Kris^

My Feedback: (1)

I bet that sounded strange when the crank let go, FC-26. that HAD to hurt. I've seen pics of 3W doing the same thing. Seems there is a weak spot called the "threaded area" on the front of the crank. One little 8mm shaft holds the entire front of the mtor together, and this is the same spot where most engines "bend" a crank in a crash, NOT from the thicker area of crankshaft behind the front bearing. Both 3w and Da use tapered snouts on the cranks, and the front hub is an interference tapered fit that holds snugly once the center nut is FIRMLY tightened.

On the other hand, BME uses a non-tapered front snout that is substantially thicker than the 3w or Da engines, and the front hub has to be pressed on with a special press. There is about .0025" of interference fit between the hub and crank, so its NOT going anywhere. The 8mm center stud screws into the crankshafts snout, not into the hub, so there is zero chance of the front hub assembly parting company unless the 15mm crankshaft is physically broken, which AIN'T gonna happen, folks. You'll disintegrate the crankcase first. and if the stud breaks, the prop merely freewheels and comes off. . YOU break an 8mm grade 8 stud. . .

People are always yelling for MORE POWER, Dick. . I say it's time to just fly the steenkeen plane!!!

gpw4653

My Feedback: (118)

I have only 1/2 tank of fuel through my 106, and it seems to be leaking fuel at high throttle, toward the rear of the engine where the crankcase goes togeather, anybody know of this problem? Thanks in advance, Gerald

BBW Walt

My Feedback: (11)

Make sure its not the cylinder bolts. After the first couple runs they tend to loosen up a bit. I have seen this a number of times. If its not the cylinder bolts sent the engine back, the warrantee is 3 yrs..Good luck, walt

fryfly

My Feedback: (8)

I agree with KLOTZ, recheck all your bolts just don't torque down the intake/carb bolts too much but make sure they are snug. Your bound to get a little fuel overspray coming from the carb itself but that's mostly from the wind going over the carb and creating a little bit of a siphoning effect.

Kris^

My Feedback: (1)

It would be best to not even touch the crankcase bolts, IMO. 3W uses aluminum bolts a lot of the time, to hold the jugs onto the crankcase, and the F-R halves together on the older style engines. Tightening them could result in a broken bolt, and even though they will probably cover that sort of problem under warranty, I'm sure whoever has to remove the broken piece will not be happy about it. If you have an actual leak at a mating surface, it will have a dark residue right along the seam itself, and spreading out slightly at the point of actual leakage. If this is happening, in a localized area, it's probably a flaw in the casting or a teensy mismatch in the machining of the pieces (.0005" will do it. . that's HALF a thousandths). Also, these parts are sealed with a "Silicone" type sealer (not your garden variety silicone, though). If it's leaking at all, something is just not right and further tightening of the bolts will in most likelihood not solve the problem anyway.

My advice is to contact your dealer about a replacement engine, and come to a satisfactory arrangement with him, before attempting any "home repairs" for this leak.

As for "fuel overspray", as intimated by FryFly. . . uh. . NO!!!! That is not gonna fly. If it occurs, it does not present the localized "leakage" you are seeing and the majority is re-ingested through the carburetor, it surely does not coat the engine with residue, and the airflow through the cowl will sweep most such residue out and away from the engine rather than coating it with the stuff. I've been running these big gassers for 5 years now. . DA, 3W's, BME's ZDZ/RCS products. . NEVER had it happen like that. In fact, if it's THAT bad, you need a new enigne anyway since the rings are not sealing and the reed valves are toast.

Glad to see FryFly finally admitting to a problem with the 3W carb blocks. . .that they crack or warp or can come "loose" and need attention. DA and BME, Brison, Fox and everyone else don't have this problem, so it would seem that 3W would finally get it fixed. . Thanks for acknowledging what a lot of people have been saying for years, Fryfly.

Diablo-RCU

My Feedback: (1)

Kris is correct. Contact the distributor. A fuel leak from the case means air can leak in and lean the mixture out. The motor can easily get toasted. I found a leak between the cylinder and case on my 3W-106. Tightening the bolts didn't fix it. On closer examination, one of the bolts was bottoming out before the head contacted the cylinder flange. A couple of flat washers on the bolt fixed it up. Either the hole wasn't tapped deep enough or something fell into the hole before assembly.

IanB

My Feedback: (1)

That is typically the problem with 3w.......................poor quality control!
Sometimes you get a good one...................sometimes a bad one

If they would GUARENTEE that I could return a motor if I had problems I would seriously consider one............but...........they do seem to have questionable aftersales service so ...........maybe not!

