Clearences and no compression !?


8 replies to this topic
  • allanh7660

Posted August 07, 2014 - 09:42 AM

#1

Hi new to this site , and a bit of an armature with a spanner lol ....
I TRIED to do my clearances and all was good ....... Double checked clearances after I changed shims , turned her over by hand a few times , no problem , so started it an let the engine tick over till warm ...... Still fine, a lot more responsive on the throttle ;-)
I took her down the road at snails pace ( low revs ) until I got to the track and give some up then down then it cut out ......
?????? Petrol -ON Tried to kick an no compression .....

  • bikedude987

Posted August 07, 2014 - 11:31 AM

#2

The three springs being held down (with the cam off) almost certainly means bent valves.  Did you get the cam timed incorrectly? That's the only thing I can think of that would kill all three.  

 

Either way, sounds like you're taking the head off to inspect. Let us know what you find.



  • allanh7660

Posted September 10, 2014 - 04:35 AM

#3

Bike dude .... You were right

  • William1

Posted September 10, 2014 - 07:03 AM

#4

A used head is a ticking time bomb. If I ever buy one used, I buy it as a core and redo the valves BEFORE I'd use it.

 

There are a few places that recondition and core swap heads:

 

Big Bore Thumpers

 

Fastheads

 

and there are others.



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  • MidlifeCrisisGuy

Posted September 10, 2014 - 10:16 AM

#5

A little tip about valve timing on WRs. 

 

Each camshaft gear has TWO punch marks.  People don't mention this when they speak of timing these bikes. When the engine is timed properly, one of the punch marks is nearly vertical (at the top of the gear's rotation) and the other one is level with the top of the head, as is commonly shown.

 

I don't know why the gears have 2 punch marks.   Furthermore, I say nearly vertical because the punch marks on some cams are NOT 90 degrees apart.  What is important when timing these engine is that you are using the correct punch mark.  As long as 1 punch mark is up near the top of the rotation and the other is level with the head and the crankshaft is in the right position, the engine will be timed properly. 

 

When you get the cams installed and the timing chain tightener tightened, I recommend that people slowly turn the engine over via the flywheel and feel for interference as they do.  There should be no binding sensations.  The engine turns over harder at some points due to the cam lobes operating the valves, but it should never feel "tight".

 

Also, be sure to reinspect it after after you kick it over a few revolutions with the kick starter, before you put the valve cover back on. 


Edited by MidlifeCrisisGuy, September 10, 2014 - 10:22 AM.


  • beezer

Posted September 10, 2014 - 10:57 AM

#6

That's the end of that bike.



  • vlxjim

Posted September 10, 2014 - 02:58 PM

#7

A little tip about valve timing on WRs. 

 

Each camshaft gear has TWO punch marks.  People don't mention this when they speak of timing these bikes. When the engine is timed properly, one of the punch marks is nearly vertical (at the top of the gear's rotation) and the other one is level with the top of the head, as is commonly shown.

 

I don't know why the gears have 2 punch marks.   Furthermore, I say nearly vertical because the punch marks on some cams are NOT 90 degrees apart.  What is important when timing these engine is that you are using the correct punch mark.  As long as 1 punch mark is up near the top of the rotation and the other is level with the head and the crankshaft is in the right position, the engine will be timed properly. 

 

When you get the cams installed and the timing chain tightener tightened, I recommend that people slowly turn the engine over via the flywheel and feel for interference as they do.  There should be no binding sensations.  The engine turns over harder at some points due to the cam lobes operating the valves, but it should never feel "tight".

 

Also, be sure to reinspect it after after you kick it over a few revolutions with the kick starter, before you put the valve cover back on. 

 

 

Just for clarity, The way you worded it, you could rotate it 90 degrees and it would be (as you worded it but) way off.

 

The other punch marks are for counting the pins in between them.

 

There should be 14 pins between the marks. If your doing the YZ mod you would align the right cam as shown and rotate the left cam one pin clockwise making it 13 pins between.

 

 

447916183_a68c2-L.jpg


Edited by vlxjim, September 10, 2014 - 03:47 PM.


  • allanh7660

Posted September 12, 2014 - 10:21 AM

#8

Beezer .... Shut the front door !!
That's good to know ....... I had it running sound ,went down the road steady, up the grass field full tilt, (was running sweet) back down

  • fdme

Posted September 12, 2014 - 01:06 PM

#9

I would think that if your timing was wrong all along that your valves would have got F*cked that very first run in the grass field whether you where giving it the beans or not :)

 

I think your timing chain might have skipped a tooth or two? Did you reassemble the tensioner properly back onto the timing chain when you reinstalled it? Or if your timing chain was very stretched than it is possible the tensioner was at its max travel and could not keep proper tension on the chain. If so you might need a new chain and or tensioner if it is not functioning properly. Just some thoughts on when you repair it.

 

Take this as a grain of salt though as I am no pro... it would probably benefit you to download the service manual.

http://www.yamahaown...ook.com.au/?r=0

its free, pages 278-280 explain how the tensioner is tested


Edited by fdme, September 12, 2014 - 01:15 PM.





 
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