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cbfb
20th November 2010, 18:12
Oh dear, I've come unstuck a bit, took the cylinders off my GSF250, inspected the pistons, everything all good, now trying to get it back together again. Er, how do you get the pistons back into the cylinder?

As far as I can see, you should assemble all four pistons on the conrods then slide the cylinder block down over them. Sounds easy eh but it's a BASTARD to do :(

Is there an easier way or a tool I don't know about or something? Manual is f all use and google isn't helping for once.

Also am I ok leaving the original cylinder gasket on? It looks fine. Will be replacing the head gasket though.

Sorry if I'm monopolising this forum lately, appreciate all your help though.

MotoKuzzi
20th November 2010, 19:00
There's a tool called a ring compressor that helps. Never done a 4 cyl m/cycle before, I imagine you would have to remove conrods from the crank and do one piston at a time?

cbfb
20th November 2010, 19:08
There's a tool called a ring compressor that helps. Never done a 4 cyl m/cycle before, I imagine you would have to remove conrods from the crank and do one piston at a time?

I have heard about a ring compressor, but I can't figure out how it would work if I'm trying to slide the block over the assembled pistons?

No the conrods stay in place and the pistons go on the little ends, then the block goes on top. That's what it says in the manual anyway...

This is what it looks like at the moment:
223997

cs363
20th November 2010, 19:14
If you want to do it that way, use the cheats method - get four good quality hose clips slightly larger than the pistons and use them as ring compressors, once you've got the cylinder over the pistons you can just undo them completely and remove them. Make sure to use plenty of engine oil to lubricate the rings/pistons.
It is a hell of a lot easier to do individual pistons and rods though, rather than trying to do the whole four at once - you'll probably need an extra pair of hands to do it that way.
Personally I'd replace the base gasket as a matter of course, you don't want to get it all back together only to find that's leaking.....

MotoKuzzi
20th November 2010, 19:15
Ok. I have only done car engines and in that case you do each piston into the bore individually with a ring compressor with conrod attached and then connect the bottom part of the rod to the crank.

To achieve what you want to do your'e gonna need 4 ring compressors and a lot of hands. Hopefully some one who knows will pop along soon.

Cheers.
Mark.

Mental Trousers
20th November 2010, 19:17
A ring compressor tool

<img src="http://www.wonderbart.com/images/09/april/piston_ring_compressor_03618.jpg" height="480px" />

You can use some of these if you're careful

<img src="http://www.cometkartsales.com/store/p&h/images/hoseclamp.jpg" />

You'll still need at least one extra pair of these though

<img src="http://upload.wikimedia.org/wikipedia/commons/b/b1/Kohanim_hands_blessing_photo.jpg" height="480px" />

FJRider
20th November 2010, 19:18
I found hose clamps (lightly fastened) on the pistons ... slide the cylinder block down ... but don't drop them into the crank area as you remove them from the con-rods ...

MotoKuzzi
20th November 2010, 19:22
Good idea, i imagine you would run the risk of scoring the rings if they were clampe too tight.

FJRider
20th November 2010, 20:30
You can use some of these if you're careful

<img src="http://www.cometkartsales.com/store/p&h/images/hoseclamp.jpg" />

You'll still need at least one extra pair of these though

<img src="http://upload.wikimedia.org/wikipedia/commons/b/b1/Kohanim_hands_blessing_photo.jpg" height="480px" />

Place a block of wood above the bottom gasket to rest the cylinder block on as you undo the clamps ... sorted ...

I used them on the top end rebuild of a GS1000S by myself ... no worries ...

jonbuoy
21st November 2010, 05:22
Car ring compressors are usually too big for wee bike pistons, nails and fingers and a helping hand will do it. Hose clamps can scratch the pistons.

cbfb
21st November 2010, 11:29
As always, some very helpful replies there. That's given me plenty to go on.

Ring compressors x 4 = a bit pricey. So will have a go with hose clamps if I can find a suitable size.

Yep I can wedge some wood under to hold the block up, good idea.

Will enlist the girlfriend to help, might take a bit of persuasion!

