I have sourced a donor bike to solve my blown engine issue. How much of a mission is it to replace the rings in a GN and what kinds of trouble can I expect to have if any? I'm mechancally able but haven't played with replacing rings or seen anyone else do it either. For anyone who has seen my other posts, the final cause of death was one of the exhaust valve stems breaking and making engine love to the head and piston top ending up melted (?) into the piston. I didn't know the parts got that hot but it's pretty much melted into it. Also, has anyone got experience with fitting other pistons into a GN that could give me a clue what to keep an eye out for at the wreckers?
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You'll have fun getting the old bits out......

Personally I'd get a new piston and rings and use teh new/old parts that you got.
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Dude you almost couldn't find an easier motor to work on.
To make it easier you could pull the motor out and put it on the bench but ya dont need to.
-remove carby,exhaust system ,tank -toss em in the corner.
dump the engine oil out. Turn the motor over to TDC--if it still turns over.
remove chain -undoo 5 bolts --remove engine.
there are 4 through bolts holding the head on and one down the cam chain side.
--aww look I can walk ya through the whole thing.
Good news is the GN shares its motor with a range of suzuki quads so any other worn parts will be cheap to find.
The most difficult part is probably the cam timing -hardly hard at all
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You'll most likely have to pull the motor out to remove the head and barrel,you'll need a top end gasket set,and preferably a chain too.There is some interchangability in pistons,but you'll really have to know what fits what....usualy found by having two motors apart at the same time.
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Then you can find out if the pistons are slightly different or not.

Voice of experience speaking Motu?

:whistle:
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At the risk of volunteering others - this sounds like a good "advanced maintenance/how things work" session for a couple of bods?

Get the motor out of the bike ahead of time (which will need to be done anyway)... and the rest is hands on work under the expert eyes of those who know.

Some very generic skills would be passed on as well as some useful specifics.

Added bonus - I'll throw $50 towards the event... beer, wine and or parts.

Let me know
MDU
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Then you can find out if the pistons are slightly different or not.

Voice of experience speaking Motu?

:whistle:

Heh,heh,my XT thingy would be a good example.My KT250 had a Honda piston in it,just a slight mod,and standard was 1mm oversize for the KT.A CB750 piston takes a TL125 out to 145,Honda Accord piston rings fit XS650s,Austin A30 bearing shells fit Triumph 650s.And yet how come the parts you buy for your bike don't fit....but parts off something completely different will?
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Heh,heh,my XT thingy would be a good example.My KT250 had a Honda piston in it,just a slight mod,and standard was 1mm oversize for the KT.A CB750 piston takes a TL125 out to 145,Honda Accord piston rings fit XS650s,Austin A30 bearing shells fit Triumph 650s.And yet how come the parts you buy for your bike don't fit....but parts off something completely different will?

That'd be the difference between a machanic and a fitter....
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Nope. That'd be the specialist parts manufacturer (Glacier, Hepolite etc) discovering that they could save money on tooling by persuading the customer to use a certain specification.
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dude your better off getting an over-size piston-kit (piston, gudgeon pin, rings, gudgeon pin retainer clips)plus a gasket kit, getting the best barrel of the two motors boring it to the size of the replacement piston. get the donor engine head checked to see if the valves are ok & seating properly then fit that to the fresh barrel.
dicking around with interchanging parts between a blown motor & a donor with unknown history is asking for trouble in the long term either way the donor is going to have to checked & measured up thoroughly anyhow, it may have an over-size piston in it already and will have to be matched to the cylinder bore before anything serious can be done to start with, if that isn't done first & the engine is put together & run theres a high possibility of it seizing from being to tight and you'll be back to square one again.
a piston kit should by rights be cheap enough as the GN has been around for donkey's years plus its the same as early DRs and also LT & LTF suzuki quads.
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yea i must ask the question--why bother with the rings thing?? --why not just bung the doner motor in
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I had always intended doing a straight engine swap, and that leaves me with a bore (i suppose you call it that on a bike?) To mess around with. The oversize piston/ring kit sounds like a go. Normally I fix things because I have to. I think I might have some fun on this because I won't have to have it running by any certain time etc. It doesn't look like there is much meat in the bore to take out but I don't know how much you need anyway? Also would want to see what valves are around and see if I can have the head ground to fit as the only bad word (apart from lack of power) I hear about these is that the heads crap out, mine died from snapped valve stem so I suppose I'd have to agree. I totally go to a workshop lesson type thing if anyone feels they have been evil enought to deserve that kind of punishment!
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