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"What a horse and pony think of a dirtbike..."


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Rangerman
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Front Brembo caliper on '91 KTM 300DXC

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Rear Brembo caliper '91 KTM 300DXC

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Penton (KTM)

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Good day for a ride.

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As big as the hills get around these parts.
Picture perfect skies.
70 degrees.
Unexpected gravel fire roads found...


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Went exploring some roads I had not been down before.

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A pleasant surprise for sure to just happen to find these dirt/gravel roads.
We have camped in this area for quite a few years and I did not know that these roads even existed.
Until today.


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Always enjoy the Rangerman vids
Keep them coming my friend. I envy you guys that are riding now. I expect to be back on the trails soon. Hopefully we get a reprieve from this Corona mess soon. Stuff is starting to reopen bit by bit.
 

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Nothing quite like an old dirt bike in the back of old pickup truck.

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One from a past woods ride.

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Here is a friend of mine's 1987 XR200.

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I sure do like old dirt bikes.
Always have.
Especially the old XR's.
Next to the 2T Yammy IT's of yesteryear these XR thumpers came in a close second for me.
The 200 makes for an excellent woods bike.
Does anyone remember Scott Summers?
Does anyone remember the 1990's?
How about dead lifting a XR600?

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Now if we can just get this up and running properly.
It is smoking much more than it should.
So much so that you would not want to ride behind it for very long.
That is the issue.
Rings (2) have been replaced along with one valve.
Cylinder bore honed (cross hatched). Not measured
Valve clearances set.
Compression "feels" adequate although not tested with gauge.
Runs decent through gear range.
Our resident KTM Forum expert has been kind enough to lend his expertise, augdog has already provided the preliminary troubleshooting and come up with some likely culprits and maybe after seeing this post he will be able to narrow it down to the prime candidate.
Valve guide wear?
Scored or over sized cylinder?
Damaged valve guide seal or valve guide seal problem?
Here is a short video of it running.


And another short one when it was warmed up a bit more.




The plug was cleaned prior to starting it and spark verified.
Here is a photo of the plug taken after this short run.

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Hopefully we can get this sorted out soon.
Maybe be able to do some woods/fields rides together.
This XR is just itching to hit the trails.
And so is its rider!


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Ah. It's a mess for certain! You can be certain most of the smoke is valve stem seals but fresh rings on a glazed cylinder will smoke a bit until the rings seat. I'm thinking compression and leakdown tests will verify my suspicion. Probably best to run a glaze breaker through cylinder if its within tolerance. Best to replace piston and rings when performing overhaul because compression ring grooves get a tapered wear pattern and new rings will flutter in loose ring grooves. Not a big deal but that's best method. I suspect this culprit is smoking through valve guides and if our amateur rebuilder didn't replace stem seals they are probably hard as a rock and fractured from previous valve removal. If you have good compression, why not pop cam cover off and replace valve stem seals without removing cylinder head and try it for awhile. I wouldn't expect a factory rebuilders result, but you could probably expect your oil smoke and plug fouling to diminish to acceptable level. Easy enough to replace valve stem seals without complete disassembly. Lock flywheel at TDC and put compressed air into spark plug hole to hold valves on seat and remove valve springs and replace stem seals. If you dont have compressed air available put small rope or twine into spark plug hole and jam piston against rope in cylinder to hold valves up while removing springs and remove rope afterwards. Try stem seals for the easy fix. If it still smokes like a freight train it will require a rework and possibly valve guides if they are worn
 

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Ah. It's a mess for certain! You can be certain most of the smoke is valve stem seals but fresh rings on a glazed cylinder will smoke a bit until the rings seat. I'm thinking compression and leakdown tests will verify my suspicion. Probably best to run a glaze breaker through cylinder if its within tolerance. Best to replace piston and rings when performing overhaul because compression ring grooves get a tapered wear pattern and new rings will flutter in loose ring grooves. Not a big deal but that's best method. I suspect this culprit is smoking through valve guides and if our amateur rebuilder didn't replace stem seals they are probably hard as a rock and fractured from previous valve removal. If you have good compression, why not pop cam cover off and replace valve stem seals without removing cylinder head and try it for awhile. I wouldn't expect a factory rebuilders result, but you could probably expect your oil smoke and plug fouling to diminish to acceptable level. Easy enough to replace valve stem seals without complete disassembly. Lock flywheel at TDC and put compressed air into spark plug hole to hold valves on seat and remove valve springs and replace stem seals. If you dont have compressed air available put small rope or twine into spark plug hole and jam piston against rope in cylinder to hold valves up while removing springs and remove rope afterwards. Try stem seals for the easy fix. If it still smokes like a freight train it will require a rework and possibly valve guides if they are worn
augdog,
I sure do appreciate you taking the time to articulate. Thanks.
You definitely have more knowledge and experience than me, my friend.
I will see what the owner wants to do but I am of the opinion that replacing the valve stem seals is the first and least expensive/complicated way to go for now especially if that remedies the problem just enough to make a difference.
I have to admit that I have never heard of using compressed air or rope/twine to hold valves open but will have to give it a try. Sounds to me like you may have done this yourself a time or two. ;)
That is what I like about old dirt bikes, you can patch them together good enough to then go have some fun.
If we proceed with this seal fix I will post results.


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I suspect most of the trouble with that little Honda is hard/brittle or damaged valve stem seals and replacement is fairly straightforward and inexpensive. The purpose of bringing piston to TDC and keeping valves closed is to prevent valves from dropping down into cylinder when spring retainers are removed for seal replacement. The methods described are to hold valve closed while spring and split keys are reinstalled. Otherwise if valves drop into cylinder, disassembly may be required to reassemble. Good luck my friend. Check back as needed for advice or a never ending stream of curse words to use....
 

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I suspect most of the trouble with that little Honda is hard/brittle or damaged valve stem seals and replacement is fairly straightforward and inexpensive. The purpose of bringing piston to TDC and keeping valves closed is to prevent valves from dropping down into cylinder when spring retainers are removed for seal replacement. The methods described are to hold valve closed while spring and split keys are reinstalled. Otherwise if valves drop into cylinder, disassembly may be required to reassemble. Good luck my friend. Check back as needed for advice or a never ending stream of curse words to use....
Thanks for additional info augdog.
Will post repair process if my friend decides to make the seal repair.


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Until he fixes the smoking you can put a bit of citronella oil in his crankcase and send him out to run around the perimeter of the yard to ward off the bugs. :D
 
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