a lot of my riding is at night so i want something brighter but without the higher current draw and worrying about melting wires or headlight housing...i have read about early burnout on some brands...any suggestions from ya'll?

'05 black/chrome
stock for now
have parts/will install

I have sylvania silver star in mine and am really pleased. Seem a good bit brighter.

I have sylvania silver star in mine and am really pleased. Seem a good bit brighter.

ditto.....i also added driving lights though.

Another vote for the Silverstar.
I run it on high beam all the time during the day and no issues with heat or burnout.
Plus it measured 22% brighter compared to the stock bulb, measured with my hand-held light meter.

Another vote for the Silverstar.
I run it on high beam all the time during the day and no issues with heat or burnout.
Plus it measured 22% brighter compared to the stock bulb, measured with my hand-held light meter.

What's the model number of the Silver Star?

EDIT: D'oh.. never mind.

After I got mine at Shucks Auto Parts for $21.00 (for one) I found out that Wal-Mart has them in pairs for $29.00.

silverstar in every thing i drive

Silverstar here too...

I use ion crystal bulbs. No need for high beam and they do attract attention.
Attenton is what we all want and need for safety.
I bought mine on e-bay from the link below.
Kuryakin has them too (bottom link)
No heating/melting of wires. I have used them for over 4 years and will always use the.
http://cgi.ebay.com/ebaymotors/AUTHENTIC-JAPAN-MTEC-H4-ION-YELLOW-CRYSTAL-BULBS_W0QQcmdZViewItemQQcategoryZ33710QQihZ010QQit emZ200030315529QQrdZ1QQsspagenameZWDVW

http://kuryakyn.com/products.asp?bn=harley&ci=3389

SilverStars...

I use the SilverStars. Great performance. GE has a version now, but I have no experience with them. If you are looking for increased lighting, but don't care whether or not it has the 'bright-white' look, check out the Sylvania XtraVision bulbs. Half the cost of the SilverStar with the same performance, but at a lower color temperature (more yellowish).

Kim

Got to go with the silverStars

I've run the Silver Star sealed beams in both of my Porsches. When I replaced the sealed beams in my 951 with Hella H4s, I ditched the stock halogen lamps and installed a set of 9003 (H4 equivalent) "Super White" lamps like the Honda/Mitsu/Rice Burner tuners run. Much better lighting than the Silver Stars.

I recently switched to 9003s in the GF's Virago and my '03. Now both bikes have plenty of light.

What is the most wattage you can use without burning up wires? I just put in a P!AA 80/100 and it made a big difference. I would like a bit more and was wondering if I should go with a Candlepower lens or a higher wattage bulb?

You gotta be careful about using higher wattage lamps. The wiring is designed for the standard wattage. Adding a "hotter" lamp draws more current through the wires. More current equals more heat. Too much heat will melt the insulation and/or connectors.

In the Porsche world when someone wants to add hotter lamps, we always recommend adding a relay and wiring the relay so that the new lamp circuit goes straight to the battery.

Personally, I use standard 9003 (H4) "Super White" 55/65 watt lamps. With Hella H4 lenses my Porsches have more than enough light. I recently "upgraded" my '03 Sportster and my GF's '87 Virago to 9003 "Superwhites" and both bikes have more than enough light.

XLCR: you already have one of the best reflectors available.I just changed mine from the HD Xenon boosted lamp (OEM is a NARVA 48676 which is a +30% type of lamp but RPB ='s rangepower blue) to a 80/85W clear bulb - 2400Lumens of light. The stock wiring will support 85 Watts. Any higher and I would be cautious. Your can test by getting good DVM and measuring back to the battery while the engine is running. Any more than 1 volt DC and there is an issue in the wiring, connections or the switches.

One thing, somehow the inside of my reflector had developed a film. Not visible when the light was off but highly visible when on. The fix was a lot of windex, a set of chopsticks (won't scratch) and a micro fiber cloth. Also, clean the bulb's envelope with alcohol.

Good luck,

SEMJPM

I have about 3 hours ride time with the 80/100 bulb. Nothing burnt out yet. I forgot to feel the wires. The bulb is so much better, I will rewire it if I have to. Other threads said it was the max wattage to use with stock wiring. I put on an extra light and wired it directly off battery in case they were wrong.

I think the reflector is one of the worst I have seen. But I am comparing to cars. No one will let me ride their motorcycle at night, and no one needs to tell me cars have two headlights.

Are you talking about the resistance in the wires causing a 1 volt drop?

