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XR200r running rich symptoms but valve adjustment was the issue

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It has been said before in the forums, but not under a search for rich running conditions. 

 

Bought a used 1993 XR200r knowing it was hard to start, idled poorly, and stumbled bad (especially when cold) at 1/4 to 3/4 throttle.  It has been a while since I have ridden, let alone tinkered with the mechanics of a bike.

 

I pulled the baffle in the muffler, making it loud, to find that is ran almost perfect.  Stumble or hesitation went away, it idled better, and had extra power.  First conclusion for me, it was jetted (by previous owners)  for the baffle to be removed, and therefore was running rich when plugged back up with the baffle.

 

List of things I did before swapping jets: cleaned air cleaner; no difference.  Changed spark plug; no difference.  Lowered needle, help a bit, but definitely not right.  Adjusted cam chain; quieted down noise.   Was just about to pull carb and start messing with jets, but decided to check valve clearance even though it did not have any valve noise that I am accustomed to with sloppy valves.

 

 Bingo, the intake valve was too tight!  After proper adjustment, .002 intake, .003 exhaust, the bike ran like it should.  Starting was easy, all hesitation and stumble gone.  Even hot starting was improved drastically.

 

Like I said, people on the forum have mentioned this many times before, but my search was for a rich condition, and tight valve clearance did not come up for what I thought for sure was a jetting problem; or worn needle; or dirty carb etc.

 

This forum saved me money, because I followed the advice of the other members, and did all the basic checks (I did not know valve adjustments were this easy on the XRs) before throwing money and time into carburetor parts.

 

Thanks thumpertalk.

 

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Interesting experience and thanks for sharing.

 

From my experiences, and I suspect other XR200 owners, tight valves are not a problem; valve issues are usually loose valves or a loose timing chain. However I have a CRF250X which are notorious for wear on the valves which reduce clearances to the point the engine is hard to start and displays difficult low speed running. 

 

So the question is how did the intake lose clearance?

If we assume the PO adjusted it wrong your problems are over but I would keep checking the intake clearance frequently for signs of a continuing loss of clearance, which would indicate that the valve is wearing into the seat. The OEM valves have a stellite coating to resist wear and if someone used lapping compound or ground the valve then the protective coating is gone. Once the valve starts to wear into the seat it doesn't end, and the result is constant maintenance until replaced.  A similar thing happens on the coated titanium  intake valves on the early CRF250/450 but the wear is cause by dirt ingestion and/or too much time on the rev limiter along with a seat material that is too hard.  The dirt ingestion is from improper air filter maintenance, and too much time on the rev limiter can cause valve spring surge and/or valve float which hammers the valve seats.

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Thanks for this post!  I was having a rich issue with my xl185 powered xr200 that I thought for sure was because I had a 200 carb on it with the stock 200 jets, but it just kept getting worse. So I noticed this thread title and dove into checking the valve clearences! Presto!

 

Reset them to stock for a XL185 and no more super rich condition, no more stumbling at part throttle, and I had to adjust the idle screw down to achieve a normalish idle RPM.

 

Was my first time checking the valve clearences and I couldn't get the right angle of attack to slip the feeler gauge into place, so I proceeded to just adjust them per the manual as it was much better to put the proper sized feeler gauge in place with the adjustment screw backed off the valve.

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Interesting experience and thanks for sharing.

 

From my experiences, and I suspect other XR200 owners, tight valves are not a problem; valve issues are usually loose valves or a loose timing chain. However I have a CRF250X which are notorious for wear on the valves which reduce clearances to the point the engine is hard to start and displays difficult low speed running. 

 

So the question is how did the intake lose clearance?

If we assume the PO adjusted it wrong your problems are over but I would keep checking the intake clearance frequently for signs of a continuing loss of clearance, which would indicate that the valve is wearing into the seat. The OEM valves have a stellite coating to resist wear and if someone used lapping compound or ground the valve then the protective coating is gone. Once the valve starts to wear into the seat it doesn't end, and the result is constant maintenance until replaced.  A similar thing happens on the coated titanium  intake valves on the early CRF250/450 but the wear is cause by dirt ingestion and/or too much time on the rev limiter along with a seat material that is too hard.  The dirt ingestion is from improper air filter maintenance, and too much time on the rev limiter can cause valve spring surge and/or valve float which hammers the valve seats.

 

Chuck.......

 

:thinking: Where do you find these stellite coated OEM intake valves you speak of...........?  I've never ran into them on 200's or any of the smaller Honda singles that I can recall?  (Some newer models I'm not aware of may be different?) Also I've seen exhaust valves receive brutal lapping with a drill and road gravel lapping compound and actually not wear through the coating..........I wouldn't recommend this though.

 

What happed here is the norm for Honda singles.............the soft intake seat and soft intake valve wear reducing valve lash.  On the exhaust side with hard parts the valve lash will normally increase.  It's this way from the little Z50 right on up and has been for many years.  ;)

 

Old School Al

Edited by Old School Al
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Chuck.......

 

:thinking: Where do you find these stellite coated OEM intake valves you speak of...........?  I've never ran into them on 200's or any of the smaller Honda singles that I can recall?  (Some newer models I'm not aware of may be different?) Also I've seen exhaust valves receive brutal lapping with a drill and road gravel lapping compound and actually not wear through the coating..........I wouldn't recommend this though.

 

What happed here is the norm for Honda singles.............the soft intake seat and soft intake valve wear reducing valve lash.  On the exhaust side with hard parts the valve lash will normally increase.  It's this way from the little Z50 right on up and has been for many years.  ;)

 

Old School Al

From Powroll with specific instructions to not grind the valves, do all the work on the seat, and not use any lapping compound. 

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From Powroll with specific instructions to not grind the valves, do all the work on the seat, and not use any lapping compound. 

 

Are you saying you got OEM "stellite" intake valves from Powroll with these instructions................? :confused:   This is all new to me............fill me in on the details. :thinking:  

 

Old School Al

Edited by Old School Al

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Got no valves from Powroll, just instructions on redoing stock valves.

 

Redoing stock valves........ok.   Would this be the stock "OEM stellite" valves you were telling about? Still waiting for details........ ;)

 

Old School Al

Edited by Old School Al

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Stock valves.

Please provide your detailed instructions on doing valves.

 

Stock..........would these be "OEM stellite"  you speak of?  We'd like to hear more about these.  Come on...........fill us in! ;)

 

You got instructions from Powroll already............remember? :facepalm:

 

Old School Al

Edited by Old School Al

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