Bugger about having to replace the gasket, I was thinking that because failure of the base gasket isn't as critical as the head gasket (i.e. just get an oil leak) I would leave it, but if you reckon it needs doing I won't argue.

rwh
21st November 2010, 12:32
Wouldn't it be easier to turn the crank so you can do two at a time? Or does that cause confusion with setting up the timing chain etc?

Richard

cbfb
21st November 2010, 12:58
Wouldn't it be easier to turn the crank so you can do two at a time? Or does that cause confusion with setting up the timing chain etc?

Richard

It would be easier, but unfortunately there's just not enough room to work in there. You wouldn't be able to get the pistons in under the block and the pins in next to the other pistons :(

rwh
21st November 2010, 14:06
It would be easier, but unfortunately there's just not enough room to work in there. You wouldn't be able to get the pistons in under the block and the pins in next to the other pistons :(

Oh - I was thinking of putting all the pistons on the conrods first, but just putting only 2 at a time into the cylinders.

Richard

cbfb
21st November 2010, 15:27
Oh - I was thinking of putting all the pistons on the conrods first, but just putting only 2 at a time into the cylinders.

Richard

:facepalm: Sorry, the brain has a day off on Sundays... yep that would work for sure :yes:

Max Preload
21st November 2010, 16:41
Lubricate the bore and gudgeons lightly with ATF (automatic transmission fluid). It burns off quickly on start up. Position the crank so all the conrods are at the same height.

You start on the middle two cylinders. Put all the pistons, with the inward facing gudgeon pin circlips already in place, into the bottom of the the sleeves just high enough that the oil ring is captive in the bores for the middle two piston, and well up into the bore for the outer two pistons, then match up the two middle conrods with the pistons and put the gudgeon pins and outward facing circlips in. Then you tap the outer two pistons down to allow those gudgeon pins and circlips to go in easily.

Max Preload
21st November 2010, 16:53
I have heard about a ring compressor, but I can't figure out how it would work if I'm trying to slide the block over the assembled pistons?I doubt very much that the dimensional constraints will allow you to.


No the conrods stay in place and the pistons go on the little ends, then the block goes on top. That's what it says in the manual anyway...That will be very difficult. Put the pistons in the liners first.

cbfb
21st November 2010, 17:03
Lubricate the bore and gudgeons lightly with ATF (automatic transmission fluid). It burns off quickly on start up. Position the crank so all the conrods are at the same height.

You start on the middle two cylinders. Put all the pistons, with the inward facing gudgeon pin circlips already in place, into the bottom of the the sleeves just high enough that the oil ring is captive in the bores for the middle two piston, and well up into the bore for the outer two pistons, then match up the two middle conrods with the pistons and put the gudgeon pins and outward facing circlips in. Then you tap the outer two pistons down to allow those gudgeon pins and circlips to go in easily.

:yes: This sounds much easier, couldn't see the wood for the trees. Will have to get a base gasket sent out (hopefully not from Japan) then will get cracking.

Many thanks :)

Paul in NZ
21st November 2010, 17:11
If you look at the bottom of the block where the sleeves stick out, is there a pretty decent champfer? ie is there a taper into the cylinder?

If there is a good sized one it is just possible to do this without a hose clamp or ring compressor provided you have help and work carefully. If you are unsure a hose clamp will help.

Katman
21st November 2010, 17:15
There's a reason mechanics aren't made overnight.

Paul in NZ
21st November 2010, 17:23
There's a reason mechanics aren't made overnight.

Is it because the manuals are still in japanese?

cbfb
21st November 2010, 17:34
If you look at the bottom of the block where the sleeves stick out, is there a pretty decent champfer? ie is there a taper into the cylinder?

If there is a good sized one it is just possible to do this without a hose clamp or ring compressor provided you have help and work carefully. If you are unsure a hose clamp will help.

Yep there is a bit of a chamfer, but the rings don't quite fit in without some effort. However if I use Max Preload's suggestion and fit the pistons one by one beforehand, it should be OK (I have tried this and because of the chamfer like you pointed out, it slides in nicely). Just wouldn't be able to get all four in at once very easily.


