Erratic Voltmeter readings

[kettle738]

Hi all, I took my first ride on my new to me 860GTE yesterday.....it starts really easily and settles down to a nice idle at about 900rpm when warm and apart from a tiny bit of popping in the silencers seems to run perfectly. This bike has yet to turn 6,000m from new (not necessarily a good thing I know) and almost everything is original.

Unfortunately it wasn't all perfect.....the indicators (turn signals) flash at several times normal speed and the starter button just produces a 'click' . (it did work previously)

I only did about ten miles and when I got home I put my digital meter across the battery terminals in the 20V DC range and it showed a healthy 12.7V, it's a one year old Yuasa and charged perfectly on the optimate with no indications of problems.

As soon as I started it up though the meter went haywire.....figures flashing on and off too quickly to read ...I did catch 18V and 13v and various others as it was flickering crazily, but there was never a steady reading. I've never seen readings like that before.

My first suspicion is the regulator rectifier and it seems there is a direct bolt on substitute from Electrex....but I thought I'd ask first ..... could those bizarre meter readings suggest or mean anything else?

On the seperate subject of turn signals....my bike has the small square block Aprilia indicators with Festoon bulbs......they show 13W, but the turn signal relay is a 40W item.....so surely that would require higher wattage bulbs? As it is, the bulbs are a struggle to buy as the originals seem to be about 39mm long and all available replacements are 44mm long which puts a lot of pressure on the connectors....any suggestions please?

Any suggestions or advice would be much appreciated as I am to electrics as politicians are to straight answers.....Mick.....kettle738.

[Craig in France]

Hi Mick,

Good to hear everything seems to be (basically) ok. (The popping is most likely an air leak somewhere in the exhaust sustem, especially if it's doing it on the overun. Just nip everything up tight. Or you're running a tad lean - check the plugs).

As soon as I started it up though the meter went haywire.....figures flashing on and off too quickly to read ...<snip> could those bizarre meter readings suggest or mean anything else?

Check your connections first, Mick. While it could be the reg/rec, they tend to fail completely rather than go all intermittent on you. That sounds more typical of a dodgy/loose connection.

On the seperate subject of turn signals....my bike has the small square block Aprilia indicators with Festoon bulbs......they show 13W, but the turn signal relay is a 40W item

If I'm reading the parts book and workshop manual correctly, the indicator relay should be rated at 28W for a bike fitted with Aprilia winkers - which, in turn, should have 15W bulbs (but 13 should be ok). 40W was for the US-spec GT and also the GTS which came with flashers with 21W bulbs. So trying changing either the flasher unit, or the 4 bulbs

(Alternatively, if the feston bulbs are really hard to find, you could change the units over for the later CEV indicators. These take a standard bayonet bulb. But it's not an especially cheap option: prices do vary, but they're getting kinda difficult to find for much less than a tenner each. )

HTH

Craig

[kettle738]

Hi Craig.....thank you for that; I followed your advice and checked all the connections to the Reg/Rectifier, and they all seemed fine; nonetheless I crimped each one very slightly to ensure a proper interference fit.

I then took a look at the fuses and cleaned the pointy ends of each one back to bright metal and the retainer posts with a fibreglass pencil until they were also free of any dirt or corrosion.

The battery showed 12.65V on the meter. I started it and if I'm honest I expected no improvement as I hadn't found an obvious fault......but to my great surprise and delight I got sensible and normal charge readings up to 14.2V from memory......superb and thank you.

The indicators still flashed too fast when the engine was revved but given the apparent mis match between the relay and the bulbs perhaps that is to be expected....I've ordered a set of 21W Festoons and we'll see what that does.

The turn signals themselves are these little square chrome jobs......I really like them, but I have noticed they seem to be thin on the ground, not a single one on ebay in the three months I've been looking so I guess I'd better look after them and not over tighten the screws etc.

Thank you for the help, much appreciated............Mick.

[abmartin]

I think that style indicator is almost impossible to find these days although I do have a set from an 860GT I owned years ago.

