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Discussion Starter #1
A lot of windshields with vents, it looks like the area / corners of the vent where the screw is attached, looks like the vent plastic has "spider web" cracks.

Is that due to the screw being over tightened when installed, and / or over time with the windshield flex that is just a stress point and it will always have "spider web" cracks?
 

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A lot of windshields with vents, it looks like the area / corners of the vent where the screw is attached, looks like the vent plastic has "spider web" cracks.

Is that due to the screw being over tightened when installed, and / or over time with the windshield flex that is just a stress point and it will always have "spider web" cracks?
I've had 3 GL1800s and 2 came with vents. I have never noticed that. Are they OEM windshilds that came with vents?
 

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Discussion Starter #4
Good question. This is on my GL1800 "F4" w/s. Maybe the factory w/s installed vents are torqued to spec. I know not to over tighten the screws, as that will cause problems (stripped threads, maybe 'spider cracks').
 

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the early windshields had gl1500 vents the cracking is more pronounced on these!! I use thin super glue!!! it workes dont get it in the threads...
 

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I would say the bolts were either overtightened or not in their respective slots on the vent.
 

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Over tightening the screws can cause cracks. But where are the cracks, at the screws, or at the threaded inserts? I have seen a number of Wing vents over the years that were cracked at the inserts. That is not due to overtightening. It is due to the pressure from the press fit. If it is at the screw head, it was probably overtightened.

That vent is made from hard, brittle acrylic. Acrylic doesn't like pressure and cracks easily wherever fasteners are attached. And over time, it becomes even more brittle when exposed to the sun.
 

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Good question. This is on my GL1800 "F4" w/s. Maybe the factory w/s installed vents are torqued to spec. I know not to over tighten the screws, as that will cause problems (stripped threads, maybe 'spider cracks').
Man ... you know, once a person gets away from OEM, all bets are off with the various problems that crop up. That sounds to me like the hole cutting process is wrong. But then the other problem with most of those windsheilds is that the plastic they are made of is to thick to even mount correctly on the Wing. Usually, rubber grommits on the front facia are removed when installing them.

Speaking of adding aftermarket stuff ... I just found out a freinds 08 with aftermarket exhaust almost dies restarting after 10 min when hot. All caused from aftermarket exhaust. Sorry ... not a fan of adding aftermarket POS stuff. I just want to ride and not always fixing the add-ons. When it is Honda line stuff, bolt-on, plug and play and pretty much never have to revisit it or repair it, or deal with all the unprdeicatable stuff like a windshild beginning to crack. Just an FYI ... most likely your crack will just get worst.
 

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Greg, I don't wear Honda OEM underwear
but on the F4 you make a good point. My F4+4 is on its second vent. The +4 is thicker and I just noticed this weekend that the curvature of the vent doesn't exactly match the curvature of the shield. With my particular shield I believe this is causing an issue, but obviously don't know for sure.
 

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Discussion Starter #11
LarryM, the vent shows the cracks. The windshield is fine. The cracks are not at the screw head. The 'spider cracks' appear at the 'bottom', just beneath the insert (or standing in front of your bike looking at your w/s, the cracks appear covering the screw).

I would guess they were caused by "age and time" (and possibly the vent curvature). As you noted,
That vent is made from hard, brittle acrylic. Acrylic doesn't like pressure and cracks easily wherever fasteners are attached. And over time, it becomes even more brittle when exposed to the sun.
The mystery is solved :) Thanks.

TravelinLite, I also have a F4+4. I was going to replace the vent with a Honda vent. However, the F4 hole is cut too small for the OEM (bought the F4 back in '06?, so maybe the hole size is now consistent). So, I had to re-install the F4 vent, which I have found and agree with you about the vent curvature. Over time, this maybe another contributor to the problem.

Why did you replace your first vent?
I was only replacing mine because a new OEM was available.
 

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Stan, if you check the F4 website, their vent is a specially modified version. The stock Honda vent will not fit. I assume it is because of the thickness, but I don't know for certain.
 

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Discussion Starter #14
Everyone, thanks for your input.
 

