no compression!

Top End (cylinders pushrods etc.)
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55panFL
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no compression!

#1

Post by 55panFL »

was going to go for a ride tonight. only made it about 2 miles before motor started to cut out then died completely. removed the sparkplugs and discovered that the rear cylinder had no compression. I removed the pushrod covers and what i think is the intake pushrod (the one towards the center of engine) is loose when the cam is on the low side of the lobe. what may have caused the valve to stay open? the bike has been running great untill now. it is a 55 FL completely stock.
1950Panhead
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Re: no compression!

#2

Post by 1950Panhead »

Valve seized in guide or something broke, check oil level, pull engine, disassemble.
Jerry
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Re: no compression!

#3

Post by 55panFL »

oil level was good. Can't I remove the head with the motor still in the bike?
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Re: no compression!

#4

Post by Cotten »

55PanFL!

Yes, the heads are removable in the chassis,
but I would investigate slowly, starting with the pushrod itself.

Then the tappet assembly, etc., to determine if perhaps a hydraulic collapsed, preventing the valve from opening.

....Cotten
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Re: no compression!

#5

Post by Huck »

What Cotten said!
Get the back wheel off the ground, pull the plugs, those lttle bitty bungie cords work great for holding the push rod tubes out of the way. Put it in gear and roll it over you'll find the issue.
55panFL
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Re: no compression!

#6

Post by 55panFL »

Cotten wrote:55PanFL!

Yes, the heads are removable in the chassis,
but I would investigate slowly, starting with the pushrod itself.

Then the tappet assembly, etc., to determine if perhaps a hydraulic collapsed, preventing the valve from opening.

....Cotten
my problem is the intake valve is not closing. not that it is not opening.
I lifted the pushrod covers and when the intake should be closed the pushrod is loose. finger over the spark plug hole and no compression at all.
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Re: no compression!

#7

Post by Bosheff »

Valve may stuck in the guide....bosheff
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Re: no compression!

#8

Post by Cotten »

55panFL!

I was hopeing the hydraulic was providing the slack.

If the valve is indeed stuck open, I must ask:
Didn't it make a helluva clatter?

....Cotten
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Re: no compression!

#9

Post by 55panFL »

Cotten wrote:55panFL!

I was hopeing the hydraulic was providing the slack.

If the valve is indeed stuck open, I must ask:
Didn't it make a helluva clatter?

....Cotten

It didnt seem to pop bang rattle or boom, seemed to cough a little. it started with what felt like it may have been running out of gas for a second, then came back to life for about 1\8 of a mile and then it just died. i was able to restart it but it seemed to be only hitting on one cylinder so i shut it off and began with removing the plugs. i had a buddy kick it over while i held a finger on the plug hole and it had no compression on the rear cylinder. thats when i decided to trailer her home and pulled the push tube covers up to inspect.
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Re: no compression!

#10

Post by 55panFL »

I plan on pulling the head hopefully by this weekend.
#1 what should i look for as a possible cause?
#2 Should I just go ahead and pull both heads off while I'm there?
#3 What will I need as far as gaskets and such to put it back together?
#4 What type or brand of gaskets should get?
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Re: no compression!

#11

Post by 58flh »

55!---I just went thru a similar problem ,If you want to pull both heads ohh --its up to you, ask yourself how much milage & does it need to be redone or just the 1-ouide & valve!---I personally did both as I rack milage on a daily basis.--use JAMES top end gaskets! & proper tools ofcoarse!----Richie----Also use castiron valve guides-(ROWE) make good ones, you will know how much over in size they will have to be once you press out the old ones!--they are usually stamped under the seal, unless a topend job was never done-(doubt-it). Set intakes to .0015 clearence in guide & Ex to .002 & use teflon seals on all!--Valves with nitrided stems are good to use! Manly makes whatever you need!---If you are at the expence of a bikeshop doing the head or heads. Make sure they know old iron!,& are reputable!--If you olny decide to do 1-head -GET a MANUAL so you can see how things work & go from there,You can drift guides out (just be careful & make sure all carbon is off the end of the EX. guide before you push it thru!
Last edited by 58flh on Fri Sep 14, 2012 12:33 pm, edited 1 time in total.
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Re: no compression!

#12

Post by john HD »

#1 what should i look for as a possible cause?
valave rotators.

if your bike is bone stock you may have them. they look like little caps about the size of a watch battery that sit on the end of the valve stem.

they were a misguided attempt to let the valves spin on the seats by pressing on the valve keys every time the valve opened. if you have them get rid of them and replace the valves!

they have a habit of breaking the tip of the valve off and letting the valve go!

john
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Re: no compression!

#13

Post by 55panFL »

564138_3609483805048_1997869165_n.jpg
I got the head off tonight. The valve Spring collar was broken. The collar was Aluminum and appears to have failed for no reason.

I see that there is Steel collars available, Should I replace them all with steel collars?

the good news is that the valve didn't appear to hit the piston from what i see (no marks on piston). I need to get a valve spring compressor to remove what is left of the old collar before I can see if the valve is free to move and not bent.

Is there anything else I should look for or inspect while I'm this far?
Thanks for all your input!!!!
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55panFL
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Re: no compression!

#14

Post by 55panFL »

I got the valves out and everything looks good. ( They spins and move up and down freely after i removed the carbon build up on them) Geuss I got lucky.

Looks as if there may have been leaking a little oil past the valve stems.
Is there a brand of stem seals that are better than another?
and should I replace the collars with steel or try my luck with the aluminum again?
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