GS500 Engine Rebuild (with pics!)

[Smokebombb]

Summary:  Complete engine dismantling and rebuilding.
Bike: 2004 GS500F
Mileage: 27,000 miles
Guide Reference:  Haynes manual

I was on a ~4 hour ride from LA to Vegas and midway experienced a loss of power and heard a loud overt banging coming from the engine.  Turned out to be blown crankpin (big-end) bearings.  The following is a set of photographs detailing the tearing down, damaged parts, and repairing the engine on our beloved GS.

The Haynes manual was my main guide, along with helpful tips from members on this forum.

Disclaimer:  This is for informational purposes only!  If in doubt, your vehicle should be worked by a skilled professional! 

Tips:
- Label every screw, bolt, nut, hose, and part with masking tape upon removal.  Makes reassembly SO MUCH EASIER.
- Take pictures before you remove an item.  Referring to these pics make reassembly SO MUCH EASIER.
- If you don't have an easy way to get a required specialized tool, be creative (examples to follow).  Sometimes the self-made tool worked just as well and cost next to nothing.

Engine removed from frame, with head and cylinders separated from the crankcase:


Peek into crankcase showing discolored overheated left crankshaft web, resulting from lubrication failure to big-end bearings.  The piston rod was also loose and wobbly:


Peek into crankcase showing normal coloring on right crankshaft web


Removing the valve shims and buckets/followers.  Yes that is my head in the oven.  The follower for the left side exhaust valve was stuck and wouldn't come out.  Based on a suggestion on this forum, I placed the head in the oven to heat up the aluminum head.  30 minutes at 350 degrees F to be exact.  The rate of heat expansion on the head was greater than that of the [steel?] follower, and although still a tight fit, once removed from the oven, I was able to lift the follower out:



Homemade valve spring compressor tool.  Got this idea from someone on this board.  Consists of a woodworking clamp and a $0.50 PVC pipe with a square cut out for access to the valve collets.


Ignition Timing rotor from right hand side of crankcase:


Ignition Timing rotor removed


Right side crankcase cover removed, revealing clutch and primary drive gear


Close up of right side crankcase with clutch removed, exposing countershaft and gear change mechanisms:


Crankcases separated, showing discoloration on left crankshaft web and piston rod:


Crankshaft removed from crankcase, with primary drive gear, piston rods, camchain, and alternator rotor still attached:


Closeup of burnt out discolored crankshaft and loose piston rod






Closeup of blown out crankpin bearings


Closeup of scored connecting rod


What good connecting rod bearings are supposed to look like.  Notice the smooth surface.



Crankshaft, balancer shaft, and a transmission shaft


Getting the alternator rotor bolt out was a pain since the crankshaft was already taken out.  I couldn't quite angle a spanner to fit onto the flat part of the rotor to prevent it from turning as I loosen the bolt as suggested by the manual.  So I came up with this contraption using woodworking clamps to hold the crankshaft in place as I loosened.



Even with the alternator rotor bolt removed, the rotor was a tight fit onto the crankshaft and would not budge.  I employed the method suggested by the manual for removing it.  I purchased a M14x1.5 bolt from the hardware store and threaded it into the rotor.  The bolt pushed against the end of the crankshaft and gradually pushed off the alternator rotor:


On the other end of the crankshaft, I had the same problem trying to get the primary drive gear nut off.  The woodworking clamps didn't work, so I held the crankshaft in place by holding the gear next to the primary drive gear with one of those oil filter wrenches that have teeth and work like pliers.  I stood on the wrench while an assistant loosened the primary drive gear nut.


So many parts lying around to keep track of!  You'll see bits of masking tape labeling each piece




With the engine disassembled, it's time to clean things up a bit.  What a difference a little cleaning makes.

Clean piston vs dirty piston:


Cleaning carbon buildup from the head with valves removed


Valve grinding/lapping is recommended.  I found the coarse and fine metal grinding compound from the local auto parts shop.  You can see the clean silver ring around the exhaust port in the after picture:




Shop rags work great


Clean crank case halves:



Since my crankshaft crankpin (big-end) journals were scored, I needed to get a new crankshaft.  Since I had a new crankshaft, I needed to get new crankpin bearings, and new main bearings, specifically sized for the new crankshaft.  The manual tells you which sizes you need.  Use plastigage to measure the engine bearing clearances.  You'll see the thin green piece along the crankshaft journal, followed by the smashed piece once the crankcase was torqued down.  Plastigage comes with a scale to tell you what the bearing clearances are based on how wide it was smashed.