Yep, the headlight wires were getting slighty warm to touch. 100 watts is pushing it. I am going to order the www.comagination.com relay kit.

The voltage drop is caused by 2 factors: guage of wire being too small for current being drawn and any loose / dirty connections in the path from battery to bulb and back.

The Sylvania Silver Star 9003 are XLent

I was told that the silverstars burn out faster than most other bulbs. Doesn't sound like there as bad as I was told since almost everyone says silverstar in this thread.
I would be carefull about those hyper white bulbs that have the blue tint to them. I bought the adjure reflector and installed a hyper white that has the bluish tint to it and the reflector housing came with a rubber boot that went over the wire harness in the back and when I had to replace the bulb the rubber was melted to the back of the reflector housing. I remember my indy telling me how hot my headlight was when I brought it in during the winter once to do some mods as well.

Yep, getting SilverStar for everything.....
- Someone mentioned GE - I used with GE Lamps and I would stick with Sylvania, any day of the week. Sylvania has good quality,
watch out for some of those "tuner" rice lamps that claim to be sooooooo bright and soooooo blue. Ya don't want to be coming home, some night and have your bulb fail @ ____mph ! :smackh :angry The quality control, just ain't there.

Went to Wal Mart last nite to look for the Sylvania bulbs and found a whole bunch of them.

However, none of them had the number mentioned above of 6158174. The bulbs were referred to with numbers like 9003 and 9007 on the packaging.

Can someone please give a better description of what Sylvania bulb I should be looking for.

No one has mentioned the H-D Xenon bulbs P/N 67864-04 or 67863-04 that list for $21.95. How do these bulbs compare to the Sylvania's?

Thanks,

Fred

9003 is the same as an H4, which is the same thing as the Harley part. You want 9003.

Thanks Gold951!

Fred

For cheaper source you might try these guys:
http://www.rallylights.com/hella/H4.asp

SEMJPM

I use PIAA bulbs on my bikes. Pricy but much brighter while still using the same wattage. I use the super plasma because I like the purple look of the low beam.

http://www.piaa.com/Bulbs/Bulbs-H4.html

Went to Wal Mart last nite to look for the Sylvania bulbs and found a whole bunch of them.

However, none of them had the number mentioned above of 6158174. The bulbs were referred to with numbers like 9003 and 9007 on the packaging.

Can someone please give a better description of what Sylvania bulb I should be looking for.

Thanks,
Fred


Osram-Sylvania ‘SilverStar’ Halogen Headlight Bulb:

P/N: 9003ST

High performance halogen bulb - Dual filament for both high beam and low beam

Sylvania web site: http://www.sylvania.com/ConsumerPro...ine/default.htm

SilverStar is whiter light, closer to the color of daylight. Whiter light helps you see better at night. And if your night vision is better, night driving is safer.
Here is a good FAQ section about these SilverStar bulbs on the Sylvania web site: http://www.sylvania.com/ConsumerPro...AskedQuestions/

About $20 - $22 from AutoZone

Thanks Turbota!

Fred

The "off road only" NAPA 80/100 halogen H4 for about $12 cannot be beat when compared to any legal bulb.

My sporty throws out more light than my car at this point.

No meltdowns, no issues and I put about 3000 miles this year with it in there, most of the time on high beam.

I have been using Hella bulbs in my car, and no burn-outs in 8 years. I had just recently converted my XL to an H4 bulb, and the bulb that the lamp housing came with (adjurl or however you spell it) has been fine for 2 years. The lamp seems to burn kind of warm with the standard 55w/65w bulb, so I really wouldn't run an 80w/100w bulb in it. Especially without increasing the size of the lamp wires to a thicker gage.

Hi all.

I went to a trade show a wile back and got to talk with the reps from the major bulb company's.
Wile they all had some type of high output bulb, either they had to raise the wattage requirements or they all hit a ceiling for output.
The one exception to this was PIAA, They have a new super plasma GT-X bulb that wile it draws the standard 55/60 watts, it outputs like a 125/135 watt bulb would. (3800k low beam and 5000k on high.)
http://www.shopatron.com/img/product_images/353/15962.jpg
I got a two pack so the boss and I could split it, so the bulb ended up costing me 31 dollar's and I know this is more then most would want to spend for a bulb, and if you do all your night riding on well lit city streets, well I would be hard pressed to spend that much either, But where i live, you can find yourself on a back road riding half blind through deer country in a hurry.
I have had this bulb on some dark back roads and i must say, i really don't need to hit the high beam, but when you do, you can see a mile+ with no problem.

