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Davis diesel heads

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Old 09-16-2005, 05:50 PM
  #1
layback2
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Default Davis diesel heads

I got the davis head for my TD .O49 and today i tryed it for the first time checking the carb setting like it said adding the disk installing the head making sure it was correct and adding fuel and FLIPPING my darn head off and it would half way started 6 times reading the work sheet to check if i missed anything and FLIPPING my arce off for what it seem for hours grrrrrrr never did get it to stay running I read were if you cant get it setup right you can send it to davis and they will set it up correct in runing condition for you is that right for 6 bucks
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Old 09-16-2005, 06:07 PM
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Default RE: Davis diesel heads

Are you using Davis diesel Fuel or ?? Davis has a special blend of diesel fuel for 1/2 A sized engines. If the Fuel is right gradually tighten in the compression screw 1/4 turn at a time, make sure there is fuel in the cylinder by priming -- flip the prop a couple of times til you hear a definate pop another 1/4 turn and you should be good to go. Once running you may want to adjust the compression and needle valve. If you are using a cox baby bee or similar integral tank you may need to change the fuel line and even the tiny rubber gasket in the back plate. Avoid over-doing the compression setting as you can easily bend a connecting rod or ? I like a lower compression setting then I strike the prop with a downward motion other guys like to crank up the compression and use a normal prop flipping motion. to each his own I guess. Good Luck,
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Old 09-16-2005, 06:30 PM
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Default RE: Davis diesel heads

gary-meyers The engine is a TD .049 the fuel is from davis the manul said to adjust the compression 1 full turn at first and set the needle valve 2 turns for the TD prim and flip the prop i have a davis prop spring for the TD .049 i tryed and tryed and tryed lol it just would not stay running i will try tomorrow again with your idea thanks
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Old 09-16-2005, 08:41 PM
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Default RE: Davis diesel heads

If it is missing and dying, it probably needs a little more compression to keep running. If that doesn't work, open the needle maybe a 1/4 turn. If it is loading down and dying probably too much compression. If it is spitting fuel out the exhaust, maybe too rich. If nothing else works, try this. Open the backplate and make sure the crankcase has no loose fuel in it. Shut the needle all the way. Now head prime and diddle with the compression until it will run out the head prime nice and steady. Now, hands off the compression. Open the needle one turn and suck fuel just to the needle, not into the engine. Head prime and maybe it will run a little longer. Keep doing this, opening the needle about 1/8 turn at a time until it keeps running. Once it starts running, it will probably be overcompressed and start to slow down. back the compression off slowly until it runs smoothly. If it starts running and keeps missing, tighten the compression or open the needle or both, until it stops missing. A flooded diesel isn't going to start and you can get a hydraulic lock using the spring starter when flooded.
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Old 09-16-2005, 09:51 PM
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Default RE: Davis diesel heads

Your right Jim Thomerson that was what it did i went back out in the shop and tryed it again reset the needle valve and compression and started to close them both 1/8 each as i primed and flip the engine over and it started and ran ruff then i just turn the compression in tell the engine sounded much better it screams now doint want to close the compression to far its set now were it sounds good now there is less then 1/2 turn left i could hear the engine sound change and a simple needle valve ajustment 1/4 all it needed.Ilet it run out of fuel cool down and re fuel and prim a small amount in carb and 2 flips and she fired right up.cool'Now my next project my russian diesel yuk much larger not a davis at all MVVS diesel have to be hand fliped no spinner or spring starter 8x6 prop look out fingers thanks
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Old 09-17-2005, 03:27 PM
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Default RE: Davis diesel heads

Get a heavy leather glove. If a diesel backfires it is overcompressed, and maybe flooded as well.

Yesterday I was fooling with a Rivers Silver Arrow 3.5cc which I have decided is not well broken in. 9 x 5 APC prop, 13,000 RPM. Stuck a knuckle into the back of the prop fiddling with the needle. Thought, "Glad I have my glove on. " and didn't think any more about it. When I took the glove off and wiped my hands on a paper towel, there was blood on the towel. There was one small cut on my knuckle. The prop had actually cut through the leather glove. If I had not had the glove on, I think I would have been on the way to the emergency room, scraped to the bone.

