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HKS update ATTN:Dave Bigelow

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jindoguy(at)gmail.com
Guest

Posted: Fri Jun 29, 2007 7:22 pm Post subject: HKS update ATTN:Dave Bigelow

Dave, Just thought I'd check in and see how your HKS is doing. I'm up to little over 20 hours and I'm beginning to figure the little engine out. I have finally figured out how to synchronize the carburetors and thought you might be interested in what I've found. 

First off, does your engine have a balance line between the two manifolds? 

Is it the latest ASTM compliant engine? Mine isn't, and the installation and operation manuals that came with my engine are the same revision level as those available online.  

As I recall, you have the vertical ( HKS terminology) intake manifolds with the carburetor over the head. These were apparently offered, as a pair, with a vacuum port on one intake manifold or on both. I say apparently because this is not documented. The installation manual has a fuel system diagram showing a single vacuum tap for the fuel pump and the text speaks of this, too (section  6.0 Fuel System and figure 5). However, newer pictures of the engine on the web site show a balance line between the manifolds.

I have the horizontal intake manifolds, with the carburetor level with the head. They have a vacuum tap on each manifold for a balance line between them and are also undocumented. 

Bottom line is this. The carburetor synchronizing instructions in the operations manual do not work if you have a balance line connecting the two intakes pneumatically. The balance tube does just as its name implies and does it quite well, too, making it impossible to synch the carbs. 

In my case, I was getting nice even vacuum readings and the engine seemed smooth. Then, I used the technique for the Rotax 912 (Line Maintenance Manual, chapter 12-00, pages 18 through 20) and the results were startling. There was a 3" difference in vacuum readings at 3000 RPM once the intake manifolds were isolated. Correcting this by adjusting the long throttle cable, and nothing else, increased the RPM to 3500. In flight, my cruising RPM, where Meadowlark can maintain level flight in still air, dropped from 4700 to 4500 RPM and max RPM at WOT went up to 6200 from 6100. I was also able to decrease idle RPM from 1750 to 1600. The manual recommends a 1400 RPM idle, but even with the carbs synched as close as I can get them I find it too rough. 

Because Meadowlark, having a very large wing, is so slow, most of the power of the HKS isn't used. Climb power is abundant, but I haven't been able to get in a dawn flight to measure still air ROC.

The flip side of the low power cruise is excellent economy. I flew a total of  4.5 hours on the last tank that included a couple of evenings of pattern work for a total of 20 landings in that time. Refilling the tank took a little over 8 gallons.

Once the rain stops, I'll get some fuel consumption numbers for the new tuning. 



Rick

-- 

Rick Girard

"Ya'll drop on in"

takes on a whole new meaning

when you live at the airport.  [quote][b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Fri Jun 29, 2007 7:35 pm Post subject: HKS update ATTN:Dave Bigelow

In flight, my cruising

| RPM, where Meadowlark can maintain level flight in still air, 

dropped from

| 4700 to 4500 RPM

|

| Rick

Rick:



Could you explain the above change in performance.



I don't understand how balancing carbs has anything to do with rpm 

setting and maintaining level flight.



Thanks,



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

Dave Bigelow

Joined: 29 Jan 2006
Posts: 103
Location: Kamuela, Hawaii

Posted: Sat Jun 30, 2007 1:02 am Post subject: Re: HKS update ATTN:Dave Bigelow

Rick,



My HKS came with the balance line between the two intake manifolds.  When I balanced the carbs with two vacuum gauges, I figured that the balance procedure couldn't work properly with the balance line open.  I plugged the balance line, and then did the balance procedure.



I have almost 25 hours on the engine now, and can't say much except it just works.  Cruise RPM for the Firestar II is in the range of 4,800 - 5,100 RPM, depending on altitude.  I haven't flown any one flight over 2.5 hours, but it looks to me like I should get slightly over 4 hours flying time on 10 gallons of gas.



I'm really liking the engine, and have made several flights now over terrain that would have made me very uncomfortable with the 503.  I'm suprised that Kolb doesn't offer the engine as an option for the FS II.

_________________
Dave Bigelow
Kamuela, Hawaii
FS2, HKS 700E

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Sat Jun 30, 2007 4:58 am Post subject: Re: HKS update ATTN:Dave Bigelow

What prop do you run, type and diameter? Do you have any details on mounting? i.e. any mods you had to make etc.?



It's interesting that the HKS weighs only slightly more than my 503 + C box. I've thought off and on about an HKS since I live at 7000'. I flew my FS II yesterday evening in 9000+ density altitude and, er, lots of full throttle was required . So more climb power would be appreciated...