The one caution I would give you is to make sure you have the headlight aimed so you get the most out of this bulb, and you are not pissing off the cars in front of you.

Yesterday I replaced my stock lamp with a Sylvania Silverstar H4 (motorcycle use) from Advance Auto. The bulb was 5 bucks off to cost $14.99.

The change was easy and while I run Silverstars in all of my vehicle, I have to say that this is the greatest difference that I have observed over the stock bulbs in any of them. Really amazing.

BTW, I have had Silverstars in 5 or more cars (currently my Wrangler and Grand Cherokee; both stock bulbs in the headlights and off road lights replaced in the past 3 years. The only bulb that ever burned out was a headlight on my Wrangler where I have taken it on a few pretty hard off-road rides.

That was the reason I bought the H4 rather than the standard Silverstars for the sportster; they supposedly are more shock resistant. If I used the 9003 bulbs I would carry a spare.

What I have noted is #6158174
After I got mine at Shucks Auto Parts for $21.00 (for one) I found out that Wal-Mart has them in pairs for $29.00.

It would be nice if somebody could edit this post. This part number doesn't work, and has caused a few of us some headaches because we read down to this post, it looks official, and then we go to the store with the part number, only to be told that part number doesn't exist.

As stated by many people later down in the post, the correct part number is:

9003ST, which is the same thing as an H4 Sylvania Silverstar motorcycle specific bulb.

I really like this bulb, by the way. I've always used them in my cars, and just never thought of using one on the bike. Glad I made the switch.

Mister B, that is the part number I have on the package of Sylvania H4 Silverstars that is right here, in front of me.
If I had a scanner I'd put up a pix.

Nowhere does it say 9003ST.
Perhaps it is packaged especially for WalMart, which is where (I think) this one was purchased.

Mister B, that is the part number I have on the package of Sylvania H4 Silverstars that is right here, in front of me.
If I had a scanner I'd put up a pix.

Nowhere does it say 9003ST.
Perhaps it is packaged especially for WalMart, which is where (I think) this one was purchased.

That's weird. The package on the one I bought doesn't have your numbers at all, and at least one other guy on here said the same thing. Perhaps Sylvania updated the part numbers.

When looking in Walmart for the part number Jay, the guy with the 883c, posted, all I found were 9003's and 9004's. Nothing close to what Jay posted.

When I learned that 9003ST was the number, bought at Target as I was with my wife and she refuses to go into Walmart.

I think Mister B might be right, the model number was changed by Sylvania and Jay found an old package.

Fred

Could be old stock.
I'll change my original post to show that it may or may not be that number.
I'd have done it before but I haven't been paying attention to this thread.

I'll let you all know when I melt down something. H4 80/100 osram bulb has got a nice white burn to it. The 05 up headlight was a big improvement in itself.

Went upstate today and the low beam blew out on me. Seems I go through a bulb every year but the past 2 bulbs were cheap car bulbs so I don't blame any one but myself for that. I was right next to an auto zone and went in and checked out the silverstars. Picked up the single pack H4 bulb and changed it in the parking lot in about 5 minutes. Definetly a difference over the regulay H4 bulb I had in there. Much easier to see at night now. I didn't even realize when I picked up the package that it said "For motorcycle use only" on it until I was ripping open the package to install it.

MikeLI_77,

That is exactly the package I have. They also had 9003ST marked packages, but when I saw the "motorcycle use" I figured that would be the ones.

The 9003ST will work just fine ... Mine has been in the bike for the last 1 1/2 years with no problem.

That bulb along with the newer model 05 headlight lense has certainly helped in brightening up the road in front of me on my 04.

BTW, the 04 and older headlight lense sucks!

Checked my package and it does not say "for motorcylce use only". Does this make a difference?

Fred

Checked my package and it does not say "for motorcylce use only". Does this make a difference?

Fred

I don't think so. As long as it's a 55/60 watt H4 it should be fine.

I think they label single bulbs like that to discourage mis-matching them on cages or other multi-light vehicles, or to make you buy two ;)


Bart

I ASSUME "for motorcycle use" indicates more vibration resistance.

I ASSUME "for motorcycle use" indicates more vibration resistance.

"Motorcycle use ONLY" is the designation in question here.

Wouldn't that extra vibration resistance be of benefit to other applications as well?


