Need Help Low Cost Valve Job on a Linhai 257 cc  By  bob123456789 (Read 4,274 times)

Another question. If it is the rings should I get the rings or the rings and piston?

Thanks for the suggestion Cyborg.

It was sitting for a fair while not turned over. Are any of the long shot suggestions work in s a situation like this before pulling things apart? Soaking the rings in diesel ....

Is it worthwhile looking in with a borescope before pulling things apart?

It will get harder to turn the engine on the compression stroke.

Thanks RockyNV.

The symptoms (low power, dies at idle,...) were there before the valve adjustment. The mechanic thought that the valve adjustment would fix them. It has 6,000 miles which seems to fit the normal valve adjustment schedule. The valve adjustment had no impact on the symptoms. The scooter had been sitting before I got it and has been sitting a lot of the time since while I try to get it back to rideable shape again. The valve adjustment by the mechanic was done after it sat overnight.

I haven't heard of ZMax. Has anyone else had any experience using it? I'll try to read up on it.

I have a narrow window when my local weather lets me work on it. I am moving into the favorable period again. I would really like to get this thing up and going reliably very soon before I can no longer work on it due to weather.

Should I mess with Zmaz or other solutions or should I start pulling the head? I have not pulled the head before and would be working alone. But with a solid support team believe I could do it. It may not be as quick as if I had it done by a mechanic but I do work for free.

At 6,000 miles its hard to imagine a 257 that would be as completely worn out as your mechanic is leading you to believe unless it was really abused, overheated, soft seized, run without oil, etc. You may have simply had a very ethanol impacted fuel system as your original problem and now its compounded by a botched valve adjustment. Yes you could have a bad valve too or you could have a bike where the timing chain is off a notch as who knows what evil lurks in the heart of a used bike.

Are you 100% confident in this mechanics ability to have inspected, diagnosed and adjusted the valves correctly? If you are then get some fuel system and engine treatment to clean the carb, valves and the inside of the engine into that bike to free up whats clogged or sticking before it does any further damage. If the rings are gummed up and stuck the longer you wait the more likely the piston and cylinder are going to get scored and require replacement. If the fuel system is partially clogged and running lean from sitting unused with ethanol in it or the valves are sticking then you are chancing burning a valve or burning a hole in the top of the piston.

The biggest issue I see with the 257 is people expecting it to perform like an European 250 however its not a 25 hp bike its only 16 hp so you won't be seeing the same 80+ mph performance from the bike as you would expect from the European bikes. When you push them at wide open throttle on the highway the fuel pumps can't keep up so they run lean and can burn valves along with the cylinder if you keep beating on them.

The Zmax needs to be run in until the engine is hot to do its job and needs to be circulated completely throughout the engine. 15 minutes minimum but 30 minutes would be better. Its all on the package.

Just don't try to ride like you just stole it or break any speed records.

If the engine is extremely gummed up inside you may see your oil turn interesting colors as it releases all that junk and frees things up.

You have to start it up immediately too or as I mentioned previously it will all be absorbed into the oil sump casting. It is designed to be absorbed by the metal and release the dirt from behind so with that in mind wear gloves and don't pour it on yourself.

Yes a good working fuel pump helps and sometimes especially at high rpm an electric is the way to go as there may be such a diminished intake pulse at high speed that even the best vacuum pump might stop pumping fuel altogether.

I have a fuel injected Aprilia and the high pressure electric injection pump has plenty of reserve capacity to support even a 1+ liter bike.