2013 DF175 Broke valve, seeking advice

[GMikeHall]

I purchased this 2013 DF175 with a damaged piston and cylinder head from a broke exhaust valve. The damage to the head can be repaired according to a few Machine shops I talked to but now I am looking into the actual cylinder which has some very light scoring on the cylinder walls. I have been looking around to see if it is possible to bore the cylinder and install a slightly over sized piston but it seems I can not find any details on doing such on these four stroke engines. It looks like the cylinders are cast iron sleeved but maybe they are nikasil and not able to be bored out? You can barely fill the scoring on the cylinder wall with your finger nail so it is substantial but possibly may could just be cleaned up with a light honing of the cylinder? I am not looking to take any short cuts and I want to get this motor going again so it will last so any advice would be great.

On another note, All the valves being white makes me think this motor was running a bit lean or maybe hot? The PO has not long replaced the water pump and done other services such as the internal anodes so maybe something failed and it ran hot? Motor only has 960hrs and the owner claimed it was serviced regularly but maybe not as it does seem there is a good bit of corrosion inside the water passages which may be way it ran hot. There is a layer of crust on the passages which may keep the water from contacting the aluminum to dissipate the heat correctly.

Thanks
Mike

[Hoosmatroos]

Hard to tell from the pictures. I think I would ask a good machine shop what best to do with the cylinders. The head seems pretty messed up.

[GMikeHall]

There are companies that rebuild heads that are way worse off that this one. They clean them, welded them up then create a CNC path off a good chamber to machine it back to factory specs. I will be looking at around $1000 for so to get he head back in good shape but that is far better than buying a new head. I found the oversize pistons finally but I am not sure I would want to do them all or just the one cylinder. I am going to take the bock to the machine shop to see if they can just do a light hone to clean it up without actually boring it out.

[Hoosmatroos]

Please let us know the outcome when able.

[GMikeHall]

I found a very low hour 260hr cylinder head, piston, rod that I purchased. The engine had been hit while being trailered so the parts are in fantastic shape. I got all the needed parts for less than it would have cost me to rebuild the head so I am very pleased about that. I am not looking into the scaring in the cylinder which looks like aluminum transfer from the piston. The rod was bent and cocked the piston in the cylinder a little causing the top edge to rub on the cylinder. I have to look more into that otherwise I may have to go with the next size up piston. Any issues with running one piston oversized and leaving the rest the same on these engines? I know on an automotive V8 there is no real big issue with doing that.

[catacom225]

Not sure if i've ever heard of any one using different piston sizes in an engine, You can speculate all you want but until you get to a machine shop your only guessing. Hopefully its only cast off from the piston and a good hone will do the job,

[GMikeHall]

I have been waiting on my Bore gauge to arrive to check the cylinder for roundness and to see if it is in spec before I take it to a machine shop. Suzuki has very tight tolerances for the cylinder and I had to get a set of Mitutoyo .0001 micrometers and a Mitutoyo bore gauge set that will read down to .0001 as well. I have been needing these tools for other projects so the DF175 is just an excuse for finally ordering them. haha All my tools will arrive tomorrow an I can figure out what I am going to be working with as far as cylinder condition.

[GMikeHall]

Good news is that all the cylinders are well within spec for roundness and bore diameter. I do still need to hone the cylinder that had the valve let go to clean up some of the light scaring but I doubt even that will make the cylinder even close to out of spec. I also received the used head and it was looking fantastic until I started cleaning all the carbon and crud from the number 2 combustion chamber. There is some fairly bad pitting on the bottom half of the chamber and that pitting extends into the valve seats so non of the valves are sealing as they should. Using brake cleaner you can fill a port with cleaner and all the over valves on the head do not leak but this one chamber all the valves leak badly. I have been in contact with the company I purchased the head from hoping for them to work with me on exchanging it or at least allowing me to return it.

Mike