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View Full Version : HKS-700 - Switching from mogas to 100LL



rwaltman
03-22-2010, 07:23 AM
Hello,

I bought an HKS-700 powered Kitfox last October, sat untouched during the winter.

I'm getting ready to get it back in the air, and my first concern is fuel. The previous owners had access to alcohol-free gasoline; I do not, so I will be switching to 100LL because:

a) I don't want to take the risk of discovering that the tanks seals or some of the piping, etc. are not good with regular car gasoline.

b) 100LL is more convenient since regular gas is not available at the airports.

c) I want to have the little extra power available from alcohol-free gas.

According to the little research I did, switching to 100LL requires also changing the oil from synthetic to something else, using additives to scavenge the lead, etc.

My questions to the group:

How many of you are using 100LL on an HKS-700?

What oil and/or additives do you use?

Any change in the engine's maintenance schedules or procedures?

Anything else are should do/know/use?


Thanks,

Roberto Waltman

Mnflyer
03-22-2010, 10:41 AM
Hi Roberto, I have used some 100LL in the HKS but not a lot as I can get ethanol free 91 oct here in MN. What I would do if I have to go to 100LL is use a semi-synthetic oil and change oil every 25 / 30 hrs, definitely would use Decalin fuel additive it will scavenge the lead from the combustion chamber, check the spark plugs every 50 / 75 hrs for lead deposits. You will not really notice any other differences in operations EGT's may change just a bit and may not. The reason for not using full synthetic oils is they do not scavenge the lead and it will build deposits in the engine and one of the places is in the oil passages, the Decalin works mainly in the combustion chamber helps with the spark plugs and valves.
http://www.aircraftspruce.com/menus/ep/fueladditives.html

rwaltman
03-22-2010, 01:28 PM
Mnflyer (http://www.teamkitfox.com/Forums/member.php?u=4) wrote:
> ...What I would do if I have to go to 100LL is use a semi-synthetic oil and change oil every 25 / 30 hrs, definitely would use Decalin fuel additive it will scavenge the lead from the combustion chamber, check the spark plugs every 50 / 75 hrs for lead deposits....

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"JPiney" wrote: (in Yahoo's HKS group)

> The factory INITIALLY proposed going to syn-blend then backed down to the standard full synthetic. They just changed the interval to 25hrs on changes when using 100LL.

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Patrick M wrote: (in Yahoo's HKS group)
> I use 100LL and althought the manual referes to a syn-blend I could not one that met the specs. The reps for the engine says use syn oil and change oil every 25hrs.
I use DECALIN RUNUP FUEL ADDITIVE from aircraft spruce.

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Thanks for the responses.

I was trying to choose between fully synthetic oil plus the Decalin additive, or this semi-synthetic oil from AeroShell - "Sport Plus 4":

http://www.shell.com/home/content/aviation/products_and_services/products/lubricants/piston_engine_oils/sports_plus4/

( I believe this type of oil was not available when the HKS-700 was introduced.)

Leaning towards the 2nd option. Time to call AircraftSpruce, so I have the oil and Decalin with me this weekend.


Thanks,

Roberto Waltman.

Mnflyer
03-22-2010, 07:38 PM
Hi Roberto, I believe you are right about the Aeroshell Sport Plus 4, and that oil was specifically developed for engines like the Rotax 9 series and the HKS engine that were designed to use automotive synthetic oils and unleaded fuels, in my opinion you won't go wrong with Aeroshell oils.

Av8r3400
03-22-2010, 07:54 PM
At a recent seminar I attended the Rotax rep from LEAF suggested using Aeroshell +4 oil with 100LL fuel, at a 25 hour change interval, with a lead scavenger (no recommendation) in the fuel for the 900 series motors.

He also said the +4 was good with auto-fuel at 50 hour change interval.

FYI

rwaltman
03-23-2010, 05:34 AM
gerald olenik wrote: (In Yahoo's HKS group)
> There is nothing about 100ll that changes oil requirement on the
> HKS. The oil should be full synthetic. Rotax 912 series also use plain
> bearings, but rely on blow by gas to return oil to the tank. The HKS
> returns oil to the tank via scavenge pumps. Lead contamination on the
> HKS is negligible. ...on the Rotax 912, significant, which is why this
> subject is so long and old. You can't hurt anything by shortening up
> the oil change interval, but using the wrong oil, based on flawed
> research may not be so benign.

Right on the money.

The starting point to all this was this phrase, in the APSU support page for the HKS engine:

"...Constant use of leaded fuels requires different lubricating oils to be used to avoid lead deposits."

But I received a couple of responses off-list from Frank Porter (APSU, HKS dealer)

With his permission to repost, Frank Porter wrote:

> I have the HKS 700E Powered Quasar-Lite that we import from Brazil and we have 6 aircraft in the US and have over 2,000 hours accumulative and all six have ran on 100LL since day one with no problems. HKS has done all their testing at the factory and all their engines have only had 100LL.

> The reason HKS is against any mineral oil, early in HKS 700E engines the mineral would coagulate in the hydraulic lifters turning them into solid like lifters and in-turn wiping out the cam.

> I use 100LL for several reasons, 1: ...
3: I listened to the HKS Engineers and I have no problem following their advice about the synthetic oils. What they said about the AeroShell Synthetic Blend has not been tested or approved for use in the HKS Engine.

> The high compression of the HKS has so little blow by that the lead in the oil is not a measurable amount and HKS covers their a__ with change the oil at 25 hours instead of 50 hours when using 100% 100LL.

> ... buy Mobile 1 100% synthetic auto oil and I use the 5 w 30 in the winter and 5 w 40 in the summer. In South Florida it never gets to cold but it does get on the hot side.

>Frank Porter
>APSU-HKS-AeroLux


So, worry-free synthetic oil is the answer.
Thanks everybody!

Roberto Waltman