Heat guard under Air Box
 

I've got my bike in pieces in the garage, about to take the valve covers off, and I have a question about the plastic guard that is in front of the front carb and under the air box (see pictures). Is there an easy way to get that off without taking the carbs off? And if I do get it off, does it need to be there? Can I just leave it off? Looks like putting the bike back together would be a lot easier with that out of the way.

My only guess as to purpose is cosmetic, or maybe routing air into the snorkel on the air box. I found the part on BikeBandit and they call it a guard/heat shield, but it's just a flimsy plastic.

http://www.rahjnet.com/stuff/Top%20guard.jpg

http://www.rahjnet.com/stuff/Right%20Side%20guard.jpg

Any suggestions would be greatly appreciated. Thanx

Roger

I seem to remember thinking the same things first time I took the bike apart. I decided to just leave it alone, looked like a PITA to get off.

I remove it when I want to lift the valve cover of the front cylinder. It improves access to the valve cover bolts significantly. Better mechanics than I am may not need to.
The heat shield is held on by 2 plastic rivets. They can be removed with a No. 2 phillips screwdriver, usually with a quarter turn and gentle prying. The plastic shield shown in the lower photograph is held on by only one plastic rivet. It's probably easiest to remove all the plastic rivets before trying to separate the little plastic shield thing at the right front from the main heat shield.
I haven't been able to remove the heat shield without removing the carburettors.
I haven't read of there being any benefit to leaving the heat shield off. It probably affects air flow to the snorkel attached to the air box.

I took mine out. I'm pretty sure air will find it's way into the box either way, makes things easier for me.

I'm leaning towards cutting the thing off and not putting it back on. My only concern was high speed airflow to the snorkel. Will there be turbulance with air coming from the front around the head stock?

I'm gonna be pretty bummed if the thing doesn't hit 150 down the front straight at Willow Springs.

Roger

The only thing I can say about it is I wouldn't think Honda would have gone to the expence of putting it in if it didn't serve some purpose.

I believe it is there to provide cool air to the intake. I also believe this is a secondary reason (or possibly the primary reason) for the cool air ducts in the fairing.

I took the threaded plastic retainers out and replaced them with RC51 fairing retainers, because they have a quick-release mechanism, making them much easier to remove and replace.

I vote for keeping the heat shield and the fairing.

I took mine off havent ran it yet but I dont think it will afect much but mabey let my carbs and rear cylinder have some more air flow. I personaly didnt see how a gaurd out of flimsy plastic could really block heat? I think the incresed airflow around the carbs and direct into the snorkle will be cooler. Sometimes the guys in the white coats dont always use their brains. take are stock suspension could be alot better? we all mod it out anyways because it just isnt that great. same with acct's, airfilters chains and sprockets.

^^ You need to learn a word called compromise (and maybe budget, too).

OP;
Personally, I don't want to think of how dirty it could possibly get under there with that cover removed. I'm skinny and don't have much of a problem getting around "under the hood" of my VTR, but stuff getting dirty for no real reason ..... sorry, that's where I draw the line.

I say leave well enough alone. It's not doing any harm where it is. (I like RCVTR's reasoning, too :D )

odd coming from someone with swapped forks, upgraded lines and disabled emissions. Not trying to start an argument just saying thats what I prefer too do and my reasoning behind it.

Those are all upgrades. I think the general forum consensus is that the suspension and brakes are not "well enough" and disabling PAIR gets rid of annoying popping from an aftermarket exhaust.

Hey now, I wasn't trying to start anything. I was just trying to convey that you might have been missing part of what the white-coats can face sometimes. I don't know if you realize it or not, but sometimes they do make a good product. At least they got the v-twin part of our engine correct. ;)

My mods weren't all done by me. The PO did the front end swap. I did the emissions stuff, but that was for reducing backfiring and less crap "under the hood".

S'all good. :)

I know their upgrades and modifications Im just saying that I belive that removing the plastic could be one as well. The white coats did get the vtwin thing right and a stout one at that ill give credit where credit is due.

My bike is pretty old ('99 with 70,000 on the odo), and it's pretty dirty under there as it is. Besides, if I wanted spit and polish I'd get a hog.

Taking a look at it, and with everything back in place the snorkel on the airbox pulls air from between the cylinders and carbs. Seems that would be the hottest place on the bike. With the plastic guard out of the way, it would pull air from between the front cylinder and the head stock, right above the oil cooler. Seems it would get cooler air there. And why not just route a ram air from the fairing to the snorkel? Were they not doing that back in '97 when they designed the thing?

I will agree that the Honda engineers didn't put much on the bike that it didn't need. That's the main reason I haven't cut that guard off already.

Roger

I pulled the heat shield out from under the front carb. I think it may be contributing to my lean condition at freeway speeds. Bike runs great at low speeds, but at anything over 50mph seems to run lean. I'll know for sure when the new one i ordered comes in next week.

