Friday, 11 October 2013

Evan's GPZ

Evan's GPZ was back in the workshop yesterday.

Evan's GPZ


Since it was last here, Evan's fitted a new USD front end off a Yamaha and a wider rear wheel off a Kawasaki. And it's gradually turning matte black...

One of the difficulties of working on a bike like this is getting all the various parts to work together. It's a subtle thing - In the hurry to get things finished, getting them to work well is often left 'til later. So that's what we were about yesterday.

One of the issues was that left front fork was leaking - not from the seal as might be expected, but from the joint between the chromed steel slider and the alloy casting at the bottom. We disassembled the whole thing and cleaned off all the old Loctite, replaced the fork seal and reassembled it again using PTFE tape. It appears to be okay so far, but the bike hasn't been ridden yet so it's possible the problem will resurface.

When Evan replaced the rear wheel, he had to use a dished front sprocket in order to get the chain alignment right. However, the sprocket didn't have any way to lock the sprocket bolt and stop it from coming loose. This is obviously not ideal...

We thought about various ways to fit a locking mechanism before deciding that the simplest way would be to drill both the bolt and the sprocket and lockwire them.

Drilling the bolt was straightforward, but drilling the surface-hardened sprocket was impossible! The 3mm cobalt drill bit barely scratched it! After another bit of thinking, I decided to grind the surface of the sprocket and then drill it. This worked well and I was feeling pretty happy with myself as the drill bit cut easily through the sprocket. Then it hit the surface hardening on the other side and that was the end of that!

Every day's a school-day apparently...

After another bit of thinking I just welded a bent washer onto the face of the sprocket and that worked fine.

Evan's GPZ
Drilling the sprocket bolt with a 3mm HSS drill bit was straightforward.


Evan's GPZ
After a failed attempt to drill the surface-hardened sprocket, another solution was devised. 


Evan's GPZ
It's not very pretty, but it works!


The last issue we looked at was the bell crank that sits on the end of the gear-shift shaft. Somewhere along the line this had been welded up. It's not really ideal - it should be a bit longer and should have a dog-leg in it so as not to foul the side-stand bracket. I'd like to take a look at this again at some point in the future, but yesterday's problem was a bit simpler. The threads were stripped so it needed a Helicoil.

Evan's GPZ
The bottom of the bell-crank had a blob of weld over the bore. The bolt was hitting this before the head of the bolt could seat, stripping the threads. The bell crank was clearanced with a grinder.


Evan's GPZ
The bore was enlarged to accept the Helicoil tap.


Evan's GPZ
The bore was then threaded with an M6 Helicoil tap.


Evan's GPZ
The Helicoil was inserted from the top and screwed down into the lower part of the clamp.


It was a pleasant way to spend the evening and I think Evan was pleased with the progress.


Evan's GPZ

Evan's GPZ






#KawasakiGPZ #Mercenary #MercenaryGarage

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