GPX750R resurrection

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Postby Mister_T » Mon Jul 18, 2016 10:50 pm

javaman wrote:Great write up!

Thanks. There is more to come. Maybe some owners will be inspired to take a closer look at how their bike works and perhaps cast a more critical eye on its maintenance. Be your bike's harshest critic.

javaman wrote:The carburetors on my GPZ is the one thing I haven't touch. I was scratching my head because the boots+carbies+boot+airbox (if seen from the left) are absolutely tight fit! So I left it alone.

Yes, it's a tight fit. Straight-fours like these tend to make carby fit/replace a tricky job. Age-hardened boots make it a bear of a job.
I still wonder how the factories assembled the bikes on production lines. Maybe the airbox went into the frame first, followed by the engine with the carbys and cables attached.
Also, I have never seen a factory shop manual show a special tool to make carby remove/refit easier.

javaman wrote:Any chance to describe this magic tool of yours?

I would show a pic but I don't have it here at the moment.

javaman wrote:is it just a plate you force the carbs/boot into?

2 plates actually. One plate goes against the engine boots, one plate goes against the airbox boots.
I dug up some sheet aluminium and cut it with tinsnips. Each piece is about 35cm by about 15cm, maybe 1 or 2mm thick.The dimensions are not critical. As long as you have enough to cover the boot holes and have enough left to grip the ally with vice grips or mole grips or similair, you are on the way.
It helps a lot to have an assistant. Shoving the carbys between the sheets take effort and you will need someone to hold the bike and/or help keep the sheets in place. You are compressing the boots on both sides. Some lube in the form of rubber grease or vaseline on both sides of each sheet helps a bit but you will still gouge the thin ally sheet a a bit, but so what.

Once the carbys are located, pull out one sheet at a time while holding the carbys in, and the carbys should drop into the boots with some minor adjustments.

I won't claim I invented this technique. I probably read it somewhere and it came back to me when the situation arose.

javaman wrote:I too had the oil cooler line touching the exhaust! Lucky I looked beneath and it was a 30-sec. fix.

Little things like this make a difference. You would not know unless you look. How many times in the past has somebody else missed that little fault that could overheat the oil and damage the engine?
Last edited by Mister_T on Thu Aug 04, 2016 9:49 pm, edited 1 time in total.
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Re: GPX750R resurrection

Postby javaman » Mon Jul 18, 2016 11:16 pm

I was thinking a spray of hot oil at full lean!! :shock:

Rubber & exhaust pipe don't mix well, although in my case it's surrounded by wire spring.
alien.gif andi - Red GPZ900R, GPZ750R1, KLR650 Tengai, KLR250
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Re: GPX750R resurrection

Postby Mister_T » Sun Jul 31, 2016 11:56 pm

This is the carby installation tool in all its primitive glory. Ruler shows size.
gpx750r_carby_install_tool.JPG
It got a workout and survived to do it again another day.

The cutout in the top sheet is not important. It was already there when I cut a single sheet in half to make the two.
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Re: GPX750R resurrection

Postby javaman » Mon Aug 01, 2016 9:44 am

Thanks... I think I got the idea :D
alien.gif andi - Red GPZ900R, GPZ750R1, KLR650 Tengai, KLR250
"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 » Mon Aug 01, 2016 8:37 pm

I took a pic of the caliper I swapped out.
gpx750r_rhf_caliper.jpg
The pic did not come out as good as I wanted.
Where I have put the red line there is a length of dust seal sticking out. This is probably why the RH disc is 0.2mm thinner than the LH disc. That dust seal is probably wedging the piston against the bore and stopping the pad retracting properly when the hydraulic pressure is off.
It is fixable but it was more expedient at the time to swap out the whole caliper. I will likely have to G-clamp the small piston and apply some hefty air pressure to get the big piston moving.

I was reading a post on some other forum somewhere, where a GPX750-owning poster described what seems to be the same issue. Is this something these particular calipers can do? I have not seen this problem before.
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Re: GPX750R resurrection

Postby Mister_T » Tue Aug 02, 2016 10:32 pm

This is part 14024-1416 COVER, HEAD GUSSET.
gpx750r_2_before.jpg
A bit weatherbeaten, isn't it?
The aussie sun has not been kind to this plastic part.