The HKS seems to be doing well, I've seen it offered more often, some trike manufactureres like Air Creation are starting to offer that motor on some of their models...



LS

_________________
LS
Titan II SS

jindoguy(at)gmail.com
Guest

Posted: Sat Jun 30, 2007 5:34 am Post subject: HKS update ATTN:Dave Bigelow

John, Look at it as though there are two separate engines hooked together. One cylinder is running at -3" Hg vacuum, the other at -6" Hg vacuum. Opening the throttle on the cylinder with the higher vacuum brings the vacuum down and the rpm on that cylinder increases. As the vacuum readings are brought into synch the overall horsepower of the engine produced increases. In my case the increase in horsepower was enough that the engine was producing the same HP at 4500 RPM that it had at 4700 RPM when the carbs were out of synch. 



Rick



On 6/29/07, John Hauck <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)> wrote:[quote] --> Kolb-List message posted by: "John Hauck" <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)>

  In flight, my cruising

| RPM, where Meadowlark can maintain level flight in still air, 

dropped from

| 4700 to 4500 RPM

|

| Rick

Rick:



Could you explain the above change in performance.



I don't understand how balancing carbs has anything to do with rpm

setting and maintaining level flight. 

"Ya'll drop on in"

takes on a whole new meaning

when you live at the airport.  [quote][b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Jun 30, 2007 5:47 am Post subject: HKS update ATTN:Dave Bigelow

|  In my case the increase in horsepower was enough that the engine

| was producing the same HP at 4500 RPM that it had at 4700 RPM when 

the carbs

| were out of synch.

|

| Rick

Does that mean you repitched the prop to compensate for the increase 

in hp?



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

jindoguy(at)gmail.com
Guest

Posted: Sat Jun 30, 2007 5:56 am Post subject: HKS update ATTN:Dave Bigelow

Prop pitch is next on the list to be evaluated, however, if I don't exceed 6200 RPM in climb, I'll leave it as is. The nature of the wing is such that I cannot do a full RPM check in level flight.



Rick



 On 6/30/07, John Hauck <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)> wrote: 	  Quote: 	
		   --> Kolb-List message posted by: "John Hauck" <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)>

 |  In my case the increase in horsepower was enough that the engine

| was producing the same HP at 4500 RPM that it had at 4700 RPM when 



	


-- 

Rick Girard

"Ya'll drop on in"

takes on a whole new meaning

when you live at the airport.  [quote][b]

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Sat Jun 30, 2007 6:00 am Post subject: Re: HKS update ATTN:Dave Bigelow

 	  John Hauck wrote: 	
		  |  In my case the increase in horsepower was enough that the engine

| was producing the same HP at 4500 RPM that it had at 4700 RPM when 

the carbs

| were out of synch.

|

| Rick

Does that mean you repitched the prop to compensate for the increase 

in hp?



john h

mkIII 	




I'm slightly confused as well - is that at full throttle at these rpms?



LS

_________________
LS
Titan II SS

jindoguy(at)gmail.com
Guest

Posted: Sat Jun 30, 2007 6:29 am Post subject: HKS update ATTN:Dave Bigelow

Lucien, My HKS is installed on a trike (weight shift control aircraft). 4700 RPM is far below engine redline (5800 RPM continuous), but the nature of the flex wing doesn't allow me to do full power and level flight at the same time. 



Rick



On 6/30/07, lucien <lstavenhagen(at)hotmail.com (lstavenhagen(at)hotmail.com)> wrote: 	  Quote: 	
		   --> Kolb-List message posted by: "lucien" <lstavenhagen(at)hotmail.com (lstavenhagen(at)hotmail.com)>

John Hauck wrote:

 	  Quote: 	
		   |  In my case the increase in horsepower was enough that the engine 

 | was producing the same HP at 4500 RPM that it had at 4700 RPM when

 the carbs

 | were out of synch.

 |

 | Rick

 Does that mean you repitched the prop to compensate for the increase 

 in hp?



 john h

 mkIII


	




I'm slightly confused as well - is that at full throttle at these rpms?



LS



--------

LS

FS II





Read this topic online here: 



	


-- 

Rick Girard

"Ya'll drop on in"

takes on a whole new meaning

when you live at the airport.  [quote][b]

Dave Bigelow

Joined: 29 Jan 2006
Posts: 103
Location: Kamuela, Hawaii

Posted: Sun Jul 01, 2007 1:16 am Post subject: Re: HKS update ATTN:Dave Bigelow

lucien,



 	  Quote: 	
		  What prop do you run, type and diameter? Do you have any details on mounting? i.e. any mods you had to make etc.? 

