Black Widow off EBay

I don't really know what I am talking about, but you could try slowly screwing into a mount with some heat....

cribbs74 wrote:I had that same problem with a pee wee. It was suggested that brazing might possibly work. Solder does not nor does CA. If you manage to braze successfully let me know. Of course the best fix is a new backplate. Congrats on your find!

The mounting isn't broken completely, only bent forward, trouble is there is a crack on one side from the bolt hole out to the edge, I'm scared that if I try to bend the mounting back into place it will snap off completely. I might try some localised heating before I attempt the bend.

microflitedude wrote:I don't really know what I am talking about, but you could try slowly screwing into a mount with some heat....

Yes, I think something along those lines may be worth trying, as Micro says the real answer is a new backplate, I don't often see them without the fuel/vent pipes though.

I'd say live with bent lug. (No one but you will notice.) Why risk breaking it off completely?

SuperDave wrote:I'd say live with bent lug. (No one but you will notice.) Why risk breaking it off completely?

Yes, that was going to be Plan "B"

Ivanhoe wrote:

microflitedude wrote:I don't really know what I am talking about, but you could try slowly screwing into a mount with some heat....

Yes, I think something along those lines may be worth trying, as Micro says the real answer is a new backplate, I don't often see them without the fuel/vent pipes though.

I'm thinking last time it was run, all but one of the screws wiggled out...

As to bending a backplate lug. consider the metal fatigue that will surely be encountered. Then what will you have? (A three-lug BW)

microflitedude wrote:

Ivanhoe wrote:

microflitedude wrote:I don't really know what I am talking about, but you could try slowly screwing into a mount with some heat....

Yes, I think something along those lines may be worth trying, as Micro says the real answer is a new backplate, I don't often see them without the fuel/vent pipes though.

I'm thinking last time it was run, all but one of the screws wiggled out...

I think it more likely that some clumsy ***** dropped it!

I vote for taking it off the engine, heating the lug and pulling it down to the mount with a screw with a washer to spread out the force. Without having seen it, I'm guessing that's what I would do. It'll run forever with a crack as long as you use a washer with the screw,

I now have the Black Widow cleaned up, I paid $9.95 for it, it may be a bit scratched here and there, but I'm not complaining!



This is the bent lug I'm refering to



And the crack across part of it



I think I will test run it before I decide how to proceed....

If flying it I think that you should re shape the fire wall accordingly and leave the engine how it is.

A tad of JB Weld will give it extra strength. That's strong stuff. An SPI set will wake it up too.

RknRusty wrote:A tad of JB Weld will give it extra strength. That's strong stuff. An SPI set will wake it up too.

I've just used that JB Weld for the first time to try to repair a broken lug on an OK Cub crankcase, I did a test beforehand and it certainly does seem to be strong enough for this sort of repair, and it's nearly the same colour as aluminium too!

I hope that cubs cleans up well and becomes a good runner.
By the way you can use cox heads on it.

You can goop it up with JB weld, then carefully bend that lug back in place. Done that before with no problems

OK, here's a question for you Black Widow experts, I'm sure similar questions have been asked before, but please bear with me!
I've now been running the BW, and I have problems, when it runs it fairly screams, but, it won't keep running, sometimes it cuts out as soon as I remove the battery lead, I've tried 3 different heads, so it's not a plug fault, then when it keeps going it screams for a short run, then suddenly stops, after it does this I get wisps of smoke off the vicinity of the head.
I'm running it on 25% nitro, and a 6 x 3 prop. The few times it's kept going long enough to switch on the tacho it's doing around 15,500.
I've done a complete overhaul, new gaskets, etc. the only thing I haven't altered is the reed, it's fitted with a mylar reed which looks in good condition and seals properly as far as I can tell.
Any ideas?

Wilf

Well to me that sound like a mixture problem.
Maybe it is too rich if not it is either the reed or this has not had a proper break in.
So replace the reed and maybe retainer ten let it run rich for a while and see did it improves later.

Wilf:

Your BW is suggestive of fuel delivery problems.

Is the fuel pick-up tube unobstructed and properly placed? Is the needle seat clear?

While your are in there try a new reed just for "grins and giggles". be sure the retainer is properly positioned too.

If after trying 3 different heads, that's definitely indicative of a rich condition.

nitroairplane wrote:I hope that cubs cleans up well and becomes a good runner.
By the way you can use cox heads on it.

Oh it will, Indra, just having to wait for the new conrod from OK to arrive

I've dismantled everything again, fitted a new steel reed in place of the mylar one, the retainer spring seemed to be a long way off the reed so I changed that too.
I have finally managed to run a full tank through it, it's still a bit uneven in the run, but I think that may be due to it not having been run for a long time. It's starting much easier too, so I'll give it a good few more runs on the 6 x 3 before I try it for flat out on a smaller prop.
All round I'm pretty pleased with my bargain!

Thanks to everyone for the usual sound advice

Wilf

Ivanhoe wrote:I've dismantled everything again, fitted a new steel reed in place of the mylar one, the retainer spring seemed to be a long way off the reed so I changed that too.
I have finally managed to run a full tank through it, it's still a bit uneven in the run, but I think that may be due to it not having been run for a long time. It's starting much easier too, so I'll give it a good few more runs on the 6 x 3 before I try it for flat out on a smaller prop.
All round I'm pretty pleased with my bargain!

Thanks to everyone for the usual sound advice

Wilf

Glad it is better!
I am sure it will turn out to be a mighty fine runner.

Is it possible this piston/cylinder was never broken in? If it was a good tight fit when new, then it overheats and begins to seize at peak RPM. It will do that until it breaks in and loosens up. Also an intermittent air leak between the tank and crankcase would cause the same symptom. That can happen if the screws are slightly too long and lose the seal when it warms up. I've got a dozen screws I bought for the BW that are too long.