1980 750 rod knock

[1980 GS rider]

I have a rod knock in my 1980 GS 750 E. I figured I would look around to see if I could locate N.O.S (hard) parts to see what kind of cash I may have to fork out to fix the bottom end of the motor. This isn't my first rodeo with engine rebuilds or repairs but, generally speaking, I have worked on newer (mid 90's and up) model motorcycles and expected things to be a bit pricey. It seems that N.O.S parts can be a bit of a unicorn to find (which I also expected). So, my question is, if I happen to find an older model GS750 motor that I can scavenge parts from will the older 750 connecting rod fit a 750 X motor crankshaft? This is all just for research at this point as I have yet to open the cases on my motor to inspect what the knock is but, I know that it's internal after inspecting the stator and ignition sides of the motor. For all I know it's a lost cause at this point due to crankshaft damage that will be unrepairable. Any info will be greatly appreciated.

[Steve]

Are you sure it's rod knock? Some engines have a noise at idle that sounds a bit like rod knock, but goes away as the engine speed goes above 1500 or so. That is what we call "cam walk", and is caused by the cam "walking" sideways. The increased pull of the cam chain at higher speeds pulls it back to center, eliminating the noise.

However, if the noise gets worse as engine speed goes up, yeah, it's probably a rod.

.

[Nessism]

Parts are readily available though a multitude of dealership sources...http://www.boulevardsuzuki.com/fiche_select.asp

Your bike has the 2nd generation GS750 engine, from 1980 - 1983 (certain models), and parts are unique to it. That model engine had oiling system problems. Promoted fix is to shim the oil pressure relief spring to increase oil pressure.

It might be easier and cheaper to just locate a good used engine.

Good luck

[sparki]

you sure the issue isn't from the clutch basket?... may be a little less noisy if the carbs are synced... if it goes away when the clutch lever is pulled or lessens, then that's your problem...

[rapidray]

Just so you know, an 1100/1150, 16 valve engine is pretty much a bolt in & a MUCH better engine choice. Ray.

[mainiac]

I have a 80 750 ex i got really cheap that i was going to get back on the road. But i came across a 78 750e that is in better shape. I might part out the 80 to get some goodies for the 78. The 80 runs, doesnt smoke or leak oil. Im pretty sure its sucking air as it revs up and down on its own. A po went crazy with black spray paint on it. what would a motor like that be worth?