GPX750R resurrection

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Rust Never Sleeps

Postby Mister_T » Sat Feb 01, 2020 2:11 pm

Hi folks. Another year, another post.

Some things happen too slowly here at Chateau T. I need to buy a big box of "round tuits" but not even eBay has them.

I finally got around to taking the cam cover off and doing a check on the valve clearances.
I was curious to see if there had been any loosening of the cam bearing cap bolts.
Readers with a long memory will recall that I cured an apparent camchain noise by finding that a few cam bearing cap retaining bolts were loose. Some others had been somewhere near finger tight.
It was nice to find that all looked and felt well inside this time.
gpx750r_cam_cover_off.jpg
Pretty clean inside. I like the user friendly valve clearance adjustment.
gpx750r_cam_cover_off.jpg (89.12 KiB) Viewed 1527 times


Eagle-eyed readers may have noticed the questionable appearance of the fuel filter in the above pic.
The concern would be justified as the filter was almost clogged with rust from the tank. The cheap filter did its job and kept the nastiness away from the carbies.
Here is a close-up pic of the filter and most of what came out of it.
gpx750r_fuel_filter.jpg
Oh dear.
gpx750r_fuel_filter.jpg (51.36 KiB) Viewed 1527 times
Any suggestions of products or services in Melbourne to fix the rust in the tank are welcome.

When I poked the feeler gauges around the rockers the only ones in spec were #3 intake.
The rest of the gaps were all below spec.
Either the rockers were never done before or somebody did them wrong in the past. I suspect the latter.

I looked up the specs again in the German FSM and compared them with the specs in the Haynes manual.
The German FSM lists two specs. When I put the words through Google Translate, the smaller spec is between the cam and the rocker, the larger spec is between the rocker and the valve stem.
gpx750r_fsm_valve_clearance_1.jpg
gpx750r_fsm_valve_clearance_1.jpg (27.38 KiB) Viewed 1527 times


The Haynes lists just one spec, the smaller of the factory pairs, but between the rocker and valve stem.
The difference is only about 0.05mm (5 hundredths of a millimetre) but there is not much gap there to begin with.
gpx750r_haynes_valve_clearance_2.jpg
gpx750r_haynes_valve_clearance_2.jpg (8.44 KiB) Viewed 1527 times

gpx750r_haynes_valve_clearance_1.jpg
gpx750r_haynes_valve_clearance_1.jpg (21.91 KiB) Viewed 1527 times


Resetting the clearances took longer than I expected because it seems that somebody in the past may have assumed that whatever torque spec for the adjuster lock nuts exists, it somehow translates to "fahrkenteit".

I can't remember the last factory manual in which I have not found an error of some sort. If I were fluent in technical German I may even find something dubious in the German FSM.
Non-factory manuals may use diagrams and specs from FSMs but the FSMs are not always perfect to begin with and then the non-factory folk also add their own errors on top.
I once sorted out an electrical issue on a friend's old 650 Bonneville "aided" by a Haynes manual which I recall my friend referred to as the "Haynes Book Of Lies".
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Re: GPX750R resurrection

Postby javaman » Tue Feb 04, 2020 9:53 am

I used POR15 kit (just search ebay about $100) which is a 3-step process to line the tank:
1) detergent
2) acid
3) lining

It had worked well the past 2 years but after some more reading there is a debate whether to line or simply remove rust using typical acid (posporic, etc) plenty from bunnings.

I would have tried just removing the rust and top up the fuel every ride first. Liners can fail eventually and it will be a harder mess to clean and fix. While acid cleaning is simple.

My tank came with that Kreem lining and it was a complete pain to remove the flaking. Do not use KREEM!!
alien.gif andi - Red ZX6R, R6, GPZ900R, GPZ750R1, KLR650 Tengai
"my dad's motorbike is cool it is all ways clean.oheter pepole' s motorbikes
are't like my dad's one it's because their is one not always clean."
-ariel circa 2007
http://GPZninja.blogspot.com/
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Re: GPX750R resurrection

Postby Mister_T » Tue Feb 18, 2020 11:55 am

javaman wrote:I used POR15 kit (just search ebay about $100) which is a 3-step process to line the tank:


I'll keep that in mind.

javaman wrote:It had worked well the past 2 years but after some more reading there is a debate whether to line or simply remove rust using typical acid (posporic, etc) plenty from bunnings.


