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  #1  
Old 01-03-2008, 02:44 AM
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Default Quick question, 1991 CR 250 exhaust valve

Hey guys,
Once again I find myself here looking for help with the old girl, she just loves to cause me pain and anguish!! Ever since I got it 4 months ago, the bike just loves to foul up plugs if I don't keep it "on the pipe". But recently (ie the last 2 plugs I had left) it started to foul them after a half hour of running time, no matter how i ride. Every time it does the plug comes out black and oily, so I am presuming its the transmission side crank seal. Decided to do both crank seals, and do a top end as well cos I honestly haven't a clue when it was done by the previous owner.

Anyway, to get to the point, I have the top end torn down and I was beginning to clean out the powervalve linkage and all that area, when I noticed that the left and right side of the PV don't move together perfectly. If they are both closed and i grab the left one and pull it out a little, it will move on its own for about 5-10 mm (1/4" to 1/3" in another language), before the other side of the PV will start to open with it

Is this normal play in the mechanism or is there something I should be worried about? At the moment all of the removable parts are at home soaking in diesel to clean them up, I will be working on it again at the weekend, and will post some pics if i get the chance.
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Old 01-03-2008, 09:48 AM
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Default Re: Quick question, 1991 CR 250 exhaust valve

not too unusual to have that play when you actuate one valve from the other. they should move pretty freely when clean, and when actuated from the spindle cam they should move at much closer to the same rate. (make sure that same spindle has the flat facing forward as you put the top end back on.

after you are done with your overhaul, if your bike still fouls plugs the first thing that i would do is to take the enrichening/choke knob and turn it down fully TIGHT with your fingers. that kills all possibility of an idle and also eleminates it as the source of overfueling. it is the worst thing about that carburetor and something i have had to do with all of the keihin powerjet carbs i have owned since 87. with that done and a properly adjusted float with a good needle it shouldnt foul, but is kind of unhandy for trail riding. consider a swap to a pwk.
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Old 01-03-2008, 09:53 AM
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Default Re: Quick question, 1991 CR 250 exhaust valve

I do believe you have the HPP valve on that year and they can be adjusted somewhat. When you have the linkage attached and the motor is not running the valves should seat all the way, if not loosen the nuts and turn the adjuster lever until they are seated (on both sides, the nut nearest to you from the outside cover). You have 2 pinion rods going down from the top to the cylinder base where the actuator bar is behind the plug. The two are very independent until the "rack" at the base so there could be some movement manual on one before the rack effects the other pinion rod but I don't know about 10mm. I am thinking the adjuster lever will tighten it up some from where you are now.
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Old 01-03-2008, 10:00 AM
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Default Re: Quick question, 1991 CR 250 exhaust valve

What Ossag said about the PJ carb as well I like the have a idle circuit myself.
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Old 01-03-2008, 10:18 AM
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Default Re: Quick question, 1991 CR 250 exhaust valve

that whole valve assembly is a headache the first time, and worse if you dont have a manual. it works very well though. of course they changed it as soon as i got used to it.

having one die as soon as you turn the throttle off is ok for me on a track of any kind, but on trails i just about insist that mine idle too. i guess the parent company of honda was too busy selling keihin pwk's to every one else to use them on their own bikes.
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Old 01-03-2008, 10:24 AM
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Default Re: Quick question, 1991 CR 250 exhaust valve

I am with you there, give me one and I will decide to use it or not!
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Old 01-03-2008, 01:37 PM
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Default Re: Quick question, 1991 CR 250 exhaust valve

Quote:
Originally Posted by garvbox View Post
Hey guys,
Once again I find myself here looking for help with the old girl, she just loves to cause me pain and anguish!! Ever since I got it 4 months ago, the bike just loves to foul up plugs if I don't keep it "on the pipe". But recently (ie the last 2 plugs I had left) it started to foul them after a half hour of running time, no matter how i ride. Every time it does the plug comes out black and oily, so I am presuming its the transmission side crank seal. Decided to do both crank seals, and do a top end as well cos I honestly haven't a clue when it was done by the previous owner.

Anyway, to get to the point, I have the top end torn down and I was beginning to clean out the powervalve linkage and all that area, when I noticed that the left and right side of the PV don't move together perfectly. If they are both closed and i grab the left one and pull it out a little, it will move on its own for about 5-10 mm (1/4" to 1/3" in another language), before the other side of the PV will start to open with it

Is this normal play in the mechanism or is there something I should be worried about? At the moment all of the removable parts are at home soaking in diesel to clean them up, I will be working on it again at the weekend, and will post some pics if i get the chance.
I am having the exact same problem with my 89 CR250 . I messed with jetting and floats and tried the choke screw down method. The choke helped it a little, but it didn't fix it. I also opted to replace the crank seals(both sides) and it is still doing it after the replacement. It has been a while since I looked at it, but I think I remember having an issue with my spark being inconsistent. Sometimes it would have a strong spark, but sometimes it would skip a spark or 2 every 8-10 revolutions. I just ordered a new coil last night. Hoping that is the issue, but if not, ohwell my coil was lookin kinda crappy anyway.

**EDIT** I was fouling roughly once every 45 min when I got the bike and 2 years later, the last time i rode before I put it away this fall, it would not even go for 10 minutes without fouling... regardless of how I was riding it. I actually ended up going through 5 of my plugs in under 30 minutes.

Heres a link to my thread:
CR250R fouling... I searched

Last edited by Tonyklem; 01-03-2008 at 01:48 PM.
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Old 01-03-2008, 04:08 PM
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Default Re: Quick question, 1991 CR 250 exhaust valve

tony, see if you can at least borrow a carburetor. drop your jets and needle in if necessary and see if the fouling goes away. the choke thing is a bandaid if you will, and any improvement tells me that the carburetor may be the problem. particularly if you are fouling going down hill with the throttle off.
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Old 01-04-2008, 01:45 AM
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Default Re: Quick question, 1991 CR 250 exhaust valve

Quote:
Originally Posted by ossagp View Post
not too unusual to have that play when you actuate one valve from the other. they should move pretty freely when clean, and when actuated from the spindle cam they should move at much closer to the same rate. (make sure that same spindle has the flat facing forward as you put the top end back on.

after you are done with your overhaul, if your bike still fouls plugs the first thing that i would do is to take the enrichening/choke knob and turn it down fully TIGHT with your fingers. that kills all possibility of an idle and also eleminates it as the source of overfueling. it is the worst thing about that carburetor and something i have had to do with all of the keihin powerjet carbs i have owned since 87. with that done and a properly adjusted float with a good needle it shouldnt foul, but is kind of unhandy for trail riding. consider a swap to a pwk.
Thats a load off my mind about the PV anyway. It was working perfectly before I took it apart, I was just concerned about the play. Yes Dhighlan its a HPP by the way. And I have a manual, just about the best investment I ever made for that thing!

About the jetting, I have considered going PWK, I know you heve mentioned it before to anybody unlucky enough to be fed by the dreaded PJ carb. Is it much trouble to get a PWK jetted properlyfor one of those older engines? And what size PWK would I be looking for? Where do I take the measurement to obtain the size of the carb? Is it at the bell mouth or at the outlet to the reeds?

Thanks for all the help lads, I'd be utterly lost without this site!!
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  #10  
Old 01-05-2008, 12:41 AM
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Default Re: Quick question, 1991 CR 250 exhaust valve

it is really easy to get them to jet. all the jets, and the jet needle from your old one will fit. the 1468 needle seems to be a really good all around choice. ebay has the carbs, but companies like sudco sell them for under 200 new. a 38mm would be my choice. the stryker design seems to work well for response on the 125's and 250's.
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