1976 XS650-C Project From Ireland

Hi all, update time again, some good, some bad, thats the way she goes but we will start off with the good stuff!!

As per the advice above I removed the advance rod to clean and lubricate it, it was very clean when I disassembled it, but I put a dab of moly grease on it just to be sure.

CAnjNCml.jpg


I did notice that on the advance unit itself one of the springs had stretched and thus was now too long to fit over the post, so it was just sitting there doing nothing. I must see if I can get a replacement somewhere. The single remaining spring is doing a job of keeping both bob weights tensioned but it’s obviously not ideal.

jGMgsPKl.jpg


1711479357100.png


I cleaned everything up and during the re-installation of the rod I realized there was some adjustment of the timing in the form of slots cut into the backing plate of the rotor for the electronic ignition.

q5oVFcil.jpg


After a couple of searches on this site it would appear that turning this backing plate counter clockwise would retard the ignition slightly, so I turned it as far as it would go, put on some heavy boots and gave her a kick.

The first kick she fired a couple of times, she wanted to start, so for the second kick I gave it a touch of throttle and brooom up she went, just beautiful!! well apart from a few backfires in the RHS cylinder, but even so, we were running, and I was very very happy!!

Then I wheeled her outside into the open air, so I wouldn’t poison myself on the fumes in the garage. I began to try and set the idle to keep her ticking over on her own, and so I could then begin to diagnose the backfire, this is when the bad things started to happen............
 
When installing the new loom, I had not bolted the rectifier or starter solenoid back into their respective places as I was checking them with the multimeter for power etc. so they were dangling on the RHS side of the bike near the kickstart,

After moving the bike outside I started her, and set the idle, the RHS cylinder had a backfire so I switched off the bike and went back into the garage (where all my tools were) to grab some carby cleaner and check for an air leak in the carb manifold. I returned, switched on the ignition and gave her a kick, but in doing so managed to knock the rectifier out of its connector and onto the ground, so I switched off the ignition and went to reattach it.

The instant the rectifier was reattached, smoke immediately started rising from the wiring loom, I instinctively grabbed the ignition to switch it off but realized obviously that it was already switched off, so now I’m looking at the bike, there’s smoke rising, the battery is clearly discharging itself into the loom, and I’m outside with no tools. So I run back into the garage grab a screwdriver and disconnect the battery, the smoke stops........

After the initial relief there comes the major downer that my brand new (expensive) wiring loom is now melted all over my dad’s bike!! I disconnect everything, pull the loom off and lay it out on the bench, this is what I see.

J6OnAdql.jpg


I removed all of the insulating tape to get a better picture of the damage and it wasn’t as bad as first feared, the ground wire took the brunt of the heat and was melted from the regulator all the way up to where it joins the rest of the ground wires near the coils, the power wire was melted from the battery, into the regulator and up as far as the starter solenoid.

The damage was really limited to these two wires, so I just pulled them out and replaced them, then crimped on some new connectors.

K7AWG48l.jpg


2cxEayUl.jpg


I had a good look at the fuse wondering why it didn’t do its job and after opening the fuse holder the answer stared me in the face......there was a screw acting as the fuse...... I'm really pissed about this, I know I should have checked it first.

Anyway, I reinstalled the harness, bolted everything back where it should be, bought a new blade type fuse holder and switched on the ignition, thankfully no smoke, but I also now have no power coming from the LHS coil..........looks like I need a new coil.

Hopefully I should be back to where I was before the incident this time next week, there’s a new coil in the post and a guy on the Facebook group that recently fitted a Boyer is sending me his old advance springs.

So that's my story so far, hope you have enjoyed the drama!!
 
Last edited:
Hey Beano, I moved to Canada in 72 from Glengormley,Ireland,was a Triumph guy for many years.
Dad had a Norton 500 single.I now have a 77 xs650 with decals from a 75 as I think they looked sweet!
Hard to keep the old girl clean with all the rain eh! I luv this old bike and it like a time warp every time
im on it. Lots of knowledge on here.It will be better than original when your done with it!
 
