Main Beam Light Pattern

[Adam]

Having just bought my Zephyr 750 a week ago, went out for my first ride in the dark today - and was rather surprised/concerned at the main beam light pattern.
Dipped is fine, and looks like this:

Dipped Headlights

When I turn on main beam though, it looks like this:

Main beam pattern

Loads of light close to the bike, and some high up on the left - but just where I want it - straight ahead - there's a big black hole.

Any ideas why this might be?

Thanks!

[Freddy]

First of all be sure you have the high and low been switch in the position you think it is. The lettering on old bikes is often faded away to nothing so hard to tell from that, obviously the high been indicator will/should light up in the high beam position but I can't see that in the photo.

Next, is the headlight original i.e someone has altered it with an LED system etc.. If it is original, go buy a new quality 150% H4 headlight bulb, make sure it fits correctly in its holder, and other than some minor up/down adjustment (located under the headlight) it virtually must work correctly as there is really nothing that can go wrong.

[Adam]

Freddy,

Definitely got dipped and main the right way around - just checked and the blue main beam light comes on when I expect it to.
The lamp is a regular H4 halogen.
I do have an LED one on the way, but it's not been fitted yet.
When I saw the pattern, I pulled over near a street light and took the headlight apart - wasn't sure if it were possible to put the lamp in the wrong way around but it seems it isn't so that's not the reason either.
The dipped beam pattern is actually quite good. Quite odd that the main beam pattern is so off.

Adam

[Freddy]

Sorry, I was interpreting your pictures the wrong way around.

Actually your low beam looks a bit high to me from the photo. Bring that back down might improve the high beam. Also be aware your headlight shell isn't original (being chrome) so perhaps that is part of the problem. Check that the headlight is sitting straight up when fitted.

Another problem in the aim, which I was intending to write in the thread where you have a picture of the bike, is the tail of the bike looks a little low to me. Might just be the camera angle. I'll measure the length of an original shock which I got sitting in the shed and let you know and you might want to measure those aftermarket shocks that are fitted. Might be correct, but at least you'll know for certain.

But if you find the ride in the back a bit hard, those springs fitted to those shocks look definitely too light. The weight of the bike alone is enough to fully compress the light bit of the progressive spring. If its like that with just the weight of the bike, when you sit on it the light bit will definitely be all coil bound. So in effect you really don't have a progressive spring, but are riding on a linear spring only (the heavy part of the rear spring). If you fit a heavier progressive spring the top lighter section of this spring will better support both you and the bike, working most of time other than heavy hits, and give a softer ride. Anyhow just something to think about.

[Adam]

Freddy,

You are a font of useful knowledge!
The rear shocks (air adjustable) were fitted by the previous owner.
I'll do a bit of research into them, to see what pressure they should be and what strength spring is on there (and what options there are)

In the meantime, knowing what length they should be, both when there's someone on the bike and not, would be really useful!

Thanks,

Adam

[Freddy]

Freddy,

The rear shocks (air adjustable) were fitted by the previous owner.

Perhaps the above explains what I'n seeing, perhaps not. I must confess zero knowledge of how air assisted rear shocks should be set up. But if I guessed I'd be thinking just like a car airbag. Basically set up like a normal shock with no air pressure (yes I know you keep a few psi in a car airbag, but that's only so it keeps its shape) for a solo no load rider, and then pump a bit of air in to reestablish correct ride height for a pillion and/or load.

Just 100% guessing though.

[Adam]

Freddy

These are the shocks the previous owner says he fitted: https://www.ebay.co.uk/itm/373115881569
Actually, I think they are closer to these: https://www.ebay.co.uk/itm/293187959763
You said in the other post the uncompressed shock length on your bike is 345mm but these are about 325mm.
Take it off the centre stand and hold it up right, then it's closer to 310-315.

This is what it looks like upright, with no rider:

Bike upright with no rider

And with a rider

Bike upright, with rider

So yes, pretty much what you said - the top springs are already collapsed before we even move!
So, what you were saying about the light being too high sounds right - the backend is a bit low and the light is pointing up.

The eBay advert doesn't give any details about the spring weight, so I'm not sure what weight I should get to improve it

Thanks,

Adam

[Freddy]

Freddy

These are the shocks the previous owner says he fitted: https://www.ebay.co.uk/itm/373115881569
Actually, I think they are closer to these: https://www.ebay.co.uk/itm/293187959763
You said in the other post the uncompressed shock length on your bike is 345mm but these are about 325mm.
Take it off the centre stand and hold it up right, then it's closer to 310-315.

This is what it looks like upright, with no rider:

IMG_20200806_165036.jpg

And with a rider

IMG_20200806_165124.jpg

So yes, pretty much what you said - the top springs are already collapsed before we even move!
So, what you were saying about the light being too high sounds right - the backend is a bit low and the light is pointing up.

