How to cut down the Givi

I wanted to share my Givi cutting experience for others thinking about doing the same thing.

As has been discussed at length elsewhere, some people feel that the Givi is too tall (for various reasons that we don't need to go into again here). I installed the Givi last winter, and finally decided that I wanted it shorter. A couple of general suggestions that I would make to people considering this are:
1) Ride with it at the stock height for a while, in a variety of conditions, and make sure that you really want to cut it. There may be benefits to keeping it taller, try to have a pretty good idea of what you stand to gain (and loose) by cutting it down.
2) Don't cut too much off at once - it's cheap and relatively easy to take off more, but not cheap or easy to put it back (I jumped right in and had some regrets later).

I'm going to show how to do it with hand tools and the windshield still on the bike. It can be done with power tools and/or off the bike (if you have, please feel free to comment).

You'll need the following:
1) Masking or painter's tape (a lighter color is probably a little better)
2) A saw. I used this mini hacksaw and was very pleased with how it performed:
3) Some string
4) A pen
5) Sandpaper (I used 80 and 220 grit on my orbital sander and then some 800 or 1500 grit to wet-sand and finish it)

I don't show this in the pictures, but put a towel or something over the dash while cutting to keep things clean.

After you've decided how much you want to cut off, tape up both sides of the windshield, covering where you're going to make the cut plus enough on each side to protect it from the saw blade when you accidentally pull out of the cut and hit the windshield:

(I cut off about 4-4.5 inches in this pass - I would NOT recommend taking off that much at once...)

Now you need to trace out the curve for the top of the windshield. There are several options for this, one being to try to copy the original top down onto your tape. I tried this a couple of different ways, and wasn't satisfied with the results (part of the problem being that the width changes, so you end up free-handing parts of it). I then decided to trace out part of an ellipse, with horizontal major axis and foci where the "ears" join the rest of the windshield:

(If your geometry is a bit rusty, here are some refresher links: http://mathworld.wolfram.com/Ellipse.html, http://planetmath.org/encyclopedia/Ellipse2.html, http://en.wikipedia.org/wiki/Ellipse).

Tape the string down at one of the foci, put your pen with the string wrapped around it in the middle of the windshield where you want the highest point to be, then tape down the string at the other foci:
(the pen isn't at the top but you can get the idea)
You can move things around to change the shape of the curve that you'll trace out, just make sure you can tape the string down securely and use symmetry to your advantage.

Keeping the string taunt, trace out your partial ellipse. Try to do it all in one or two passes and make a nice clean line - if you end up with several lines then it makes cutting more of a challenge later on. If you mess up, just re-tape the front and try again. You'll end up with something like this:
(This picture shows where I made a second cut. All told, I took off about 5-6 inches - probably a LOT more than most people will want to.)


Now just cut along the line. I found it was easier to control everything with the hacksaw blade installed "backwards" (cutting on the forward stroke). It also seemed to help to have some sort of lubricant on the blade (I used engine oil). Just take your time and make sure you're staying on the line. The cutting was fairly easy, and moved quickly (for hand tools) once I got going.

Once you finish the cut, smooth off the edges with sand paper. Do not remove the tape until you're done sanding! I started with 80 grit on my orbital sander and used that to shape the corners and round the edge a little, the changed to 220 grit on the orbital to get rid of the swirl marks left by the 80, and finally finished it off with an 800 or 1500 grit (not sure which) wet sand. The final result looks as good, if not better, than the factory edge.

Take off the tape, rinse off the plastic particles with plenty of water, and clean off any tape residue and fingerprints.

You can't see the edge very well, but here's a view after my first cut:


Overall, I'm very happy with the cut, although not quite as happy with how much I took off. I added a homemade Laminar lip/windshield extender to gain back some of the height, which I think is going to work out well, but I'll post on the separately once I've had a chance to ride with it a little more.

It looks like you did a good job. I tried to cut mine down about 1 1/2" and didn't do as good of a job. But then I didn't sand it at all either. I planned to but just didn't get around to it. I like your idea but I just used a compass (if I recall the name right. The item with the pencil at one end and the sharp point at the other)

But it does seem you cut a lot off. Is there a reason you did this? Or did you want to put the Laminar Lip on after cutting. Good job though and thanks for posting.

edbancro
Thanks for the detailed pictorial and directions.
Looks like most anyone should be able to do it with these directions.

JeffR wrote:

It looks like you did a good job. I tried to cut mine down about 1 1/2" and didn't do as good of a job. But then I didn't sand it at all either. I planned to but just didn't get around to it.

