Need help - rattling noise when throttling

[bleeble]

so, what about the connecting rods?

Are you asking me? If you are, I don't know what kind of bike he's got and I'm not inclined to do someone else's work for them when they can easily do it themselves. I picked up a crankshaft and connecting rods for $10 + shipping. It took a whopping 15 seconds to find a bunch of stuff like this: link. Pistons and rods for $35 shipped.

[psyguy]

what condition are your connecting rods in

was asking "archania"
a cracked piston, i doubt, would give the sound he explained

[Archania]

everything else looks good.
Just that cracked piston and split ring.
the pistons did move very smoothly when turning them by hand.
Just ordered the parts and the gasket set.
I did look on ebay but nothing for a 81 GS650G.
And the gasket set was a pita to find.. just hope the one i "won" from ebay comes and is the correct one...

[tkent02]

everything else looks good.
Just that cracked piston and split ring.
the pistons did move very smoothly when turning them by hand.
Just ordered the parts and the gasket set.
I did look on ebay but nothing for a 81 GS650G.
And the gasket set was a pita to find.. just hope the one i "won" from ebay comes and is the correct one...

If you are going to bore anyway, why not use 750 pistons?
Little more displacement can't hurt.

[BentRod]

you may want to look into WHY you piston cracked.. just an observation.
also, you may want to check your valves, at least the ones servicing the damaged piston, to see if they have been smacked or not. any marks on the old piston head is a dead give away, but if the damaged piston hit the valves then the stems could be bent, and may not seal properly.

Suzuki is a pita for piston rings (Rather expensive), but if you are going to be taking the cylinders off, then honing all 4 and putting in all new rings is most advisable, although if an experianced mechanic takes a look and thinks they are ok, you may not need to hone all 4.
also, while the head is off, you could perform a leak test on the valves. clean the head up best you can (head being fully assembled) and place it upside down over paper towel. fill the cylinder heads with varsol or laqure thinner and let sit for 10 minutes. if you find any varsol on the paper towel, you need to have your valves and ports ground.

you could also take a disassembled head, valves and 3 pistons to a garage or rad shop and have them hot tank the parts to get all the carbon off..

I could go on if you like, but one last thing. when you knock out the wrist pins, inspect them too. make sure they are not tight coming out and don't forget to remove the circlips.

[Archania]

I think due to the age of the bike and that it probably was never serviced like it should have.
And due to the cost factor - this is the route i'm going