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October-2020
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Post  Aero on Wed Oct 14, 2020 5:43 pm

One of the TD's  I have has a Kirn NV. I have tried a few times to get the engine to run, however it only runs on a prime. This is using a small Perfect brand tank. I have disassembled and cleaned the NV three times and am at a loss.

Also, as I received the engine, it has a small piece of silicone fuel line on it. I would assume this may be for a seal or to keep the NV from rotating during operation.
Someone in my club told me with this NVA it needs to be run on a bladder.

I think I will take it to work and put it under the shop microscope to have a close look at it. Maybe even give it an ultrasonic bath.

Any advice appreciated!

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Post  Jason_WI on Wed Oct 14, 2020 5:59 pm

Clean the 3 small holes in the venturi with a small wire. Also make sure you can see light through the needle valve body with the needle removed. Shine a flashlight in and you should also see light out the small hole in the center of the needle valve body. It looks varnished up so I would soak that in denatured alcohol and clean it up.
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Post  Ken Cook on Wed Oct 14, 2020 6:49 pm

Flushing with a syringe will immediately tell you if the spraybar is clogged which more than likely it is.
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Post  Aero on Wed Oct 14, 2020 11:40 pm

Thanks for the replies!

I will give the body, needle, and venturi a thorough cleaning.
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Post  getback on Thu Oct 15, 2020 10:19 am

Hello Allen , The KK don't have to have a Bladder to run But will bee your go to for a Bladder run if you ever decide to try one . Very Happy The above response should take care of ur problem , let us know . Small Cox Logo
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Post  ffkiwi on Fri Oct 16, 2020 2:18 am

Don't forget that these are FINE THREAD needle valve assemblies...128 TPI.....so you need to open the needle about double the number of turns you would with a standard Cox TD 049 needle assembly-which for the latter is about 5 turns open for starting, from memory....so with the KK assembly, all things being equal...ie clean and no blockages...you could expect to need it open 9-10 turns for starting (NOTE-I'm talking suction feed settings here, not pressure!)

So if you only opened it the usual number of turns-the engine would not draw enough fuel to run-so runs out the prime and stops. In standard form, these KK assemblies had a small cylindrical nylon seal that abutted the brass body to act as an airseal on the needle OD. These did wear and leak-and quite a few users simply replaced them or supplemented them with a short length of silicone fuel line over the needle and the needle inlet-exactly as yours has.  Part of the problem is caused by quite a long needle valve overhang-which accelerates the wear-hence the original seals often wear out, letting air in-which is bad enough on suction-and far worse on any pressure system.

As a bonus, the piece of fuel tube also helps the locking effect of the seal, so the needle valve usually stays where you set it, without creep.   One final thing to check-these needles are only brass-and relatively easily bent in a crash-so if your needle is bent that might well affect the way it adjusts-though any bend is likely to occur where it exits the metering block; likewise check the very tip to see that it is not bent or burred (unlikely-but not impossible....)

Normally these are good units-and virtually all my TD 049s/051s are fitted either with these or the Ace R/C unit-which is effectively the same but with a plastic rather than brass body.

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Post  Aero on Sun Oct 18, 2020 8:36 pm

Cleaning done. I will get the TD back together and give it a go later this week.

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Post  fredvon4 on Mon Oct 19, 2020 11:21 am

If ever needed Cox international has the black plastic NV seal

https://coxengines.ca/cox-.049-.074-spray-bar-seal-10.html
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Post  sosam117 on Mon Oct 19, 2020 2:17 pm

fredvon4 wrote:If ever needed  Cox international has the black plastic NV seal

https://coxengines.ca/cox-.049-.074-spray-bar-seal-10.html

It's always a good idea (just in case), after cleaning to replace gasket/seals. Most common place for leaks.
That black plastic NV seal gets hard and brittle. that's why you'll see a piece of fuel line over the NV and black seal.
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Post  Aero on Mon Oct 19, 2020 10:36 pm

sosam117 wrote:
fredvon4 wrote:If ever needed  Cox international has the black plastic NV seal

https://coxengines.ca/cox-.049-.074-spray-bar-seal-10.html

It's always a good idea (just in case), after cleaning to replace gasket/seals. Most common place for leaks.
That black plastic NV seal gets hard and brittle. that's why you'll see a piece of fuel line over the NV and black seal.

Yep. Looks like I may need to place an order or two for parts. I have a few reedys that need some attention, too.
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