Quote :

I like your idea but I just used a compass (if I recall the name right. The item with the pencil at one end and the sharp point at the other)

Yes, that is a compass, and so you used the arc of a circle instead of an ellipse (although, mathematically, a circle can be thought of as an ellipse with both foci at the same point ). My top edge is probably a little more 'flat' (depending on where the center of your circle was).

For any else wanting to use this method, you can obviously play around with different circles/ellipses and see which look you like best before you commit and cut. Heck, you could even make the major axis vertical!

Quote :

But it does seem you cut a lot off. Is there a reason you did this? Or did you want to put the Laminar Lip on after cutting.

Well, that's a rather long story. I started off wanting some venting to cool things off in the summer and to [hopefully] find a way to reduce/eliminate the back pressure push that some people feel at highway speeds (I wasn't too bothered by it, but if I could get rid of it and vent, then why not). Bill (honda_silver) suggested some vents here which I was going to use, but I didn't have (and couldn't find for a reasonable price) a hole saw that was large enough. So, I decided to cut instead. But I wanted to try to try cutting off a larger piece and then make a lip out of it. I did try, but the results were rather dissapointing (I don't think it was large enought or the right shape). I made the mistak of attaching it with nylon nuts/bolts and ended up with four holes along the edge of the windshield that looked ugly and, I thought, might cause cracks later on. So, I cut off another inch or so to get rid of the holes.

I actually like it better with that extra bit off - with the first cut, I was getting a lot of turbulance around my helmet, after the second it seems to have moved the turbulance down. It gives a nice amount of air flow for around-town summer driving or short highway trips, but I'll want more protection for winter or longer trips. The homemade lip I'm working on now seems to be living up to most of my expectations, but we'll see...

I cut my GIVI twice. I really like your idea of taping the string down to create a flattened arc. I free-handed it, and it came out pretty well (I used a protractor?? as a scribe and traced the edge, but the corners end up free-handed because the width is different), but not as good as yours. Most people probably don't even know I cut it. I used an 18V jigsaw with a metal cutting blade with good results.

I bought a Laminar Lip (it is a universal model that is 15 inches wide at the widest part - the bottom). It made the GIVI much, much better because it made it quieter. I am currently using it on the stock shield with the Laminar Lip for the summer, and get more airflow on my arms. For the winter, I will probably go back to the GIVI/Laminar Lip combo. The LL works better when you have more overlap between it and the shield (i.e., if you raise the LL too high, it does not funnel the air over your head well).

One HUGE benefit that I discovered after putting on the stock shield/Laminar Lip combo is that the quirky handling has disappeared. Sudden gusts used to knock me around with the GIVI; the stock shield has none of those issues. Much more relaxed riding.

Laminar sells extra hook and loop fasteners so that you can switch from one shield to another. I've had mine to over 90 mph without any sign of coming loose. Good product.

buddy19520 wrote:

I cut my GIVI twice. I really like your idea of taping the string down to create a flattened arc. I free-handed it, and it came out pretty well (I used a protractor?? as a scribe and traced the edge, but the corners end up free-handed because the width is different), but not as good as yours. Most people probably don't even know I cut it. I used an 18V jigsaw with a metal cutting blade with good results.

I bought a Laminar Lip (it is a universal model that is 15 inches wide at the widest part - the bottom). It made the GIVI much, much better because it made it quieter. I am currently using it on the stock shield with the Laminar Lip for the summer, and get more airflow on my arms. For the winter, I will probably go back to the GIVI/Laminar Lip combo. The LL works better when you have more overlap between it and the shield (i.e., if you raise the LL too high, it does not funnel the air over your head well).

One HUGE benefit that I discovered after putting on the stock shield/Laminar Lip combo is that the quirky handling has disappeared. Sudden gusts used to knock me around with the GIVI; the stock shield has none of those issues. Much more relaxed riding.

Laminar sells extra hook and loop fasteners so that you can switch from one shield to another. I've had mine to over 90 mph without any sign of coming loose. Good product.

Can you post a picture of your installed laminar lip ?

I will try to take a picture and post it, but it will be two weeks. I am going out of town Saturday and don't have the time to learn to add pics to the post.

It is not pretty - it is utilitarian. On the stock shield it looks too large. On the GIVI, its okay. The weather finally cooled off a little this week (73-80 degrees near dusk, compared to 90+ last week), and I will probably go back to the GIVI when I get back. I'll try to get a pic of both stock and GIVI.