Bart

Two days before I read this XL forum, I had bought the high performance bulb that the H-D dealer lists for $21.95 (part #67074-2) Already opened and installed, haven't rode at night yet. Anyone know how this compares with the Sylvania SilverStar for better ability to see at night? Otherwords, should I keep the one I just bought as a spare and go ahead now and get the SilverStar? Or is the difference minimal and not worth the investment? Thanks all, ride safe.

Don't know if this is the same bulb I bought about two years ago to replace the bulb in my '03 Sportster. But the H-D bulb I bought ($19.95) did improve the quality of the headlight over the stock one that came with the bike. Can't tell you how it compares to the Sylvania Silverstar however.

Fred

I don't do much night riding, guess I'll wait and actually try the new H-D bulb out first, then go from there. Thanks all.

After reading all this, I went out and got a Silverstar H4 bulb for my lamp. It's the standard 55/60 watt bulb. It seems to work better than the stock lamp, that's for sure. It doesn't put out more light, it's just more white than the stock bulb. It does make obstacales in the road a little more visable.

I tend to ride with my low beam all the time and this made it easier to see at night. I adjust my light so the beam projects further without needing the high beam.

The part number for this Sylvania Silverstar was "H4 ST". It had writing that said "For Motorcycle Use Only" going up the side of the package. Can't really miss it. Cost about $19-$21 at Autozone.

Hey,
I was looking for advice on bulbs,and found it it this thread.Going to try the Silverstars..I had one of the HD better bulbs but it went on me.The regular bulbs like everyone agrees on are not very bright.Gets pretty dark around here at nighttime.
Pete

Silverstars seem to work pretty well. Another important thing is making sure you light is adjusted properly.

I have a buddy who complained of his light being really weak and driving with the high beams all the time. It wasn't till he was behind me that I realized the problem. The thing was pointing about 4 feet about where is should have been. He had put shorter shocks on the rear without adjusting the light.

I've acutally been looking into aftermarket driving lights to supplement the headlight. I worry about the headlight going out on a deserted road or on the freeway. It's bothersome to think you only have one light and if that goes out... :wonderlan Motolights seem like a really good lights and our bikes can handle the extra load. At over 300 bucks they aren't cheap but I've seen them in action and they sure work well.

:geek For what it's worth I've been running an :wonderlan H4 80/100:wonderlan for almost a year and just about 7,000 miles without problems. It is my understanding that this is about as "hot" as one should get with H-D wiring. I got mine for $15.99 at good ole J&P under the "German Touring" banner 380-887 is the part number. They do have a 55/60 and a 100/130 but I'm sure that last one would be too hot. This bulb throws out alot of light and has a very servicable pattern. I run "high" beams during daylight rides and my wires tolerated this bulb and a hot midwest summer.:geek There are many choices, I only pass on that I've been very pleased and I ride some dark county roads coming into the bright city as I often work the midnight shift at a city hospital.:tour :tour

rICK

That's too risky for me, I play it safe. :geek

I'm sure it puts out a hell of a beam though. Even flipping to the 60 watt high beam is a substantial difference. Althought the light pattern gets all funky when I go to high beam. But I have my light adjusted so that the low beam extends pretty far. I think the way harley suggests adjusting the light is aweful! With low beam at night you can only see like 30 feet in front of your bike.

I installed the 70/65W Osram lamp from http://www.rallylights.com/. The lamp is a clear envelope H4 XENON filled lamp that does not tax the wiring.
Below are few before and after test results. The meter used was a GE light meter normally used to setup stage lamps. It measurers the light falling ON a subject. The extact foot candle readings are not that meaningful, the comparisons are. Best gain is with the low beam.

SEMJPM
__________________________________________________ _________
Stock 55/65W = low beam peak 90 foot cancels, high beam peak 100 foot candles
New 70/65 W = low beam peak 155 foot candles, high beam peak 125 foot candles.

* Stock lamp is the HD Xenon lamp (55/65W) which is supposedly rated for a higher output than a plain 9003??
** Measurements taken for peak reading at 34" up from floor and 12 feet from lamp assembly of stock HD 2005 clear reflector with 12.9 VDC at lamp terminals.

How can I get ahold of Adjurl company it self instead of through other distributors? Do they have a website?

Adjure Inc. lighting (http://www.adjureinc.com/)

Feeling like I should express my desire to make my Deuce happier...like flowers for my bride...I stopped in to get the Sylvania bulb to make it brighter.....Autozone...almost as cheap as Wally World...and they had lots...so I grabbed the GE hi output equivalent without even noticing. Oh well, they are maybe a little better than stocker and the Deuce knows I care.
John

I had the silverstar go out on me a couple of months ago. Replaced with A Phillips version 9003, This one went out tonight. of course I got the dual pack. Which may be the problem, I'll go look for the MOTORCYCLE USE ONLY bulbs this weekend.