So, to getting looking nice, the following steps were taken:
gpx750r_3_scuff_it_up.jpg
Scuff it up with a plastic scourer


Then:
gpx750r_4_plastic_primer.jpg
Applying this should help the process along
gpx750r_4_plastic_primer.jpg (156.58 KiB) Viewed 7522 times


Get it wet and wait a bit:
gpx750r_4a_plastic_primer.jpg
A bit blotchy, should have cleaned it with wax-and-grease remover better
gpx750r_4a_plastic_primer.jpg (321.14 KiB) Viewed 7522 times


Light coats of colour:
gpx750r_5_light_coats.jpg
A few light coats should do it
gpx750r_5_light_coats.jpg (295.09 KiB) Viewed 7522 times


Whoops, too much orange peel:
gpx750r_6_too_much_orange_peel.jpg
[sigh] Not quite right
gpx750r_6_too_much_orange_peel.jpg (338.9 KiB) Viewed 7522 times


Rubbing it down with wet P2000 wet-n-dry:
gpx750r_7_2000_wet-n-dry.jpg
P2000 should do it
gpx750r_7_2000_wet-n-dry.jpg (259.58 KiB) Viewed 7522 times


After a final light coat of paint:
gpx750r_8_after_final_coat.jpg
That's more like it
gpx750r_8_after_final_coat.jpg (278.39 KiB) Viewed 7522 times


Before:
gpx750r_1_before.jpg
Hmmm, looks a bit neglected
gpx750r_1_before.jpg (69.41 KiB) Viewed 7522 times


After:
gpx750r_2a_after.jpg
Much better
gpx750r_2a_after.jpg (81.69 KiB) Viewed 7522 times


I could have gone with satin black paint which may have given a slightly more authentic finish. No biggie, I'll see how I like the gloss, It would not be hard to change it if I want.
Ah, but what about that screw? It does looks a bit secondhand. I'll cover that in the future.
Last edited by Mister_T on Tue Aug 02, 2016 10:43 pm, edited 1 time in total.
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Re: GPX750R resurrection

Postby Mister_T » Tue Aug 02, 2016 10:40 pm

A wider shot for the full effect:
gpx750r_2b_wider_shot.jpg
gpx750r_2b_wider_shot.jpg (109.16 KiB) Viewed 7522 times
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Re: GPX750R resurrection

Postby javaman » Wed Aug 03, 2016 9:30 am

I've been thinking of painting plastics myself! But a bit worried I would ruin it.

I read that you can use a hairdryer to 're-blacken' plastics... have you done anything like that?

I might try it in a hidden location just to see.

is your bike running yet? Maybe we should go for a ride on our old machines ! :D
alien.gif andi - Red GPZ900R, GPZ750R1, KLR650 Tengai, KLR250
"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 » Wed Aug 03, 2016 10:57 pm

javaman wrote:I've been thinking of painting plastics myself! But a bit worried I would ruin it.

Practice makes perfect. Plastic primer helps. Since most road bike plastics are fairly stiff (and hence brittle) you can do without the flex agent in the paint that is used on things like modern car bumpers.

javaman wrote:I read that you can use a hairdryer to 're-blacken' plastics... have you done anything like that?

Last I heard this technique could be used to reduce the severity of scratches on the surface, particularly on softer car interior plastics. In my case, I doubt that heat would have made the same impact as paint did on the Cover,Head Gusset.
Even if heat does work, I suspect that heat is trickier to apply than paint. Imperfect paint can be rubbed back (as occured in my post) and done again. Damage from excess heat might be irreversible.

javaman wrote:I might try it in a hidden location just to see.

There are plenty of plastics on our bikes which the factory painted with 80's paint technology.
Practicing refinishing is one good reason not to throw broken panels and parts away.

javaman wrote:is your bike running yet? Maybe we should go for a ride on our old machines ! :D

The bike started first click on the last maintenance startup on the weekend. The bike is club rego'd but there are various things that I still want to get done before peak riding season. The alternator belt is just one of them, then there is a coolant change, another oil and filter change, this list goes on and on.
I have no information about the bike's service history so I have to pretty much check over everything, eventually.
Poster "GPX Denis" is doing up a GPX750, hopefully his will be ready to run next month or so. Maybe this year there can be a forum Melbourne "red plate" ride.
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Re: GPX750R resurrection

Postby javaman » Thu Aug 04, 2016 10:52 am

I know what you mean. Even until now I am keeping a close eye on oil level, baby the throttle, etc. Just like a new bike :lol:. It still cringe me remembering that oil line which touched the exhaust headers.

