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piston fun :(

first timer

first timer

Forum Sage
3336927466_4e4bfed262_b.jpg


3336091547_df6d02e755_b.jpg



SO it appears the wrist pin on the #1 piston has been hammering the circle clip. There is about 1mm of movement side to side on the wrist pin. and it looks like the circle clip has been driven deeper into the groove.

none of the other pistons have cracked around the clip but there appears to be some good movement there and some hammering on the clips as well.

SHould i be looking for 4 good used pistons? it's the damn 1000cc 16v motor so all pistons are discontinued. I am guessing the 1100 pistons are a bigger diameter then these which are 69mm w/ 18mm wrist pins.

the cylinder walls seem good so where ever that piece of piston is it didn't score the wall when it left.
 
That's basically the 16 valve 750 pistons. I don't know if you'll have unintended consequences (such as the piston being too long and blowing the motor), but the GS750 kits from wiseco come in at 70mm w/ 18mm wrist pins.
 
Glad to see the piston fragment didn't score the bore, very luckly! Now I understand the request for the pistons, read the other post first, cheers.
 
first timer said:
3336927466_4e4bfed262_b.jpg


3336091547_df6d02e755_b.jpg



SO it appears the wrist pin on the #1 piston has been hammering the circle clip. There is about 1mm of movement side to side on the wrist pin. and it looks like the circle clip has been driven deeper into the groove.

none of the other pistons have cracked around the clip but there appears to be some good movement there and some hammering on the clips as well.

SHould i be looking for 4 good used pistons? it's the damn 1000cc 16v motor so all pistons are discontinued. I am guessing the 1100 pistons are a bigger diameter then these which are 69mm w/ 18mm wrist pins.

the cylinder walls seem good so where ever that piece of piston is it didn't score the wall when it left.
Click to expand...

That piston is a mess. Looks like that pin is further than 1 mm from what's left of the circlip. Is the circlip removed from the other end? If not, you need to investigate why there has been so much free play between the clips and the wrist pin. I suspect that someone has mis-matched the wrist pins and the circlips.

I would look for some new replacement OS pistons. If you don't want to bore, good luck with the search for replacement second hand pistons!
 
I typed in GS1000 piston on ebay and it looks like there are some being sold individually and then there are wiseco kits being sold as well....but I don't know if I am looking for the right pistons.
 
I bet money it was broken before installed into the bore.

By the way the piston pin circlip opening HAS to be at 12 o clock or 6 o clock.otherwise they will pop out. that does make a mess of the cylinder.

just a tip for those who do not know.
 
no wiseco pistons, unless i want to go to a 1166 bore, I am sure there are plenty 1000 8v pistons but not so many 16v 1000 pistons.... I'll double check.

Talked to Ray, he suggest just using a 1100 block and pistons for now until i can find some 1000 pistons or get a set custom made. I rather not bore the cylinder because I would like to keep the bike stock, the 1000cc 16v is what makes it unique.

I'll pull the wrist pin and measure it today and see whats up. I am sure the motor has been apart before since the crank has been welded plus the original owner told me they welded it.

There is an intresting idea, anyone know if a 16v 750 wiseco kit would work with the Kat? What makes the 750 and the 1000 differant? the stroke?

What is the typical side to side tolerance for wrist pin movement?

I'll pull the pistons and take some more photos.

thanks Guys,
Ryan
 
trippivot said:
I bet money it was broken before installed into the bore.

By the way the piston pin circlip opening HAS to be at 12 o clock or 6 o clock.otherwise they will pop out. that does make a mess of the cylinder.

just a tip for those who do not know.
Click to expand...
why? a circlip in a groove, installed correctly will not pop out just because its not facing the right way. where did this information come from? i have been building bike engines for over 20 years now and have never worried about where the circlip sits and have had no failures yet!
 
Never seen any specs for wrist pin to circlip end clearance. I would expect it to be in the 0.006" - 0.010" range. Any closer than that and you would be struggling to fit the second circlip in the groove.
 
Agemax said:
why? a circlip in a groove, installed correctly will not pop out just because its not facing the right way. where did this information come from? i have been building bike engines for over 20 years now and have never worried about where the circlip sits and have had no failures yet!
Click to expand...

That's a good question - I was told when I was a lad about spinning the clip in to the right position and was too young to ask why. I've always made sure the clip is in the 'right' position but you've got me wondering now.
 
THe clips probably walk a bit. I found clips at different positions, some in the "wrong" place, when I took a 550 apart last year. I suspect this failure was metal fatigue pushed by detonation but who knows for sure. Could just as easily been a bad piston or flawed casting.
 
I pull my pistons and took some pics, seems like most of them are in good shape, # 4 might have a little bit of wear around the circle clips but nothing major.

See the link below, i put them in a group and labeled each photo related to piston number. Please comment. The last two pictures in the group are one of my pistons (the extra carbony one, which has a bigger spark top) and the ones Katana_man (OSS) has offered me (the ones with the smaller spark top) Does the size of the spark top matter? As long as both pistons have a dia of 69.400 - 69.415mm?

http://www.flickr.com/photos/monknuts/sets/72157614913506095/

I also measured the side to side clearance of the rods as shown in the book, they all seem in spec #1 = .533mm (the bad clip piston) #2 = .508mm #3 = .406mm #4 = .432mm. The standard range in the book is .10 - .65mm with a service limit of 1mm. So they seem ok. I also tried measuring the small ends with my digital calipers and they all seem to be just under 18mm, I needed to hunt up a bore gauge to be more accurate.
 
Can't see anything that would suggest the pistons are bad, except for the broken one of course.

I don't understand why that one piston (labeled "piston") seems to have the extra raised area in the middle while the other pistons don't have it. The group photo (labled "piston 2") don't show the piston with the raised area either. Is that an extra piston or what?
 
You can't use the 750 pistons in the 1000 because the compression height is WAY different. Ray.
 
Hey FT,

I don't know spit about piston swaps, but I noticed what
looks like a fair amount of scoring in the bore of your #1 rod.
Is that shallow enough you to take out with a hone? The wrist
pin is scored too, but noone seems to mention that. Is that kind
of wear typ. when you get these apart? Or is that a sign of a lubrication
issue?
 
trippivot said:
I bet money it was broken before installed into the bore.

By the way the piston pin circlip opening HAS to be at 12 o clock or 6 o clock.otherwise they will pop out. that does make a mess of the cylinder.

just a tip for those who do not know.
Click to expand...

I installed my circlips with the opening 180 degrees from the opening in the piston. Isn't that what the factory manual states?, Ted
 
Shaughn said:
Hey FT,

I don't know spit about piston swaps, but I noticed what
looks like a fair amount of scoring in the bore of your #1 rod.
Is that shallow enough you to take out with a hone? The wrist
pin is scored too, but noone seems to mention that. Is that kind
of wear typ. when you get these apart? Or is that a sign of a lubrication
issue?
Click to expand...


I am not sure, Ray, Trip, Bueller? Anyone care to comment, I don't have enough experience to comment.
 
Circlips

Circlips

I'e never heard of, or ever paid attention to circlip positions. The only thing that's really important is to make sure they are seated in the groove properly.

I can't imagine the small mass difference of the opening having any effect.
 
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