Diablo-RCU

My Feedback: (1)

That's why engines have warranties. If there is a problem, you send it in for repair, not to get a new one. The frequency of warranty repair is very low but it happens with all brands of motors. I think some modelers have unreasonable expectations. Nothing is perfect 100% of the time and lasts forever. These are machines.

IanB

My Feedback: (1)

God bless rcu................I got kicked out of DOD for saying just what I did above..................go figure

Antique

My Feedback: (4)

UH Kris..The little 8mm stud holds only the hub onto the taper, not the entire front of the motor together... Semantics ?
The new style 3W cases are held together by 6 SOFT steel round head bolts..The cases are assembled using anerobic Loctite, and the bolt threads are sealed with some other stuff that gets really tight..If you try to take the case bolts out without heat you will end up with rounded out heads, then you must drill the heads off to get the cases apart...Been there....
The cylinder bolts are drilled through almost on top of the rear case bolts, so a long bolt in a short hole will bottom out against the case bolt..Doesn't take much...
It's hard to machine a perfectly flat surface on a thin casting like the 3W, so sometimes a little lapping on a very flat surface will take down the high spots to the level of the low spots between the case bolts..Easy does it here, too much lapping will make the case halves touch the bearing bores before sealing the joint....
Careful with your reply, we know what happened before

Kris^

My Feedback: (1)

Careful with your reply, we know what happened before


Not sure what THAT means. . .but oh well. . .

I have yet to figure out why 3W has not grooved that parting line, so that you in effect get a "o-ring" seal where the case halves mate together. . That is an awfully large sealing area, and as Rcign1 has intimated, the casting is rather thin. I've come to the conclusion, after seeing just bout every chemical sealing technology eventualy leak, that the only PROPER way to keep two mated pieces from leaking is to use an o-ring, along with a permanently flexible compound such as 3M Weatherstrip adhesive. I've torn down motors 2-3 years after installing a gasket with this stuff, and it's still slightly pliable, tenacious as hell, and you MUST grind it off with a wire wheel or ro-loc grinding disk. Anearobic sealers are okay, but after hearing the litany from Aircraft Internationaly about how they use this stuff, then seeing how it does NOT seal in many cases, I've sworn off it for any "sealing" I have to do on one of my model engines.

We can go on and on and on about this, but the bottom line is this .. it's just NOT a good idea to go around trying to get one of the new top-bottom split crankcases ( or any other, for that matter) to seal. If it's leaking, send it in for repair. . its under warranty

As for the "little 8mm stud" on 3W engines. . if it breaks, the WHOLE front of the motor. . aka HUB assembly. . is gonna part company with the crankcase and jugs. I saw one do that at Joe Nall 3 years ago. . a Guy was runnign the motor up and WWWWOOOOOOOOOHHHHHOOOOOOOOOO the hub/spinner/prop went zinging across the runway about 100' before meeting the ground in a most destructive way. Kind of makes you appreciate the tremendous amount of power these engines put out.

Antique

My Feedback: (4)

Must be why 3w puts Loctite on the taper

Kris^

My Feedback: (1)

they do???


I was SPECIFICALLY told, by both DA and 3W to NEVER use any sort of loctite on this mating surface, since it is not as secure a "fit" as metal-metal contact, no matter what kind of loctite you use. The preferred method is to mildly heat the hub in a pot of hot water, slide it onto the shaft and TIGHTEN the center-pilot/nut until you break a sweat.

So says both Dave J at DA, and Gerhard at Aircraft International. . . I've tried the "loctite" method. . . nope, sorry, it slipped and sheared the woodruff key and damaged the hub, even though I had TIGHTENED it. . . .Metal-metal has never slipped for me.

Antique

My Feedback: (4)

Sorry Kris^, EVERY 3W I have ever taken apart has had some sort of compound on the nut and taper..No other engine has been this way...The residue smells like Loctite and looks like Loctite...And it always takes some heat on the hub...
I heat the hub with my MonoKote blower, slip it on, and use my 3/8 drive air torque wrench on the nut...With green 680 stud and bearing mount Loctite...Takes HEAT on the nut and hub to loosen it again....It must be working, the nut won't even budge without the heat, even with the torque wrench..

Kris^

My Feedback: (1)

OH. .you're talking about the NUT, , , ,not the front of the crankshafts taper that the hub slips onto.. . Watermelons and qomquats here, I guess I don't loctite the nuts when I reassemble either. . thought loctite red would probably be a good idea.

Antique

My Feedback: (4)

The sentence says nut AND taper.