New top end SMOKIN!


9 replies to this topic
  • tullymars

Posted February 27, 2005 - 05:59 PM

#1

Just did the topend on my 94 xr650l,new piston 1mm over,cut the valve seets,and yes,faced the valves...I know what honda says,but anywho when I first fired her up everything went well,tons more power,no oil leaks nor signs of smoke.Well,after about a week it started pumping a lil oil,got a little worse everyday,check the compression, wow...100lbs.Checked my valve lash again and one exhaust valve is TIGHT,cant get clerance on it,pulled the head,seet is good and the valve hasnt tulipped,goona grind the stem a little and try it again.Anybody ever had a valve get so tight so fast?Ive lapped xr valves before with no problem...but not this time.

  • frankstr

Posted February 27, 2005 - 06:11 PM

#2

Maybe the valve stem has streched, Can't see why you would have to grind MORE off the butt end of valve unless to much was taken off of seat or valve face........... :)

  • tullymars

Posted February 27, 2005 - 06:28 PM

#3

Well,its not all that uncommon to grinde stems when doing a vavle job...Ive had it done before,mainly on heads with shims,usually threaded adjusters are able to get them in clerance...first time for everything.

  • michaeln

Posted February 28, 2005 - 03:28 AM

#4

check the compression, wow...100lbs.


When you checked the compression, was the engine fully warmed up and did you disable the auto decompressor first?

Also, did you have the throttle held wide open during the cranking?

If you didn't disable the auto decompressor, then 100lbs would be very good compression.

  • bootlegger2

Posted February 28, 2005 - 03:30 AM

#5

doing cylinder heads for a living things you look at when doing them is how much the margin is left after grinding the valves was it a sharp at the edges sometimes there is enough left and most of the times there isnt if they were to thin they could have sunk up in the head but shouldn't make it suck oil or burn it did you put on the new seals to ?
sinking up in the head would sure make them tight maybe should have replaced the valves this time were they a little groovy before you did the grinding and had to take a lot off to get them smooth again
get them adjusted and redo the compression check better yet do the air leak down check use your compression hose as the air source to go in to the cylinder then listen for the air to be leaking out ,test done on top dead center , listen in the exhaust the intake and the crankcase for leaking air

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  • tullymars

Posted February 28, 2005 - 04:01 AM

#6

I pulled the valves out,it didnt suck it up in the head,I was sure that was the problem.I couldnt get any clearance out of one exhaust valve,when I initially put it together I got clearance out of all the valves,but one exhaust tightened up quickly.

  • tullymars

Posted February 28, 2005 - 04:03 AM

#7

When you checked the compression, was the engine fully warmed up and did you disable the auto decompressor first?

Also, did you have the throttle held wide open during the cranking?

If you didn't disable the auto decompressor, then 100lbs would be very good compression.

Doesnt have a decompressor,its an L model...electric start,yea throttle open

  • frankstr

Posted February 28, 2005 - 05:05 AM

#8

the ex. valve has strecthed or the seat is loose and pounding it's way into the head, When I work on any head with inserts I alway's check them to make sure there tite.
Upon the smoking, Maybe you accidently tore a stem seal, Make sure you use the plastic sleeve on the top of valve before installing stem seal..........
I have been doing cylinder head's and eng. mach. work for over 20 year's, Gosh, that make's me feel old :)
I've got all the equipment in my shop to do cyl.head's and bore cyl's.....

  • michaeln

Posted February 28, 2005 - 07:37 PM

#9

Doesnt have a decompressor,its an L model...electric start,yea throttle open


Mine's an L model too, and I can assure you it has an auto-decompressor (unless you have an aftermarket cam that does away with the auto-decompressor).

  • Hayden

Posted March 01, 2005 - 12:27 AM

#10

If you dont mind me asking, how many miles did you have on your 94?


Sir Hayden

94 L





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