Crankshaft balancer, crankshaft, and transmission shafts in place in the upper crankcase half.  All bearing surfaces are lubed up with molybdenum paste.


Before reattaching the crankcase halves, you need to place a sealing gasket between them.  There is no preformed gasket -- you need to use gasket maker.  Some people use that red RTV gasket maker, however I heard it has the potential to ball up and clog vital oil passages.  Plus it's bright red and can be an eye sore when squeezed out between the crankcase mating surfaces depending on your taste.  So instead I used Yamabond 4 liquid gasket from my local cycle shop, and let it cure overnight.  Supposedly it doesn't ball up and clog oil passages, and it's an inconspicuous grey:


Closeup of the gasket maker in place


The gasket maker outlines the perimeter of the crankcase half.


Engine back in the bike.  Fired her up and took her for a test ride.  Since I have a new crankshaft and piston rod, I have to follow Suzuki's running in procedure for all new engines.



Listen to her purr

[jmelchio]

Fantastic job. Thanks for sharing.

How long did this take you?

Joris.

[Smokebombb]

This took me about 8 weekends, including 3 weeks waiting for parts to come in. I ordered from www.cheapcycleparts.com, www.powersportsplus.com, and my local cycle shop.

[rayshon]

Nice, how much did you pay total for the parts? I imagine engine parts would be pricey

[Smokebombb]

About
$580 crankshaft
$80 connecting rod
$175 for all the replacement gaskets, o-rings, and bearings
Plus all the miscellaneous stuff like engine cleaners, lubes, rags

Total ~$875

Some people suggested just buying a used engine and swapping it out however I have no way of knowing the condition of a used engine and I valued the learning experience of a rebuild anyway. 

[steezin_and_wheezin]

incredible write up!! really well photo'd, i will be reading over this many times to come!!

preciate it for sure mang!!

[NikonAndy]

This is brilliant. Thank you so much for posting this. I just picked up the exact bike (same color and everything) and it looks like I'll be doing the same thing, tearing her apart and rebuilding. I can't express how much this helps encourage me.

[tcmia]

Excellent write up.  Thank you for sharing. 

[Joolstacho]

Sorry, don't wanna be a know-all at all, but inexperienced guys will be reading, and may think everything is correct here.
2 things... Way, way too much grinding paste on the valves, you only need a few light 'dabs' around the valve circumference. Just makes cleaning it all out more difficult (you don't want any of this left in the engine).
Way, way too much sealant around crankcase joint. 98% of this will get squeezed out of the joint, some of it inside the motor, risking blocking oilways. Just smear it on really thin, but as even as you can.
I admire what you've done mate, goodonya,  I'm just thinking that less experienced guys attempting this sort of work maybe need pointing in the right direction.
Hopefully more experienced mechanics might add a few tips?

-Jools

[weedahoe]

Totally cheaper to buy a replacement engine and I would NEVER eat anything out of that oven again. Seriously, putting a metal aluminum head in it with fuel, oil and other residue on it is as poisonous as using an oven after using it for powder coating.

[yamahonkawazuki]

yamabond. ive used that stuff often

[007brendan]

Sorry, don't wanna be a know-all at all, but inexperienced guys will be reading, and may think everything is correct here.
2 things... Way, way too much grinding paste on the valves, you only need a few light 'dabs' around the valve circumference. Just makes cleaning it all out more difficult (you don't want any of this left in the engine).
Way, way too much sealant around crankcase joint. 98% of this will get squeezed out of the joint, some of it inside the motor, risking blocking oilways. Just smear it on really thin, but as even as you can.
I admire what you've done mate, goodonya,  I'm just thinking that less experienced guys attempting this sort of work maybe need pointing in the right direction.
Hopefully more experienced mechanics might add a few tips?

-Jools

It's not like you can really use too much lapping compound, it's only gonna grind the areas that seat against each other.  It's not like you're going to grind away too much by using more compound.

[Joolstacho]

No, my point about using too much grinding paste is, - it's just POINTLESS isn't it?
You only need enough paste to grind the seat and valve, what's the point of using excessive paste only to have it squelch out off the seat first spin of the grinder and then dribble it's way down onto the ports and make the clean up harder?
-Jools

[The Buddha]

No, my point about using too much grinding paste is, - it's just POINTLESS isn't it?
You only need enough paste to grind the seat and valve, what's the point of using excessive paste only to have it squelch out off the seat first spin of the grinder and then dribble it's way down onto the ports and make the clean up harder?
-Jools

Lapping compound I thought was to be used when lapping it by hand ?
Cool.
Buddha.