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Going Diesel

Old 05-18-2005, 10:41 PM
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IBrakeForNobody
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Default Going Diesel

Hey all,

I have decided to convert my OS 40 LA to diesel...I have some newb questions that have probably already been answered 5000 times but I just want to make sure its the same for a OS 40 LA...

Umm...what do diesels burn? Like diesel fuel from the gas station?
I heard burning cooking oil works...will it really?
Does motor oil work?

I understand I need a new head...umm...where do I buy one and how much do they run?
Can i still use the same prop?

Thanks for looking!
IBrakeForNobody
(Goin' Diesel [8D] )
Old 05-18-2005, 11:28 PM
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SGC
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Default RE: Going Diesel

Model diesel motors use/burn a mixtue of (basic mix) equal parts Ether, liquid parafin, castor oil.
Ether- lowers the ignition temperature /and compression needed to acheive same
Liquid parafin- Fuel- can be Kerosine, Auto Diesel, Jet A, Lamp oil. Kerosine burns cleanest.
Castor oil- lubricant- can be 10W50 motor oil, synthetic oils in some motors- recomend Castor in an LA.
Davis make diesel conversion heads and have premixed fuel.
Props- Diesels generally produce more torque so can swing larger props ( at lower revs) to produce the same thrust at lower fuel consumption .
Stewart
Old 05-18-2005, 11:54 PM
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Default RE: Going Diesel

Thanks for the relpy...

So I can't just burn diesel fuel....thought so. Umm...what is ether and where can I get some?

Thanks
Old 05-19-2005, 01:54 AM
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Default RE: Going Diesel

Ether = Diethyl ether, its used as an industrial solvent these days but due to its use in the past as an anesthetic , and its volatility its a controled substance here.
Most find a freindly chemist to purchase it from, but since you are in the USA , Pre mixed fuel would be an easier option . I beleive there are about 4 suppliers that will post fuel in the USA.
As ether is also used by illicite drug makers, you will get 1001 questions as to why you want the ether.
Ordinary auto diesel can be used in the fuel mix, as above, but ether is needed as well. This is because our model diesels opperate at a lower compression ratio.
Stewart
Old 05-19-2005, 08:43 AM
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Default RE: Going Diesel

ORIGINAL: IBrakeForNobody

Hey all,

I have decided to convert my OS 40 LA to diesel...

I understand I need a new head...umm...where do I buy one and how much do they run....

Contact A J Coholic - he's a member of this forum, and a good man to do business with.
Old 05-19-2005, 09:52 AM
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Default RE: Going Diesel

So I can't just burn diesel fuel....
Without ether in fuel are same as glowengine without glowplug, the ether are a ignitor for mainfuel kerosene, autodiesel or lampoil etc..

Ether ignites in lower compression temperature than mainfuel.

Jens Eirik
Old 05-19-2005, 04:54 PM
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Default RE: Going Diesel

I have used spray can starting either with very good results in the past. A spray can will make about a quart of fuel. If you can get it you can add 2-4% amal nitrate (sp) to drop the crompression and smooth the ignition out.

Before anybody gives you their trick fuel formula try the old formula of 1/3 either, 1/3 clear kerosene and 1/3 castor oil plus your nitrate if you wish. It works pretty well and your engine won't overheat.


HTH - Steve B.
Old 05-19-2005, 05:40 PM
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Default RE: Going Diesel

Davis Diesel Developement has a head for the LA .40 and the .46 and Davis fuel is easy to get, in my opinion it is the best fuel you can get.
Old 05-19-2005, 07:04 PM
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Default RE: Going Diesel

Go with the Davis fuel, do not forget you get about twice the run time per tank on diesel so actual cost based on this less than glow fuel
ALso the LA series although a plain bushing engine it is very easy to set up ans usally bought as a first engine not a barnburner on glow
but keeps on ticking. The real surprise comes with the Davis Diesel head gobs power, one of the best conversions for not a lot of
bucks martin
Old 05-20-2005, 06:32 PM
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Default RE: Going Diesel

k thanks for the replies, guys! I'm looking forward to the diesel conversion. [8D]
Old 05-28-2005, 08:29 AM
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Default RE: Going Diesel

hey all just wanted some info on a OS 40 la. i have had it for about 3 yrs and i never got it up and running and last week i pulled it out and some how burned up the piston and sleeve. i can't get it to rev up either it tach's about 2800 rpm and when i open the Throttle the engine does not power up and i'm running on Davis diesel that is about 3 yrs old and the can was sealed and u could still smell the either in it. i even tried to and either to it with a can of starting fluid and now it won't fire ( didn't fire before i tried it either it stopped running) so can someone tell me whats wrong i have a Davis diesel head on it and running on Davis diesel fuel. i need HELP BADLY CAN'T AFFORD A PAW DIESEL.
Old 05-28-2005, 09:17 AM
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Default RE: Going Diesel

DId you break it in on glow, if so the needle settings will be little rich for Diesel operation but not much, normally when they won't accelerate the compression is set too high. You should be using at least a 12x6 or 12x7.
Old 05-29-2005, 06:37 PM
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Default RE: Going Diesel

