GPX750R resurrection

[Mister_T]

Since the tank is off I figured it might be a good time to pull off the upper triple clamp and look into dismantling and cleaning the igniton switch. That was the idea but the upper clamp does not want to come off. Maybe a gear puller would help but I'll consider that a last resort.

So much blackness

gpx750r_tank_off.jpg (113.6 KiB) Viewed 11710 times

Sometimes the switch would take a bit of jiggery pokey to get the bike to light up. Whether a new 5-wire repro from ebay would be any better than a cleaned up 30 year old OEM part is open to debate. For now I'll make do with cleaning the connector for the ignition switch.

Not great but not real bad either

gpx750r_ignition_sw_connector.jpg (62.28 KiB) Viewed 11710 times

The spades are not quite as bad as they look in the pic but there is a bit of greenery growing there.
Since a little cleanup up and shoving the connector back together firmly the switching has been quite reliable so far.
I'm getting less than 1 ohm resistance across the switched power terminals so that will be ok for a while. The ignition switch is held on with shear bolts so the upper clamp would still have to come off one way or another. I'll let some squirts of Inox work their magic and try again some other time.

[Mister_T]

The Inox worked its magic and the upper triple clamp was able to be removed with careful application of a hitting stick.
The ignition switch came out without any bother and is actually pretty clean inside.

After a minor cleanup is goes straight back together

gpx750r_ignition_switch_dismantled.jpg (61.16 KiB) Viewed 11695 times

The kill switch will probably be dirtier as the right hand switch block sits out in all weathers.

[Mister_T]

This is the live power terminal feeding into the ignition switch.

This can be improved

gpx750r_ignition_switch_power_terminal.jpg (60.85 KiB) Viewed 11682 times

[Mister_T]

What is inside an errant Nichiwa X05FN plug cap?

Konnichiwa Nichiwa

gpx750r_spark_plug_cap_contents.jpg (39.38 KiB) Viewed 11665 times

The brass plug which connects to the spark plug can be unscrewed with some effort. The red thing is the ceramic resistor and it is spring loaded against the brass plug.
In this case the resistor actually meters fine.The problem is at the upper end of the spring where it is corroded. Somewhere inside the top of the plug cap there is a gap between the terminal and the spring. Sealed off as it is you would think there would never be any problem but there you go.

In theory the spring could be cleaned up but getting deep inside the plug cap to clean up the insides would be rather difficult.

gpx750r_spark_plug_cap_spring.jpg (39.85 KiB) Viewed 11665 times

To convert a plug cap like this one to a non-resistor type all you would have to do is cut a small metal rod to same length as the resistor and swap it in.

[Mister_T]

Just when you thought it was safe to peruse the GPX & GPZ section, I'm back. Has it really been a year since my last post?

I finally got around to getting a new front tyre. I ended up choosing a Bridgestone BT45 which I have never used before.
Here is a pic of the profile:

This profile looks conducive to tipping in and exploring cornering clearance.

What better way to run in a glossy new front tyre than do a loop out through the Dandenongs to Reefton Spur, Black Spur and back home?
Generally when I get bike tyres done I take the wheels off myself and take them in to the bike tyre shop. This time I didn't have adequate tools to remove the front wheel myself so I let the shop remove and replace the front wheel. [sigh]
The trip started care free but by the time I got to Warburton and well before the really fun bits, the front end was making squeely scrapey noises in time with the front wheel. I stopped off to check if the front wheel was about to fall off.
The speedo drive was hot as was the bottom of the left fork leg, both much hotter than the front discs. The right hand fork slider bottom was only lukewarm. The bearings seemed ok and there wasn't a lot of drag so I had a ciggy and continued.

The Bridgy BT45F seems to work nicely. I notice the front end stands up under front brake in a corner less than the old BT17F did, both of which stand up less than I remember my RC17 did.

Made it out there, scuffed up the front tyre and made it back with the noises continuing on and off. Well, I didn't scuff up the last centimetre on the edge of the tread since the front end is a bit questionable but I'll leave that for when I've acquired some more tools and figured out what I've paid to get fucked up.

Now I'll have to think about what rear tyre size I'll choose next time that gets changed. The stock rear is a 140/70 V18, I may go for a 130/80 V18.

[Mister_T]

The front Bridgy seems to have been made in the 23rd week of 2018 going by the DOT code:

gpx-750r_BT45F_DOT_code.JPG (25.08 KiB) Viewed 11143 times

The tyre scuffed up ok. Still a bit of chicken strip on the side to get rid of:

A pleasant afternoon's work

gpx-750r_BT45F_run_in.JPG (70 KiB) Viewed 11143 times

[Mister_T]

No, I'm not collecting used swimwear, just trying to figure out what why it got hot and made noise after the tyre shop had it's hands on it.

This sight greeted me when I removed the front wheel and worked the drive off the hub:

gpx-750r_speedo_drive_1.JPG (102.97 KiB) Viewed 11142 times

The sticky-outy bits don't look stock to me.