Looks like it's going to be a cracker spring time rides :twisted:. Its's still too cold now. I had a win purchasing $24 ebay heater grip which looks nice and integrated. Mmmmm toasty! 8)

http://www.ebay.com.au/itm/262068961949?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
12V 22mm Heated Motorcycle Handlebar Handle Bar Grips Hand Warmers Black

Image


Image Image

Taking off the bar-end was not easy! I had to spend $20 to but an impact wrench!
alien.gif andi - Red GPZ900R, GPZ750R1, KLR650 Tengai, KLR250
"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 » Thu Aug 04, 2016 9:33 pm

That is a tidy installation. I'll have to consider fitting such devices.
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Re: GPX750R resurrection

Postby Smitty » Fri Aug 05, 2016 7:15 pm

Mister_T wrote:I took a pic of the caliper I swapped out.
gpx750r_rhf_caliper.jpg
The pic did not come out as good as I wanted.
Where I have put the red line there is a length of dust seal sticking out. This is probably why the RH disc is 0.2mm thinner than the LH disc. That dust seal is probably wedging the piston against the bore and stopping the pad retracting properly when the hydraulic pressure is off.
It is fixable but it was more expedient at the time to swap out the whole caliper. I will likely have to G-clamp the small piston and apply some hefty air pressure to get the big piston moving.

I was reading a post on some other forum somewhere, where a GPX750-owning poster described what seems to be the same issue. Is this something these particular calipers can do? I have not seen this problem before.


.. never had this issue with my GPx7fiddy
GOTTA LUV the 12R!!
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Re: GPX750R resurrection

Postby Smitty » Fri Aug 05, 2016 7:19 pm

Head gusset.. gone grey?

I just used the stuff you get in Repco and Autobarn to make grey car bumpers .. black again
worked a treat on my GPx

was like this - http://www.ebay.com.au/itm/MOTHERS-BACK ... SwzJ5XahXP
but I think it was Meguiars (not Mothers)
GOTTA LUV the 12R!!
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Re: GPX750R resurrection

Postby Mister_T » Fri Aug 05, 2016 10:03 pm

Smitty wrote:.. never had this issue with my GPx7fiddy

Ok.
With the number of other Kwaks using the same caliper, including the very popular GPX250's, some sort of reputation should have surfaced if a design flaw was the case.
It would be sort of nice to think that it was not the result of somebody replacing the seals and leaving a couple of centimetres of dust seal sticking out and saying "fuck it, too hard".

Still, when I pull apart that caliper I'll measure the distance between the dust seal groove and the end of the bore. Perhaps the combination of an out of limit disc and worn out pads could allow the dust seal to peek out of the bore. New pads for these don't have a lot of meat on them to begin with.
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Re: GPX750R resurrection

Postby Mister_T » Fri Aug 05, 2016 11:10 pm

Smitty wrote:Head gusset.. gone grey?

Yes, it's a sign of old age, going grey in the gusset.

Smitty wrote:I just used the stuff you get in Repco and Autobarn to make grey car bumpers .. black again
worked a treat on my GPx
was like this - http://www.ebay.com.au/itm/MOTHERS-BACK ... SwzJ5XahXP
but I think it was Meguiars (not Mothers)

Funny you should mention that. I have been considering ways to darken the fading paint on the engine.
Ideally I should pull the power unit out and respray it. I doubt I will be doing that any time soon.

I have been experimenting on the engine with a wax/polish/restorer for black plastic bumpers. Some would call it a "gel", I would call it black goop that you would not want to get onto your good clothes.
It has worked fairly well on the plastic ignition pickup cover which seems to be a traditional part that becomes noticeably grey next to the black engine cases. I use an old toothbrush to work it into the fins.

We all know the cylinder block should be black and shiny. When the cylinder block goes matte and grey it really stands out around the shiny black and dark grey bodywork.
As far as I can tell, the black goop has darkened the engine somwhat. I put some shine on top of the gooped engine parts with a layer of silicone spray. Hopefully that gives it a shine and makes the dirt easier to get off next wash. I don't know yet how the goop handles engine heat.
Of course, if I ever do repaint the power unit I will have to go a bit nuts with the wax-and-grease-remover to prepare it properly.

You probably won't find a dedicated black-engine polish in a car parts store, but searching the net came up with this: http://www.performancemotorcare.com/blo ... -to-black/

Anybody got any better suggestions?

Edit add:
It seems that S100 Engine Brightener can be bought through the mail from http://www.s100.com.au/ .
In for a penny, in for a pound, I have ordered a can and will report on its performance.
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