The eBay advert doesn't give any details about the spring weight, so I'm not sure what weight I should get to improve it

Thanks,

Adam

I just rechecked the distance between the factory shock center to center mounting 'holes', and it is definitely 345 mm. That's off the bike, but this will be the same fitted with the bike on the center stand, rear wheel off the ground.

So trust if you don't mind if I be totally honest, I'm only trying to ensure you get the best from your new purchase. Double check your's to make sure it is 325 mm. So with this information we can assume the shocks are definitely not what the own says he fitted. The ebay advert says they are black, and center to center 360mm. Your's are definitely not those. It would be nose down with the back jacked up 15mm (other adjustments being correct).

So...... I'd start by asking the previous owner does he still have the original factory shocks. If so, get them off him and refit. But be aware being the over 20 years old they will be shot and need rebuilding. If he hasn't got them ........

The shorter length shock has dropped the rear of the bike 20mm. To me that's completely unacceptable. If the front of the bike were adjusted correctly, it would ride like a 'chopper', nose up making it hard to turn into corners, and prone to dragging hard parts when cornering. Both situations I think are potentially dangerous. In the picture of the e-bay advertisement you think may be yours, those are adjustable length. You will be able to tell looking at the bottom of your shock and seeing if there is a lock-nut. If they are length adjustable you may be able to 'recover' some of the correct length this way. You don't want to over do it and not leave enough thread in the shock making it structurally unsound. But while this may get the bikes geometry better, you still we have a shock with a reduced travel length internally so more prone to bottoming out.

Regarding the springs, if you took them off the shock and went to a motorcycle suspension specialist (or just take the whole shock, they can remove the spring in seconds with a proper spring compressor) they will be able to measure the current spring weight in a machine, and should have a suitable heavier replacement. You don't need an expensive brand spring, the relatively inexpensive stuff make in Asia like YSS is perfectly fine as far as springs go. In practice there are generally only 2 weights of progressive that each brand make for a given size. A light and a heavy one. It's not like linear springs that come in a whole incremental range.

What would I do ......... I wouldn't waste time and money mucking around with what's on the bike if they are 325mm center to center, they are simply the wrong shock absorbers. I'd replace them with correct length ones. Now that is a whole lengthy topic of itself, so I'll just leave it at that and more than happy to discuss that if this is the way you decide to go.

P.S. Also be aware that just about any 'budget' shock you buy on the internet will come with an underweight progressive spring on it, and should be changed. Doesn't have to be, but it aren't going to give a decent ride unless you do. So add the cost of a set of new springs to the budget shock price and all of a sudden they aren't that much cheaper than a decent one from a suspension shop fitted with the correct springs.

[Freddy]

So yes, pretty much what you said - the top springs are already collapsed before we even move!
So, what you were saying about the light being too high sounds right - the backend is a bit low and the light is pointing up.

Just want to clarify one point. It's not the incorrect spring weight (the near coil bound light section of the spring just from the weight of the bike) that is causing the tail of the bike to sit low. That could be 'corrected' (wrong word as it won't be correct) by simply cranking in preload to get the tail of the bike to rise further up in the air. The headlight is pointing skyward because of the 20mm short rear shock absorbers. Even that could be 'corrected' by cranking in massive amounts of preload and forcing the shock to be nearly topped out even sitting on it, but that would just be all wrong and give a REALLY bone jarring crap ride. Well not unless you want the ride of a 'hardtail' Harley.

The shorter shock is the cause of the headlight pointing skyward (and it will make the bike handle no well near as well as it should). The underweight progressive spring will not give as good a ride as possible, using really only using the heavy section. A heavier progressive spring will put most of your ride on a more enjoyable lighter spring (the top bit of the heavier progressive spring). It will also significantly improve ground clearance when cornering which can be a problem with the 750 (bike not sinking so low in its travel).

[Adam]

Freddy,

That all makes sense.
Not having ridden a Zephyr before (or any big bike for 12+ years) I'm rusty enough to not really be able to judge the handling.
However, when going round a very tight roundabout near me (it's not small, just an odd shape, with a point at one side of it) I managed to touch the exhaust down.
It's also an after-market exhaust, and I can see it's a little wider than the stock exhaust so in combination with the lower suspension, it must be much closer to the ground when cornering.
It was my daughter's first time as pillion too - she wasn't impressed!

The previous rider restored the bike last year, so I think it's unlikely he still has the old shocks. And besides, they are probably a bit knackered anyway.
He may have bought the wrong length if the springs were knackered and shorter they should have been!
I don't think the ones in the original eBay link were the exact ones - he did say they were the same make, but not the same 'model' so I think the ones on the bike are 320mm not the 360 from the advert.

So, if the length is supposed to be 345, do you think these 340mm ones would be a good starting point: https://www.ebay.co.uk/itm/254627651834?
Once I get those, I can look at some stronger springs too.

Thanks!

Adam