Beano, great photos of the bike! I would never have imagined just how much a bike can change with time. Did your Father own this from new? Good move getting a new harness. By the time you mess with and clean up an old harness you end up wishing you had bought a new one. The only issue is that sometimes the new harness has some little variations that can get frustrating to sort. But all your connectors will be shiny, new and trouble free..

@Paul Sutton Thank you, he was the second owner, i believe he bought the bike in 1979. Yes i thought it would be a good move too........until it went on fire.

Hey Beano, I moved to Canada in 72 from Glengormley,Ireland,was a Triumph guy for many years.
Dad had a Norton 500 single.I now have a 77 xs650 with decals from a 75 as I think they looked sweet!
Hard to keep the old girl clean with all the rain eh! I luv this old bike and it like a time warp every time
im on it. Lots of knowledge on here.It will be better than original when your done with it!

@XS650D Canada is a long way from Antrim!! difficult times back then i believe, glad it all worked out for you. im hoping to turn the bike into something the old man would be proud of, this site is an absolute treasure trove of information, ive often found myself getting lost for hours in various threads, its fantastic!!.


@TwoManyXS1Bs thanks for that info, very much appreciated.
 
Awwww Beano - what a drag. I can just imagine the panic you felt and the heartburn on seeing that smoke.

Dammit - I’m comin’ over to help. I’ll just take me a few weeks to get the dough together and clear off the rest of my life so that I can get away.

All seriousness aside, it sounds like you’ve got it in hand.

Cheers and keep at it!

Pete
 
Still waiting on the postman, so I hooked up the electric starter to make life a small bit easier for when the coils finally do show up, she seems to spin ok, just makes a horrible grumbling noise when engaged for more than a second or two.

Apparently that's normal and hopefully should save some wear and tear on the ole knees!! Plus I now have the added advantage of being able to start the bike when it's on the workbench etc.
 
Last edited:
Finally another update!

I’m only managing to get a few hours here and there with the bike these days unfortunately, but things are being done…………just slowly. Since the last update I've installed the new coil, then after attaching the battery a big spark from the fuse caught my eye.

This indicated to me that there was a large current draw coming from before the ignition switch, and a trace of the red wire from the battery led to the rectifier…………

I'm now sure that this was the culprit for the previous incident.

However, just to be 100% I disconnected both the regulator and the rectifier, and switched on the ignition, all seems good, thumb the starter and she fires right up.

I pulled the rectifier and checked it with the multimeter which confirmed that the diodes were passing current in both directions through the three white wires, and luckily after a rummage through my box of spares I found another one which tested good.

So, I plug it in and the fuse holds strong, but as soon as I switch on the ignition the fuse pops again. I did a few searches on this website which lead me to curly’s guide and a recommendation to disconnect the brushes, which I did and when I switched on the ignition it didn’t blow the fuse.

According to the guide this strongly indicates a regulator fault and lists more steps to confirm it.

The next test says to check for voltage at the green wire to the brush, so I do that and get a big fat 0, I follow the wires back to the regulator and check them for voltage, there’s 12v going into the regulator on the brown wire but only 0.03v leaving on the green. So I rip out the regulator and it looks pretty toast. the contacts are all bent out of whack and theres no spring left in the metal.

MegTd60l.jpg


XSWhj0xl.jpg


I’ve decided I’m going to take the advice given in some of the other build threads I've been following and have ordered myself a brand new 3 phase rectifier and a new VR115 voltage regulator as well so that should solve at least that part of the problem once and for all.

The next thing to do was to test the alternator, so again using curly’s methods I went through the steps. As the brushes were already disconnected I measured them and they are 12mm so that’s fine.

Next up is the slap test which the bike failed, it didn’t create any magnetic field whatsoever.

Then it’s the stator test and the resistance measured between each combination of wires was 0.7ohms, and infinity between each wire and ground. unplugging the yellow wire to the safety relay made no difference. This value seems high.

