhaul done on it?

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I noticed my '01 did the same thing when I pressure tested. I looked for hours trying to find the leak. Is there a fix? Does it need to be fixed?

Paul

01 CR250

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the bushing that the shaft sits on might be worn, or not there at all...is the engine new, or has it had some time and/ or overhaul done on it?
The engine is new, but it had been stored in two pieces (cylinder/bottom end) since '01 when I bought it. It was assembled and shipped to me by a reputable outfit (still reserving judgement here), so I have no idea about the presence of the bushings (haven't gotten that far yet). In reviewing the manual, it seems that the pinion shaft and lower bushing are supposed to have been coated with Moly 60 paste; maybe they didn't do that. I've been reviewing the manual looking for some sort of o-ring, but I guess the bushing(s) appear to be all that seals the power valve area from the tranny area??

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I noticed my '01 did the same thing when I pressure tested. I looked for hours trying to find the leak. Is there a fix? Does it need to be fixed?

If you believe the "hold 6 psi for 6 minutes" theory, mine sure needs to be fixed. If I pressurize it to more than 1.5 psi, it drops to 1.5 psi almost immediately, then holds there for a while. The bike also appears to be running really rich off idle (jetted correctly according to all I can tell) which is what caused me to start pressure testing to begin with.

EDIT: Since I posted this thread, I found this over on another forum. Seems to answer some questions.

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If you believe the "hold 6 psi for 6 minutes" theory, mine sure needs to be fixed. If I pressurize it to more than 1.5 psi, it drops to 1.5 psi almost immediately, then holds there for a while. The bike also appears to be running really rich off idle (jetted correctly according to all I can tell) which is what caused me to start pressure testing to begin with.

EDIT: Since I posted this thread, I found this over on another forum. Seems to answer some questions.

I was also checking the engine before re-jetting. My bike ran rich until I changed to an S-7 nozzle. (I have a Mikuni carb.)

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I was also checking the engine before re-jetting. My bike ran rich until I changed to an S-7 nozzle. (I have a Mikuni carb.)
I'm pretty sure the linkage shouldn't leak. At a minimum, it wouldn't make sense to dump exhaust into the tranny :excuseme: .

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I'm pretty sure the linkage shouldn't leak. At a minimum, it wouldn't make sense to dump exhaust into the tranny :excuseme: .

Thanks for the link to the other forum. I'm going to look in the manual to see if there are wear limits on the bushings or if they need to be re-greased. I'm curios to know if the exhaust is causing the crank case to build up too much pressure. I developed an oil leak on the larger gasket on the clutch side after an enduro a couple of weeks back.

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I developed an oil leak on the larger gasket on the clutch side after an enduro a couple of weeks back.
The transmission is fairly well vented through the vent tube, but I suppose it's possible. BTW, there are wear limits given for the shafts.

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where can i get this paste? im going to do a top-end soon and want everything to last as long as possible..for some reason im doubting my honda shop will have it, or they'll give me something else and say that'll work

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My local dealer does stock it, but if all else fails, you should be able to order it through Service Honda.

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Thanks Mike. I searched over there but came up with very few hits. I guess I was using the wrong key words :excuseme: .

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Mike,

In your post, you indicate that the pinion shaft and drive shaft bushings are different with the the drive shaft bushing appearing to be the real air barrier. Is this true? The reason I ask is that the fiche indicates they are the same part number. I haven't torn the power valve apart yet, just trying to plan ahead.

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The bushings are the same. What I meant in that post is the air shouldn't get past the bushing(drive shaft I think) closest to the powervalve. You don't need to tear apart the power valve to swap them out but you do need to take the cylinder off. I first made the mistake of trying to use grease to seal those bushings but I think the heat caused the grease to fall out. The moly paste seems to be holding much better.

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The moly paste seems to be holding much better.
Cool. I've got Moly 60 in the garage. Thanks :excuseme: .

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I also am having the same problem, I am working on a friends 01 CR250R and it doesn't hold any pressure. I stopped by the dealer today to get the Moly 60, I also consulted the manual, the manual says to mix the paste with premix oil 50/50, are you guys doing this or just using straight paste. To be honest I think using straight paste would probably be better, no?

*on a side note, just to voice my findings. I initially found my leak at the exhaust valve "stoppeer bolt" this thing wasn't even tight (I blame the previous owner as he just bought the bike a couple weeks ago). I tighted that up and sprayed it with soap & water solution and no more leaks there, no all the leaks are coming from the bottom half of the motor, crankcase breather hose, when I plug that up I get leaks out the counter shaft (not around the seal but right through the spline) however I am not worried about that (not yet anyway) my goal is to see if I can't get the leak to stop at the pinion shaft 1st.

I also wanted to ask because the manual says nothing, but what do you guys do about the power valve bearings, do you lube them, if so with what, regular high temp bearing grease? moly paste? nothing?

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yes you mix them 50/50 mix of moly and 2 stroke oil. you lube ALL the PV assembly from left to right and center of the cylinder through. the shafts that goes down the cylidner to the base motor.

i also saw a thread about packing grease on the empty area of the crows foot on the base motor. did this to my other 01 but not the other. the one that didnt have this pack of grease runs well.

also. iv heared of ppl doing leak down test on any 2 stroke to pack grease all around the PV assembly when leak testing. never heared packing grease on certain spots on the PV assembly when doing top ends.

last but not least. i find this updated TT website is much slower to respond than the older one. too much advertisement? maybe too much processing going on? its only TT not other sites.

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