1981 cbx project

Hey, what projects are you planning or preparing for? CBX, other motos, workshop, WHATEVAH!
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BakkerCBX
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1981 cbx project

Post by BakkerCBX »

Last summer I bought myself a projectbike, a 1981 cbx 'prolink'.
The former owner had imported this bike from Switzerland in an unknown state. He had the engine touched up and rebuild the carbs.
He was planning on building a sort of 'cafe racer', so a few parts were not there anymore...
Image
The engine didn't run. only tested the compression, which was between 100 and 120 PSI cold. It is fitted with a new starter motor and the upgraded Kawasaki dynamo.

First things to tackle:
complete brake rebuild (ss brake lines and fresh caliper seals) rear brake master cylinder was completely corroded so i used a GSXR 1000 07/08.
chain kit
new tires (old ones were from the other century)
original fairing

First reason for the bike not running/starting were the electronics. The wiring was stil original, but a new ignition switch was needed. This isn't a straight forward swap! Many thanks for this topic: viewtopic.php?f=21&t=11720
Another reason was the carbs. I serviced them with help of the booklet from Mike Nixon + the rebuild kit from Randakks. A few minor things were wrong + not working: the idle jet rubber plugs were installed, but only the 1979 models use it and the accelerator pump passages were clogged.
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Before synchronizing I checked the valve clearances, then i found a broken camchain tensioner... The cam chain probably skipped a tooth, cranking the engine was hard. It took a while before I had a replacement (they are expensive).
Image

To install the new tensioner the head has to come off. Good time to observe the valves and cylinders. What is your opinion about the boring, piston and valves from what you can see?
Image
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Well the bike start at this moment, but the clutch doesn't work. For what I believe there are 3 types of clutches? 6-pin clutch (1978/79), 9-pin clutch (1980) and the prolink (1981/82). I don't know the exact differences, but one is the length of the outer clutch guide. At some point someone swapped the prolink clutch for a 9-pin clutch but not the clutch guide. With the new guide the clutch works, it only rattles very much.

All assembled and complete this is how the bike looks at the moment:
Image
My to do list for the moment:
- New oil hose (leek from the top near the cooler)
- Clutch rattle fix
- Suspension (progressive springs for the front and a new rear shock)
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Larry Zimmer
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Re: 1981 cbx project

Post by Larry Zimmer »

Bike looks excellent. Nice post. Thanks. Regarding the engine components, I'll have the experts comment. Have fun this Summer.
Larry Zimmer
cbxlarry@sbcglobal.net

BakkerCBX
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Re: 1981 cbx project

Post by BakkerCBX »

Larry Zimmer wrote:
Sun Apr 18, 2021 11:27 am
Bike looks excellent. Nice post. Thanks. Regarding the engine components, I'll have the experts comment. Have fun this Summer.
Thanks Larry, you to! The bike still needs a bit of work, but all is there.

EMS
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Re: 1981 cbx project

Post by EMS »

Hello Tristan!

Welcome t the ICOA forum. several of your pictures do not show up on my PC. May be a problem on my end.
The difference between the Prolink clutches and the 79/80 is more significant.
The Prolink outer clutch basket has torsion springs instead of rubber dampers. You should try to get an original Prolink clutch.
The only other way to get rid of the rattle will be to replace the rubber dampers, which involves opening the basket and riveting it back together.
Not really rocket science but elaborate.
I am a little confused about the "rubber plugs" in the carbs. You are correct, they were only used in the 3-jet 1979 version, but make sure, you have the correct carbs. They should be stamped VB65A... on the outside of the No 1 carb.

The markings on the cylinder wall in one of the pictures do concern me a little. I would try to hone this. Did you have a chance to look at the pistion in there?

BakkerCBX
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Re: 1981 cbx project

Post by BakkerCBX »

EMS wrote:
Mon Apr 19, 2021 9:56 am
Hello Tristan!

Welcome t the ICOA forum. several of your pictures do not show up on my PC. May be a problem on my end.
The difference between the Prolink clutches and the 79/80 is more significant.
The Prolink outer clutch basket has torsion springs instead of rubber dampers. You should try to get an original Prolink clutch.
The only other way to get rid of the rattle will be to replace the rubber dampers, which involves opening the basket and riveting it back together.
Not really rocket science but elaborate.
I am a little confused about the "rubber plugs" in the carbs. You are correct, they were only used in the 3-jet 1979 version, but make sure, you have the correct carbs. They should be stamped VB65A... on the outside of the No 1 carb.

The markings on the cylinder wall in one of the pictures do concern me a little. I would try to hone this. Did you have a chance to look at the pistion in there?
Hi EMS,
Hmm, I load the pictures and put a line in the text. but it only shows the pictures at the and of the post.
I've seen the clutch rubber dampers on the internet. Is the modification done by only a drill press or is a milling machine needed?
The carbs are indeed the VB65A, and now everthing is according to the schematics.

daves79x
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Re: 1981 cbx project

Post by daves79x »

Tristan - you need to get the clutch rubber kit from Six Center. Obviously, you need the 9 rubber kit. The instructions are with them and are very clear. Just know that you MUST file the heads down on the new screws supplied (the instructions clearly state that, but guys don't and have to take it apart again). They will hit the oil splash guard if you don't.

Dave

BakkerCBX
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Re: 1981 cbx project

Post by BakkerCBX »

The bike is turning 40 in June. The goal is to get it up and running by then.
Last week I did a test ride for 10km, but not very impressed yet.
There were multiple oil leaks:
- The oil lines (which will be restored by Tevan)
- Valve cover gasket is doesn't seal very well.
- The alternator conversion which is installed leaks from the mounting holes
- B cam chain tensioner bolt sips oil (maybe from the valve cover gasket)

Handling wise I have installed a new Hagon shock and planning to replace the front springs to progessive springs.

Also the carbs needs to by synchronised, I have tried but it seems impossible to reach the synch adjustment bolts.
I have the carb synch wrench, but there's to little space...

Some parts ordered (gasket set, clutch dampers and inlet rubbers):
(found a great video about replacing the clutch dampers: https://www.youtube.com/watch?v=9dhRV5TajjQ)
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BakkerCBX
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Re: 1981 cbx project

Post by BakkerCBX »

The clutch rubber replacement is done, nice and relatively small project to do.
Currently I am rebuilding the front forks, great time to replace a new valve cover gasket.
Space is thight, so the gasket installation was tricky.
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daves79x
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Re: 1981 cbx project

Post by daves79x »

If you 'sag' the engine by loosening the upper rear engine mount bolt (don't remove it), and all the triangles are removed the engine will sag enough to make the job easier. Full tilt is even better. If the exhaust is on, you should loosen the rear mount bolts too.

Dave

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