I'll also have a look at the common "rust converter" products. Phosphoric acid? Maybe a few cans of Coke will do the trick?
The GPX tank has the added disadvantage of having to close the extra hole for the guage sender while treating the tank somehow.

javaman wrote:I would have tried just removing the rust and top up the fuel every ride first. Liners can fail eventually and it will be a harder mess to clean and fix. While acid cleaning is simple.


I guess lining is ok until the tank is dented somehow. Then the lining could crack up or complicate repairs. I would not fancy doing any welding on a tank that has a lining in it.

javaman wrote:My tank came with that Kreem lining and it was a complete pain to remove the flaking. Do not use KREEM!!


I wonder how the present owner of my old KLR600 is going. That tank got Kreem about 27 Years ago.
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Did It Again

Postby Mister_T » Tue Feb 18, 2020 7:00 pm

While the tank is off I figured I might as well clean the right hand switchblock.
Such is life with an old bike, it is easy to be consumed by the "might-as-wells".
I just wanted to check the condition of the contacts and renew the dirty old grease. It came up nice.
gpx750r_rh_switchblock.jpg
One down, one to go.
gpx750r_rh_switchblock.jpg (57.05 KiB) Viewed 1408 times
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Re: Did It Again

Postby Smitty » Wed Feb 19, 2020 7:54 pm

Mister_T wrote:While the tank is off I figured I might as well clean the right hand switchblock.
Such is life with an old bike, it is easy to be consumed by the "might-as-wells".
I just wanted to check the condition of the contacts and renew the dirty old grease. It came up nice.
gpx750r_rh_switchblock.jpg



... first thing I did with mine
(as the switch block kept playing up)
GOTTA LUV the 12R!!
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Re: Did It Again

Postby Mister_T » Mon Feb 24, 2020 9:12 am

Smitty wrote:... first thing I did with mine (as the switch block kept playing up)


What was it doing?
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Re: Did It Again

Postby javaman » Tue Feb 25, 2020 3:35 pm

Mister_T wrote:While the tank is off I figured I might as well clean the right hand switchblock.
Such is life with an old bike, it is easy to be consumed by the "might-as-wells".
I just wanted to check the condition of the contacts and renew the dirty old grease. It came up nice.
gpx750r_rh_switchblock.jpg


The "might as wells" are dangerous! as I had taken more than I could chew before...

These days a plug replacement job *is* a plug replacement job not valve adjustments "while we're here" and it usually ends up being the bike in parts and not rideable for weeks lol
alien.gif andi - Red ZX6R, R6, GPZ900R, GPZ750R1, KLR650 Tengai
"my dad's motorbike is cool it is all ways clean.oheter pepole' s motorbikes
are't like my dad's one it's because their is one not always clean."
-ariel circa 2007
http://GPZninja.blogspot.com/
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Re: GPX750R resurrection

Postby javaman » Tue Feb 25, 2020 3:37 pm

Mister_T wrote:
I wonder how the present owner of my old KLR600 is going. That tank got Kreem about 27 Years ago.


I poured 1-2 L of acetone (!) to get rid of mine and it melts the thing but still was really messy.

But I sort of wished I did not line it using POR as well as the metal looked good already after the acid bath.

Now I will dread the day when that POR fails because Acetone is not going to chew it
alien.gif andi - Red ZX6R, R6, GPZ900R, GPZ750R1, KLR650 Tengai
"my dad's motorbike is cool it is all ways clean.oheter pepole' s motorbikes
are't like my dad's one it's because their is one not always clean."
-ariel circa 2007
http://GPZninja.blogspot.com/
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