Last night I put in a PIAA gtx super plasma (vibration resistant)60/55W=135/110 -what a a difference-I can see!!:clap

Last night I put in a PIAA gtx super plasma (vibration resistant)60/55W=135/110 -what a a difference-I can see!!:clap



Ide be careful with that wattage...check your harsess...

The cool thing about these higher output lamps is they draw the same amount of current that a halogen or incandescent lamp does.

The lamps that doxbike installed draw 55 watts on low beam and 65 watts on high beam, but the light output is equivalent to a "normal" lamp that draws 110 and 135 watts.

I use similar lamps in my Porsche and in my bike. Much better light and no worries about frying the connectors or the wires.

Ide be careful with that wattage...check your harsess...

The wires, lens, & bucket are all cooler than with the standard bulb I took out so I'd assume that is a good indicator, yes?

I'm surprised nobody has mentioned the Philips Vision Plus bulbs.

Decided to upgrade the 9003/H4 bulb in my wife's '92 a couple months ago, so started researching the I-net. I ended up choosing the Philips, and yes, she says it's a definite improvement over the original OEM.

As has been thoroughly pointed out here, the most popular bulbs are Silverstars - work well, easy to obtain and priced right. But there are better bulbs. Keeping the price on the lower end the Philips Vision Plus is one. Not only brighter & whiter, but has historically proven that the filaments are heavy duty and don't break prematurely in our heavy vibration environment like the majority of halogen bulbs do. Drawback - cost is higher than Silverstars, and definitely more difficult to locate. Seems that these Philips bulbs are more popular in the U.K., and thus most all distributors are from 'over there'. There is one place out in CA I found that stocks 'em, and gets 'em out within a couple days.

A definite top dog in vehicle lighting is PIAA - and the price comes right along with it. Advice on this behalf, as is told elsewhere in this thread: watch your wattage - both input current/power draw from the battery, as well as light/lumen output, or actual photon emission output. Two entirely different areas to be concerned with, and both can cost you repair money if you don't be careful of your choices. Put a bulb in there that draws too much current for your wiring harness and you'll be smellin' burning silicone wires in no time. Stick a 110 watt equivalent output (very subjective whether these numbers are true) into a 65 watt housing with a internal reflector cup and you'll watch that thing disintegrate over the next couple months from the heat - trust me on that one as I experienced that exact effect on my cage fogs after swapping out the OEM's with high-output PIAA's.

Yep, getting SilverStar for everything.....
- Someone mentioned GE - I used with GE Lamps and I would stick with Sylvania, any day of the week. Sylvania has good quality,
watch out for some of those "tuner" rice lamps that claim to be sooooooo bright and soooooo blue. Ya don't want to be coming home, some night and have your bulb fail @ ____mph ! :smackh :angry The quality control, just ain't there.

Got the Sylvania H4 SilverStar installed !! ....it ROCKS !!!

I'll be honest with you guys. I read these light bulb threads, got all motivated and went out to PepBoys and bought the silverstar bulb. Didn't check for a "motorcycle use" lable though. Darn thing was nice and bright but burned out on me after less than a month. Luckily, I kept my stock bulb. Unluckily, I had to change it out at about 5 a.m. before I could go to work.
Next time, I'll check for the right info on the bulb or quit listening to the voices in my head....

This is from a thread awhile back.

I was confused by that awhile back because both bulbs had the same stats on the web site. I wrote a letter (E-Mail) to the Osram-Sylvania tech people. The following is the question and reply.


Dear Sir, or Madam,
I use Silverstar bulbs in all four of my cars. I like the performance of the product. I want to use the SilverStar in my motorcycle, and was told the 9003 would last longer then the H4.
I do not see any difference in the specifications between the two bulbs on you web site other then the statement that the H4 is for motorcycle applications.
My question is; What is the difference between the two bulbs, and why should I use the H4 on my bike? Thank you.
Sincerely,


Thank you for your inquiry. Most motorcycle applications request the H4 as most vehicle application request the 9003. The difference between the two is that the H4 has a higher filament tolerance to undergo shock and vibration that comes with motorcycle operation. You are correct, other than this difference both lamps are designed to the same voltage, wattage, base type specifications and can be interchanged.

Thank you.

