ThunderAir Kit Install

wjreece's picture

Please thank BoomerSooner for this tutorial!

Everyone who has installed a ThunderAir kit has said how easy it is, so I thought I would try my hand at it. And once again, I’ve succeeded in turning a simple task into a Rube Goldberg, but they were right, it’s so simple, even programmer can do it. :)

What you’ll need:
4mm hex tool.
5mm hex tool.
11mm wrench.
NOTE: I suggest using a hex driver if you have one. It will make this a lot easier.
Flat-blade screwdriver.
Recommended:
Torque wrench.

CAVEAT:
If you are installing the VERTICAL Teardrop airfilter, read my comments at the bottom before you start!

So let’s begin!

What you’ll get from Thunder Air:
An adapter kit for the 1300 (Type B), and the filter style of your choice. I selected the teardrop shape, mainly because I’m tired of the round filter that’s always been on my old bikes!

I will make note here that the adapter kit I received and the kit pictured on the thundermfg.com site look different. I’ll comment on this after the install. And if you’re wondering why the filter looks odd, I put the rain guard on it and forgot to take it off for the pic. :()

Remove the four 4mm hex screws holding on the outer cover:

Remove the cover, exposing the stock air filter:

Gaze fondly upon the old air filter, remembering the good times, then toss it aside like it’s your Ex:

Remove the three 4mm hex screws that surround the throttle body opening. They are holding on the stock air box:

A hex driver really helps out here:

The stock airbox has a “spike” at the bottom sticking into a grommet. Angle the airbox out and lift up. You’ll have to wiggle it around a bit, but don’t try to pull it completely off yet:

Now that you have the airbox away from the engine a bit, the crankcase breather hose is attached to the back with a compression hose clamp. Don’t worry if you can’t get your fingers around it to squeeze it open, just carefully wiggle the hose off:

I’m lifting off the airbox from the bottom grommet here. The left side of the pic is the bottom of the airbox with the “spike”:

Here’s the throttle body with the airbox now removed from it:

The bottom bracket that was holding the stock airbox can be discarded. Remove the two 5mm hex screws:

Re-install the screws and re-torque to spec(7.2 ft-lbs):

There are two gaskets on the back of the stock airbox you will be re-using, so carefully remove them:

Place the gaskets into the adapter:

Screw the L-Barb (the plastic elbow) into the bottom of the adapter:

NOTE: If your adapter has the external filter instead of the L-Barb, others have reported installing that behind the fake cover on the left side(where some have relocated the horn).

All screwed in. I suggest snugging it up and then backing it off one turn at first. I’ll explain why in just a moment:

Attach the 3/4" hose (supplied with adapter) to the other end of the L-Barb:

Slide the 3/4" hose into the crankcase breather hose. The adapter comes with a screw-type hose clamp, but I re-used the stock compression clamp. Make sure the breather hose does not kink! If you left the L-Barb a little loose, it should turn easily towards least resistance. If you left the L-Barb snug, then you may have to over-tighten it a bit to get a good angle:

Bolt the adapter to the throttle body, re-using two of the 4mm factory hex screws and using the one from the adapter kit. Re-torque to spec (2.9 ft-lbs):

All installed:

Close-up of the L-Barb and crankcase breather hose. Make sure the hose is not kinked:

Time to install the filter itself. Take off the filter back-plate by removing the two 11mm hex nuts:

Lifted away exposing the filter:

Attach the back-plate to the adapter using the two 4mm hex screws supplied in the adapter kit:

Air filter back-plate in place. I originally was going to put on the vertical teardrop, but switched to the hortizontal:

Align the filter and front-plate onto the back-plate:

Re-attach the filter and front-plate to the back-plate with the two 11mm nuts. It goes without saying, don’t over-tighten! You’ll crush the filter.

Stand back and admire your work:

You’re done. Go riding!

Afterwards:

OK, if you here, then:
A) You are incredibly bored, or
B) You want to install a Vertical Teardrop air filter.

I mentioned at the beginning that the adapter kit I received was different from the one pictured on the thundermfg.com site. Mine contains the L-Barb to supply air to the breather hose from the adapter, whereas the kit on the site shows a filter that would connect to the breather hose instead.

I don’t mind the L-Bard design, but unfortunately this design is incompatible with the vertical teardrop filter I selected! The top bolt to connect the front-plate & filter to the back-plate is in the exact position as the L-Barb that exits from the bottom of the adapter. In this photo, you can see the L-Barb screwed into the adapter and I’ve connected the filter back-plate. You can see the white of the L-Barb easily showing through the back-plate bolt hole:

You can also see in this photo just how much the back-plate and adapter are from being able to bolt together, due to the L-Barb being in the way:

I talked to Travis at Thunder Mfg, (a very nice guy, BTW) who confirmed you can’t use the L-Barb with the vertical teardrop, BUT they can provide a plug for the L-Barb hole and an external filter(as depicted in their adapter kit photo) for the breather hose, which will then allow you to install the vertical air filter. Some people have reported installing the external breather filter behind the fake cover on the left side of the engine( where others have re-located the horn).

