AMB

Ok group while running my Irvine 20 diesel, the grub screw holding the pressure against the compression screw vibrated out, having some spare irvine 40 heads LOL the screw and brass plug went right in (now secured with blue locktight) since the irvine 40
was now an extra since all my irvine 40s now wear the Davis one, Still wanted to replace the screw in the 40 irvine head not having access to I think a BA grub screw inserted a 6/32 SAE tap, nice tight fit so pulled out the compression screw ran the tap thru, put the compression screw back in put in
a 6/32 grub screw resolved , will still have to put in a brass or teflon plug in front of it so we do not bugger the threads,
THX Bob Davis nothing ever falls out, or gets loose on any of yours, martin

Hobbsy

My Feedback: (102)

Martin, Fiery and I just did some "horse tradin" and I sent him and extra factory Irvine Diesel head and I'm getting an Irvine .20 Diesel crank in return. After you guys talked about the missing tension screws, I checked the .40 head and sure enough the grub screw was absent. I stole one from a nose gear collar that had been locktited, it went in with a little drag and hopefully won't come out on its own.

AMB

Dave glad you got a crank , will check the shelves and see how many stock irvine 40 diesel heads I have in case any of the group
needs one I think over the years two have gone to "those in need" martin
Hmm looks like we are down to one, the one I just did the grub screw thing on

Recycled Flyer

Martin, why do you 'need' the grub screw at all?

Many diesels get along just fine and dandy without them and perhaps a lock nut on the comp screw itself would suffice here, if indeed its needed.

denoferth

My Feedback: (71)

My Irvine 40 is also missing the lock screw but I’m more concerned with the smoke coming out the lock screw hole. The counter piston seems very tight so what could be causing the smoking? I'll do the 6/32 tap idea and come up with a brass pad for the lock screw but I have another problem causing me fits. When it runs, it runs well and will idle for long periods with no problems and run right up when the throttle is opened. Getting it started is problematical though. I have a muffler so I prime through the carburetor. It needs to be very wet to start and when the prop is turned bubbles can be seen running back to the tank. It will start if flipped backwards and run at slow speed but not accelerate in that direction. I bought it used on eBay and haven't gotten around to disassembling it yet. Any ideas?

Hobbsy

My Feedback: (102)

This is probably not the problem but I had a SuperTigre .45 give me fits, it turned out the guy who sold it to me rotated the cylinder about 45 degrees when he put diesel head on it. My guess is that he didn't get the bolts holes lined up on the first try and rotated the head which in turn rotated the cylinder. Its worth a peak though.

Recycled Flyer

Hi mate,
If there is 'smoke' coming out of the lock screw hole then you definitely have a leaking contra piston and the fact that it maybe tight does not guarantee a gas tight seal.

This is backed up by the quote "It needs to be very wet to start." The wet mixture would somewhat mask a leaking contra as fluid will take longer to floww past any leak than gas would.

The bubbles back flowing towards the tanks should only be the reaction caused after the positive fuel flow being suddenly shut off by the cranks inlet timing and is only natural when slowly turning the engine over by hand.

Cheers.

AMB

Yup can live without the grub screw a nut works fine but now you need a wrench for the nut plus the allen adjuster, I dumped the lock nut on my Enya diesels and made lock bars much easier martin
and Denoferth you are getting blow by on the contra if its hissing and leaking thru the grub screw hole martin

denoferth

My Feedback: (71)

Thanks guys. I suspected as much. This 40 had a lock nut on the compression screw when I got it but it would vibrate down the screw so I removed it. I'll pull it apart and see if I can line up any marks on the contra piston and sleeve. I got a PAW on EBay that had it's cylinder rotated so that's a possibility as well. Guess I'll know when I get it apart. The fuel goes back into the tank even when the prop is flipped smartly so I suspect I have a leak somewhere in the carb body. Originally I had too large a diameter fuel line and suspected that was causing a leak but that has been replaced and clips installed on the tubing. The instructions warn not to plumb the muffler vent but it does run better when hooked up. OH well, It's been over 40 years since I flew any models powered with diesels so I expected a steep learning curve. I had hoped to get it into a Big Bee before cold weather sets in but now I have to strip the fabric from the wing as it’s warped into a propeller, (about 2� positive on the starboard and 2� negative on the port). Weights, irons and heat guns only succeeded in cracking some wood.

Recycled Flyer

Try soaking the stripped down wing in the bath tub over night and letting it dry out pinned down onto a building board.

Must admit though, radio carby's are not my forté and could you get back to us if you do indeed solve the leak problem?

Thanks mate.

denoferth

My Feedback: (71)

Might be awhile but I will.

