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998 std vs 1098 std pistons
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Author:  cush [ Tue Dec 29, 2009 9:37 am ]
Post subject:  998 std vs 1098 std pistons
Looking about minisport, I see that there are 1098 standard bore pistons available, http://minisport.com.au/prod26.htm but no 998 standard pistons

The bores are the same, so is there a difference in the pistons skirt, or gudgeon attachment, or are they actually the same thing?
Author:  TheMiniMan [ Tue Dec 29, 2009 9:48 am ]
Post subject: 
998 pistons are tall

1098 pistons are short

ie: 998 crank is short stroke so therefore tall piston

1098 cranks are long stroke so therfor short piston
Author:  cush [ Tue Dec 29, 2009 9:54 am ]
Post subject: 
So are 998s available new in standard sizes?
Author:  TheMiniMan [ Tue Dec 29, 2009 9:58 am ]
Post subject: 
Ahhh,,, hang on a min & i`ll check



i`ll just get my glasses on




won`t be a sec







Karcraft list them as part number (998 STD) set of 4 pistons inc rings




:-)
Author:  cush [ Tue Dec 29, 2009 10:32 am ]
Post subject: 
That's funny, because the website doesn't list 'em.
Author:  GT mowog [ Tue Dec 29, 2009 11:30 am ]
Post subject: 
cush wrote:
That's funny, because the website doesn't list 'em.


AE Hepolite P/N 20773 STD

Karcraft P/N 998 STD

http://www.karcraft.com.au/catalogue/pa ... 0&part=998
Author:  850man [ Tue Dec 29, 2009 11:39 am ]
Post subject: 
Why do you want std pistons? Most blocks these days have worn bores and require boring & oversize pistons. Fitting std pistons to a std bore that has been honed will most likly give you to much piston to bore clearence and you will end up with a smoky, oil burning "reco" motor. I suggest you purchase 020 oversize pistons and do the job properly.
Author:  cush [ Tue Dec 29, 2009 12:02 pm ]
Post subject: 
850man wrote:
Why do you want std pistons? Most blocks these days have worn bores and require boring & oversize pistons. Fitting std pistons to a std bore that has been honed will most likly give you to much piston to bore clearence and you will end up with a smoky, oil burning "reco" motor. I suggest you purchase 020 oversize pistons and do the job properly.


Maybe it's not for a 998 block :)
Author:  850man [ Tue Dec 29, 2009 1:22 pm ]
Post subject: 
Hotted up 850??? Excellent :D
Author:  Phat Kat [ Tue Dec 29, 2009 2:59 pm ]
Post subject: 
850man wrote:
Why do you want std pistons? Most blocks these days have worn bores and require boring & oversize pistons. Fitting std pistons to a std bore that has been honed will most likly give you to much piston to bore clearence and you will end up with a smoky, oil burning "reco" motor. I suggest you purchase 020 oversize pistons and do the job properly.


I know where you're coming from, and I'm probably just spliting hairs, (and I know that cush has already come back and advised that they are not for a 998)... but you don't always need to over bore the block... your better off getting the motor apart and seeing what it actually needs..

I have one of those funny late GT blocks that are basicaly a small journal 11 stud, thick flange 1100S blocks... know the one :) anyway, it was a total virgin, standard bore size. I pulled it down and it turned out that it just needed a hone,, not bad for a 30 something year old donk hey :) the piston to bore clearance ended up 0.0035", so next time round it will probably need over boring (0.004 is the max clearance recomended,, by the factory anyway)...

Or, you could just overbore it anyway and keep it down to 0.0025 at the min clearance (provided it isn't going to revving its guts out its whole life :lol:)

But yeah,, I reckon check it out and see what it needs... these engines aren't being made anymore so why put one that much closer to the scrap heap... or, put yourself closer to needing sleeves which are more expensive than just a bore or hone. :) :) :)
Author:  drmini in aust [ Tue Dec 29, 2009 5:33 pm ]
Post subject: 
It's not just a piston clearance issue, but more one of bore wear.
By the time it has .001" more clearance well down the bores, it's worn oval and tapered more up the top where the rings change direction. Even if you hone it out, it's not good for compression and oil sealing.
A series donks wear their bores more than you think- by the time the rings are worn out, they really need a rebore and bigger slugs. :wink:
I would NEVER put standard pistons into an old std bore motor. It's not as though you are really extending the block's life. There are heaps of common oversizes available now, whether it's a smallbore or a 1275.
eg 1275-
+.020, .040, .060, 72.5mm, 73.0mm, 73.5mm, 74.0mm.

That's 7 friggin rebores mate.. then, you can sleeve it!
:lol:
<edit> or see me for a std bore block and start again.

Smallbores (998) nearly as good-
+.020, .040, .060, .080, .100, .120.

(1098) +.020, .040, .060, .080, .100, .134" (Imp 68mm)
Author:  Wombat [ Tue Dec 29, 2009 5:59 pm ]
Post subject: 
I have a set of standard NOS 998 pistons for sale at half price if anyone wants them. :roll:
Author:  subwayseth [ Tue Dec 29, 2009 6:22 pm ]
Post subject: 
What does a re bore cost anyways?
Author:  drmini in aust [ Tue Dec 29, 2009 6:40 pm ]
Post subject: 
$100-$150. You get what you pay for.
I have a 1098 block here a member got done a few years ago with the $100 job and the pistons are too loose... needs another rebore & pistons after about 5000 miles.
It had ring gaps of about .025" with new rings...:cry:
Author:  TheMiniMan [ Tue Dec 29, 2009 9:40 pm ]
Post subject: 
i may be wrong here, (i often am) but i think cush is looking at doing a "square-ish" bore from an old 850 block like the one Deano (74snail) was talking about in another thread

so,,, if i`m right,,, then all this talk (typing) of re-bores & bore wear & why go bigger if it don`t need it etc etc etc,,, probably means nothing to Cush

??? yeah???

:-)
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