Machine Builders Network+ Forums Thread Like Summary - over-powered CadDigger 628 and newbie questions

I purchased a CadDigger 628 over the weekend. I'm the third owner. The previous owner replaced the orignal engine, which should have been 5HP, with a 13 HP engine, and then tore the bucket apart digging with it. It's so over-powered, I need to use two hands to steady myself enough to make the small movements necessary to control it reasonably.

This is the first I've ever worked with hydraulics. I read a bit about using relief valves or restricting the flow. Would that be practical here? The seller told me the pump was original, and that it's 2.6 GPM, although I can't find any markings to confirm that.

I believe the proper thing to do would be to put a more appropriate-sized engine on it. I see that I can get a 6.5 HP Harbor Freight engine for $160. It already has a LoveJoy connector, so that part should be easy. Then I'd need to buy or make a bracket to mount the pump to the engine. The engine mount has a bolt hole circle diameter of 92 mm, which doesn't match with any NEMA size I can find. The pump only has two bolts. How can I find a bracket to connect these? If I need to make one, I do have a tiny DC welder, but not much experience with it.

I appreciate any advice.

if you're not changing the pump, the engine swop will not make a difference in the way the machine operates,other than the point at which the engine stalls under load. RPM is RPM as the pump sees it,the only gain you will make is less fuel burned per hour with a smaller engine. I'd stay with the 13hp and look into relief valve settings by installing a couple pressure gauges in the various parts of the system so you can see whats going on..after some seat time in getting to know the machine you can sense when you have a hyd.circuit loaded up and when you should back off the valve or the relief valve cut in and dump pressure back to the tank.We have a few here that have built machines(myself included) and can offer advice,be sure to post photos of what you are talking about when you do..some machines out there have had pumps and valves replaced with other than design parts which adds complication to diagnosing whats wrong if a machine doesnt operate right..maybe we can help you.Welcome abourd..

for starters I'd go with a tee in the pressure supply line to the valve from the pump,mount the gauge to that tee..use a 5000psi gauge to give yourself some gauge headroom when reading at high pressures. Surplus Center has it all in stock for the most part,they have an awesome selection of adapters and fittings.From the looks of it this is an open center system(flow from pump thru valve,back to tank with all valves in neutral) at 2500psi or lower. relief valves are only going to actuate when they reach 'cracking pressure' or the pressure where they will open and dump back to the tank,or in this case, the valve will bypass flow back to the return line,or hose that goes back to the tank. It sounds like you have too much flow in therms of GPM, or pump flow..which is maybe why some one put a 13hp engine on it, so they can reduce flow by only running the 13hp engine at 1/2 throttle, halving the flow vs. full throttle, but still have enough power to run the pump. Try running the hoe at half throttle and see if it's more manageable to operate.

If the engine isn't running, there is no pressure.