GS650G Katana , Japanese home market model I think 1982.

[LeT]

Having just commented on a refresh fostered by lockdown measures, I thought I would begin my own thread. I'm going through a Japanese home market GS650G Katana. It seems to be in a specification that is between X and Z model years, as we know them in the UK. I bought it as an import from a London dealer Bat back in 1989. I've had this bike in its sorry state for an embarrassingly long time. I rode it everywhere in the early 1990s for holidays and work, including finally commuting weekly across the Pennines between York and Manchester. It 'broke' coming off the M62 at a junction for Manchester. Loud rattling noise from the engine. I nursed it home and then parked out up ready for diagnosis but ... life got in the way: lack of time, space, tools then other projects, children. I'm sure you know the story. Maybe the only slightly unusual thing is that I never got rid of the bike, despite many house/garage moves.

Finally, lock down had given me time and other projects got done. So I'm having a go.

[GregT]

They go quite well. We got quite a few here in NZ as grey imports. They were a favorite in Japan to have an aftermarket pipe fitted - usually a 4:1. Also usually without sorting the jetting....

Red and yellow - or silver and black. A lot on them interchanges with other 650G models. Skinny rims though...

There's probably some cosmetic bits in NZ wreckers yards. Google is your friend.

[2BRacing]

Would like to see a photo of your bike to see how it compares to the version we got here in South Africa.

My older brother bought this one new in 1981 and sold it to my son last year. It only has 10,000 km on the clock! The fairing was an aftermarket addition.

[LeT]

The differences I know about are an 80kmph warning light with Japanese characters in the centre console, no oil cooler and ANDF forks.
Here s pic of the photos.app.goo.gl/A1XrEP2YoKAwEFW58Japanese centre console

[LeT]

Funnily enough, my bike had an aftermarket fairing too. It wasn't really stored to what I wanted at the time (weather protection) and the lights for got by a stone on the M62, cracking a lens. It's coming off as part of the refurb anyway.

https://photos.app.goo.gl/ezzw8P6C37uCzgcF8

I haven't got the hang of photos yet. That should be a link to Google photos.

[LeT]

Would like to see a photo of your bike to see how it compares to the version we got here in South Africa.

My older brother bought this one new in 1981 and sold it to my son last year. It only has 10,000 km on the clock!

Well I will post photos but they won't help much for that comparison. Your son's bike is s beauty, mine is a beast with 87500km under her skinny wheels. But I want to make her purr again, like a contented Kat should.

[LeT]

Here are some pics:

https://photos.app.goo.gl/gCrQT7grZ2ZsiiwLA

Wash off and initial dismantling. The seat lock was seized so I had to wallop the linkage from under the rear wheel arch to get it off. I found a bonus in the tool tray: a spare key on s katana key fob!

The petrol cap was seized on too but that responded to WD-40 soaking for a week and progressive wiggling of the key whilst pressing down on the cap to relieve spring pressure. Looks surprisingly good inside. 1990s petrol did not contain ethanol in the UK.

[LeT]

I came across a very nice French site with comparisons between model years and markets http://katana.france.pagesperso-orange.fr/650CM3.html. It has a gif switching from variant to variant. I'll try to embed it here:

[LeT]

Getting to the bottom of the engine rattle

I've been beavering away at the engine.


I'd read a buyer's guide review of the GS650Gs some time ago and it says cam chain guides can fail so I assumed that was my problem. I put two and two together and decided, "ah ha! That's my rattle then."

The slipper side is at the front of the engine and can be removed after the camshafts have been taken out. However the tensioner blade is at the back and clamped under the head so would be much more work to sort out. Further more, I have a problem with my exhaust, the header fasteners seized on. That's normal, I know, from having read around plenty on GSResources now. But mine are a bit different in that they are stainless bolts I used to replace the originals years ago and to have seized into the exhaust collars.

IMG_20200516_181604 by LeT544, on Flickr


So I was mentally committed to doing a top end year down, after easing out those bolts. But I wanted to go careful to save the exhaust collars. Much soaking, prying and tapping seemed to have little effect. Ok. So let's see what the cams situation actually is.

Next problem, one of the M5 screws on the pickup cover is seized.

IMG_20200521_151138 by LeT544, on Flickr


I drilled it out very carefully to discover/remember doing a repair here 30 years ago. So I'll be exercising JB Weld soon.

So I could get a spanner on the crank to turn the engine to TDC. Cam cover off now. I went VERY careful with those bolts, I can tell you. Every one, quarter turn tighter then half turn loose, all around, only then start removing on a criss cross pattern. The bike is starting to like me again!

IMG_20200521_172733 by LeT544, on Flickr

The cams look ok and the cam chain had not slipped - HOORAY - because there are still 20 links between the 2 and 3 reference marks on the can sprockets.



So next to get the cams out properly, after removing the cam tensioner body. Ah, yes, that means getting the carbs off...

Actually, it wasn't too horrible. I helped myself by pulling the loom right back through the frames and removing the coils for max access and minimum risks of dropping much into the engine once the can cover was off. Plenty of WD-40 around the rubbers as I rocked the bodies backwards, plus a piece of wood as a pry bar. Probably 15m x 25mm, about 12" long (this is an inclusive measurement reference )


I then had a good memory, of replacing the inlet rubbers so they are only 30 years old, rather than 40 years old.

IMG_20200521_175947 by LeT544, on Flickr

So the cam tensioner could come off.

[steve murdoch]

An example of "cam walk" that might be the source of your top end rattle.

https://www.youtube.com/watch?v=GZtAZZVCpxs

[LeT]

Thanks Steve. Very useful video. I had that with my GS425 - really loud at tickover but disappeared when the revs got above about 3k and never an issue whilst riding. I was sure it was a serious problem when I first heard it - small ends or something. But then on investigation I could see where the cams had been banging against the sides of the cam bearing caps. They seemed to self-centre when the engine span up so I rode it more than 50,000 miles like that, no problem. And then holed a piston ... but that's another story for another time.

[LeT]

So I've made some more progress on the rattle. Camchain tensioner off, no prob with carbs out of the way. The cam bearing caps came off OK, a little too easily as I was about to discover. But the bearing surfaces look ok.
[IMG]IMG_20200609_094458 by LeT544, on Flickr[/IMG]

So, cams out I could get at what I think was the problem. Except it wasn't -the tensioner blades were all intact.
[IMG]IMG_20200609_093933 by LeT544, on Flickr[/IMG]

Ok, so tried to measure camchain for wear. Very hard. The manual gives a max length for 20 links but the frame got in the way for my ruler and, ok, my eyes aren't what they once were. It seemed loose by feel but following the manual was about right on the limit. Except the manual illustrates measuring between 20 pins, not links. Hmm. Then I remembered the tensioner and looked at my own pic, in the post above. No movement left. It was at full extension. So I went ahead and replaced the cam chain, splitting a new DID 120 link chain with my Dremel and wiring it to the old one to pull through.
[IMG]IMG_20200608_142929 by LeT544, on Flickr[/IMG]

[IMG]IMG_20200608_172517 by LeT544, on Flickr[/IMG]


I wrapped everything down with rags to minimise risk of abrasive particles entering the engine and the Dremmel gives his control so all good. New Japanese soft link to join up the ends of the DID, pins secured by mushrooming the ends with a drive chain took, the trickiest part of the operation because it was way too big and clumsy really. But it sure is secure.