For the slip ring test the resistance was 9 ohms between the rings and infinity between the rings and ground, this value seems way too high.

So what do ye guys think?? I know the regulator is stuffed and hopefully will have that addressed in the next week or so, but do ye think the rotor is kaput too?? I suppose its one more thing to check off the “to do” list for the recommissioning anyway.
 
Last edited:
I think the slap test only works when the rotor is powered, and if you have the brushes removed, it wouldn't be. I think when testing the white wires from the stater, the actual reading you get isn't as important as them all being the same, which yours are. Yes, 9 ohms between the rotor slip rings is high. Make sure they're clean. I got very high readings at first (up near 15 ohms) on the one I'm fixing up but the slip rings were filthy (black actually) and that was the cause. Cleaned up, they read the proper 5 or 6 ohms.
 
Hi all, some more updates to be had, and of course more advice sought!!

The new rectifier and VR-115 regulator arrived and were installed, I will fabricate a proper bracket for it at a later stage in the build.

I also cleaned the slip rings with some carb cleaner till they were shiny and squeaky clean, unfortunately it made little difference as the resistance is still in the high 9 ohm range and the battery is still not charging...........its looking likely that I may have to start saving up for a new rotor, oh well.


lHUPObrl.jpg


ROsEtM7l.jpg


Not to dwell too much on the electrical side of things I decided to check the valve clearances, and they were all spot on perfect. Dad had clearly already set them and there is evidence of a brand new timing chain having been fitted (I found an old chain placed in the new chains wrapper with the date sticker saying 2005) However I did notice some pitting on a couple of the valve adjustment screws and am wondering if they may need replacement??


tZLpF47l.jpg


GgToVNFl.jpg



So that just leaves us with the running issues.

When I initially got the bike fired up it was clear that there was work to be done regarding the bike running properly, and after already getting spark and checking the valve clearances/compression it pretty much leaves us with the fuel system, with the right cylinder suffering much more badly than the left.

The right cylinder would backfire upon startup and then cut out altogether and a dead slide was eventually diagnosed. I pushed up the slide and blocked the top port to see if the diaphragm was holding vacuum and it dropped like a stone.

So once again it was out with the carbs, and off with the carb tops.......... how did I miss this the first time round???

tPlkt9Pl.jpg


diPvSzjl.jpg


And the cause?? Well there was an impression in the top surface of the carb that had a burr at each side, which i reckon pinched the diaphragm causing the pin hole.

Z0MqGE7l.jpg


O6DD0xXl.jpg




So I dressed it up as best I could with some sandpaper. Unfortunately I don't seem to have a spare diaphragm in my box of spares, so I just plugged the hole with some epoxy as a temporary cure and luckily enough it passed the slide drop test, so back into the bike they went and a warm fuzzy feeling was felt as the right hand exhaust pipe warmed up for the first time!!

I'm very happy that things are moving along but there's always something with these old bikes and the next problem to resolve is air leaks...........everywhere.

Spray carb cleaner on the throttle shafts, bike revs up.
intake manifold, bike revs up.
choke chamber gasket.....yup you guessed it bike revs up.

So before I go ahead and order all of the above, does anyone know if there are there any other o-rings etc that I should change while I'm at it?? I might as well order them all together and save on the postage!!
 
Last edited:
Last edited:
I have used genuine VW valve adjuster screws: 8mm tappet/valve adjuster screw for 1200cc to 1600cc air cooled engines.

Be warned, there are lots of poor quality VW screws for sale on Ebay so I stress the "Genuine" aspect. The simple test is the screw should have a polished domed end that contacts the valve. It will not necessarily have a mirror polished finish, but will be pretty good. A fine file should just slide off the polished end if it is hardened.

I bought some screws from Machine 7 at a bargain price of £4.50 each.The ends were not polished but blackened and more conical than domed. A file cut into them so I returned them. I have contacted my original source to see if the genuine screws are still available from him and will let you know.

