Author Topic: The camchain tensioner screw/bolt  (Read 193 times)

Offline Macabethiele (Ted)

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The camchain tensioner screw/bolt
« on: February 03, 2021, 05:31:31 PM »
https://flic.kr/p/2kymoFkCam chain tension bolt by Macabe Thiele, on Flickr




The above photo is of the camchain tensioner before I attempted to remove the cylinder head. There were 3 washers between the lock nut & engine for some reason. I guess the reason for so much threaded bolt showing is due to chain wear as screwing it in seemed to release the tension - that seemed illigical to me as I thought screwing it in would increase tension!
Honda CB400F2 under restoration
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Offline K2-K6

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Re: The camchain tensioner screw/bolt
« Reply #1 on: February 03, 2021, 05:48:03 PM »
The bolt doesn't tension as such, it just locks (when you tighten) the tensioner mechanism at the place it's set to.

Unlocking the bolt lets the internal mechanism move to it's "correct" position via it's own spring,  you then lock at that position for all subsequent running until the next time you want to alter it. 

In effect,  you just nip the main bolt onto the internal tensioner,  then secure that position with the nut to now prevent it backing out.

Offline djb

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Re: The camchain tensioner screw/bolt
« Reply #2 on: February 03, 2021, 05:49:57 PM »
My understanding is that screwing it in does not increase tension. It only locks the adjustment made by the internal horseshoe/ spring arrangement. If the horseshoe is seized or spring worn, tightening this further will only bugger up the thread.

Offline Macabethiele (Ted)

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Re: The camchain tensioner screw/bolt
« Reply #3 on: February 03, 2021, 06:07:46 PM »
That makes sense - my Haynes manual refers to screwing the tensioner in to release tension so that's what I did. Both sides of the curved tension arrangement have come out just fine.

Present issue is the cylinder head is stuck to the block - I've removed all 12 of the cylinder head nut & washers but the head will not budge - the block & head will lift slightly together instead. I was hoping to remove the head & block to make the engine lighter to lift out.

I'm pretty sure I can't lift them out stuck together whilst in the frame still - not enough clearance. Currently squirting WD40 down the stud area and on the outside of the head gasket. I guess there are some locating dowels holding it together.

Any tips on seperation or do I just leave it alone until the engine is out?
Honda CB400F2 under restoration
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Jeep Grand Cherokee WK
Mercedes R129 SL500

Offline taysidedragon

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Re: The camchain tensioner screw/bolt
« Reply #4 on: February 03, 2021, 11:19:04 PM »
Try tapping it sideways all around with a soft hide mallet or similar. Edge on to the fins, but not too hard or they'll break. Keep trying,  it will move eventually.
Gareth

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1977 CB400F

Offline Macabethiele (Ted)

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Re: The camchain tensioner screw/bolt
« Reply #5 on: February 04, 2021, 10:04:38 AM »
Try tapping it sideways all around with a soft hide mallet or similar. Edge on to the fins, but not too hard or they'll break. Keep trying,  it will move eventually.

Currently I have the head & block raised by about an inch and have it supported by a block of wood on the carb inlet connection things. I was hoping that overnight gravity might do its bit but no joy so far. Obviously I am tempering my rubber mallet strikes as I do not want to damage any fins. Squirting WD40 onto the visible head gasket but no movement as yet.

Presently having a long think before I do anymore to persuade the parting.
My guess is that someone has used an adhesive when fitting the head gasket.

Update cylinder head seperated using a plastic wedge as used by double glazing fitters - no damage caused !

« Last Edit: February 04, 2021, 05:50:07 PM by Macabethiele (Ted) »
Honda CB400F2 under restoration
Jeep Grand Cherokee WJ
Jeep Grand Cherokee WK
Mercedes R129 SL500

 

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