Author Topic: Installing pistons  (Read 5753 times)

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Offline cadler

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Installing pistons
« on: April 04, 2005, 11:27:55 AM »
I am ready to reassemble the old 1971 cb750 with formerly stuck heads.
We are putting in the new pistons and was wondering.
Is it better to put the pistons into the cylinder and then attach the rods or should we attach the pistons to the rods first and slip on the cylinder head. Seems to me the the first one may be safer and easier but this is my first rebuild
Thanks
Craig

Ibsen

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Re: Installing pistons
« Reply #1 on: April 04, 2005, 02:27:33 PM »
Mount the pistons on the rods first. Then work on the middle pistons when you start to enter the pistons into the cylinders.
Here is a picture that shows how to set it up. And this guy has used a golf tee for compressing the rings. And the clamps on the studs prevents the cylinder block from sliding down. You can lower the cylinders by moving the clamps. And remeber to get the position of the piston ring gaps correct.



 

schmidbc

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Re: Installing pistons
« Reply #2 on: April 21, 2005, 09:29:50 AM »
Sorry to bring this up again.

I'm following everything in the picture above with the clamps and the blocks of wood, but I cannot figure out the golf tee idea.  How does it work, or does anyone else have anything else that they've tried?  I have to piston ring compressors but they cannot be removed after the cylinder is in the sleeve.

Any proven ideas are welcome! 

Thanks,

     -Brian.

Offline Quail "Owner of the comfortable k8"

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Re: Installing pistons
« Reply #3 on: April 21, 2005, 11:19:39 AM »
Only let the ring compressor slide a little ways down the sleeve, then tap the piston to the bottom of the cylinder and the compessor will fall off. The ring compressor I use is no more than a cone that sets on top of the cylinder and the piston slides down the cone and it compress the rings and they just drop into the cylinder.  I love that tool,came from vw subaru datsun I can't remember.
These wonderful little birds are great flyers, delicious eating, excellent for training your hunting dog, and just fun to shoot,or stuff and keep around the house.  Bobwhites can be put with other types of Quail and have very large penis's.  Quail are very popular with the babes.

Offline Tim2005

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Re: Installing pistons
« Reply #4 on: April 21, 2005, 11:29:40 AM »
Ring compressor? I just go slowly and use my fingernails, has always worked so far (no blocks or clamps either, just gravity to hold it in place). One other hint - clean out the cylinder stud holes really carefully first, in case the studs disturb any muck & it drops down into your spottlesssly clean bottom end. 

Oh, is it just me, or does it look in the photo that the guy forgot the base gasket?

schmidbc

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Re: Installing pistons
« Reply #5 on: April 21, 2005, 12:27:37 PM »
Yes, it did I didn't see one either!

Thanks for the advice, I'm planning on using the fingernail method although I agree with the clamps vs. the hands....since I've already got them sitting around!  My ring compressor dosen't jive with the in-the-bottom method of pistion application.

Everything's clean, I had the head and cylinders gone through by a machine shop, they were in bad shape.

Offline MRieck

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Re: Installing pistons
« Reply #6 on: April 21, 2005, 07:14:59 PM »
Ring compressor? I just go slowly and use my fingernails, has always worked so far (no blocks or clamps either, just gravity to hold it in place). One other hint - clean out the cylinder stud holes really carefully first, in case the studs disturb any muck & it drops down into your spottlesssly clean bottom end. 

Oh, is it just me, or does it look in the photo that the guy forgot the base gasket?
The blocks and clamps are good...I use the tapered end of a toothbrush to push the rings in. DON'T be afraid to tap on the cylinder with you the palm of your hand to push it down! As long as a good chamfer is there no sweat!
Owner of the "Million Dollar CB"

Offline dpen

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Re: Installing pistons
« Reply #7 on: April 22, 2005, 01:04:12 AM »
How many ways are there to do something? I use normal hose clamps used on radiator hoses etc. They slide down the piston easily as the block is pushed down.

Offline Paul

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Re: Installing pistons
« Reply #8 on: April 22, 2005, 04:32:01 AM »
Another way of getting those pistons & rings in is to use either shim strip or cut a coke can / soda can.. wrap it around the piston and rings and use a tie wrap / cable tie to keep the rings compressed enough. the lot will slide out of the way whilst being lowered, snip the tie wrap to remove.....easier than trying to pull out hose clips afterwards.
Paul.
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gerstle

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Re: Installing pistons
« Reply #9 on: April 22, 2005, 07:54:15 AM »
i am the only one here that thinks having the correct tool for the job is a beautiful thing, expecially when that tool only costs $10?  You can get a good piston ring compressor that fits these bikes for $10-11 at any decent auto parts store, why hack it?  Don't get me wrong, i am a cheap SOB.  But this is a fairly important part or your bike, and it's worth the 10 bucks.

schmidbc

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Re: Installing pistons
« Reply #10 on: April 22, 2005, 07:57:25 AM »
I've searched hi and low in the metropolitian Cincinnati area for someone who has piston ring compressors that will fit this bike....with no luck.  As such I'm going to have to try one of these other methods I think.

Does anyone use assembly lube for this job or is everyone in the habit of using motor oil?

