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Author Topic: Weird compression loss!  (Read 601 times)

dampking

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Weird compression loss!
« on: May 23, 2013, 06:13:57 AM »
So... it was cold and pretty awesome after a hail storm! I was already late for work so I got things packed and went to the garage and the moment I hit the kicker I felt something weird. Went for it again and figured that ther's no compression! It's like as if the decomp is "half-on". I tried multiple kicks and no luck but there were times when the compression was actually building up. After few zillion kicks she came back to life... at first there was a VERY small burst of black smoke but nothing after that..

I am totally confused as to what is happening or what just happened! After I reached work... I tried kicking when the bike was hot and compression was pretty good at that point. Kicker was rock solid!

any idea who's the culprit here? At first I thought rings but then again.. I didn't see much smoke gushing out.

ROVERMAN

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Re: Weird compression loss!
« Reply #1 on: May 23, 2013, 01:06:58 PM »
From the description it sounded as if it was flooded and the rings were washed out with fuel, float/needle valve issue?
Robert & REnfield.

dampking

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Re: Weird compression loss!
« Reply #2 on: May 23, 2013, 01:30:24 PM »
Not sure, my carb is pretty much in good shape but its pretty unusual for an AVL to have that low compression. Stock AVLs are around 150 psi compression power which is a big deal when it comes to kicking it. The compression was so low that it couldn't take the weight of my right leg :P (BTW I weigh only 55kgs :P ) That's when I thought that ther's something wrong! I did check with few of my friends and they are telling me to check the tappets. Maybe they are too tight I guess.

-Sanket

DanB

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Re: Weird compression loss!
« Reply #3 on: May 23, 2013, 02:46:40 PM »
Quote
they are telling me to check the tappets. Maybe they are too tight I guess.
I'd start there.  But that wouldnt explain why it suddenly 'came back to life' and why you had compression later on.  Be interested to hear what its like when cold again.   

Could be a valve / tappet got stuck?  Also, to Robert's point, I would check on fuel flooding into the engine.  Might want to pull the oil filler cap to check if you smell gas in the case.  If so, change oil immediately and check the fuel float & needle valve.  Did you leave the petcock on?
Suppose I were an idiot, and suppose I were a member of Congress; but I repeat myself. ... Mark Twain
2006 AVL Electra

boggy

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Re: Weird compression loss!
« Reply #4 on: May 23, 2013, 02:58:02 PM »
Two things that have happened to me:
1.) The decomp lever was just a little bit raised up after using it to shut down the night before. Reach down an make sure that lever isn't pulling up right where it goes into the engine.
2.) My clutch cable was adjusted too tight so it was pulling enough even with the lever out to disengage it. 

I had one additional instance where it happened when I pulled the bike out of storage in the dead of Winter to give it some kicks.  It acted as you described so I just put it away and the gremlins must have froze to death.
2007 AVL
2006 DRZ400SM

DanB

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Re: Weird compression loss!
« Reply #5 on: May 23, 2013, 03:26:03 PM »
Quote
I pulled the bike out of storage in the dead of Winter to give it some kicks.  It acted as you described so I just put it away and the gremlins must have froze to death.

What could have caused that Boggy?  Sounds like something 'froze' open or what not.  I've not heard of nor experienced that when I had mine running in sub-zero weather (friggin cold ride indeed).
Suppose I were an idiot, and suppose I were a member of Congress; but I repeat myself. ... Mark Twain
2006 AVL Electra

boggy

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Re: Weird compression loss!
« Reply #6 on: May 23, 2013, 05:18:48 PM »
Not sure. Only thing I can think of is maybe the oil and clutch plates were so cold that when I pulled the clutch they got stuck disengaged? 
2007 AVL
2006 DRZ400SM

dampking

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Re: Weird compression loss!
« Reply #7 on: May 23, 2013, 09:12:08 PM »
I'd start there.  But that wouldnt explain why it suddenly 'came back to life' and why you had compression later on.  Be interested to hear what its like when cold again.   

Could be a valve / tappet got stuck?  Also, to Robert's point, I would check on fuel flooding into the engine.  Might want to pull the oil filler cap to check if you smell gas in the case.  If so, change oil immediately and check the fuel float & needle valve.  Did you leave the petcock on?

Yea, when the piston was going up to the TDC mark, it was gaining little bit of compression. So I hit the decomp to see if I was going to loose any more compression. Well that never happened so I kept decomp as it is and kicked and decomp lever came back to it's original location, where it was before. So the decomp was disengaged and even after that there was no compression. So I kept on kicking when it was gaining compression.. after few kicks I got lucky and hit it real hard and she came back to life :P 

I almost decided to take a leave from work that day but it worked! it's all good now but I guess I will get tappets checked. Also the bike clocked 40,000 kms, planning to get the head removed and prolly get the rings checked and clean the hot spots in cyl head. I was running rich for sometime.. and yes at times I do forget to switch petecock to "Off" position.


DanB

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Re: Weird compression loss!
« Reply #8 on: May 24, 2013, 01:21:30 AM »
40,000 km!  Bravo
Suppose I were an idiot, and suppose I were a member of Congress; but I repeat myself. ... Mark Twain
2006 AVL Electra

dampking

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Re: Weird compression loss!
« Reply #9 on: May 24, 2013, 11:31:36 AM »
:D

dampking

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Re: Weird compression loss!
« Reply #10 on: June 15, 2013, 11:17:46 AM »
Update - Got the tappets checked, my mech said that the "inlet tappet" was way too tight! Now it's back to it's original clearance and I feel a lot of compression already! Thank you all for your inputs :)

Regards,
Sanket

TejK

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Re: Weird compression loss!
« Reply #11 on: July 03, 2013, 04:06:21 PM »
Update - Got the tappets checked, my mech said that the "inlet tappet" was way too tight! Now it's back to it's original clearance and I feel a lot of compression already! Thank you all for your inputs :)

Regards,
Sanket

Loose tappets save lives and valves :) I would strongly advise to set tappets yourself and not leave it to the mechanics. I have seen most of them set tappets with the engine still warm and it results in the compression loss at cold starts.

Correctly adjusted tappets result in remarkable changes in the bike's overall responsiveness and performance.

dampking

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Re: Weird compression loss!
« Reply #12 on: July 03, 2013, 04:33:32 PM »
I will have to. That's what my friend suggested :)