Problem: Trouble keeping velocity above 250 (all over the place)... having to recock it after firing a few shots.

Things I've replaced: New front and rear bolt O-rings... new drive spring. Same issues...

I'm thinking the issue is with my power tube or the valve itself. Was thinking about getting a DOP or JCS power tube, but I don't think either comes with the valve itself, which very well may be the issue. Going to open her up again, take the power tube out and remove the valve (which I've never done, any ideas?)...

Just curious if I'm on the right track or I should just retire her and get a new 98 Pro :)

rathrock wrote: Problem: Trouble keeping velocity above 250 (all over the place)... having to recock it after firing a few shots. Things I've replaced: New front and rear bolt O-rings... new drive spring. Same issues... I'm thinking the issue is with my power tube or the valve itself. Was thinking about getting a DOP or JCS power tube, but I don't think either comes with the valve itself, which very well may be the issue. Going to open her up again, take the power tube out and remove the valve (which I've never done, any ideas?)... Just curious if I'm on the right track or I should just retire her and get a new 98 Pro :)

Does it ever go full auto just before is doesn't recock?

It has on occasion. I've checked for any noticeable cracks, tested the air line (no obstructions), verified all my O-rings,etc...

I cleaned the valve as best I could, put a few drops of #9 in there, reassembled the marker (complete with Blue loctite on the valve retainer screws) and put the marker back together again.

One thing I did do different was remove the Tippmann CAR stock... it's got a different look than my stock end-cap (the stock endcap has an opening for the drive spring, with I believe 5 holes drilled around it.. the stock has only one plus the addtional one for ACT markers I imagine. Not sure if that could conceivably be the problem, but at this point, I'm about to wash my hands of it, buy a 98 Custom or 98 Pro and send her back to Tippmann for repair (and use it as a backup marker).

I've thought about buying JCS Blew tube and a complete valve assembly, but by the time I do that, a few extra bucks gets me a brand-new gun...

I'm really at a loss as to what it could be at this point :(

u just grab the exposed part of valve and pull after you have removed the 2 screws that attach  it 2 the gun.  but u might want 2 check out the trigger mechanism springs (the springs mixed up could prevent the bolt latching if u shoot 2 fast), also u might want 2 try replacing the rear cocking springs.

CRAZY PENGUIN wrote: "Going to open her up again, take the power tube out and remove the valve (which I've never done, any ideas?)" u just grab the exposed part of valve and pull after you have removed the 2 screws that attach  it 2 the gun.  but u might want 2 check out the trigger mechanism springs (the springs mixed up could prevent the bolt latching if u shoot 2 fast), also u might want 2 try replacing the rear cocking springs.

Crazy,

It is usually a good idea to have some slight idea as to how a marker works before you start dishing out solutions. Try this for the valve information...about post #16.

Rathrock,

From reading the other interactions here I'd conclude that the main power spring is the problem. If you have changed the stock with the original style back cap than you have probably changed the compression of the power spring slightly.

If the depth of the hole into which the power springs fits is ever so slightly deeper (than what was working previously) there is reduced energy to the hammer. The hammer therefore hits less hard not opening the power valve as much as needed to get a full charge of gas. That means that the hammer receives a reduced blow-back charge of gas so the hammer does not travel far enough to the rear to engage the sear. The hammer then drops from that point with even less energy opening the valve even less.

This may lead to what many call "burping", the marker behaves as if the tank were low...a short burst of full auto with the hammer stopping at rest against the valve pin.

Some times the initial blow-back may be so low that the hammer falls with so little energy that it just comes to a stop against the pin...no "burping."

Put a BB or two into the hole into which the spring sits (back cap or stock) then install the spring with its rod. The rod is pushed forward slight increasing the compression of the spring and thus imparting more energy to the hammer. 

The BB is trapped under the head of the spring guide rod and won't cause any trouble.  You could also go to the expense of a Maddmann aftermarket spring kit which contains a stronger spring.

Since you made a change of the stock, that is the change that impacts the compression of the spring. Now the original question was asked way back in January and has been bumped up to yesterday by Crazy...who is obviously looking for anyway to get his post count up...he now has 2.

Rathrock, if you have a solution now or have thrown up your hands and gotten rid of the marker, let us know...one way or the other.