Crosman/QB Valve Stem Rebuild Starter
Crosman/QB Valve Stem Rebuild Starter

Our Price: $199.00

Quantity in Stock:(Out of Stock)

Product Code: CRQBSRKST

Valve Stem Rebuild components for Professional Rebuild of the Crosman Old School & QB Exhaust valve Assemblies. Can fit many other models and makers. This kit gives the DIY a good variety of components so he/she can rebuild all the Old School CO2 Crosman and modern QB & TF guns. Made in USA by Mac1. A propane torch can be very helpful to get the brass head to separate from the steel stem. A .2" through hole in a steel plate centered in a .375" .125" deep recess will allow you to drive the stem out of the head when properly supported. The seal fits in the brass head and you use a 1/8" hole in a hard plate to drop the long end of the stem in and drive the head and seal onto the stem. It is a good policy to use a permanent thread locker in the brass head for insurance. Once the head is pressed together it can be trued and faced off to ready it for use. I chuck the head at the step or full length of head and make sure the run-out on stem is eliminated. I face off the seal and polish with 4 oooo steel wool. Heat the entire gun up to toasty when you first charge it so the seals will be supple and the pressure will be high. Making sure there is no damage to the valve seat where the seal sits is very important as the Mac1 seals are hard enough so you can leave the gun charged all the time. Getting it to seal initially can be impossible if there is any seat irregularity. Polishing the seat is often required to remove any scratches or abuse. If you use the parts that make for the most reliable repairs imaginable a DIY project can be the best investment you ever made in an airgun. Quality parts last. Your time is wasted when you use inferior parts.
Those that don't have a lathe to cut the seal after install need to spin the head in a driil motor with seal fitted to brass head prior to assembly to get a reasonable finish on the exhaust valve seal so it will work. Once assembled the DIY needs to be certain the stem runs true and chucking the head and spinning assembly will show you if it got bent on assembly. The stem needs to run true to the head and the thru hole needs to be true to the seat or hard seals won't make adequate contact.
This Kit includes;
2X long stems for 160 & 600 and others guns that use shorter stem you can make from this stem
2 short MKI stems
16x Exhaust valve seals
4x MKI Complete Exhaust Valve w/return spring
10X 111-026 Valve springs for MKI, 150, 180, 400, & 160
6x MKI Small head
4X S&W 78/79 small replacement head (fits factory S&W steel stem)
2x 600 valve head
4x 160/150/180/400 head
These components should be able to rebuild 20 CO2 exhaust valves for under $10 each. For hard core DIYs or Pro Tuners. If you have the skills don't let them go to waste using inferior components.
Crosman & QB Valve Stem Rebuild Procedure-Mac1 HowTo

Share your knowledge of this product. Be the first to write a review »