GPX750R resurrection

[Mister_T]

Nothing to report on the S100 Engine Brightener front. There is a variety of concoctions on the engine at the moment and to give the S100 a fair test I would really have to hose the engine with Prepsol first. I'll see how the stuff already on the engine lasts with heat before I apply the S100.

[Mister_T]

Something that has bugged me since I first test rode this bike is the sidestand. It works fine as a sidestand but seems to get in the way when it is retracted and I want to shift gears up.

This is as far as I can get this boot under the shift lever:

gpx750r_limited_shifter _clearance_1a.jpg (107 KiB) Viewed 9749 times

A slimmer boot like my much-worn Alpinestars GP Pro can slide under the shifter a bit further, but the sidestand spring still prevents my foot getting right under.

It seems like a bit of a design flaw. All the parts look stock to me.

gpx750r_limited_shifter _clearance_2a.jpg (71.97 KiB) Viewed 9749 times

And from this angle:

gpx750r_limited_shifter _clearance_3a.jpg (90.74 KiB) Viewed 9749 times

I have tried loosening the pivot for the shifter and sliding it up in the slot (after this pic was taken) and it helped a little bit:

gpx750r_limited_shifter _clearance_4a.jpg (130.18 KiB) Viewed 9749 times

and I appreciate that it is nice to be able to fine-tune the height of the shift lever, but really, it is a small compensation for a sidestand that plain gets in the way. When the sidestand is down there is no issue. I have been entertaining thoughts of removing the sidestand and its bracket altogether.
Any design is a compromise in many ways, but I think Kawasaki could have done better here.

[javaman]

I got the problem the other way wuth gpz. I want to lower the shifter but it would hit the exhaust! Very annoying I want to get a torch and bend it

[Mister_T]

Still considering fuel petcock options. The tank hangs over the tap and clearance to the head and carbys is an issue.

GPX750R_fuel_tap1.jpg (172.08 KiB) Viewed 9674 times

[Mister_T]

Did a bit of fiddling with the sidestand on the weekend.
A TeamRC17 Australia colleague suggested taking some play out of the sidestand so the spring would not pull the sidestand sideways as much.
On removing the sidestand, the end did appear splayed a bit:

That is not hard to change with judicious use of a vice:

After:

I modified the spring slightly as well. Not pretty but every little bit counts:

gpx750r_limited_shifter_clearance7.jpg (103.56 KiB) Viewed 9674 times

This boot fits under the shifter pretty reasonably now:

gpx750r_limited_shifter_clearance8.jpg (228.36 KiB) Viewed 9674 times

[GPX Denis]

i'm trying to remove the cooler pipe at the back of the motor there's a leak from the far left o ring but i can't quite get the pipe out so have removed the alternator on the right hand side and trying to remove the starter motor which is on the left side have removed the two bolts that hold the starter motor but it won't budge i'm sure there's only two bolts holding it in tried using a bit of force but don't want to be too heavy handed any help appreciated i should mention the bike is a GPX 750

[Mister_T]

so have removed the alternator on the right hand side and trying to remove the starter motor which is on the left side have removed the two bolts that hold the starter motor but it won't budge

Something is mixed up here. The alternator is accessed on the left hand side. The starter motor is accessed on the right hand side.

As far as I can see, only 2 bolts hold the starter in:

GPX750R_fsm_Starter_motor1.GIF (117.34 KiB) Viewed 9592 times

If it does not want to come out, my guess is the O-ring on the boss that slides into the crankcase is stuck there after about 29 years in one place, and there are probably some oil deposits holding the boss to the crankcase as well:

GPX750R_fsm_Starter_motor2.GIF (30.73 KiB) Viewed 9592 times

[GPX Denis]

Sorry my mistake it is the alternator on the left hand side that is causing the problem

[Mister_T]

Sorry my mistake it is the alternator on the left hand side that is causing the problem

In addition to the 2 socket-headed bolts, there is the bracket to remove as well as the clutch slave cylinder.

gpx750r_a_lh_carb_pissing_alt.jpg (157.03 KiB) Viewed 9561 times

You can see where my bracket has spent some time in relation to its bolts, and how much the alternator has been adjusted from the beginning.
At one stage I did loosen it all off but it did not move so I tightened it all down again and will leave it until I have a new belt to install.