Offline Paul

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Re: Installing pistons
« Reply #11 on: April 22, 2005, 02:16:17 PM »
One piston ring compressor...I agree there are tools for every job but...It's easier if all the pistons and rings are compressed at the same time (I'm not buying four tools), when your done throw away the makeshifts 'cos one shouldn't need them for quite some time. Once off tools are an elaboration of someone elses simpler idea.  ;)
Paul.
It hurts to admit when you've made mistakes, But when the're big enough, the pain only lasts a second

Offline Quail "Owner of the comfortable k8"

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Re: Installing pistons
« Reply #12 on: April 22, 2005, 09:24:24 PM »
I  used copper wire on a tractor once. (desperate times and you will think of a way)  Yes the engine will smoke for a little while but when the wire wears away it is just fine.  Open it back up and all the cylinders had a nice copper coating.  I do not recomend this, I just remembered it.
These wonderful little birds are great flyers, delicious eating, excellent for training your hunting dog, and just fun to shoot,or stuff and keep around the house.  Bobwhites can be put with other types of Quail and have very large penis's.  Quail are very popular with the babes.

CHUNG

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Re: Installing pistons
« Reply #13 on: April 22, 2005, 10:17:10 PM »
I'm not able to read all the replies but here's my 2 cent's worth:
Assemble all the pistons, rings and clips first. Then have the base gasket and O-rings ready to go and get your cam chain tensioner in order. Get all these "other" detaIs in order so you don't have to do it twice.
Place #2 and #3 @ TDC. I use two small flat blade screwdrivers for ring compressors. Hardwood is a pain but can be made to work. Wood vs metal is a finess issue, don't gouge anything and the metal tools work better. I've done the thing with beer cans and hose clamps and they just give you too many places to screwup. The ONLY time I ever trashed a ring was using this method. (custom rings too;-(
 Get 90 deg on either side of the ring gap and squeeze the rings into the funnel at the base of the sleeve. Rock the block to one side and do one ring at a time. Then tap the block down and catch the ring on the other piston. Tap it down and do the second ring, repeate.
Ease the block down onto the pistons one ring at a time until you have all three ring on #2 and 3 in the bore. Then roll the crank. This will bring the pistond down toward #1 and 4. Repeat the above steps. when the outter two are in the bore, tap the block down to the cases.

Offline dpen

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Re: Installing pistons
« Reply #14 on: April 23, 2005, 01:02:25 AM »
Use nice clean motor oil for all engine re-assembly

Offline Glenn Stauffer

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Re: Installing pistons
« Reply #15 on: April 23, 2005, 04:09:10 AM »
A tip from the Greenspun Archives:


I just put my bike back together without proper clamps. I made some clamps out of a 1 inch wide strip of aluminum flashing. Heres how to do it: Cut a strip of flashing about 2 inches longer than the circumference of the piston, cut half way across the flashing about one inch from the end, cut half way across the strip on the other side about an inch from the other end. You can then wrap it around the piston and squeezing tightly align the slots and push then into one another. Getting the distance between the slots right is the key, once you have done one use it as a template to make the other 3. I put all the pistons half way up and fit the strips around the pistons, they should be quite tight and hard to fit. Fit them so they are level and overlap the top ring a few mm. Tilt the engine forward and carefully lower the cylinder onto the engine, once you have the top of the pistons in the holes, start to gently tap the cylinder and it should move down over the pistons. You may have to adjust the strips a bit to stop them going into the bores, once the cylinder is past the rings you can remove the strips by tearing off the ends and they'll pop off. Worked for me. It would work even better if you could fold over the top of the strips to made it wider so it would have less tendancy to go into the bore. You could use aluminum tin cans instead of flashing. Be very careful a ring doesn't pop out before its in the cylinder, if it does you can poke it in with a pointed bit of plastic. Make sure your cam chain tensioner and chain are in position first, I didn't and had to do it twice. I've used hose clamps and tin can strips before.


--Glenn

Ibsen

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Re: Installing pistons
« Reply #16 on: April 23, 2005, 05:41:37 AM »
Sorry to bring this up again.

I'm following everything in the picture above with the clamps and the blocks of wood, but I cannot figure out the golf tee idea.  How does it work, or does anyone else have anything else that they've tried?  I have to piston ring compressors but they cannot be removed after the cylinder is in the sleeve.

Any proven ideas are welcome! 

Thanks,

     -Brian.

The golf tee is used to push and compress the piston rings as you enter the pistons into the cyclinders. It is hard plastic, but not hard enough to make any scratch maks in the pistons. :)

schmidbc

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Re: Installing pistons
« Reply #17 on: April 23, 2005, 05:28:01 PM »
 ;D

Cheers to everyone who chimed in to help with this.  After plenty of clean motor oil, some three bond, a new gasket and prodding with my fingernails, the pistons and accompanying rings are properly installed in the cylinders!

This forum has been a real help!

     -Brian.


Offline MRieck

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Re: Installing pistons
« Reply #18 on: April 23, 2005, 06:35:18 PM »
I'm not able to read all the replies but here's my 2 cent's worth:
Assemble all the pistons, rings and clips first. Then have the base gasket and O-rings ready to go and get your cam chain tensioner in order. Get all these "other" detaIs in order so you don't have to do it twice.
Place #2 and #3 @ TDC. I use two small flat blade screwdrivers for ring compressors. Hardwood is a pain but can be made to work. Wood vs metal is a finess issue, don't gouge anything and the metal tools work better. I've done the thing with beer cans and hose clamps and they just give you too many places to screwup. The ONLY time I ever trashed a ring was using this method. (custom rings too;-(
 Get 90 deg on either side of the ring gap and squeeze the rings into the funnel at the base of the sleeve. Rock the block to one side and do one ring at a time. Then tap the block down and catch the ring on the other piston. Tap it down and do the second ring, repeate.
Ease the block down onto the pistons one ring at a time until you have all three ring on #2 and 3 in the bore. Then roll the crank. This will bring the pistond down toward #1 and 4. Repeat the above steps. when the outter two are in the bore, tap the block down to the cases.
For the future he is right-I have factory tools to hold the skirts but this is good detail. Tap, tap tap. Nice job Wayne.
Owner of the "Million Dollar CB"