	


Using a Powerfin 66 inch 2 blade with the HKS 2.58:1 gearbox.  It's the same prop I used with the B Box Rotax 503.  I did have to dial in some more pitch to keep the RPM under red line.  I pitched so I would reach red line at full throttle at 55 mph.



I did the project with the help of Jerry Olenick at Green Sky Adventures.  He has all the mounting info, pictures,etc, and is planning on offering a bolt-on kit.  I did the entire conversion without drilling any extra holes or cutting or welding the Firestar stock mounts.  It is literally a "bolt on" conversion.

_________________
Dave Bigelow
Kamuela, Hawaii
FS2, HKS 700E

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Sun Jul 01, 2007 5:07 am Post subject: Re: HKS update ATTN:Dave Bigelow

 	  jindoguy(at)gmail.com wrote: 	
		  Lucien, My HKS is installed on a trike (weight shift control aircraft). 4700 RPM is far below engine redline (5800 RPM continuous), but the nature of the flex wing doesn't allow me to do full power and level flight at the same time. 



Rick

	




Understood, so am curious how you know you're now getting more hp at 4500 than you were before at 4700?

Not sure how this can be determined at anything other than full throttle and even then without some relatively sophisticated means of measurement?



Or is the throttle setting vastly lower now than it needed to be before or ?



You should be able to do a full power run in level flight by pulling the bar all the way in, if you don't exceed Vne in the process. I got my fun racer up to over 80mph that way with the XP11 wing fitted, though it had some more to go still.... With the single surface, it'd still climb 500fpm at full power with the bar all the way in though.



I flew trikes for about 4 years too, I loved em, but I'm glad to be back in 3-axis 



LS

_________________
LS
Titan II SS

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Sun Jul 01, 2007 5:11 am Post subject: Re: HKS update ATTN:Dave Bigelow

 	  Dave Bigelow wrote: 	
		  lucien,



 	  Quote: 	
		  What prop do you run, type and diameter? Do you have any details on mounting? i.e. any mods you had to make etc.? 

	


Using a Powerfin 66 inch 2 blade with the HKS 2.58:1 gearbox.  It's the same prop I used with the B Box Rotax 503.  I did have to dial in some more pitch to keep the RPM under red line.  I pitched so I would reach red line at full throttle at 55 mph.



I did the project with the help of Jerry Olenick at Green Sky Adventures.  He has all the mounting info, pictures,etc, and is planning on offering a bolt-on kit.  I did the entire conversion without drilling any extra holes or cutting or welding the Firestar stock mounts.  It is literally a "bolt on" conversion. 	




Ah, the Olenik's, ok.... Can't do better than working with those guys. I had Tom Olenik do maintenance on a couple of my 503's and he does just superb work.....



They're doing lots of good support on the HKS now too.



I do have a spare powerfin 68" in 3-blades. Does the HKS turn right hand in pusher config like the 2-stroke? hmm... I'll have to keep that prop around then 



LS

_________________
LS
Titan II SS

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sun Jul 01, 2007 1:06 pm Post subject: Re: HKS update ATTN:Dave Bigelow

Hi Rick,



Good post. I have been trying to get everyone to do a pneumatic sync. Just doing a mechanical sync. is no substitue. Two different critters. The mechanical sync only sets the idle screws and does not adjust the cables. The pneumatic sync. doesn't touch the idle screws, but adjust the unevenness of the cables. Don't forget to turn the idle mixture screws (on the underside of the carbs) on the Rotax 912 1.5 turns during the mechanical sync.

If you don't do a pneumatic sync then one side of the engine is trying to run at a different rpm from the other side.

A pneumatic sync can effect the engine vibration, temps, hp and rpm depending on how far out they are. I have had people fly in to Tucson so I could do a complete sync. The last one was a Zenair and he was 4" of vacumm out and he couldn't tell by the running engine. I have people call me all the time on how to do a sync and talk them through it while they are at the airport.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Sun Jul 01, 2007 7:16 pm Post subject: Re: HKS update ATTN:Dave Bigelow

Roger Lee talked me through the carb sync for my 912-s, and it needed it !!!   Once you understand the procedure, its very straight foward and easy to do.   The only hard thing is getting the small hose clamps back on the balance tube after you are done   



Thanks Roger !!!



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Mon Jul 02, 2007 6:46 am Post subject: Re: HKS update ATTN:Dave Bigelow

Hi Mike,



Your Welcome.



Anytime



It does make a difference.

I have tried to tell people that if it hasn't been done in the last 100 hrs. or never then it needs it. Like you said, once you've done it once then it's very straight forward.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

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