Ear Shave Performance Question - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 7 (permalink) Old 04-27-2018, 10:42 AM Thread Starter
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Question Ear Shave Performance Question

So, I've been reading through this forum quite a bit, but I cannot seem to find a conclusion.

Does the Ear Shave help performance?

Some say yes (the bike breaths better), and some say no (you lose the the surge tank added mid-range torque).

The procedure I found says to rejet from stock 132/38 to 142/42. This is a size of 107.5/110.5% compared to stock. This would imply one of 3 things:
1. A power increase of 7.5% to 10.5%.
2. Increasing fuel 7.5% to 10.5% changes the bike from running lean to running rich. It sounds like it's factory tuned lean to accommodate emissions, and allow for better high altitude running.
3. An efficiency LOSS of 7.5% to 10.5% and no net increase in power. Thus, a 7.5% to 10.5% loss in MPG.

So is there any conclusion on this? I'm not interested in cosmetic only mods. I can't justify the cost/time if I don't gain a boost somewhere. If that's the primary purpose, I'll pass on this mod (but I don't judge those that do it!).

Thanks!


'89 Vulcan 750 Bought 4/12/18 @ 17805.9 miles $800
Purchased stock. Wrecked once
22490.0+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB
110/90 Front Tire
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages
Ear Shave (wo/ coasters) 40/140 NO shims 45MPG
MCCT conversion

Planned modifications:
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance
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post #2 of 7 (permalink) Old 04-27-2018, 12:09 PM
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Rejetting to 42/142 is not necessary and even a bad idea, IMHO. I live in FL (elevation 0) and 42/142 was hopelessly rich and the performance of the bike was no better with all that extra fuel being dumped into the engine. I recently re-jetted down to 135/38 (one size up on the main jet, stock pilot) and I am much happier with the results.

I believe it only increases power if you were in a situation like mine, where the carbs and jets were clogged hopelessly and needed to be remove, cleaned, and replaced. Basically, I regained lost power, but can't tell if I gained any over what the bike made from the showroom. Removing the surge tank makes carb removal for cleaning easier, so the earshave does that and increases the induction noise so it SOUNDS faster. I don't believe anybody has done A/B testing of a stock bike w/clean carbs and stock intake vs a bike with a stock-jet earshave, or a re-jetted earshave. The difference and kicker for me was ease of maintenance.

The stock air system with a set of K&N's should be no more restrictive than a set of pods. Rejetting for an earshave is not necessary, even at sea level, based on my anecdotal evidence. I think you may gain a bit of low-end torque if you do like I did and shim the needle and re-tune the idle mix screws.

If you want hard numbers, probably out of luck. If you want to be a dyno guinea pig, that'd be awesome! If you want an anecdote, mine is unreliable because my performance was hindered by dirty carbs. That said, my anecdote says the mod was well worth it. My carbs are clean and I still have good torque at all revs, especially at 4k-6k RPM. AND I was able to go back in and correct my mistake and successfully re-jet the carbs in about 2 hours after a year of running way too rich.

If you want a bit of a performance upgrade for (nearly) free, set the clearance on your pickup coils.

Earshave+Rejet (38/135) NGK Iridiums MCCT Conversion Slipstreamer S03 Windshield Custom Extended Backrest Custom Highway Bars MOSFET R/R LED Underglow Volt+USB In-Dash Two-Wire & Blue-Wire Mod Satin Black Engine Paint Dampers Parts - Jets: Main=99101-393(#132 stock)/Pilot=n424-22 Pilot(#38 stock)
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post #3 of 7 (permalink) Old 04-27-2018, 03:53 PM
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My carbs are stock, earshaved, and I can't imagine having more torque/performance than I have now. It seems better than stock, but I didn't get much seat time before the shave. Probably 10 miles before I dove in with all the work.

I just have no complaints, nice low-end above 2300rpm, strong mid-range punch from 4000-7000rpm, and it will go well beyond redline if you let it.

When you have to clean your carbs, you'll be happier if the airbox is gone. Nobody escapes carb cleaning.

edit: I can't get better than 44mpg, the power is too much fun.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf

Last edited by Spockster; 04-27-2018 at 03:59 PM.
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post #4 of 7 (permalink) Old 04-27-2018, 04:04 PM
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The UNI PK92 filters are about 1/3 the price of K&N, if that helps any with your decision. I like how the foam is easy to clean and re-oil. Don't think they are selling the chrome ones any longer.

edit; Your signature says you're already earshaved?

If you open up the pipes much, you'll most likely need some jetting.
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2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf

Last edited by Spockster; 04-27-2018 at 04:08 PM.
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post #5 of 7 (permalink) Old 04-27-2018, 04:38 PM Thread Starter
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Spockster, I modified my signature to draw attention to the planned modifications.
It was all a blur before, but no I have not done the ear shave yet.


'89 Vulcan 750 Bought 4/12/18 @ 17805.9 miles $800
Purchased stock. Wrecked once
22490.0+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB
110/90 Front Tire
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages
Ear Shave (wo/ coasters) 40/140 NO shims 45MPG
MCCT conversion

Planned modifications:
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance
Jason Pittenger is offline  
post #6 of 7 (permalink) Old 04-27-2018, 07:43 PM
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I'm in the totally stock exhaust, carbs, intake, etc. camp, and I plan to stay that way. Sure it's a lot of grief to remove and replace, but that shouldn't be necessary as long as I care for the bike properly. Some people enjoy the challenge of modifying exhaust, rejetting, etc. Personally, I don't get much out of it. I enjoy the power and efficiency of the stock bike. Is it possible to get more performance out of the bike? Sure, probably, but I'm pretty skeptical that there is a measurable increase. I think it's probably more likely to be a decrease in many cases.

Years ago I had an '81 Yamaha XS650. I laid it down and rashed the exhaust pretty badly. Ended up buying the bike back from the insurance company and replaced the stock exhaust w/ a 2 into 1 Mac system. The bike never ran properly after that despite re-jetting numerous times. Yeah, I know different bike, different issues, etc.

Also had a '97 Suzuki Intruder for a couple of years. Owner had swapped out the stock exhaust for a Cobra system, but never bothered rejetting the carbs. Bike ran way lean, and turned the oil black in a very short period. Was also loud and obnoxious to my ears. It was fun at first but got old fast. I was able to re-jet and get it to run acceptably, but was way more trouble than it was worth (to me!).

I learned from those experiences that this aspect of ownership is just not my thing. . . . It's a free country, though. Everyone needs to decide what they want to do with their bike!

GDI
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post #7 of 7 (permalink) Old 04-27-2018, 08:49 PM
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