Uk GS750 project

[Turbell]

Hello from rainy England.
Short intro, GSXR750L0 owner, lots of bikes previous, fancied something comfy and retro so I looked at quite a few US import CB750 but they were way too much for something I wanted to do clean and tidy up job on.
A trade contact suggested a GS750 as a better option, so I had a search about and found I could buy a decent GS for the same money as a CB wreck.
I ended up buying a '78 GS750 that was imported from the US in '96 and had only done 50 miles since '06 out of a total of 31k.
It was in far better condition than many UK bikes I have seen half its age! But it had been a victim of the weekend frame brush painter and the reason it had done so little mileage was due to the fact it hadn't run properly for years.
Carb rebuild later and I have got it firing on all four, but it needs a final set up I think to get the best out of it.
I believe I have a charging problem as I am only getting 12.5 volts on idle and it doesn't rise much as revs increase, also adding load drops it below 12.
I have tested the rectifier and it is open circuit both ways, so I think that is cooked. I have searched on here for rectifier/charging help but some links don't seem to work, but from what I understand the Polaris R/R is the way to go? I'm not being lazy but there is a lot of info on here and I am trying to sift out what I need to know, I want a decent set up I can rely on as I do want to use the bike not sit and look at it!
What's the best way to put pics up on this site? Do you use photobucket ? etc
Thanks for reading, Ryan

 

[londonboards]

Ryan - Welcome to another Brit.

Yes use Photobucket or Google photos and cut and paste the link after clicking the little picture frame icon in the editing box.

Pretty much half of this forum is about GS electrical/charging issues. You are right - there is a hell of a lot to wade through. Start with the electrical system health check which you will find here: GS Electric Health Check.

You will almost certainly need a new reg/rect but check the condition of the stator too for good charging or any shorts.

Next thing is a big wiring overhaul. There needs to be some extra earths installed and all terminals and connectors need cleaning. You can in addition, do the starter relay mod and cut out the charging circuit that goes to the headlamp shell. Check all wiring for burns and worn areas.

This is going to take time but it's worth it.

See what happens if you don't: Rectifying an Electrical Problem in Italy.

Join us on the UK GS Owner Facebook page if you want to find someone local to you. See the link in my signature.

There has never been a better time to be a GS owner.

Greetings

 

[Guest]

Just replaced my R/R with the polaris unit feels great to have a healthy charging system.

 

[Turbell]

Did the quick electrical health check about a week ago, but haven't had time to post due to other projects, but as I said the rectifier is open circuit all ways.
Here's my results,
Ignition off = 12.13V
Ignition on = 12.13V
Idle =11.98V
2500rpm = 12.60V
5000rpm =13.40V
back to off=12.30V
I've done the common earth mod ,and obviously need a new rectifier, would this explain the battery being very gassy? as the rectifier turns Ac to Dc so am I charging my battery with AC ? Thus frying it?
Mean anything to anyone?

 

[Wraith]

Frist welcome
Yes this sounds right, the max volts you want is 14.5 at 3-4000 rpm at tick over it shud be about 12.5-13.5v and go up to 14.5v as the rpm incresecs.

 

[uk gs nut]

Turbell, where in UK are you. If your close I could possibly help out.

 

[Turbell]

Thank you for your replies guys, sorry I'm not very quick off the mark, but I have a major long term project in the paintshop as we speak, so I'm afraid the GS is only getting a few hours here and there.
I want to post some pictures and show where I have come from on this and where I have got, but I seem to have little time at the moment but promise to post some pictures up when I get time.
Uk GS, I'm in Dronfield Derbyshire, between Sheffield and Chesterfield. I'm well on the way with the project with only a front end rebuild and the charging issue to sort so hope to have the bike on the road in August/September, we are going to northern France in July to do the WW1 sites and I was threatening to take the GS but I think I will play it safe and take the GSXR !
If I can sort a reasonable priced R/R out, there is only a front tyre to buy so outway will be minimal, a couple of hundred will be all I've spent.
I'm looking forward to riding it and it should make a welcome change to what I am used to. What surprised me was how light it felt after trying a CB750 SOHC, that shocked me how heavy old bikes can feel, but the Gs feels far nicer, never threatens to want to tip over and take you with it.
Thanks for your interest,