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f-4 vent

If you contact f-4 they are very helpful there are some washers that can be installed to make the vent tighter to the windshield it also helps to clean and lube the vent mechanism once in a while as it does collect road dirt, this will keep it opening easy
 

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I installed a vent on my VTX1800N. The fasteners were not over tightened. The plastic spider webbed in about 2 months. I was at the largest supplier/fabricators of boat Windshields in S. Florida to pick up some plastic for another project. I asked the owner to look at the windshield. He said they are caused by vibration when the vent curve does not exactly fit the contour of the windshield. I had only tightened the shield to close a 1/16" opening in 2 corners of the vent and the fasteners were not much more than hand tight :shock:.
The windshield was Lexan from Honda. That was an expensive lesson. Make sure the vent sits in place flush all around with just light hand pressure. If not don't use it :cry:.
 

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Good question. This is on my GL1800 "F4" w/s. Maybe the factory w/s installed vents are torqued to spec. I know not to over tighten the screws, as that will cause problems (stripped threads, maybe 'spider cracks').
I love my F4 but will admit the vent has been nothing but trouble.

The F4 folks machine a stock vent to accommodate the thicker windshield. They also include little washers to act as spacers during the install. If you get the position wrong on these your vent will crack and spider.

My first vent failed to have enough lip on the machined area and as a result would not stay properly connected with the windshield. It eventually broke and a I purchased a replacement. It didn't fit much better unfortunately.

I'm currently using parts from the two vents to get one reasonably mounted vent. Not the greatest fit but it's holding so far.
 

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Discussion Starter #19
He said they are caused by vibration when the vent curve does not exactly fit the contour of the windshield. I had only tightened the shield to close a 1/16" opening in 2 corners of the vent and the fasteners were not much more than hand tight :shock:.
Just so I understand, because of the vent curvature, the vent should "not" be tightened to sit flush with the w/s. If it is, then the vent will crack?
 

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This has been one of the more interesting threads that I have read on this board in a long time. I'm impressed with the way the problem is being worked out. This is a message board at its best.

I do not work in the plastics industry. But I do have a lot of experience with damaged plastics, and finding ways to prevent future problems.

I agree that vibration can crack plastic. But it is much more complicated than that. Pressure is probably an even bigger cause, and you have to factor that in.

This thread had me curious, so I went out and looked at my 2 year old F4+4. The vent was installed when I got it, and was pretty much a set it and forget it install. Fortunately I did not find any spider cracks.

When I inspected it, I noticed that on one side the vent was flush. But on the other side the vent had about a 1/16" gap. When I pushed on the vent, I was able to force it flush against the windshield. That means it isn't hanging up on anything.

I have not checked the tightness of the screws. But I don't think this is due to one side being tightened more than the other. It is probably due to an inconsistency in the forming of the windshield. This is something you can't see with the naked eye.

What I see on my windshield is a manufacturing problem. Small windshield manufacturers probably cannot devote the resources to the type of expensive equipment that a company making tens of thousands of OEM windshields can. This probably results in a little more inconsistency. I am making a guess as to why the inconsistency exists, because I know the guys at F4 build the best quality windshield they can offer.

This creates an installation problem that there really is not a correct solution for. You don't want the vent to be loose, because vibration can crack it. But you can't crank it down flush either, because the excessive force could crack it. This creates a no win situation.

It seems to me that each windshield has to be treated differently, depending on how closely the shield was formed to match the vent. If you can install it flush without causing undue pressure on the vent, than that is the best course to take. But if the vent just does not match the shield closely enough, you are going to have to find a happy medium. You have to find a balance between tightening it enough to prevent vibration, but not so tight that it will crack from excessive pressure. Unfortunately there is no hard fast rule here. It is a matter of feel. And sometimes that feel is only developed by exceeding the extreme and finding out the hard way.

Whether it works or not is hit and miss. If it doesn't it is not your fault. This is simply not an ideal situation. Plastics are a great thing. But you have to work within their limitations. Using fasteners to bend and force two mismatched pieces of plastic together is not the way to build a reliable product.
 
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