earlwb

I have a pre-WWII BFBH one myself. Great for when the engine irks me a little. I normally use it to change the wheel bearings out in my Harley though.

Rudolph Hart

Well i guess it was me that just got hammered.As an aside and with the exchange rate still good i bought a jr9503,stiffer sticks than the old dsx7 and took some getting used to but i did'nt mind that.No expo on the throttle curve for my saito engines when flying so it helps when you want to throttle them up gently while flying.

Do americans indulge in putting big props on small fourstrokes or do they just hold world series competitions for sports that are only conducted over there?

Hobbsy

My Feedback: (102)

Is this what you call large, a Bolly 10.5x5 on a Saito .30? It turns at 10,200 on 15% WildCat Premium Extra.

Ernie Misner

That's a pretty setup Hobbsy! What type of fuel filter is that with a bowl?

Thanks,

Ernie

johnS555

My Feedback: (27)

How is the balance with only half of a prop on there ????? .......

or is that an obstical seclusion ???? ( good settup)......

earlwb

I thought they had some sort of throttle curve you could dial in on the JR TX, not Exponential.

I am inclined to try big props on some two stroke engines too.
Here is my P86 Twin Mustang with two Saito FA-40a engines on it for power. Yes it has lots of power too. it only needs about ten feet of runway to take off of the grass with.



How about a K&B Twister .60 with a 14x6 Master Airscrew prop on it?

ckreef

To make a long story short I think I hydro locked my .91 4s and something broke internally. The glow plug area is ok and after removing the rocker covers the valves are moving like they should but I have no compression what so ever and I'm not sure the piston is moving at all.

Any ideas ?? Is there a disassembly "web link" some one can provide so I don't muck it up when I take it apart to figure out whats broke.

Please help as it was running great 10 mins before this and I am completely bummed

Ernie Misner

Was the engine inverted and got flooded? That will sometimes snap the crank pin right off. Hopefully some one will have a good link to tearing it down or you can send it to Horizon or other repair services. If you think it might be flooded always see if you can turn it over by hand before hitting it with the starter.

Good luck and keep us posted,

Ernie Misner

ckreef

Yes it's an inverted setup and yes it probably got flooded (my mistake). Unfortunatly I didn't realize the flooded situation before I put the electric starter on it

Hopefully some one can supply a good link as I would much rather tear it down myself then to send it off. Would just like a little guidance before I proceed.

SrTelemaster150

Just remove the intake manifold/carb & that will allow you to remove the backplate. You will be able to see the crank/conrod after that.

earlwb

You can easily remove the carb and intake manifold from the back of the engine. That then lets you remove the backplate so you can see inside the crankcase. You can then easily tell if you broke the rod or the piston or the crankshaft or something.

Ernie Misner

Run a search, this thread and forum, lots of info in the William Robison Complete Notes as well. It is at the top of the Engine Forum. Tearing it down will be fairly straight forwardward but on re-ass'y you will need to time the cam shaft. You will use heat from a propane torch, heat gun, or oven when removing the prop hub, crank and/or bearings. A puller can be used on the prop hub before removing the crank otherwise it can come off after heating and tapping on the front of the crank. When tapping put the nut on the crank threads and use a piece of hard wood and hammer. If the bearings don't come out with the crank you can leave them in unless you want to replace them. If they stay in place but you do want to replace them you'll have to re-heat the case and then with a gloved hand slam the case rear down on a piece of wood or tap them out from the front. On reass'y you can check the cam timing - both valves will be slightly open when at TDC on the intake stroke. Let us know..... try Paul at RC Bearings if needed.

Ernie Misner

clytle374

Here is a picture of the engine I got recently. The seller is stating that this scraping is from tighten the prop nut down which pulled against the bearings and being pulled by the prop. Also that the crank can heat up and expand causing the scraping. Am I crazy? Or is this not normal?

Cory

Also that seems to be fuel staining on the crank and bearings, but why not on the rod and crank like I've always seen?

radial1951

*
Cory,That's a long way from "normal". What a load of rubbish the seller is feeding you! The crank expanding...

I would think the only way the side of the rod can touch the case is if the rear bearing is completely shot, allowing the crank to move forward. There must also be enough clearance in the piston to allow the rod to float forward with the crank...

The "fuel staining" is RUST. The alloy rod and case won't rust. You may have seen castor oil stains previously.

Regards, RossG
radial1951
_____________

Rudolph Hart

Hi Dave is that a saito fuel filter?
No,thats not what i call large re props.From memory i was running a 10x6 mas on the 30 and it would rip it at full throttle.I usually prop my saitos so that they won't exceed high nines in flight.

My bad earl you were right about the throttle curve but i don't use it yet.The throttle stick has ratchet clicks so i've settled for that.
How far over the recommended max prop size have people tried?.Is it dangerous to overload the engine at lower revs?

Hobbsy

My Feedback: (102)

It appears that a foriegn object/substance got under the rod, I see plenty of clearance the way it is sitting in the picture.

clytle374

There is less than .004"(bites 2 sheets of paper) when you press the rod down with your finger at BDC. It is possible that something something was in there, idk. The seller is now stating that this is normal wear and the 9/10 engines ran for over a year would have this scraping. I've heard all I can take out of him, he is supposed to refund my money.... I'm holding my breath. Anyway I bought a brand new 100 last weekend.

Cory

ckreef

I am now totally confused (see above posts)

Saito .91 had no compression (most likely due to inverted and totally flooded). I took the engine off the plane. The carb and intake tube off. Removed the back plate. The crank case was soaked in fuel with a large puddle in there. There was nothing broke that I could see. I cleaned out all the excess fuel and Itried turning it over (by finger method) . It now appears to have full compression (could barely turn it over w/ finger method) and piston is moving as expeceted with valves moving as expeceted.

Any thoughts on this before I put it back together and try to run it ???

And NO I am not crazy although from my posts above even "Me-Myself-& Irene" think I'm crazy.

blw

My Feedback: (3)

Cory, did you buy the engine locally so you could get your money back?

You probably checked compression with the throttle closed the first time.

Edit for grammer

rexracer

I posted a bunch of props I tested on my .40a one page back. I don't know what you concider large, but I'll probably fly the Beaver I'm building for this engine with a MA-S2 12x6 prop. It turns over 9k static. I bet it would turn a 13x4 MA-S2 at about the same. The 12x6 actually spools up very quickly.

ckreef

I assume you are posting to me. I don't really recall the trottle position but yes probably closed the 1st time.

Could you please explain so I have a better understanding. My brain must be missing something.

clytle374

The used engine was long distance via paypal. The new one was local.
Cory

orthobird

My Feedback: (1)

hello

Ernie Misner

If the throttle is closed all the way tight, when the piston goes down on the intake stroke it can't suck any air, fuel, or anything at all in - so it just creates a vacuum in the combustion chamber. Then when the piston goes up for the "compression stroke", no compression will be made because there is merely a vacuum in there. Making sense now? I puzzled over that a few times myself! Another "gotcha" is when it will have compression when you turn it one way, but not the other. Anyone know why?

Ernie Misner

FNQFLYER

Old Fart, my big hammer is a 15 pound sledge hammer head on a piece of steam pipe used on engine abusers, errant cats and the odd snake (water python) that wanders into the shed.  I have acquired a Blacksmiths "training anvil"  (that is what is says on the side.
Re props, I am hearing that some one is producing Bolly clones, do you have any info.
I am also trying to locate some Sherlock props but am having no success from my WA contact can you advise??
Good day today, appears as if wet season has passed us by up here, just lots of blue sky, eagles and a new club to join at Mareeba.
Catch ya later