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Discussion Starter #1
Hi there!
Im new to the forum, if i make any mistakes please correct me :)

I have restored a KL600B, everything was looked at except the inside of Cylinder/ Piston / Valves.
It starts and idles great and runs good when its warm. it spits out a Little blue/white smoke when starting and gets better Pretty quick (smoke disappears). But after idling for about a minute or so it starts to smoke quite badly. Also when its warm and you shut it off and restart after a minute or so it smokes very blue (Maybe oil dripping down the valve seals??)

-Compression was in spec last time i checked (would have to redo the test to give you a number)
-the Crankcase ventilation port does not emmit any smoke or oil vapor (I disconnected it from the airbox to verify it isnt vapor thats causing the smoke)

I would suspect worn Piston rings or valve stem seals but it has compression and runs good. Maybe there is something i have overlooked or that is typical for These machines?
Thanks for your help!

Greetings from Switzerland
-phstka
 

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I will suggest that the cylinder, piston, rings & valve stems were Not fogged with storage oil thru the carburetor intake when the bike was stored, how long ago?

Therefore there was/is probably some light surface rusting of the cylinder & rings. This may polish off with more run time. Did you squirt or spray any oil into combustion chamber, prior to rotating the engine over, during cosmetic restoration?
Nowadays, people with smart phones can purchase borescopes/cameras on a wire to insert thru small holes and have a look inside.

The construction of the valve train mostly reduces the possibility of oil passing between valve stems & guides. But if the cylinder was removed for piston & ring replacement one would want to refurbish the valve & seat faces and replace the valve seals also.

Is there any chance that the engine oil is contaminated with fuel?
 

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Discussion Starter #3
Thanks for your answers!

The bike has not been runing in over 10 Years. As far as i know no storage oil or Special Treatment was applied (but at least the spark plug was still in). I unfortunately do not know why it was neglected by the previous owner (could be that the smoke Problem was there before)

I sprayed a Little bit of oil in the cylinder before the first start, changed the oil and let it turn over a few times without a spark plug to make sure there is oil pressure. that first start was probably a year or so ago and it ran for approximatly 30min to an hour or so since then (so the oil in the cylinder should be gone by now)

My Problem is that i cant get it registered here in switzerland with it smoking blue, i have imported the KLR from France and have to therefore go through an Emissions and Sound testing procedure) because of that i cant really just drive it for a while and look if it gets better…. I could just let it idle for a longer time and see if it fixes something

a friend of mine has such a Little camera, i will try to have a look inside for sure!

the engine oil does not smell like gasoline, it was coloured a Little white when i drained it (but that could just be from small bubbles of air from it running before- it did look normal after it was sitting for a few minutes)

-phstka
 

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I can only suggest that a proper top end rebuild will be required to eliminate that much smoking.

The engine may have had improper air filter servicing in its past history. An un-oiled foam air filter passes all of the fine dust straight thru, wearing on lots of parts.
 

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Discussion Starter #7 (Edited)
Thanks for your help!

Today i took the Top End apart and discovered that the Bore has a few Pretty Deep scratches at the exhaust side of the cylinder...:SadSigh:
You can also feel them by hand so i think they are Deep enough to let oil pass up into the chamber/damage the rings!


while i was at it i discovered that the timing chain has a Little bit of Play in it, you can move the chain about 8-10mm between the camshafts (up and down)... is that amount of slack normal?
I could post a Video for you to see if that would help :smile2:
the timing seems fine (Looking at the marks on the camshafts) so the chain lenght should be ok.

-phstka
 

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There is supposed to be a chain slipper in the top of the valve cover to take up some of that. But I have to ask if you had only pulled the center cap & spring of the cam chain tensioner or had you removed the Complete tensioner already?

You probably won't be able to post links, pics or video until you have 15 total postings. (Anti-Spam measure)
 

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Discussion Starter #9 (Edited by Moderator)
There is supposed to be a chain slipper in the top of the valve cover to take up some of that. But I have to ask if you had only pulled the center cap & spring of the cam chain tensioner or had you removed the Complete tensioner already?

You probably won't be able to post links, pics or video until you have 15 total postings. (Anti-Spam measure)
The Slack was present after just lifting off the valve cover with the tensioning mechanism still in place! It may just be a normal amount but if i am rebuilding the whole top end i want to be sure to make it perfect...


Would this chain slipper be attached to the valve cover or screwed in to the head somewhere?

-phstka
 

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It is the black block mounted inside the valve cover.
 

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Discussion Starter #11
Success!!

I did a full top end rebuild (With a known good cylinder/Piston/head i had from another bike), it is running again and the blue smoke is a Thing of the past :grin2::grin2:

My old cylinder had deep scratches in it and the piston/rings were pretty damaged too. thank god i did the rebuild now, i dont know how long it would have survived before a catastrophic failure.
I also did regrind the valve seats and changed the valve stem seals. After rebuilding and setting the right valve clearances the bike sounds much better then before (way less clatter!)

Thanks to everyone that helped!
 
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