Bruce

[Craig in France]

Excellent, Mick. I always like easy solutions, me! (I can't remember whether I've said this before, but: don't put too much faith in that fuse box. Those spring retainer posts just love to spread, starting off the corrosion you just found. Also, all the power goes thru the 15 amp fuse. Consequence, if ever you happen to have the headlamp on, an indicator flashing and you then choose to activate the brake - well, you risk having everything stop, including the ignition . DAMHIK).

As Bruce has said, those indicators are indeed rare. I don't remember ever seeing any on eBay (altho', fair to say, I haven't been looking particularly). Look after them well ...

Ciao

Craig

[kettle738]

Thanks Craig,....I took the 860 out again this afternoon and I now have a better understanding of how she runs......starting and idling are still fine, but the popping through the silencers is almost entirely on small to moderate throttle openings.....typical minor load cruising throttle and she pops and bangs a fair bit.

This doesn't seem to happen on large throttle and hardly at all on the overrun. When I got home, she was at full temperature, ticking over easily on the drive, there is no excessive soot in the exhausts....reasonably clean when I stuck a finger up each one......but the exhaust does smell a bit rich. The previous owner will have gone through the carbs, but I'm happy to take a second look just in case.....is there anything unusual for instance in setting the float height? with my old Jap bikes the measurement is taken with the carb held at an angle until the float tang just touches the sprung tip of the float valve without compressing it at all......not upside down with the weight of the float resting on the valve as so many diagrams suggest......is it the same with the Dellortos?

I will happily absorb any advice re carb settings please......I balanced the carbs a few days ago and they balanced beautifully at idle and at 2,500rpm but as said they do seem a bit rich to me.

Mick...............kettle738

[Craig in France]

Is there anything unusual for instance in setting the float height?

Yes/no, Mick. It's not difficult but (as with most things ...), it does need to be done right.

All is explained in the very informative Dell'Orto manual, " A guide to the choice, setting and use of tapered-needle motorcycle carburettors" . IMO, this guide is worth getting anyways as it gives a good explanation of how the carbs operate.

You can buy a hard copy direct from Eurocarbs, the Dell'Orto concessionnaires in the UK - they even offer them on auction on ebay, e.g. auction 261005809733. Or you can download it, for example from here (which just happens to be the page describing setting the float height ):
http://www.ducatimeccanica.com/dellorto ... o_3_2.html

Or there's the full version here: http://jonathanvingiano.com/misc/dellorto-manual.pdf

The only other thing I would add is that I have found it practical to make up a simple 'Go/No Go' gauge. Here's a photo - it is literally no more than a piece of hardboard cut out to the correct float height (18mm).

[kettle738]

Hi Craig.......I took the carbs out today, everything is stock, jets, throttle slide etc and quite nice and clean inside.

The only thing I noticed that needs attention beyond cleaning is the float height.......21mm both sides, where as I understand it, it should be between 17.5 and 18.5mm.

I have done one.......bending the arms of the floats to achieve the desired adjustment, having read another post on the subject.......I admit to being sceptical on that point, I thought it would almost certainly be easier to bend the valve tang....but on close inspection it's definitely sensible to bend the arms.

One thing though......I have noticed on other threads that 21 or 22mm seems to be the height set at the factory.....I'm certain mine have never been altered...why would that be if it should be 18mm? that's quite a difference.

Sorry for the unclear photo......but it the float height gauge at 21mm as found.

Best...........Mick........kettle738

PS Bruce......sent you a pm

[Craig in France]

I have noticed on other threads that 21 or 22mm seems to be the height set at the factory.....I'm certain mine have never been altered...why would that be if it should be 18mm? that's quite a difference.

Hmm - that had me scurrying to the books!

Typically, both the 860 workshop manual and owner's manual are silent on the subject . However, as well as the Dell'Orto Guide:

1. Both the 1975-1977 750/900SS manual and first edition Darmah manual, each being subtitled "Supplement to 860 GT/GTS Workshop Manual", say 17.5 -18.5mm.

2. Ditto the Pantah manual and the Laverda RGS manual, both bikes also being users of PHF carbs.

So that makes 5 sources each claiming 17.5-18.5 . Do you know the origin of the 21mm?

Craig

[kettle738]

Hi Craig........well nothing scientific unfortunately......I read a couple of threads among the hundreds I've been ploughing through which mentioned re setting float heights and it was re setting them from 22mm IIRC.