Reason I think the engine, though bought well used, is not broken in completely, is that after it runs a couple of minutes very nicely, it starts to heat up, overcompress and slow down.
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Old 09-17-2005, 06:04 PM
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Default RE: Davis diesel heads

This MVVS has never been started and i have tryed for days with not pop or fart from the motor wondering why its such a pain
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Old 09-17-2005, 09:01 PM
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Default RE: Davis diesel heads

Layback which MVVS 61 or 15 factory head or davis conversion? Bench the engine DO NOT hook up the fuel line..You can easily flood it
Back compression screw out about 3 turns from the bottom prime the engine and flip turn in the screw about a half turn and keep flipping till it fires turning in the screw till it does If it really kicks back, back out the screw a little, on a good prime when right it will run
for several seconds before stopping, now hook up the fuel line start about 3 turns out on the high speed needle At this point adust needle till smooth running slowly back out the compression screw till you get the typical miss then turn in slightly till running smooth again then you can adjust the compression and needle for best running. if it slows down you are overcompressed, lean or both. Once you have the setting you will find that you always be within a half turn on the compression and needle for smooth running. make sure your fuel is ok and have not lost ether martin One more thing I was breaking in an Irvine 53 on glow before putting on the davis head
and had a bad time getting it running right Mr Davis was laughing and said I had forgotten how to adjust a glow engine martin
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Old 09-17-2005, 10:33 PM
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Default RE: Davis diesel heads

The one i have is the MVVS 15 factory head i will try tomorrow with the setting you said thanks dieseldan will let you know what happends first were is my glove lollol

oh one more thing i read Teflon Discs for Davis Diesel heads. some people do not use them i thought they help protect you piston is that correct or do you even have to use them at all can you answer that thanks
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Old 09-18-2005, 01:33 PM
  #10
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Default RE: Davis diesel heads

Well new day and have tryed all ideas from you guys and from the manul and nothing not a pop fart crack just flip my brains off still nothing to report it just woint show me that it will run now i am wondering what else to check maybe just clean it up and make a display out of it.grrrrrrrrrrrrrrr
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Old 09-18-2005, 08:27 PM
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Default RE: Davis diesel heads

I bet you flooded it.[&o]
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Old 09-18-2005, 08:41 PM
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Default RE: Davis diesel heads

I agree!
Most diesels only need primeing with either a couple of drops in the intake/ or a splash of fuel in the closed exhaust port, anymore useually floods them. This then results in you needing the compression lower to flip/turn over the motor, the motor may give a few enemic burps/pops (or crunch a knuckle) in this condition, but as it clears the fuel the compression quickly drops and nothing.
Best to flush out the motor with alcahol, let dry, and start from scratch.
1/ close the needle
2/ prime into the closed exhaust port against the side of the piston, then flip. If it doesnt fire after 3-6 flicks , screw the comp doun 1/8 turn reprime and try again.
3/ repeat till it runs on the prime-wont run long.
4/ when it fires from the prime open the needle to approx run setting , reprime and start.
Hope this helps
Stewart
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Old 09-18-2005, 08:46 PM
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Default RE: Davis diesel heads

Thanks guys ok will try again maybe i i did flood it i changed to prop to a larger 9x4 sence the engine will take a larger one and it is easer for me to flip will give it a try tomorrow again
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Old 09-19-2005, 08:23 PM
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Default RE: Davis diesel heads

if the above suggestions do not work, Also is your fuel Ok ? I just pulled the head on my MVVS 09
and the contra is in the cylinder bore. Turn the screw all the way in and slowly try to rotate the engine by hand if the contra goes down far enough to strike the piston at TDC BACK it slowly till there is no interference, then try and start it you will be quite overcompressed
back out till you get a miss. then readjust (wait till it warms up for final adjustment) martin
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Old 09-19-2005, 08:25 PM
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Default RE: Davis diesel heads

if the above suggestions do not work, Also is your fuel Ok ? I just pulled the head on my MVVS 09
and the contra is in the cylinder bore. Turn the screw all the way in and slowly try to rotate the engine by hand if the contra goes down far enough to strike the piston at TDC BACK it slowly till there is no interference, then try and start it you will be quite overcompressed
back out till you get a miss. then readjust (wait till it warms up for final adjustment) All of the suggestions you have on these post are
100% on just try this too martin
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Old 09-19-2005, 09:19 PM
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Default RE: Davis diesel heads

I checked it and no it does not hit the piston and the fuel is new just got it last week got one can of davis 1/2a and one can of davis mix for larger engines i will try in the am again and report what happends thanks dieseldan and all who is helping me out
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Old 09-19-2005, 09:33 PM
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Default RE: Davis diesel heads

