ive pulled my block apart on the little 998 i had sitting around and it looks like it was rebuilt fairly recently, the crank has been balanced and the rods and bearings look pretty good.. i want to put it together just to use while i build a good big bore engine. i can still see the previous hone marks.. can i get away with just having it honed and putting it together again with new rings.. i dont really see the point in spending the extra money on a motor that is just going to be used inbetween engines if its not required

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Potato

Get somebody to measure the bores, top and bottom. If only worn .001" or so a hone job and rings will work. For a while. Not as good as a rebore and new oversize pistons.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

ok, so if i was to rebore and everything, what sort of specs should i be telling my machinest to bore it to. also what pistons should i fit, flat tops?

ive been allowed to build this engine so its fairly nice, so let me know what to get to get a 998 going nicely on the road..

cheers

sean

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Potato

I would definitely use flat tops, it's hard to get decent compression in a smallbore (with a reshaped combustion chamber) otherwise.
Hypatec +.080" pistons are good value, and you can still bore to +.100" or +.120" later.
http://www.minisport.com.au/prod1092.htm

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

sweetness so i just tell the guy to bore it out +.080"? im new to the whole measurments game

edit : sorry the pistons are held with circlips to the gudgeon pins.

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Potato

These Hypatec smallbore pistons all have circlips.
If you don't like them or want to rev it hard, any decent engine builder can make you up some PTFE buttons instead. These have to be made to suit the piston and pin, so they are a nice neat fit.

If you use circlips, always fit them with their sharp edges OUTWARDS.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Isn't the way to do it normally to give the machinist the piston and say make it fit? instead of them boring it out to a dimension and hoping its all sweet? You should probably also give them the rings so they can check the gap. Or do people just chuck the rings in out of the box usually?

im not going to be revving the guts out of it.. nothing more the prolly 5 grand at a serious push otherwise just the normal 2-3500rpm..

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Potato

Yes you will, it's a 998 They spin so sweetly, you'll be at 7 grand before you know it

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Simon

The adventures of an owner builder in the Tallarook Ranges

Yep, you are right on both counts.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

im a p plater so 5000 rpm probably means 7 lol, just like when you tell the police your speedo said you were doing 100 when you were doing 130..

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Potato

ah ok, seems like the logical option, obviously why i didnt think of it

cheers for your help everyone

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Potato

Go the 100" ups , get a fun grind cam, get a 202 head and put some slightly bigger valves.....blah blah blah.....it will sing we have the technology

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http://www.youtube.com/watch?v=nDMkVq1jRGU

yes but how far do i want to go for a motor between motors if that makes sense, i want to keep all the extra money that doesnt have to be spent for a twin cam engine later on. id be happy with a nice reliable little 998 to keep me going for 6 months or so

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Potato

build a boggo +20" 998 then.....or go the whole hog now and bolt on the new head later.

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http://www.youtube.com/watch?v=nDMkVq1jRGU