Tight valves...


3 replies to this topic
  • terryfryar

Posted April 28, 2013 - 07:10 PM

#1

Bought a 2001 WR426 a week ago. Been in a barn for awhile, but I did hear it run. Didn't ride it, just started it and shut it off. Was a good price, and I couldn't pass it up!

Got it home and went through the usual things....empty the fuel, full carb cleaning, oil....etc. Bike is in pretty good shape....head, swingarm bearings are good, fork seals good....not too bad! Oil and coolant come out good and clean.

However, I decided to check the valves. Supposedly, this is a "low hour" bike. The exhaust valves were in spec, however all 3 of the intakes were very, very tight! I could not get my smallest gauge (.038mm) to fit. I thought maybe I wasn't at TDC, but I tried 3 times and made sure...I just could not fit any of the feelers in there!

Couple of questions:

1. What could cause such wear on the intake valves? Not cleaning the air filter? Why are the intakes so tight, but the exhaust valves seem to be fine?

2. Where do I go on the shim sizing since I can't get a gauge in there? Just take the existing shim size and subtract what it's supposed to be (.10 to .15)? So if it's a 1.9mm, I'd need to get a 1.8 or 1.75mm shim?

3. Should I also replace the cam chain at this point? It looks pretty good...tension is good, chain looks ok......

Thx!

  • Krannie McKranface

Posted April 28, 2013 - 07:36 PM

#2

[color=#282828][background=rgb(252, 252, 252)]1. What could cause such wear on the intake valves? Not cleaning the air filter? Why are the intakes so tight, but the exhaust valves seem to be fine? [/background][/font][/color]
[color=#282828]][background=rgb(252, 252, 252)]INTAKES ARE TITANIUM, AND THE COATING GOES BAD AFTER A WHILE. THIS IS NORMAL. THE MOTOR IS PROBABLY NOT LOW HOUR.[/background][/color]
[background=rgb(252, 252, 252)][color=#282828]A POORLY MAINTAINED AIR FILTER WILL [/size]ACCELERATE[size=4] THIS PROBLEM IMMENSELY.[/color][/background]
[color=#282828]THE EXHAUST VALVES ARE STEEL, AND ARE NOT AS SUSCEPTIBLE TO WIDE HEAT SWINGS.[/color]


[color=#282828][background=rgb(252, 252, 252)]2. Where do I go on the shim sizing since I can't get a gauge in there? Just take the existing shim size and subtract what it's supposed to be (.10 to .15)? So if it's a 1.9mm, I'd need to get a 1.8 or 1.75mm shim?[/background][/color]
[color=#282828][background=rgb(252, 252, 252)]YOU CAN SHIM IT, BUT....... IF ALL THREE VALVES ARE TIGHT, YOU PROBABLY NEED HEAD WORK. DO A LEAK DOWN TEST AT THE VERY LEAST.[/background][/color]
[color=#282828][background=rgb(252, 252, 252)]ALWAYS GO LARGER FOR THE SHIM GAP[/background][/color]

[color=#282828][background=rgb(252, 252, 252)]3. Should I also replace the cam chain at this point? It looks pretty good...tension is good, chain looks ok.....[/background][/color]

[color=#282828][background=rgb(252, 252, 252)]DUDE, YOU MOTOR IS 12 YEARS OLD! YOU SHOULD DO A COMPLETE HEAD REBUILD, CHAIN, PISTON, RINGS, WRIST, AND TENSIONERS[/background][/color]
[background=rgb(252, 252, 252)][color=#282828]IF YOU MEASURE THE CHAIN AGAINST[/color] [/background][color=#282828][size=4]A BRAND NEW ONE, YOU WILL SEE IT HAS STRETCHED QUITE A BIT.[/size][/color]

[color=#282828][background=rgb(252, 252, 252)]OTHERWISE, YOU JUST HAVE A TIME BOMB....[/background][/color]

Edited by Krannie, April 28, 2013 - 07:38 PM.


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  • terryfryar

Posted April 30, 2013 - 05:11 AM

#3

Hey K, no need to yell now! ;-)

Thanks for the info! You think it'd be worth switching back to the SS valves for the intakes? I know I'd have to use SS springs as well, but if I"m gonna replace em, I'll do it all...valves, keepers, springs, seals. I'm not too worried about performance....more concerned with longevity....

  • NitrousR1

Posted May 24, 2013 - 02:24 PM

#4

Both valves will last a while but the steel valves will last longer plus you can lap them lightly if need be. The titanium valves Are great and light but when the coating wears off they move pretty quickly. Also definitely replace that cam chain. You will be amazed when you compare your old one to the new one. Do a leak down test and I highly advise to do a top end before it blows and you have a $2000 rebuild




 
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