Another angle:

gpx-750r_speedo_drive_3.JPG (71.92 KiB) Viewed 11142 times

It's a bit hard to see inside the drive to see the gear, but now I know what seal to get:

gpx-750r_speedo_drive_2.JPG (104.56 KiB) Viewed 11142 times

I filed off the sticky-outy bits one by one:

gpx-750r_speedo_drive_4.JPG (52.14 KiB) Viewed 11142 times

The hub seemed undamaged but I noted the bearings felt a bit dry:

6302Z bearing, single Z is single metal shield. I won't be banging the bearings out, lubing them and banging them back in. I may go for ZZ type (double metal shield) or double rubber shields when I change the front wheel bearings.

gpx-750r_speedo_drive_5.JPG (350.02 KiB) Viewed 11142 times

I cleaned it all up and lubed it as best I could. It's all back together now and ready for a test ride.
I have had never taken off the front wheel before and maybe it was already this way when the shop pulled it off but you would think they have seen enough speedo drives to know when something looks wrong.
I can see how it could have been screwed up and refitted but it is still disappointing.

[Mister_T]

It seems I did a reasonable job on the speedo drive which no longer emits untoward noises.
Out of curiosity I filled the tank to check the fuel consumption. The bike used half a tank to do the Reefton run and I calculated a consumption of 4.16 litres per 100km.

Contemplating the front tyre, I wonder if there are any disciples of Dave Moss suspension videos who would like to comment on what the appearance of the grooves have to say about the front suspension settings. The leading edges are feathered and the trailing edges are still sharp:

gpx-750r_BT45F_grooves.JPG (109.06 KiB) Viewed 11134 times

[Smitty]

It seems I did a reasonable job on the speedo drive which no longer emits untoward noises.
Out of curiosity I filled the tank to check the fuel consumption. The bike used half a tank to do the Reefton run and I calculated a consumption of 4.16 litres per 100km.

Contemplating the front tyre, I wonder if there are any disciples of Dave Moss suspension videos who would like to comment on what the appearance of the grooves have to say about the front suspension settings. The leading edges are feathered and the trailing edges are still sharp:

gpx-750r_BT45F_grooves.JPG

BT45s.. loved them on my ZX750F (aka GeePeeXX750)

I ran mine at PI on a couple of track days... great grip and feel
but does make the front end work a bit ( a Kwaka plus btw)



you will note from that pic... PI is an anticlockwise circuit

[billwest]

There is a chance that the "shop" forced the speedo drive in, without actually lining up the slots correctly.

[Mister_T]

There is a chance that the "shop" forced the speedo drive in, without actually lining up the slots correctly.

Yeah, I figure the axle got torqued up then the wheel was turned a bit to check. That is when the error was noticed and then the axle was loosened and the drive realigned.

[billwest]

This happen on my ZRX some years ago, and they used so much force that it also cracked the speedo housing.
Hence .... I usually remove wheels myself.

[Mister_T]

I came across this short (1 minute 11 seconds) Dave Moss vid that seems to relate to the wear on my new front tyre as shown in the pics I previously posted:


It would appear that my front rebound damping is insufficient. That is not a surprise given the condition of the fluid currently in there, and, was it ever ideal from the factory to begin with?
Adjusting the rebound damping on a GPX750 pretty much means changing the fork oil. Then the compression damping gets changed as well whether you like it or not.
In theory I could remove the ESCS electric anti-dive gadget and fabricate an alloy plate with an adjustment screw between the two oil ports to provide some limited compression damping adjustment. That means only one fork leg gets compression damping adjustment which may require uprating the stock flimsy sheet alloy "fork brace" which feels more cosmetic than functional. Yeah, I have some ideas for that, too.

Oh golly wouldn't it be nice to have the adjustability of modern bikes. So many ways now to get the suspension just right, but that also means (being pessimistic) so many ways to get it all horribly wrong.

[Smitty]

... I found it similar on mine

new stiffer springs + 15w fork oil
and a 8mm higher level made for a
vast improvement


ps
u kept the fork air adjusters?

[Mister_T]

new stiffer springs + 15w fork oil

What springs did you use? I see Wemoto Aus lists Hagon and Wirth springs.

and a 8mm higher level made for a vast improvement

Retaining the oil height difference left and right (per FSM)?
I assume the extra oil height in the right hand fork (the one with the ESCS) is to provide a bit more rising rate air springing to compensate a bit for the extra mass of the ESCS unit.

Edit add: Looks like I got the oil heights mixed up. Checking the German FSM, the left fork oil should be 120 +/- 2mm from the top of the fork. The right fork should have the oil 149 +/- 2mm from the top. Out of all the bikes I've had, this is the only one that specs different oil heights.

ps u kept the fork air adjusters?

??? I didn't know the GPX front end had that (although my RC17 does).