 

[Turbell]

Here Ya go photos as bought, mostly original, had a repaint at some time but decent job, shabby in the detail, engine cases streaked by carbs leaking.
Would only run on two maybe three then fourth would chime in, but not for long.
Stunk of petrol and on draining the oil that stunk as well. It had a top end rebuild by someone I turned out to know, so before I bought it I had a word with him and he confirmed it was basically sound but needed time and a bit of money getting it sweet, the PO had run out of patience with it and had a fair bit of trouble with people claiming to know how to get it running as it should but ignoring the basic problem of 37 year old carbs wanting a rebuild with a few new bits and a basic setting up. All they wanted to do was put plugs 'n' caps on it and recommend electronic ignition ( which he had fitted, but wouldn't fix the carbs would it?)
I don't claim to be an expert but at least it runs on all four and revs reasonably cleanly. I'll leave the final set up until it is legal and on the road so I can see how it feels under load and also when it has had a run to clear it out a bit.

 

[Turbell]

When I did finally get it running on all four it was clear although the exhausts were original and sound looking, inside was a different story and on removing the L/H side I could hear a large part of the inside rattling about so i had to cut it were the silencer met with the collector, the large bit below is what came out.....



The smaller bit is what came out of the baffle end, someone had repaired the ends of the cans with braze metal, which was probably fine at the time but the flux used is very corrosive so that had been eating away from the inside, added to that where they didn't use braze they had just pushed exhaust cement in, which was now getting blown out now the engine was actually producing some real pressure.



I made a new piece of baffle from the bit that came out of the collector and welded a flat plate over the end, which was wasn't easy due to the thin plate burning through............





Then drilled through to find the baffle and welded it in.............



Welded the collector back on and there you go, I had to paint the ends black to cover up the repairs, but they cost zero, are quieter than before, but a little fruitier than OE I think and look nice.......

 

[Turbell]

And here's the cases removed and polished, I used a scotch pad last as I don't want mirror bling, more an original satin look.





Rear end stripped and rebuilt.......................



Caliper rebuilt, new braided hose, wheel stripped and polished and repainted in Ford Graphite grey...........



So I am getting there, don't want to do a full nut and bolt job, just make a already sound fairly corrosion free bike look nice from ten feet.
Perhaps if I get on with it I may buy another basket case if I can find one cheap and do a proper vapour blast, replate job....but we'll see!

 

[GSXR7ED]

I'm looking at this thread...I like 750s and I've also been to England. (Feeling pretty good today)


Ed

 

[Guest]

How do neighbour. Welcome to GSR, liking your plans for the 750. Maybe meet up in Matlock on day soon?

 

[Fjbj40]

Looking real good so far.

 

[Guest]

The work you're doing on your GS is motivating me to start on mine.
Keep up the good work and don't spare the pictures.

 

[Turbell]

Thanks for positive comments, makes it worthwhile there is some interest.
The front end is now stripped off, forks rebuilt, wheel refinished just need some new head bearings as slight notching in bottom race. Then just a bit of paint and a repair to the headlight bowl and we are good to go.
The R/R issue is my only sticking point i.e what to go for, the Polaris is not easily available here, is there an alternative and could someone point me towards the headlight connector mod, is this referring to one of the stator outputs going into the main loom as shown on my Haynes manual?
I'm not bad on wiring when I understand what I am trying to achieve, but I am struggling to get my head around what is required........sorry...the stator checks out OK no shorts produces same Ac on all outputs.

