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Post  Aero on Wed Oct 14, 2020 3:43 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 3:59 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 4:49 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 9:40 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 8:19 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 12:18 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 6:36 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 9:21 am

If ever needed,  Cox international has the black plastic NV seal

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


Last edited by fredvon4 on Tue Nov 03, 2020 10:24 am; edited 1 time in total
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Post  sosam117 on Mon Oct 19, 2020 12:17 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 8:36 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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Post  Aero on Sun Nov 01, 2020 5:17 pm

Got it back together. Another issue that I found was a crack in the carb/venturi body. I'm going to take a shot at firing it up soon. Had family happenings this weekend.

Spins nice and has good compression.  Going to give it a drink of Sig Champion 25%.



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Post  sosam117 on Sun Nov 01, 2020 6:22 pm

Aero wrote:Got it back together. Another issue that I found was a crack in the carb/venturi body. I'm going to take a shot at firing it up soon. Had family happenings this weekend.

Spins nice and has good compression.  Going to give it a drink of Sig Champion 25%.



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If you have problems with the crack, clean the engine well (alcohol or acetone?) to remove any oil residue.
Then using JB Weld, try to push the JB Weld into the crack.
It's only a temporary fix.
It is better to purchase the aluminum venturi body from our Cox vendors.
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Post  Levent Suberk on Sun Nov 01, 2020 6:53 pm

In a thread Mauricio made a ring to fit on a cracked venturi. However I couldn't find that thread.
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Post  Jason_WI on Sun Nov 01, 2020 7:10 pm

That’s a different engine than what was originally posted. Either way I prefer the plastic carb bodies vs the aluminum ones. Air leaks between the aluminum carb body and crankcase were problems on the ones I tried. Maybe the newer aluminum ones addressed that issue.
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Post  sosam117 on Sun Nov 01, 2020 9:23 pm

Jason_WI wrote:That’s a different engine than what was originally posted. Either way I prefer the plastic carb bodies vs the aluminum ones. Air leaks between the aluminum carb body and crankcase were problems on the ones I tried. Maybe the newer aluminum ones addressed that issue.

Jason,
I use the "black" Permatex (very small amount using a toothpick to apply) on either end of the aluminum carb body and have had no problems.
The black Permatex is rubbery and stays that way. I've used it on PAW mufflers to seal the muffler to the head without any leakage.
Nice thing about the car body is that it tapers, so you can get the sealant on the crank case then slide the venturi body up into place.
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Post  MauricioB on Sun Nov 01, 2020 10:07 pm

Levent Suberk wrote:In a thread Mauricio made a ring to fit on a cracked venturi. However I couldn't find that thread.

Here I am friend, I will share photos again.
The previous thread is in the forum, but I have not looked for it ...
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ring made of aluminum alloy, filed and adapted by hand, glued with epoxy.
Definitive solution, you will never have problems again!
You can do it in bronze too ... I have done it and it gives a very good appearance, especially if the crankcase is black! Thumbs Up
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Post  MauricioB on Sun Nov 01, 2020 10:12 pm

here you have an engine Tee Dee .049, to which I made the repair of the crankcase with an aluminum alloy ring and I also made a bronze acceleration ring!
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Post  Aero on Mon Nov 02, 2020 7:43 am

The original carb body was cracked and I happened to have a new black one to replace it with. I don't have much of a spare parts bin. I assumed the red and black ones were the same. I should have explained it a bit more. I will try the fixes you all have posted to have the cracked one for a spare. Sorry about that.
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Post  davidll1984 on Mon Nov 02, 2020 10:13 pm

Just litle trick for plastiques part make them like new use wd40 it help flexibilité of matériel old plastiques part tend To dry if Not used for very long it crack in displays case just spray on part let it wit t'il its dry part gain flexibilité bad point if part is alredy crack is To late it can help new Not used engine plastiques part
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Post  stuntflyr on Sat Nov 07, 2020 9:32 pm

Another thing to watch for is Dale made venturis with larger id for pressure fuel systems. If all is clear and it draws fuel but doesn't do it well enough to take off and flames out on take off you might check it against a stocker to see if it's oversized.
Chris...
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