When I found mine were set at 21mm.........and I am as certain as you can be of anything that they will not have been disturbed......it just clicked that perhaps Dellorto set them at 21 or 22mm for a reason......who knows?.....but I'm not a great believer in coincidence.

I did also find that my air mixture screws were 1+1/8 turns out on the horizontal cylinder and just less than 1 turn on the upright.....for now I have moved both to 1.5 turns out as a starting point.....I'm as certain as can be that they WILL have been disturbed in the recent past.

I also found when removing the carbs that I hadn't tightened down the new rubber isolators sufficiently, the front carb in particular was very stiff to turn and the inlet manifold and gasket turned slightly with it....so they have been treated to a thin smear of Hylomar (as it's easily wiped off later) and an extra turn on the nuts.

They will be back on shortly, I'll let you know how it turns out.

Replying to you in Montpellier gives me a strong yearning to be heading for the Channel Tunnel and all points south.....must resist.

Best..........Mick........kettle738.

[machten]

+1 on what Craig said. 17.5 to 18.5 is what I've been using for the last 35 years. Works fine!

kev

[wdietz186]

Don't worry too much about the seeming richness at idle, the cams have a fair amount of overlap so some mixture ends up in the pipes at lower speeds. Better to have a stable consistent idle. It will also account for some of the popping at lower speeds. The rest of the popping is likely due to the sudden ignition advance that occurs around 2000 rpm. You'll learn to live with it.

[kettle738]

The carbs are back on and she's running again; once warmed up I had to adjust the idle screws to get a steady tickover......and from there I adjusted the mixture screws which I had previously left well alone. There was very obvious response to the mixture screws which confirms the idle circuits are clean and functioning and it was quite easy to obtain the strongest steadiest idle.....and then back it off with the idle screws to about 900rpm where it seems happiest.

The biggest drawback to the entire task was probably removing the fuel tank.....that >:|!!! >:|!!! link tube between the fuel taps is a royal pain. It took about half an hour to drain the tank using both taps and the fuel flow seemed borderline pathetic, so I thought cleaning the fuel taps at the same time might be a good idea. Is it me or does that link pipe have to run quite so close to the rear exhaust clamp?.....it bothers me enough to hold it clear with a cable tie.

Once the taps were opened up it became obvious why the fuel flow is so weedy......the ports within the tap are absolutely tiny.......which is amazing really, given the size of the outlets and the large bore fuel pipes....I was expecting to find some sort of obstruction by debris to explain the poor flow, but it seems the obstruction is built in

I suspect I am very lucky to have a GT that starts, runs and idles as well as it does, but I'm waiting to see if altering the float heights changes it's road manners at all. My next plan is to do nothing beyond a bit of riding and an oil change.....although I can't help wondering what a modern ignition kit would do.

Last thing.......having put it all back together, set the idle and put her back in the garage, I spotted a small tube on the bench......the reserve tube from the left hand fuel tap......I'd forgotten to put it back in before the fuel filter .......next job confirmed.......only half an hour or so to (nearly) drain the tank.

Mick.........kettle738

[Craig in France]

Good news, Mick. As you say, the carbs seem to be in good nick, and clean to boot - which often isn't the case .

The biggest drawback to the entire task was probably removing the fuel tank.....that >:|!!! >:|!!! link tube between the fuel taps is a royal pain. Is it me or does that link pipe have to run quite so close to the rear exhaust clamp?.....it bothers me enough to hold it clear with a cable tie.

(You know, I have no recollection of that pipe . Must be getting old ...)

Now, I haven't given this much thought; so, at the risk of appearing stupid ... What's that pipe for? Other models don't have a pipe between their taps - Darmah, MHR and (I think) SS, for example. I mean - could you get rid of it entirely?

P.s. Just explain, tho': You didn't need to drain the tank just to remove it, surely? Or was that only for cleaning the taps?)

[machten]

Both the 750 GT and 750 Sport have the link pipe. I've always assumed it was to facilitate access to as much of the fuel as possible (that resides in the low points on either side of the tank) for both carbs when you're down on reserve.

Don't know how effective it is in reality.

Kev