Virago screws are not all the same size. The XV535 screw is too small i.e. 6mm. The XV750, XV1000 and XV1100 will fit (Part 4X7-12159-00-00). The Virago screws have an Allen key head which is a lot easier when setting the gaps compared to the original XS screws. The VW screw has a slotted head and is better than the XS but not as easy as the Virago to adjust

Check your local VW Dealer for a price. I would expect £6 - 10 each. Maybe consider XT500 flat ball adjusters, but I am not sure there is much feedback on their use in the XS650:

https://www.ebay.co.uk/itm/XT-TT500...h=item48976ce715:g:LoIAAOSw-0xYd3uR:rk:1:pf:0

If you have trouble getting new screws then you can aways post the old ones to me and I will regrind them for free if the damage is not too extreme.
 
Thanks everyone for the quick reply's!!

The elephant foot adjusters are an upgrade that is on my radar but I will probably wait until it needs some top end work before I go ahead with it.

@Paul Sutton thanks for your kind offer, I searched using your suggested part number for the virago screws and found them for £5.82 each here:

https://www.ajsutton.co.uk/spares/partimage.asp?gpn=4X7121590000&uid=427526262

I thought it was a very reasonable price so I've ordered 4 of them as well as the throttle seals and carb gaskets so should have them sometime next week fingers crossed.

My brother said he would make me a rotor pulling tool on the lathe, so I'm awaiting that too........

I cant really think of anything else that I can start on the bike until these parts arrive which kinda sucks because I'm on 2 weeks leave at the moment and have nothing else planned, oh well!!
 
Last edited:
My original source of genuine VW screws has dried up. Apparently they are hard to get now. You got a good price on the genuine Yamaha parts. Good luck with the build.
 
But new stock style screws don't address the underlying issue - a poor design. They will eventually wear and go to shit just like your originals did.
 
But new stock style screws don't address the underlying issue - a poor design. They will eventually wear and go to shit just like your originals did.

I have considered this and it is an upgrade that I plan to do in the future, but two factors swung it towards the virago adjusters for me at least.

1. The replacement parts are dirt cheap and the replacement process is quite easy.
2. Even though I know the design is poor, at the price they're going for, (and because they're so easy to replace) I can afford to treat them as consumables and change them out every couple of years as part of a service regime.

To me its just not worth the effort right now, I will definitely consider it come top end rebuild time though.

Please don't take this as me disregarding anyone's advice, I really do appreciate the advice, especially from senior members like yourself, that's why I'm here after all.

I'd like to think I'm not one of those members (that we all see plenty of), that willfully disregards the informed advice of senior members. Believe me its all taken on board, there are many ways to skin a cat....
 
Last edited:
No problem, just as long as you realize you're just changing band-aides here, which you seem to.
 
Presents have arrived, thank you Mr Postman.


NDlmKmYl.jpg


qe7EOQRl.jpg



I decided to start work on the throttle seals first as I’m really interested to see if it solves my running problems, so I pull them out and bring them to the workbench.

First up, strip em:


5LQYff7l.jpg



Then it was time to remove the butterfly valves, the screws holding the butterfly on the left side carb have clearly been out before and they came out no problem at all.


b6YNzcWl.jpg


9Nx1VEAl.jpg



However the screws in the right hand carb were still staked in place, it was no big deal though, less than 5 mins with a file and they screwed right out.


eGNETnrl.jpg



A pic of one of the offending seals.


F8iTnCjl.jpg
 
Last edited:
Then it was bath time for the carbs.


fnGF5QAl.jpg



Reassembly of the shafts.


SIchaJNl.jpg


ZfNzvzul.jpg



I took the opportunity to replace the o-rings on the main jet while they were out. The old ones were squashed and well past it.


IrP4MqTl.jpg



Reassembled the floats and float needles.


f00Ofrql.jpg



Set the float heights to spec.


ovySt4tl.jpg



Reassembled the choke chambers.


0kgzqzol.jpg



And done!!


uYQhnKGl.jpg
 
Last edited:
Back
Top