There's a reason mechanics aren't made overnight.

+10. I enjoy learning though, especially when something really tricky comes right.


Is it because the manuals are still in japanese?

LOL well at least it keeps people coming back to KB!

cbfb
25th November 2010, 20:37
Just a quick update, I had a crack at this tonight. A wee bit tricky but not nearly as bad as I thought it would be.

Tried putting the pistons in the block and installing like that, no go, far too little room to work. So installed the pistons on the conrods and lowered the block down, 2 pistons at a time (inside first) with a bit of help from fingernails and a flat, thin bit of metal. Even did it all on my own without an adult helping :)

THANK YOU to everyone who replied, appreciate the help.

Crasherfromwayback
25th November 2010, 21:16
But I think you'll be doing this all over again.

Next time...why don't you ask a nice mechanic if you can watch him/her do it correctly. It's great that you want to be able to do such things...but you were way over your head.

cbfb
26th November 2010, 07:34
But I think you'll be doing this all over again.

Can you elaborate before I bolt the head back down? If there's something you think I've missed I would appreciate the advice. I have followed the service manual to the letter and given the crank a few turns since putting the pistons back, all seems ok. Many thanks.

Crasherfromwayback
26th November 2010, 11:57
Can you elaborate before I bolt the head back down? If there's something you think I've missed I would appreciate the advice. I have followed the service manual to the letter and given the crank a few turns since putting the pistons back, all seems ok. Many thanks.

I simply think you've bitten off a tad more than you can right now chew. Good on you for having a go mate, and I hope it all works out ok!

cbfb
26th November 2010, 12:05
I simply think you've bitten off a tad more than you can right now chew. Good on you for having a go mate, and I hope it all works out ok!

Ah OK, thanks, I've done everything in the manual, checked the piston, bore, pin dimensions, replaced the circlips etc etc as it instructed. Hope I've done everything right. This was the only bit I got stuck on cause the manual said to just whack the head back on... but that's what KB is for.

Anyway cheers will hopefully get it finished on Sunday and fire it up.

Crasherfromwayback
26th November 2010, 12:18
Ah OK, thanks, I've done everything in the manual, checked the piston, bore, pin dimensions, replaced the circlips etc etc as it instructed. Hope I've done everything right. This was the only bit I got stuck on cause the manual said to just whack the head back on... but that's what KB is for.

Anyway cheers will hopefully get it finished on Sunday and fire it up.

Good stuff. Make sure you turn the engine over by hand before you try and fire it up, just incase you have the valve timing wrong. Bending those lil valves is expensive!

Pete

cbfb
26th November 2010, 12:22
Good stuff. Make sure you turn the engine over by hand before you try and fire it up, just incase you have the valve timing wrong. Bending those lil valves is expensive!

Pete

Will do, thanks :niceone:

ps have also checked the head isn't warped, not done the valves as i don't have the tools/knowledge.

Juzz976
26th November 2010, 15:18
Car ring compressors are usually too big for wee bike pistons, nails and fingers and a helping hand will do it. Hose clamps can scratch the pistons.

+ 1

I have 2 little plastic scissor jacks just for these occasions.

They were out of a set of toys for my son:innocent:

Max Preload
26th November 2010, 15:24
Tried putting the pistons in the block and installing like that, no go, far too little room to work. So installed the pistons on the conrods and lowered the block down, 2 pistons at a time (inside first) with a bit of help from fingernails and a flat, thin bit of metal. Even did it all on my own without an adult helping :)I fail to see how that can be the case. The gudgeon pin is below the oil ring assembly. With the oil rings just inside the bore, the gudgeon hole is still below the skirt of the liner.

cbfb
26th November 2010, 15:30
I fail to see how that can be the case. The gudgeon pin is below the oil ring assembly. With the oil rings just inside the bore, the gudgeon hole is still below the skirt of the liner.

I won't argue with you, cause it sounds like you know a lot more than I do, but because of the chamfer at the bottom of the cylinder, I found that with the gudgeon hole beneath the liner, there was enough room for the 2nd ring to come unstuck in the chamfer and make it tricky to get back in. So I found it easier to put the pistons on the conrods first. But I can see your point, it looked like it should work but I just wasn't dextrous enough.