Delilah Jones
OSRAM SYLVANIA
Automotive Lighting Division
Ph: 800/347-3420
Fx: 800/347-3411


Just thought I'd pass it on....:D

...
Thank you for your inquiry. Most motorcycle applications request the H4 as most vehicle application request the 9003. The difference between the two is that the H4 has a higher filament tolerance to undergo shock and vibration that comes with motorcycle operation. You are correct, other than this difference both lamps are designed to the same voltage, wattage, base type specifications and can be interchanged.


I didn't know this, the 9003 designation and what it means that is - thanks for that detail.

I must have got lucky when I picked up the Philips bulbs I mentioned above as they are in fact labeled 9003 H4 right on the front of the twin-bulb package. This must in fact be the reason I've read of good success in these particular bulb filaments not breaking prematurely.

Incase anyone needs a bulb. Just got mine off amazon.com for $10. they're going for $19, w/a $5 discount, and $5 rebate.

Marc

Anyone interested in better headlight performance should consider a relay in the headlight circuit. I bought a complete dual H4 relay harness for my Yamaha from a website called easternbeaver.com. Weird name, great products. I was amazed at the difference, much brighter. Visit this site, lots of info on the effect of voltage drop through the stock harness. For stock wattage or higher wattage bulbs.

Also, rallylights.com mentioned in this thread has some good info on their site.

This is from a thread awhile back.

I was confused by that awhile back because both bulbs had the same stats on the web site. I wrote a letter (E-Mail) to the Osram-Sylvania tech people. The following is the question and reply.


Dear Sir, or Madam,
I use Silverstar bulbs in all four of my cars. I like the performance of the product. I want to use the SilverStar in my motorcycle, and was told the 9003 would last longer then the H4.
I do not see any difference in the specifications between the two bulbs on you web site other then the statement that the H4 is for motorcycle applications.
My question is; What is the difference between the two bulbs, and why should I use the H4 on my bike? Thank you.
Sincerely,


Thank you for your inquiry. Most motorcycle applications request the H4 as most vehicle application request the 9003. The difference between the two is that the H4 has a higher filament tolerance to undergo shock and vibration that comes with motorcycle operation. You are correct, other than this difference both lamps are designed to the same voltage, wattage, base type specifications and can be interchanged.

Thank you.

Delilah Jones
OSRAM SYLVANIA
Automotive Lighting Division
Ph: 800/347-3420
Fx: 800/347-3411


Just thought I'd pass it on....:D

Another definitive answer from Osram/Sylania about the differences between the 9003ST/H4ST.

Hello,

I trust you are doing well?

I will start by stating that OSRAM SilverStars and SYLVANIA SilverStars are two different products. While both the Sylvania and OSRAM SilverStars
provide increased lighting, the North American (Sylvania) SilverStar
bulbs have an amethyst blue coating to help give the whiter light
appearance. The European (OSRAM) SilverStar does not have a coating for
the whiter light; its increased light output and whiter light is created
through a different proprietary gas mixture. Both bulbs offer greater
luminance or increased brightness than their standard halogen
counterparts. The OSRAM SilverStars are not available to purchase in
the United States because they do not meet DOT regulations here. They
are manufactured to meet ECE (European) standards.

9003 and H4 are different names for the same part. American automobile
manufacturers tend to use the 9003 designation; European automobile and
American motorcycle manufacturers tend to use the H4 designation, so we
package this part using both part numbers 9003 and H4. If your
motorcycle use either part H4 or 9003 as original equipment, you can
upgrade to SilverStar using either part 9003ST or H4ST. Please do not
hesitate to contact me directly if you have any other questions or
require further assistance.

Sincerely,
Heather Kennett
Consumer Care Specialist
OSRAM SYLVANIA, Inc.

These gals from Sylvania aren't really giving you the true scoop on the difference between 9003 and H4 and one of them is totally off the mark:

In 1992 US regulations were amended to permit the use of H4 bulbs in automotive headlights. However, the US regs specified closer production tolerances than was typical for European H4 bulbs. These tolerances specifically dealt with the placement of the elements and how much it could deviate from spec. Bulbs meeting the tighter tolerance were required to be labeled 9003. They could also be labeled H4, but they could only be labeled 9003 if they met the US spec.

The net result has been, for the most part, that all bulb manufacturers tightened up their production tolerances on H4 bulbs so that all the bulbs they produce could be labeled as either H4 or 9003.

Bottom line: You can use a 9003 bulb in your Harley headlight without any worries about it not being "tough enough" for motorcycle duty.

I just checked the bulb that came in my stock Harley headlight. It's marked 9003.