Rimfire Central Firearm Forum banner

YoDave Kit Pictorial

164K views 194 replies 112 participants last post by  Boatninja 
#1 · (Edited by Moderator)
Hey everyone,
With all of the new CZ owners sprouting up around here with questions, I thought that a thread that showed the installation of YoDave's Kit might be beneficial to some. I picked up my new 452 Lux in 22lr this morning, and I figured it would make a good guinea pig. I used the leftovers of the YoDave Kit that I purchased for my Son's Scout.

There are several good fixes for the CZ trigger, and there are even different ways to install the YoDave Kit. This is just my method, not the definitive one. Use what works for you. Just be sure that you end up with a safe trigger! Use the bump test, and cycle the bolt repeatedly to be sure your trigger is safe. YoDave recommends that modifications be done by a gunsmith, and that the final trigger has at least 14 thousands of an inch of sear engagement.

And now to the pictures.
I obviously used YoDave's Kit. It comes with four springs of different strength, and four shimming tubes of different thicknesses.
You can order the YoDave Kit by going to www.ebay.com and performing a search for "CZ 452". The kit should be easy to find. At this time, Dave is selling them for $15 plus $3 shipping.



In the next photo, I am pulling the trigger back with my thumb (no shimming tubes have been used yet). The gap shows how far back I can pull the trigger on the Lux without disengaging the sear (the firing pin has not been released). There is an obvious gap between the "shoulder" on the trigger and the face of the sear. If I release the trigger, the trigger returns to the forward position and the gap disappears. The larger the gap that you can produce without releasing the sear, the more creep you are likely to feel in your trigger. Not all triggers have creep that needs to be fixed. Some are great out of the box.



Support the trigger bracket with something solid, yet non-abrasive. Drive out the front pin with a 1/16" punch. The smaller punch allows the peened edges of the pin to bend up and in, making it easier to remove. Gentle yet firm is how I describe it. You don't want to wail on it, and break the trigger. Be sure that your support block does not interfere with the pin moving down while you tap it. I do not remove the front pin completely. I allow it to stay attached to the right side of the trigger bracket. If you are going to replace the front pin with the provided roll pin, remove the front pin completely.



The rear pin is larger and can be removed with a 3/32" punch. Mine was stubborn, and needed more firm than gentle. Again, be aware of where you place your support under the trigger bracket. Keep it close to the pin, but don't block it.



I usually turn the receiver upside down to finish removing the rear pin.



The trigger will come completely loose at this point. You can replace the factory spring with a lighter one now. I had already used the two heavier springs in my American and Scout, so I was left with the second lightest spring. It turned out to be too light for a hunting rifle, but more on that later. You can also place one of the shimming tubes under the sear at this point. The front pin will go back through the tube when you replace the trigger. I recommend starting with one of the thinner tubes first. I used the thickest one to exaggerate the effect, but I will exchange it for a thinner one later. (it probably wouldn't have hurt to purchase a new YoDave Kit before I started, but I like to think of myself as thrifty :))



You are ready to reassemble the trigger now. Make sure the pins line up with the opposite hole. Hitting harder won't do any good if the pin isn't started in the hole. :)



The tube placed around the front pin acts as a shim between the front pin and the receiver that does not allow the trigger to move forward as far as it did before. This reduces the engagement with the sear, which reduces creep. IN THIS PHOTO, I BELIEVE THAT THE ENGAGEMENT IS TOO LOW FOR A SAFE TRIGGER. The rifle passed the bump test, but this is a field rifle, and I did not feel that the amount of engagement was safe for hunting. If this was a benchrest only gun, I might have left the trigger this way. However, in the interest of my hunting partner's health, I decided to put the thinnest tube in instead. I believe that we have a responsibility to err on the side of safety when modifying a gun.



Here is the engagement with the blue tube instead. Much safer. I also switched back to the factory spring. I simply removed the nut and washer to reduce the pull weight. Now I have a trigger with very little creep, and a light but safe pull weight. After taking these photos, I purchased another YoDave Kit, used one of the stronger springs and replaced the nut and washer. This allows me to fine tune the trigger pull weight, which I prefer.
Be sure and do your safety checks before you're done. I prefer to do the bump test before I reassemble the rifle. Cycle the bolt, and then use a rubber mallet to hit the rear of the receiver behind the bolt. This allows you to give it several good whacks without fear of damaging your wood stock. If the sear does not release, you should be good to go.



And here is the final product. Mmmm, don't CZs just make you smile. :D



I hope this helps answer some of the questions that need pictures in order to understand. Feel free to add your own comments or advice. Enjoy those new CZs!
OKShooter
 
See less See more
10
#4 ·
excellent post!

I have to mention that before you knock out the front pin you should try the trigger with just a new lighter spring. I found I didn't even need a shim at all. I just changed the spring and its perfect on two guns so far. Some guns have more or less creep from the factory. Mine didn't have much but YMMV.
 
#5 ·
I would like to offer some 2 cents, when i did my Yo-Dave upgrade, I used a rubber mallet to test the trigger, the "Slam test" if you will,

cock the rifles bolt, then take the rubber mallet and give a decent blow to the buttstock, if the sear disengages, then it is an unsafe trigger and further adjustment needed.

My 2 cents :D

yo dave rocks
 
#12 ·
I would like to offer some 2 cents, when i did my Yo-Dave upgrade, I used a rubber mallet to test the trigger, the "Slam test" if you will,

cock the rifles bolt, then take the rubber mallet and give a decent blow to the buttstock, if the sear disengages, then it is an unsafe trigger and further adjustment needed.
Great addition on the rubber mallet. I knew I would forget/miss some things.
Thanks for the nice comments. This forum is a great wealth of knowledge. You guys have been very helpful over the years. Thanks :t
 
#15 ·
Great job OKShooter.
Good idea to use the 1/16" punch on the front pin. I think many use a punch too close to the pin size (3/32" or 2.5 mm). Since the pin is peened, the peening isn't necessarily concentric with the hole. So, if they are off just a hair, they aren't centered, and the pin won't move. So, they grind off the peened part or get a bigger hammer. It pops loose easily if you start it with a pointed punch.
 
