FX Impact valve stop adjuster issue. Low power unless set way out.

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DanielL

DanielL

Member
Nov 15, 2019
743
18
Michigan, United States
Something weird is going on with the valve stop of my FX Impact.

Overview:

The symptom is the valve stop has to be adjusted way out or else it severely limits power. Even when set out it seems to drift and the power starts going back down.

Background:

I wasn't reaching expected velocities with the stop set at 3 rings. I moved it to 4 and it made a dramatic difference in velocities. A while later, when tuning the hammer spring and reg I was experienced lower than expected velocities again and I backed it to 4 and 1/2 and that got me back to expected velocities.

Today, same issue and I'm out to past where a fifth ring might be. Open more didn't help so I closed it till it wouldn't go in further which turned out to only be at about 3 rings. Test fired and the valve didn't even open. Backed it back out to 4 and a half and came back to full power.

Slowly it is drifting down in power again.

Anyone know what the culprit is?
 
Hi DanielL, 

We are sorry to hear you are having difficulties with your Impact, When you get a chance DM us with your name, number and email and we will get a tech to contact you and hopefully walk through the issues and see what the best course is to get your impact running the way it should. 

Regards, 

FX Customer Service Support
 
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I want to thank Dankleinman and FX-USA. Dankleinman walked me through how to confirm the issue was with the valve rod assembly. FX-USA took the trouble to call me and walk me through the repair process.

Turns out the valve stop had walked all the way off the valve stem assembly. The height of the stop should have measured between 5.7 and 6 mm. Mine was sitting up at 12.7 mm!

The fix was refreshingly simple because the problem occured at the valve stop end. It entailed removing only the shroud, bottle and valve stop assembly. From there, after draining the reservoir, it was just a matter of pulling out the tail of the valve stem, cleaning the threads and loctiting it back into place. 

It's really nasty windy, cold, rainy and snowy here in Michigan but I'm hoping for a tiny break in the weather to Chrony it now that it's fixed. 
 
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All good. With the fix it is now pushing JSB 34.95 gr. at 980 fps and 72 fpe at 150 bar with plenty of spring to go to a higher pressure. In fact, thinking of turning the pressure down and using more spring. Getting about 38 shots before it falls off the reg. Before I had the problem I was getting something like 1005 fps from them up at 165-170bar from the 700mm barrel.

The 600mm .30 is doing 950 fps with 44.75 gr. JSB’s and 928 fps with 47.2 gr. NSA’a for 90 fpe. Bet it could do 100 fpe easy.


 
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