Ram Air is not an easy thing to do on a carbureted bike. A carburetor relies on the pressure in the float being the same as the ambient air pressure. The carb is then calibrated to provide approximately the right mixture throughout the RPM and throttle position range.

when you pressurize the intake, it changes that calibration and you then have vehicle speed as a variable. You could try to equalize the floats to the airbox, but the pressure there pulsates, so then you get chaos.

Much easier with fuel injection, because of the mass air or MAP sensors, and the ability to look up injection pulse widths from multi-variable tables.

That's my one-level-above-rudimentary understanding.

understandable. today was my 1st time out with the black piece out and pair disabled. I also did valves and CCT adjustments. The bike felt tighter it was idling about 200 less than before so I adjusted that my m4 cans had me backfire on almost every decel and now almost never. Didn't really have it over 60 but it didn't feel to be running lean. I got a 30mile commute at 80 tomorrow so Ill see how it does then hopefully well. If i do have to add the black piece back on I think it will be just to block air from being forced into the airbox while still allowing air to pass around the rear carb and head. I wont be off work and home again till Thursday night so thats when Ill post my findings.

well I got home a little early. heres my findings. bike seems a little tight actually a little to tight feels as if its got like a brake slowing the flywheel. When I did my cct's(a lil off subject i know) but the lobes where up and i went finger tight and 1/4 off. im going to back them out another 1/4 and see what I get. The bike stumbles alot more. not sure if i didnt hook a hose all the way or what but it not only went for a every once and awhile stumble at 2000 it does it almost all the time at constant 2000rpm and now again around 3-3500 cant tell if its doing it on the road as all ive ridden has been freeway and now im super receptive to any little change in sound and of course pairinoid. but when I tucked in all tight I didnt really feel anything could have been driving throught it and didnt hear it. Im going to lossen the ccts check for vacum leaks then if its still happenning make a partial sheild under then worst case put the old one back on.

Thanks for listining, my names andrew and im a motorcycle addict

More heat on the carbs will lean out the mixture, so removing the heat tray will do that, not enrichen the mixture. The heat tray does not effect intake velocity or volume if the snorkel is in place on the airbox.

Whatever your "feeling" or more or less backfiring should not be related to the heat tray...

wasnt tring to relate it to the heat tray directly just the fact that I added I disabled pair and since if someone does a search for pair this thread came up I figured out I might as well contribute to that.

Im curious about how you figure that the heat tray does not effect intake velocity. I can see both ways so Im not bias just trying to figure it out. Im sure that a little more air is finding its way in easier but I can also see how alot of it is being blocked I mean it does have to go around the lower clamps, oil cooler, frame, snorkle then air filter. So if we could get both sides on this ill lend my ears.

Intake is thru the snorkel only, the heat tray has no bearing; if anything, the heat tray my smooth the air toward and/or minimize turbulance at the snorkel opening (the airbox/filter is totally dependent on the snorkel.

The general rule of thumb is : 1 % increase in horsepower every 10 °F decrease, so the reverse is true.
You may try to hook up an exterior cheap thermometer with a probe and tape the display on the handlebars with the shield on and off, you will get the scientific evidence.

First go trough all the hoses and simple stuff, if it check OK, check your cams alingment, sounds like a tooth skipped somehow. The chain tention will not cure anything.

So I've got the bike back together (after some other problems). I ended up taking that heat shield off, and putting the airbox back on is a piece of cake.

But when I took it out for a spin, I noticed that when I get the bike up over 100 there is a hesitation/stumble. When I slow back down it smooths out again. I'm guessing it's because the air is routed differently to the snorkel, because I didn't change anything else that would effect the motor.

I'm gonna tear the thing apart again tomorrow and see if there is another way to block off air flow. It really is a lot easier to work on now.

Roger

Same thing happend here Im gonna make a small peice either out of plastic or aluminum to sit flush with the frame crossmembers right under the snorkle like the front of the sheild dis just not wrapping around the carbs and crap. still gotta figure out how im gonna do it yet.

double-sided foam tape and use the heat tray as a template and add mounting tabs...

you talking about just the foam tape? I thought about that as I have a huge roll But I am worried about the mabey ripping off or getting sucked and blocking the snorkle like a vacuum. Mabey on the cheap you could use some cardboard with foam tape on the down side to add some rigidity and heat protection? or a thin sheet of plastic or plexi glass?

So that answers that question...

I took the bike apart again and cut out a new guard out of aluminum. Went through a bunch of cardboard templates first, but turned out pretty good. Blocks up the hole coming up from the oil cooler, and blocks the sides a little bit, but not as much as the original. I can still get my hands in there to put the airbox back on.

http://www.rahjnet.com/stuff/newguard.jpg

So took it out for a quick spin and it was still pulling at 140.

I'll update if I have any other problems with it. I'm sure the aluminum isn't gonna block heat as well, and I may go in and put some sheet metal screws in to hold it on better, but the fit is pretty tight as it is.

Roger

I like that design bassically going for the same thing now but I dont think ill have mine go up the sides just the base.

I think that would work too. I don't have mine going too far down the sides, and there is a pretty big cutout for the throttle cables.

Do you have anything to protect cables and hoses from getting cut by the aluminum? Just a thought.