Thanks for the help
Dennis

AMB

Denoferth The Irvine has that big brass contra, It may be possible to machine a groove for an O ring, I do not know if it has ever been done before on the stock irvine head, it is a brass contra and leaking or not a tight fit in the head the contra might need a little taken off in order to get it back in the head with an O ring, I am not recommending this as a fix just an idea
The real fix would be a Davis head ( if available) he did do a short production run a few years back for the Irvine 40 diesel, GREAT UPGRADE, quite a few were issued to resolve any issues with the stock irvine head,. Made an excellent engine even better no issues, have 5 yup 5 myself and a number of us on the site have upgraded with the Davis head Irvine 40The
The contra is quite large and heavy might require 2 O rings again a questionable fix.

I do have a spare stock Irvine 40 diesel head if of any interest just send me a private PM
Your best solution would be the Davis head if available martin

denoferth

My Feedback: (71)

Don't know. Mine is really tight and is in the freezer right now.

classicracer

Dear all,

yesterday, while running my irvine 40 on the test bench, the grub screw vibrated loose and just before I could stop the engine running the screw fell in the grass...
I also have an Irvine 20 but the grub screws seem not to be the same as it doesn't fit the 40.
Does anyone has a replacement grub screw?

The irvine 40 with missing screw


The irvine 20

ffkiwi

I don't own a an Irvine 40-but the 20 has a 4BA grub screw to act as a compression lock-I would guess that the 40 one is also BA, but possibly a larger size-3BA (less likely) or 2BA(more likely). BA grub screws are available from ModelFixings in the UK (www.modelfixings.co.uk) and they currently list 2BA grub screws in 1/4" 3/8" 1/2" and 3/4" lengths...........
4BA has a nominal diameter of 3.6mm and 2BA a nominal diameter of 4.7mm so it shouldn't be too hard to check using drill shanks, what size the hole where your missing grub screw should fit is-ie if you can get a 4.4 or 4.5mm drill into it, it's likely to be 2BA. [FWIW BA threads are most commonly used (and hence available) in the even number sizes, even though odd number sizes exist in the BA thread range-which goes up (or down) to 16BA]
Finally-all is not lost-if you can't get a grub screw-use a piece of thick silicone fuel tubing pushed over the comp screw thread in between the top of the head and the T-bar of the compression screw to act as a lock. Obviously this will need to be a bit thicker (longer in length) than the distance it fits into, so that when installed on the engine it is under some compression to create resistance to the screw turning. The exact length of this piece of fuel tubing you'll have to determine by trial and error-obviously you start with a piece that's a bit too long.........

ChrisM
'ffkiwi'

AMB

WELL GROUP found an other irvine 40 diesel mounted in my backup VMR Apache ll the plane was sort of way back in my plane room it a "virgin Irvine"
factory Irvine head I missed it when I changed them all over to the Davis heads ( yes grub screw is in it) martin

Mr Cox

Are anyone using their grub screws?

The Irvine .20D works fine without it, just like paw engines do etc.

AMB

the PAWs use a locking lever on the screw . An other idea would be to slip a short
piece of metal tubing over the compression screw then put on a flat washer that will not slip
up the tubing then use a spring under the washer between that and top of the head. martin

Mr Cox

None of my PAW engines have, or even need, a locking lever. In fact I can't think of any of my diesel engines that actually need a locking mechanism, although some are supplied with it.

[email protected]

When I drop screws in the grass I go to my tool box and get out the telescoping tool with a strong magnet on the end. These tools are used by mecahanics and come in handy from time to time. Jack

Hobbsy

My Feedback: (102)

That magic extension tool is also handy for installing blind nuts in the back of a firewall. and for fishing dropped screws out of the fuse.

AMB

Hobbsy great idea for the blind nuts I used a 6" curved medical forceps not the best in some cases usless for access martin
going to Harbor freight and get one of those babies

classicracer

Hi there,

I "scanned" the area around my test bench with a huge magnet I found in a woofer speaker.
Back OT, whenever I spin the prop on the Irvine 40, I can see small bubbles appearing from the hole the grub screw once was in. I can also hear a "hissing noise" as the compressed air ascapes. So this means the contra piston is leaking. Does any of you have a replacement for this? I would like to have this engine up and running.

Kind regards,

Jo Michiels

AMB

Jo does the engine run OK? if it does do not fret over it...just put in a screw, I have diesels that weep around the compression screw and they run fine

just see how it runs it runs ok no issue


martin

AMB

one more thought contact Davis diesel it possible he may have one left if he does great upgrade all mine wear them martin

HOBBSY 4 TRYS ng