[GPX Denis]

I don't know how i missed that maybe because it wasn't the same as the other two but all good now many thanks for your good advice and patience now just waiting on the cooler pipe to be repaired thankyou again much appreciated Denis

[Mister_T]

In the fun and exciting realm of motorcycle repair and maintenance, not all good deeds go unpunished. I have performed numerous good deeds on the GPX so I knew that statistically at some stage there would be some kind of punishment.

This is the rear sprocket carrier from the subject GPX.

Looks innocent but it harbours a dark design secret.

gpx750r_sprocket_carrier.jpg (236.41 KiB) Viewed 9475 times

In the perfect world of the Factory Shop Manual, special tools are close to hand and things come apart the way they are supposed to.

Replacing the sprocket carrier bearing should simply start by banging on the inner ring of the bearing and the whole bearing should gradually slide out, right? No, not in the real world.
In the real world, the inner ring and the cage and balls come out and the outer ring stays firmly in the sprocket carrier, like this:

[sigh] What can you do?

Normally this should not be a problem as any sensible designer of something that holds a bearing with an interference fit would provide a couple of recesses where a drift rod would catch on the edge of a bearing outer ring (or cup in the case of a tapered roller bearing) and let you tap it out.
Not so the rear sprocket carrier here. In this case, the sprocket carrier has a lip just behind the bearing outer ring.

Closeup:

Somebody has had a go at this in the past. I suspect there was no success and the worn bearing inner ring and cage was whacked back together.

gpx750r_brg_outer_ring_closeup.jpg (231.68 KiB) Viewed 9475 times

Getting the remnant of this bearing out will be umm, "interesting", no thanks to insufficient design.
I was looking forward to trying out new chain and sprockets in combination with a non-wobbly sprocket carrier bearing.
The tight spot on the old chain probably didn't help the cause of the old bearing.

[Smitty]

.. getting the outer race of a bearing out of its housing?
and nowhere to press or punch it out?

get a small VERY sharp cold chisel and hit the inner of the race with it
in about 3 or 4 places around the inner circumference .. putting a groove in the metal
it should fall out/pull out....

[Mister_T]

The ball groove is not as deep as it looks in the pics, which is probably why the inner ring and the cage came out so easily. Judging by the brass cage, the bearing is the factory original.
I think I owned a chisel once but I can't remember where it is.

I'm thinking about a permanent solution even though I don't expect to have to change the bearing again.

Either of these items should make short work of cast aluminium:

gpx750r_cylindrical_burrs.jpg (231.42 KiB) Viewed 9456 times

[javaman]

Having just changed my wheel bearings last week, it would have been a nightmare scenario indeed!

Let us know how you go in solving this

[Mister_T]

The sprocket carrier is modded and the bearing outer ring is out:

Maybe I should have bought the Dremel router table 20 years ago when I bought the Dremel.
Kawasaki really should have provided recesses like I have made.

gpx750r_modded_sprocket_carrier.jpg (122.76 KiB) Viewed 9439 times

The outer ring shows that it is indeed the original, which is a 7006. Online part number cross-references show that this bearing is also used in a number of other Kawasakis.

The following contains moderate geekery. Reader discretion is advised.

Downloadable pdf bearing catalogues from Koyo (OEM supplier in this case) and NSK show that a 7000-series bearing is a "angular contact ball bearing". These are different to the customary "single-row deep groove ball bearing" that we tend to think of when we think of ball bearings, such as our bikes' wheel bearings.

A single-row angular contact ball bearing looks like this:

As fitted to the bike, the rear wheel would be on the left and the swingarm on the right.
A 7006 bearing is 30mm X 55mm X 13mm with a brass ("copper alloy") cage.

Angular_contact_ball_bearing.JPG (64.05 KiB) Viewed 9439 times

Since these bearings have a contact angle (30deg in the case of the 7006), they can sustain significant axial loads in only one direction together with radial loads.

Deep groove ball bearings can sustain axial loads in both directions. I have acquired a deep-groove single row ball bearing of the same dimensions to use in the sprocket carrier, a 6006.

It is interesting how Kawasaki used the 7006 in this application. I wonder what axial load it was expected to tolerate and whether this in in excess of the practical limits of a 6006. Looks like I'll have to find out the hard way.

Kawasaki knew that the inner ring and cage would easily come out of the bearing when struck from behind, particularly if the bearing is worn which is why you would replace it, and yet there was no provision made to simplify the bearing outer ring removal.
Maybe they just want to sell new sprocket carriers.