Max Preload
26th November 2010, 15:41
I won't argue with you, cause it sounds like you know a lot more than I do, but because of the chamfer at the bottom of the cylinder, I found that with the gudgeon hole beneath the liner, there was enough room for the 2nd ring to come unstuck in the chamfer and make it tricky to get back in. So I found it easier to put the pistons on the conrods first. But I can see your point, it looked like it should work but I just wasn't dextrous enough.Ah right. It must be quite a long lead in! But why didn't you use your other 3 pair of hands? :lol:

Had I found myself in that situation I'd have combined the two methods. Pistons in the bore up to the oil ring and then the gudgeon then the oil rings.

Piston rings are quite delicate. You should have probably used plastic rather than metal when pushing them in though.

cbfb
26th November 2010, 15:44
Ah right. It must be quite a long lead in! But why didn't you use your other 3 pair of hands? :lol:

Had I found myself in that situation I'd have combined the two methods. Pistons in the bore up to the oil ring and then the gudgeon then the oil rings.

Piston rings are quite delicate. You should have probably used plastic rather than metal when pushing them in though.

lol, yeah octopuses would make awesome mechanics.

Point noted, will use plastic next time. Hopefully won't have damaged them, didn't have to use much force at all, just a flick to get them in place.

disorderly
28th November 2010, 02:51
I worked on alot of 4 cylinder bikes doing top end recos etc... it is possible to use your hands while a 2nd pair of hands hold the barrels
1. make sure you put base gasket ,dowels and any o rings that may go on the base as its a pain to take the barrels off a 2nd time.
2. oil rings making sure the ring gaps are staggered (make sure ring ends are opposite sides of each other)
3. I start with no 1 and 4 pistons rotate so they are at 12.o clock, 2nd person lowers barrels over studs now squeeze top rings of both pistons with fingers and work top of piston into barrel while 2nd person lowers gently still holding most of the weight of barrel a gentle tap with a rubber hammer downwards, repeat with 2nd piston ring. the oil rings are not so bad but make sure that the upper and lower oil rings DONT overlap they touch end to end ( hope that makes sense )
4. rotate and repeat with 2 centre pistons these are tricky due to tight space but it can be done just remember this is not a brute force job it can be very easy to break a ring if your not careful
I worked in a motorcycle dismantlers for 10 yrs and performed this many times i hope this is of some help just take your time and good on ya for giving it a go I think the more you do work on your own bike the more you learn the more confidence you get and its all good !!

cbfb
28th November 2010, 02:57
I worked on alot of 4 cylinder bikes doing top end recos etc... it is possible to use your hands while a 2nd pair of hands hold the barrels
1. make sure you put base gasket ,dowels and any o rings that may go on the base as its a pain to take the barrels off a 2nd time.
2. oil rings making sure the ring gaps are staggered (make sure ring ends are opposite sides of each other)
3. I start with no 1 and 4 pistons rotate so they are at 12.o clock, 2nd person lowers barrels over studs now squeeze top rings of both pistons with fingers and work top of piston into barrel while 2nd person lowers gently still holding most of the weight of barrel a gentle tap with a rubber hammer downwards, repeat with 2nd piston ring. the oil rings are not so bad but make sure that the upper and lower oil rings DONT overlap they touch end to end ( hope that makes sense )
4. rotate and repeat with 2 centre pistons these are tricky due to tight space but it can be done just remember this is not a brute force job it can be very easy to break a ring if your not careful
I worked in a motorcycle dismantlers for 10 yrs and performed this many times i hope this is of some help just take your time and good on ya for giving it a go I think the more you do work on your own bike the more you learn the more confidence you get and its all good !!

Well, I see where you're coming from, I very gently pushed the rings up gently gthrough through the cylinders. All good, pushed up AOK.

Cha :)

C

cbfb
28th November 2010, 03:01
Fingered

Really that far fingerered?

cbfb
28th November 2010, 03:17
A ! As described above, cool to everyone who slaggs off process butts ass