Quote:
Originally Posted by spldart
Ok. I got a question.
78 mm is definitely WAY out of tolerance for suzuki spec for the cylinder.
What kind of reliability are people doing the 78 mm overbore getting?
... and the 76 mm overbore?
I can believe crazy stuff like that has been done but I'm curious about longevity.
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pardon me....way out of tolerance ? sure if u use stock boring (3,5mm stock boring...after honing process it will be very thin or....gone)....but in here we ALWAYS buy new diesel engine boring
gz have 3,5mm stock boring
very good question...durability and reliability
- story is....back then several years ago when boreup and strokeup is not popular for commuter bike (at those time people still doubt about durability after the mod)...coz...yes...many of boreup mod blow (broken) and cylinder jugs was rip apart....and u can say if its totally fail...big yes...(perhaps its happened early 2000 , i don't recall it precisely)
but...for certain people (street illegal racer or even legal cub bike race FFA trophy) its not too expensive to repair when their engine blows(just need 1-2days to overhaul + about USD100-150....they dont care as long as they win and get some hundred USD or trophy...(nowadays theres still many cub race whether legal and illegal...both of it still have huge fans)
so...in FFA class....cub that originally for example 125cc....may free to tune till the max include increase displacement as big as they can do....
when it blows....they will start over and over to repair those broke engine....
so...in the end...many of bike tuner (garage) realize...."why dont we do some research to mod engine for non-racer person ?" so they can have faster bike without buy new bigger bike...
still...precision honing machine(plus few other purpose of machinery) and high skills/experienced tuner guy absolutely needed for this kind of mod...
since its just needed few hundred bucks (in USD currency)....theres many people interested with modding engine (moderate specs....not race specs)
coz even its fail...its wont damage their(bike owner) wallet too much...
years by years passed....and in the end....they (mechanic/tuner) has many experienced for mod up commuter engines without being fail (coz they was learned what kind of things that makes their mod fails in past)
so...i will make sure if the mechanic competent before send my bike into garage (not all mechanic have certain skills and experience and high precision honing machine...cnc machine...etc)
but if 3 factors above are met....boreup and strokeup bike will ready even for interstate long haul journey
even few garage offer exclusive research for each person(depend on bike owner budget)....(but its need long time...about a month from start to finish)
PS : there's 2 most reason why boreup engine blow
- compresion ratio is too high (after boreup/strokeup....we need to measuring cylinder compression and make sure its not to high that can make piston tear apart)
- thickness of boring....yes , originally GZ has 3,5mm thickness boring...so we need to stay in those measurement no matter what or better if we can add little more thickness (exsample 4mm) measuring after honing bore process done