 

[Turbell]

I have made the decision to go with the Polaris R/R but its going to have to wait until my finances are in better shape, but never mind I have had a week of new deliveries, a new Avon for the front, new front pads and headbearings.
Here's why I needed new pads................................



Yes that's right nicely greased friction area......god only knows how it had a MOT pass on it.

The front end is now fully stripped carrying on with the theme of doing an area at a time and rattle can painting that part of the frame, I don't want a total strip down as I have other projects on, so if another job comes up on something else I may need to shelve this at any time, so better to keep it mainly whole then nothing gets lost or I start losing interest and it's pushed into boxes and behind things!!!
Forks stripped, polished and re-sealed, again I have only polished them satin, not bright I don't want to go all show glo'............



Front wheel scrubbed back and polished with a scotchpad then masked up ready for paint,....that takes patience.....



But worth it in the end.



Look what I found in the headlight bucket!



Can't be helping my electrical issues, speaking of which, have any brits got guidance on the sidelight issue as there is only high and low on the bars yet I have a sidelight bulb in the headlight unit which looks like it was tee'd into the ignition live, but hard to tell as it all fell apart when I took the 'light shell off.
I could do the same and go with daytime running sidelights using IGN live, but if I feed the rear light it would feed the headlight as well.
I'm not sure where I stand legally on this, i.e what lights I must have for the MOT, so may need to go and see the tester.

 

[Turbell]

With front stripped off I thought I may as well replace the anti theft tab as it had broken off, so I made a new one and welded it on..........



Then a quick rub down, etch and a coat of black on that area and now all the frame was tidy, it's not show standard and it won't stand up to a salty British winter but it's tidy and in keeping with making the bike look nice and original with a touch of patina.........



I also repainted the top and bottom yokes ( triple tree ? ) and fitted new pyramid parts taper bearings, and here's where the fun starts. I trial fitted the yokes so I could get an idea of the position for the anti theft lock tab, and the bearings won't tighten, after much head scratching it appears the top bearing cannot travel down the stem as it is not machined far enough, so the outer races will never pinch into the headstock, just my luck, so off to the machinists today to get the stem turned down a little further down.



Never mind plenty of jobs to get on with, next up tackle the broken headlight bowl, I have some two pack auto repair cement that will do this.

 

[GSXR7ED]

Nice Work

Nice Work

Good morning sir, thanks for the update. It's been a long time since I've heard the term, "MOT". Keep up the good work!

Ed

 

[posplayr]

Did the quick electrical health check about a week ago, but haven't had time to post due to other projects, but as I said the rectifier is open circuit all ways.
Here's my results,
Ignition off = 12.13V
Ignition on = 12.13V
Idle =11.98V
2500rpm = 12.60V
5000rpm =13.40V
back to off=12.30V
I've done the common earth mod ,and obviously need a new rectifier, would this explain the battery being very gassy? as the rectifier turns Ac to Dc so am I charging my battery with AC ? Thus frying it?
Mean anything to anyone?

I just saw these numbers, you mid typed the first or second number they should not be the same. I would guess not charging but an issue on the first to numbers do not want to jump to a conclusion.
sorry it is late looked again and based on the first three numbers I assume the battery is not too bad(in other words despite making not much sense) you are not charging and stator should be checked especially led to ground at. 5k rpm.

 

[Turbell]

Posplayr, you probably right about the first two readings, I can't remember if I wrote them down wrong or typed them wrong, whatever.
I have just re-read the stator test pages and think I may have misinterpreted the stator to ground test, because I am pretty sure I had a reading and If I am right in thinking I should have zero?
I think the best way forward, is when I have built the front end built back up, and have everything connected up in the headlight area, re-do all the tests from the basic health check through to the stator tests and post the results for you to interpret, If you don't mind............probably going to be in for a new stator at this rate !
I have dropped the front stem to be machined so the headstock bearings can be tightened up properly but that is going to be a week, then I can build her back up and have a look what's cookin' and what isn't.
Thanks for your interest and input, Ryan.