So, the lesson here is – don’t order off the website, call and talk to them so they can send all the parts you will need.

Also in this photo, I see what I think is a flaw in the design. Look at the throttle body opening and the top edge of the back-plate. Notice that the top portion of the back-plate is blocking the air flow into the throttle body. While not a large blockage, this is going to cause turbulence into the opening - I expected better from a kit that is supposed to maximize airflow!

You can see how much it is blocked a bit better in this photo. I have removed the adapter and laid it on top of the back-plate:

Travis at Thunder swapped out my vertical back-plate with a horizontal one, which solved the L-Barb problem(I didn’t want the external breather filter), but I still see the throttle intake being a bit blocked:

I marked the back-plate as how it fits from the back of the adapter:

This may look like a fair bit, but if you look at it from the point of view as seen from the front, there’s not a whole lot that can be removed:

Anyone know of a good way to grind out aluminum?

Comments

External Filter for Crankcase Breather

OK, for those that want to use the external filter for the breather instead of the L-Barb, there’s not much more that needs to be done.

What Thunder will send you is a plug for the hole in the adapter and the filter:

Screw the red plug into the hole in bottom of the adapter. It seemed to fit a little loose for me, so I used a bit of thread tape:

If you are installing a vertical air filter, you may have to install it from the inside so that the plug will not block the air filter screw:

Remove the fake cover from the left side of the engine. There is a single 5mm hex screw in the front that is holding it on:

Then pull at the top of the cover. There are two “spikes” stuck into grommets the need to be pulled out. They’re pretty snug, so don’t be afraid to use a little force:

Here’s looking through the engine from the left side. You can see the breather hose in the middle in its original position:

< photo not found >

Attach the 3/4” hose (supplied with adapter) to the other end of the external filter, just as you would the L-Barb:
< photo not found >

Attach the external filter to the breather hose. I used the hose clamp that came with the adapter instead of re-using the compression clamp. I did this because where the hose connects to the external filter is smooth, while the L-Barb has expansion ridges to grip the hose:
< photo not found >

All together:
< photo not found >

I was going to fabricate some kind of mount to hold the filter behind the fake cover, but the end of filter is covered in rubber, so I don’t mind it hanging loose behind the cover. Here’s everything together and putting the cover back on:

Bolt the adapter to the throttle body, re-using two of the 4mm factory hex screws and using the one from the adapter kit. Re-torque to spec (2.9 ft-lbs):

Continue on with the directions above to install the air filter and finish the install.

Addendum:
While putting the fake cover back on, It looked to me that the breather hose is too long to comfortably fit behind the fake cover. I pondered it a while and was afraid that the line would kink and restrict airflow, so decided to do something about it. I could either replace the breather line with something shorter, or cut the existing line. I didn’t want to cut the original line at first, in case I ever wanted to put the stock airbox back, but in the end this is what I did. Otherwise, I would have had to perhaps remove the gas tank to run another one. Yuk. I cut about 2” off the breather hose so that the external filter would rest behind the fake cover and just barely touch it, instead of being smashed into it. If I ever put the stock airbox back, I’ll leave the external filter in place and just plug the airbox where the breather hose used to go.

Boomer Sooner
Potestatem obscuri lateris nescis

If YOU ever want to replace

If YOU ever want to replace that hose it costs $40.00+ at your local yammie shop. (ask me how I know).......
Anyway, along the lines of the crankcase fumes/pressure, I HAD mine run into the back of my thunderair kit. It actually (the crankcase), has SO much pressure, it (after oiling), would literally blow the oil OUT /onto the back of the engine. I ended up running an aftermarket crankcase filter (similar to the one that comes in the kit, only NICER), right behind the engine. (I still smell fumes, but not HALF as bad as when I had it running thru the air cleaner itself.
I experimented with ALL sorts of sizes of hoses going into/back of air kit. Figured maybe I was creating a high pressure zone (reducing/reducing/reducing), until it'd literally SQUIRT the crankcase pressure out under HIGHER then normal force, forcing the air cleaner not to be even working as an air cleaner, just a catch all for crankcase pressure.
Anyway, if you ever 'measure' the actual crankcase pressure, I had over one inch (pulsating of course), @ idle, and more off idle, 2,000 rpm. I had someone else here on these forums do the same test and got the same exact readings, so what I"m saying is, (and I was paranoid at first when I thought about it), NO, my engine is not toast, NO it doesn't use ANY oil /leaking or otherwise, it's just the nature of the V twin beast. Lots of crankcase pressure. Two HUGE pistons thumping up and down, up and down, that pressure has to go somewhere. With the stock air filter setup, ALL the fumes were FORCED into the air cleaner/intake. (take it apart, look at it). NOW with the thunderair (i.e. OPEN), setup, the pressure pushes it OUT, (along with the crankcase fumes). You'll also notice (if you change brands of oil like I did a couple times), THAT all oils will smell different coming out the crankcase as fumes...........some are tolerable, some are not. I found lucas to be the WORST smellling oil/vapor wise. Amsoil and yamalube are tolerable. (still pisses me off, but it's tolerable). My .002 and then some.