Use the 1/2 A fuel martin
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Old 09-20-2005, 08:37 AM
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Default RE: Davis diesel heads

Ok dieseldan thanks
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Old 09-20-2005, 04:36 PM
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Default RE: Davis diesel heads

OK guys heres a update i fliped my rudder off hehehe and nothing happend so i took off the prop and put a prop spinner on and prop and got my electric starter out and give it a few spins with small drops of fuel like you guys said and wam a hit pop run a few seconds and tryed to get the compression half way set so it would run long enought to try to set the needle valve and poof the darn thing flew off the stand.lol glad i was standing a long side the motor and not in front so i clean it remount it on the stand.nuts and bolts this time lol refuel and hit it once and it ran about 3 seconds trying now to set it were both the compression and needle will let it stay running longer.

New update this afternoon went out to shop and fired that baby up but there is a problem the compression valve does not work ok the reason i know is when it started and i got it to stay running and adjusted the needle valve were it sounds half way good i tryed to adjust the compression and nothing it went all the way and no change in the motor sound but the craking sound did smooth out some and stay running just no high speed running if there is any.IN fact something funny while it was running i was trying to adjust the compression and unscrewed the knob all the way out in my hand and it never turn off.lol so now what paper weight hehehehe
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Old 09-21-2005, 08:12 AM
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Default RE: Davis diesel heads

Layback2,

If you had turned the compression screw out some and opened the needle valve, it may have cooled the contra enough to let it move. If that is the case, the pop you heard was the contra hitting the adjustment screw. No problem.

If you then leaned it out, the contra may have stuck again.

Use an intake prime to start. An exhaust prime may be giving you a false setting since it will fire at a too-low compression setting.
If it is running at a too-high compression setting, pull the fuel line and stop it, or richen it until the contra frees itself so you can adjust compression. Don't let it continue to run over-compressed.

Once you can adjust compression properly, keep lowering compression until it misses slightly, then increase until it smoothes out. Then adjust needle. Then do compression again, etc. Don't make final adjustments until it is at normal operating temperature. This will take about a minute. As it heats up it will need less compression to run.

Compression adjusts firing timing so you will find that as you change prop sizes (load) you will need to readjust compression for the optimum setting. Do a series of one or two minute runs, followed by complete cool down for break-in.

Don't give up on MVVS. I have two .15 diesels and three .09 diesels (and a .15 glow). All run well.

Note that these are only opinions, individual mileage may vary.

George

Edit: Additional thought. When you say factory head do you mean that you converted a MVVS .15 glow to diesel? My .15 glow is ABC and all my MVVS diesels are iron/steel. This may cause the binding you refer to, although I would think it would get more loose if too hot.
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Old 09-21-2005, 12:56 PM
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Default RE: Davis diesel heads

Gcb this is not a converted glow engine it is a diesel mvvs remake from russia iron/steel .15

not glow at all and never was i bought 2 engines one was a .09 and the .15 has a iron sleeve and steel piston
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Old 09-21-2005, 01:18 PM
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Default RE: Davis diesel heads

I was under the impression the MVVS engines were made in the Czech Republic?
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Old 09-21-2005, 07:59 PM
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Default RE: Davis diesel heads

All mine 09,40,61 Czech Rep. martin
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Old 09-21-2005, 08:13 PM
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Default RE: Davis diesel heads

well iam not sure what to do about the motor but clean it and put it away i still have a .09 that has not been started hope the same problem does not happend if so! paper weights and woint buy for that person again i will try again tomorrow to see what gcb told me to try woint hurt hope it works it starts easy now but under power i know theres more to it thanks
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Old 09-22-2005, 08:18 AM
  #25
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Default RE: Davis diesel heads

layback2,

As you check out the .09 for filings, tight screws, etc. make sure you check the screw that holds the venturi in place. I had one a little loose from the factory. On the plus side, you can turn the venturi so the needle is angled back, if you like.

One of the .09's had a crankshaft that was a little tight. It freed up upon break-in. Symptoms were that the crankcase got a little hotter than normal during break-in. No problem if you break it in with a series of short runs plus thorough cool down between runs.


George

Edit: You might check out this site for diesel running and break-in: http://www3.bc.sympatico.ca/dieselcombat/index.htm

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