#18 ·
I installed the Yodave kit on my CZ452 Varmint in 17HM2 just a few weekends ago and would add these observations:

Removing the front pin - I carefully filed off the peened end of the front trigger pin with a jeweler's file and then just knocked it out with pin punch. The front trigger pin could then be easily inserted and removed while I tested the effects on creep of each of the 4 tube shims. Once I settled on the tube shim for me (one up from the thinnest), I replaced the original front trigger pin with the roll pin that Dave supplies in the kit. The roll pin is a press fit and will not fall out. If you try to reuse the original front pin, it should be re-peened to keep it in place.

On Using the original spring - I tried the original spring without the adjusting nut and washer. Trigger pull dropped exactly 1 lb. -- from 4 lbs. 6 oz. to 3 lbs 6 oz. However, note from the picture that the spring is not seated flush with the bottom of the rod on which it compresses/decompresses. The coils of the spring are hung up on the threads of the rod on which the nut turns. Eventually, the spring may creep its way down to the base of the rod, and in doing so, the trigger pull weight is going to lighten. Rather than reuse the original spring, I used the second heaviest spring that Dave provides, together with the original nut and the washer. This produced a pull weight of 2 lbs. 4 oz. By turning the adjusting nut down a ¼ turn, a pull weight of 2 lbs. (my objective) was achieved.

Dress the ends of the spring you use - unlike the original CZ spring, the springs that Dave supplies are just cut to a prescribed length. The ends of the spring should be dressed, or flattened so that more of the spring end contacts the seat in the receiver and the nut/washer assembly. One of the easiest ways to do this is to use a grinding wheel on a Dremel tool. Insert the grinding wheel, turn on the Dremel, set to the lowest speed, and lightly press the end of the spring against the top of the rotating grinding wheel. Repeat this for the other end of the spring until you have achieved the desired effect.

Use Loctite on the threads of the spring rod - the factory did not use any thread locking compound on the threads of the rod of my rifle. The factory also uses a stiffer spring so the nut is not likely to move. In the interest of thoroughness, I used a drop of low strength Locktite on the threads to keep the adjusting nut where I want it to give me a 2 lb. pull.

Torque up the action screw - on the 452 Varmint, there are 3 slotted screws that pass through the trigger guard. The front and rear screws are short wood screws and the center screw is a machine screw that holds the action to the stock. When removing the machine screw, I set my torque wrench (FAT wrench from Midway) on 10 inch lbs. The torque wrench just clicked. I then set the wrench for 15 inch lbs. and got the same result. I next set it to 20 inch lbs. and the screw backed out. That told me that it was torqued in at 16, 17, 18, 19 or 20 inch lbs. When reassembling the action to the stock, I used the median value - 18 inch lbs. - to tighten the action screw.

Take the opportunity to replace the action screws - I purchased a Torx head screw set from Rimfire Technologies for around $24. A Torx head screw is easier to torque up than a slotted screw and looks better too.

While the action is out of the stock - The Varmint is free-floated. However, when testing this with a piece of paper pulled between the stock barrel channel and the barrel, the paper would bind in several places. While the action was out of the stock, I lightly sanded the barrel channel with extra fine sandpaper, taking care not to round edges or disturb the even gap between stock edge and barrel. I then applied 2 coats of Tung oil to the barrel channel. Now the gun passes the paper test with flying colors. If your CZ is like mine, take the opportunity to address this issue while you have it apart.

Cheers
John
 
#19 ·
Some excellent points exring. However, I will disagree with a couple.

The roll pin makes a great replacement for the front trigger pin. However, if you do not file the peened edges of the front pin, it will be nice and snug when you tap it back into place. And, as Steve mentioned, the front pin will come out easily if you use a pointed punch or a smaller punch (1/16") like I did. Minor point, but it does allow users to redo the trigger without an additional roll pin.

In my example, the original spring is threaded onto the base rod very snugly. It is not going to creep up or down. However, I would prefer to leave the nut and washer on the trigger rod. It would allow for much more adjustment later on. I just didn't have the spring that was needed to provide the desired trigger weight, so I compromised.

The nut on the spring rod should not need Loctite if you use the factory washer with it. You will notice that the washer is not round in the middle. It has a flat side that prevents it from spinning around the trigger rod. The washer also has a ridge on its top side that corresponds with a groove on the bottom of the nut. The spring pressure will hold the groove on the nut over the ridge on the washer, which will prevent the nut from turning. No Loctite needed, though I'm sure it won't hurt anything.

Good point on the light sanding of the barrel channel. I too found that the "raised grain" inside the barrel channel interfered a bit with the paper. A very light sanding was all that was needed.
 
#20 ·
OKShooter
No doubt there are many ways to accomplish this modification. My observations are offered as an alternative to your approach -- not necessarily as the only way to do the job. As noted in my post, by filing off the peened end of the trigger pin, I was able to easily slip the pin in and out of the trigger as I tried all 4 of the shim tubes before settling on the right one for me. If this kit is about anything, it's about trial and error. For my taste, I prefered to use a new trigger pin.

Your experience reusing the original spring was a bit different than mine. The original spring coils on my spring got hung up on the threads, preventing the spring from seating properly and preventing all of the coils from fully compressing. Glad yours fit better than mine. However, for my style of shooting, the original spring sans nut/washer still produced too heavy a trigger pull.
Cheers
John
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top