Author Topic: Barrels on but pistons won't move, what's going on. Help me !!!  (Read 2197 times)

Offline billdn

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #15 on: May 22, 2022, 08:22:11 AM »
Are you sure the rings were fitted the right way up? They are normally marked with a T which goes uppermost.
Oh yes made sure of that  resorting to jewellers eyeglass to check profile of rings. Oddly not marked with a T but an R on top surface.⁹

Offline billdn

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #16 on: May 22, 2022, 08:24:50 AM »
https://youtu.be/ViEjQ7B1uM8
The above will give you a good understanding of what you are measuring with the end gap and how to do it Bill.
You don't measure piston/ bore clearance with a feeler gauge, you need a bore gauge to determine the bore measurement accurately. The difference between the skirt measurement of the piston and the bore is the piston / bore clearance. This should be about 1 thou inch maximum clearance. Unless you have measuring equipment with lots of decimal points, you won't get an accurate reading. I'll just have a look in the manual to see what the ring end gap should be as I can't remember.
Edit.... It was easier for me to take a photo.

(Attachment Link)
Useful clip Julie, explained it well. The photo from manual I gave a photocopy of to engineer shop. Hopefully he read it 🙏 😬

Offline billdn

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #17 on: May 22, 2022, 08:30:19 AM »
Another possibility is a scraper side rail has twisted, been there
Could well be as it was roughly around that point that things started to get difficult when fitting barrels. But all 4 ,although they are very fine and came in 3 parts. Something else to rule out.
Cheers Bryan

Offline Bryanj

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #18 on: May 22, 2022, 10:13:34 AM »
The R is a different make, all ltters/numbers face upwards

Offline billdn

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #19 on: May 22, 2022, 11:34:16 AM »
No. 3 piston out as oil scraper ring bent, 🤨 good shout Bryan ,sadly. Also left score in barrel,  back to engineering shop tomorrow to see if salvageable 🤞.
Ring end gaps on first and second ring no greater than 0.25 ,as 0.20 went through but 0.20 +0.05 wouldn't,  oil scraper gap no more than 0.40.
BTW piston without rings on slid perfectly through all bores.
Stay tuned !

Offline billdn

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #20 on: May 22, 2022, 11:40:45 AM »
I assume the new pistons were numbered from when the rings were gapped to each cylinder when it was bored out or have you done that part?
Not quite sure what you mean Ted?
It was a full rebore to +.25 and new pistons/rings to suit , would they need matching to each bore separately?

Online McCabe-Thiele (Ted)

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #21 on: May 22, 2022, 12:19:07 PM »
I assume the new pistons were numbered from when the rings were gapped to each cylinder when it was bored out or have you done that part?
Not quite sure what you mean Ted?
It was a full rebore to +.25 and new pistons/rings to suit , would they need matching to each bore separately?
When Graham bored my block it was sent back to me with the rings fitted & the piston crowns marked with the cylinder bore with an ink marker. If you gapped your own rings then you would presumably match them as you went along. I'm assuming that in reality each piston will have a tolerance as will each bore so there will be clearance variation for each ring in each bore before you gap them imho. I'm not an engineer - I have found through experience with car engines that some rebores are not as exact as they should be. That's why I rate Grahams skill in this area. Sadly the place I used for cars as long since closed - Wylde Engineering in Derby were old school.  Do you think the ring was bent when fitting the pistons,? I found that really difficult as you can't see or really feel what's happening. All my previous piston fitting on cars has been from the top

Hopefully the bore marks are not too deep and can be honed out.
« Last Edit: May 22, 2022, 06:12:01 PM by McCabe-Thiele (Ted) »
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Offline Bryanj

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #22 on: May 22, 2022, 10:37:43 PM »
In 40 odd, some say very odd, years i have never had to gap a japanese piston ring.
I have had a scraper rail twist building a 1200 wing so it can happen to the best of us, dont feel bad about it, as long as the scratch is not too deep it will run, it al depends on what you realisticly want the bike to do

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #23 on: May 23, 2022, 10:15:11 AM »
In 40 odd, some say very odd, years i have never had to gap a japanese piston ring.
I have had a scraper rail twist building a 1200 wing so it can happen to the best of us, dont feel bad about it, as long as the scratch is not too deep it will run, it al depends on what you realisticly want the bike to do

Interesting to read about never having to gap Japanese rings Bryanj
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Offline Bryanj

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #24 on: May 23, 2022, 11:31:37 AM »
Their QC seems to be good, to be honest never had to gap Hepolite either, as long as you ordered the correct size in the first place,

Offline Sesman

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #25 on: May 23, 2022, 11:34:05 AM »
I ‘gapped’ the ones I bought from Japan and they were all spot on. It was an annoying but necessary waste of time.

Offline billdn

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #26 on: May 23, 2022, 02:20:38 PM »
Footnote to above  gaps on all rings were spot on, so can't blame rebore.
On plus front the engineer reckons where the  scratch is below rings even at lowest point so rebore not necessary 😉 . To be on safe side thought I'd order new ring kits for all pistons.  Weirdly +.25 ring kit (genuine Honda btw)  £29.13 whereas after market replacement full piston kit inc rings etcetera just 90pence more. Go figure 🤔.  So ordered full set again .
BTW anyone want 4 unused +.25 pistons sans rings? Thanks for your comments,advice and support all.

Offline Nurse Julie

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #27 on: May 23, 2022, 02:25:58 PM »
Use the original set of pistons with the new rings you are buying Bill. The rebore would have been done to those pistons, not the replacement pistons you're buying.
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Offline billdn

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Re: Barrels on but pistons won't move, what's going on. Help me !!!
« Reply #28 on: May 23, 2022, 04:57:01 PM »
Use the original set of pistons with the new rings you are buying Bill. The rebore would have been done to those pistons, not the replacement pistons you're buying.
Good call Julie, hadn't thought of that .
Cheers
Bill

 

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