I must assume you wrote this before you called me and we dermined the deep scrarches in the cylinder were brought about by the fact your engine ate dirt.
Old 05-29-2005, 07:56 PM
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Default RE: Going Diesel

sorry dup. post
Old 05-29-2005, 07:58 PM
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Default RE: Going Diesel

Since have you the head a new piston and liner sounds like a fix even a new LA 40 less than a new PAW and I have both a PAW40
and Davis conversions for my ST40 which I prefer over the PAW40, do not get me wrong the PAW BB 40 diesel is a fine engine but think the ST carbs better I put a MVVS carb on my PAW ..........martin
Old 05-30-2005, 05:41 AM
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Default RE: Going Diesel

then tell me why it won't start now and when it does it won't rev up and i have leaned out the compression and everywhere in the middle same thing it won't run smooth if you lean out the carb it starts a hit and miss so u have to richen it back up or it will die. if i need a new carb then how much is that. also like i told you i'm trying to run it on old davis diesel fuel and i put some either in it to make sure that wasn't the problem
Old 05-30-2005, 06:07 AM
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Default RE: Going Diesel

Does your engine have normal compression without the DDD head in place, but with the stock head? If it doesn't, that is one of the problems you have to fix first. Fix the compression problem first. Then buy a new batch of fuel from DDD and mix that up.

Old model diesel fuel is bad news. Like you said, you can smell it with the can sealed. If you can smell it, the ether is evaporating. You NEED the ether to get the engine started reliably and to run correctly. I know that you attempted to address this problem by adding starting fluid ether. If the ether leaked out, chances are the aromatics contained in the kerosene did too. You need fresh fuel.

Keep the fuel tank at the proper height. That is, the centerline of the fuel tank should be no more than 3/8ths of an inch below the level of the carburetor jet (spray bar). It should never be above the level of the spray bar. Centered is perfect.

Proper prop selection is a big help too. I'll assume you are running a larger prop than you would with the glow head in place.

First things first. Get the compression taken care of. **** has OS.40FP engines up for auction all of the time. It may be less expensive to buy a used engine in good condition than to replace the piston and sleeve of your engine with new parts. Do your homework.

Good luck and report back as to your progress.

Ed Cregger
Old 05-30-2005, 06:49 AM
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Default RE: Going Diesel

It's perfectly normal for it to miss when you lean the highspeed needle, where is the airbleed screw set, it should be about halfway across the airbleed hole. How is your tank positioned in relation to the carb? I'm asking a lot of questions but these are things that I take into consideration when setting up a Diesel conversion, I have an LA .46 and a LA .65 conversion so I know the LA is a good conversion cadidate. When you ran it as glow did it hold full throttle without the rpm wavering up and down?
Old 05-30-2005, 07:19 AM
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Default RE: Going Diesel

yes but thats when it was new. after i put the diesel head on it it didn't rev up cause i was told to small of prop so i went and got a 11x 7.5 prop and it's doing the same thing so is it possable i got a bad head from davis diesel if so how would you know
Old 05-30-2005, 07:30 AM
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Default RE: Going Diesel

As Hobbsy stated make sure the fuel is ok. You also stated a miss if running and Cutting in and out , it is undercompressed you may be only a half turn or so out too far SLOWY increase the compression see if the miss goes away. If you are all the way down on the screw
and its still there you have a lack of compression (IE) worn piston/liner the engine must be in TOP Notch shape to run right , quite simple miss under compressed. slowing down after starting over compressed also allow the engine a minute to get up to operating
temp before adjusting mixture or compression martin
By the way I have atleast 12 davis heads from .10 thru 90 and have NEVER had a bad head make sure it is seated properly remove the
head and look at it it should at the most flush in the head or a little resessed if flush and srill missing under compressed as a last resort
remove the head shim and re install )and hope you get a good seal also if you do turn the engine by hand and make sure the piston
clears the head before trying to start
Old 05-30-2005, 05:12 PM
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Default RE: Going Diesel

got it running thats for the help
Old 05-30-2005, 05:50 PM
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Default RE: Going Diesel

OK davec sounds like you are there what rpms are you getting now and what prop?? remember you want to run at the least compression without the miss you can tweek the needle now remember unlike a glow engine if too lean it will slow down and stop
also do NOT overcompress and try and compensate by running rich you should be within a half turn or so on both the needle and compression screw for a purrrrring engine, once you hear it running right you shuld be able to nail it each time with slight adjusments
welcome to diesel land martin
Old 05-30-2005, 06:50 PM
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Default RE: Going Diesel

i'm getting about 8800 rpms wide open and the compression screw is about a 1/2 a turn out not sure where the needle valve is and i'm turning a 11x7.5 prop
Old 05-30-2005, 07:48 PM
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Default RE: Going Diesel

Not bad also understand you have a new piston and liner, when it is well seated maybe an other hour of running the compression will pick up and you will backing out the compression screw you will pick up close to an other 500rpm also your needle will only have to change about 1/2 turn in or out at this point for a good tuned engine you now can confine your fiddling to a fiddle martin

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