Crankcase vent

Great writeup.

My concern is venting the crankcase vent tube directly into the throttle body and not through the filter.

It looks like you could accumulate a lot of oil residue in the throttle body. In stock configuration there is a residue on the filter element from the crankcase gas.

What have you found and what are your thoughts?

Interesting

Hi Kmac!

Now that is a VERY interesting question, and something I hadn't considered. I did happen to take it apart this weekend to look at it, and so far everything looks clean.

Perhaps I will direct this question to Thunder and see what they have to say.

UPDATE: OK, I talked to Travis at Thunder, and he said they tested this alot with the v-stars and they never had any issues with it going directly into the adapter. He said the way the engine is designed, it has a longer path through the engine and the chances of anything coming back through the breather line are very minimal, as opposed to a Harley, whose engine design pretty much necessitates an external filter.

Something to keep an eye on, though. If there are any concerns about it going directly into the adapter, Thunder has no problem with sending you the external filter.

What we need is someone who has this configuration that has ridden with it a lot longer than I have and have them pull the filter off and see if they see anything accumulating in the adapter.

Boomer Sooner
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Addendum

I took a good look at the crankcase breather hose this weekend. This line starts at the back of engine at the top of the block and then goes up and over the rear cylinder and then into the airbox. It looks like the chances of anything blowing back through the line(like oil) is pretty unlikely.

Boomer Sooner
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Gains

J brock
Hi BoomerSooner, looks like a good mod. What did you gain More HP...?

Gains

Hi J Brock,

Without a dyno test, I really don't know how much the increase is. I have read elsewhere, though, that the gains are about 3 - 5 hp.

Enjoy the ride!

Boomer Sooner
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Great info

Thank you for the great info.
What is the cost for such a mod ?

decro

Cost

Howdy Decro,

It's $80 for the adapter and for a plain filter kit it's about $190, if you order directly from Thunder. You can probably find it for less by googling a bit.

Enjoy the ride!

Boomer Sooner
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adapter

Very Intresting
do you have a Address were i can order that adapter ?

Since there is almost NO Aftermarket for the V Star 1300 here in Germany, because that Bike is not very popular here.

THX & Greetz Deven

okay i found it my self.

okay i found it my self. I´m planing to use a hypercharger....but i have a V-star 1300 (A Model) ??
Do i have to mount a Powercomader with the Hypercharger ?

greetz
dev

powercommander

Hi Devenkiller

You don't have to install a powercommander for just an airkit install. I and many others have been running just fine without one. There are others that have changed the pipes as well and recommend getting one then. Adding a fuel module will get you a power boost, though. If you do choose to go with a fuel module, I would recommend a Cobra fi2000r closed-loop unit. If you do some quick searching on this site you will see that almost everyone that has used the cobra unit has been happy with it. Some people have had issues with the powercommander. I think this is due to there currently not being a map for our bike.

update: I just saw the photos of your ride and that is one awesome bike. For that machine I would definitely suggest adding a fuel module to it.

Boomer Sooner
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Power commander

I have the vance & Hines 2 into one installed with the stock fuel system. If I put the air kit on also,do I need to install the cobra or a similar device?

Tonka

The Great Debate

Hi Tonka!

What you have asked is a matter of great speculation on this site. If you do a little searching, you will find equally compelling arguments for both sides.

Personally, I would add one with a mod to pipes and air kit. But before you travel that road, here's something to try: After you install the air kit, remove the positive cable from your battery for a few minutes(you'll have to reset the clock, oh, and make note of your trip odometer, it will reset to zero). The stock fuel manager adapts to your riding conditions, and removing power will reset it and allow it adapt to the air kit + muffler. It will still probably run a little lean(just my opinion), but others have reported good results. Ride it this way a while, and then if it doesn't perform the way you want, add a fuel manager. I'm biased, but I recommend the Cobra FI2000R.

Boomer Sooner
Potestatem obscuri lateris nescis