I have a 2002 honda shadow ace deluxe 750 and then engine started having a metallic ping and some smoke. This was for a short period of time. Now the engine will start but it wont stay running. Took it to a local motorcycle shop and they said it was a piston ring. I was hoping someone here could chime in with their knowledge. I appreciate any help you guys/girls can offer. Thanks. '
You might want to try here: Motorcycle Resource and Information Center, Discussion Forum, Chatroom, Vendors List
I can tell you that's weird. Those 750 ACE/Spirit engines are so reliable as to be spooky. Anytime a ring fails, low oil level would be the first thing that comes to mind.
go talk to the guys over at Motorcycle Resource and Information Center, Discussion Forum, Chatroom, Vendors List as there are some damn good mechanics over there. the shadow engines are about a bulletproof as you can get and a ring problem just doesn't sound right. you can't judge a ring problem without the engine being apart.
A good tech can easily diagnose a ring problem via a leakdown test, without teardown. You may not know EXACTLY why until a visual inspection is done, but a sharp tech could make a real educated guess based on evidence that's more easily accessible, such as low oil level, intactness of air filter or debris in the carb venturi (in case of foreign matter ingestion), excessive carboning (based on build up visible in exhaust and intake ports). The symptoms (noise, smoke) are consistent with a piston/ring failure, but other things are possible. Guess the point is because of the reliablility record of this model, and the potential cost of the repair, you wanna be sure. Unless you trust the shop implicitly, you may want to quiz them on 'how they know what they know'...or get a second opinion.
Joe: The old shade tree mechanic's (i.e., my) approach when rings are suspect is to do a compression check. A bleed down test (requires a compressor and bleed tester = expen$ive) is the fanciest/best way to do it but a regular old compression tester (cheap) is completely adequate. If one (or more) of the cylinders indicates low compression, a differential diagnosis is required to determine if it's valves, blown head gasket, or rings/cylinder wear causing the low compression. Pump a few squirts or teaspoons of oil into the cylinder and check the compression again. If the compression improves, it indicates that the rings or cylinder is the issue. The oil was improving the seal there. If it doesn't improve it's either valves or head gasket. Best of luck, Stoo
To know that it is leaking at the rings is the easy part, what else is wrong and what caused the failure is the improtant part. I doubt the rings just failed and doubt even further that a new set of rings will cure it. I had a Perkins in today that I am waiting on the ok on to rip it down that has a problem with the the bores, rings wont fix it , most likely damage to the bore from heat and rings are just one of the many things that it will need to repair .
If that's the case here's what normally happens. The ring gap becomes nonexistent. Lets say you have ring gap of .020 and they close up to .007 when normal or just a little higher temps. If for some reason the cylinder gets a lot hotter the rings expand more and that .007 goes away and the ring ends butt together. If they try to expand farther they will bind and break. Sometimes taking a piece of the piston, between top ring and top of piston, with it. Then it will score the cylinder wall also. Which most likely an over bore and larger pistons will be required. If that's the case. Then when it gets repaired you want to make the ring gap to the widest factory tolerance and or .005-.010 more. Even with a wider gap you will not really use any more oil or get more crank pressure than normal. As was said do a leak down test first.
I've always used Honda's specs as close to dead center as possible on rebuilds with very good results. I know the specs may seem tight...but they're not pulled out of 'thin air'. Manufacturers design piston and rings via shape and alloy to expand with the type of cylinder lining used. The only reasonable ways to vary ring end gap is to use a looser piston to cylinder fit...not good as piston relies on cylinder contact to shed heat...looser yet and piston skirts start breaking. Filing rings might be OK for an old Briggs lawnmower...but for a brand new set of ACE rings...I personally wouldn't go there.
Dizzy I take it you never built any racing/performance engines from your quote: "The only reasonable ways to vary ring end gap is to use a looser piston to cylinder fit...not good as piston relies on cylinder contact to shed heat. Filing rings might be OK for an old Briggs lawnmower...". It's common practice when building a performance engine. Yes the auto engineers know what they are doing. They also have to make compromises for general use, emissions and so forth. I've never heard of changing piston size for ring adjustment. Don't even know why anybody would do that. The pistons don't get rid of heat by touching the cylinder. If you see scratches on the piston then they are rocking in the bore and that's not a good thing. It's not how the rings fit on the piston that you have to worry about. It's how they fit in the cylinder bore. You have to put the ring in to the cylinder without the piston then you measure the gap between the ends of the ring. Under all circumstances there is a specific gap with +/- tolerances for gap size. If the motor being used will be generating more heat in to the combustion chamber, IE N02,Nitro,high cr,more hp etc the ring gaps have to be a adjusted wider for the extra heat that is made inside the cylinder. Most manufacturers of rings will give different specs for different apps. If the stock motor has the rings on the lowside of the tolerance along with the bore and the motor gets hotter than what it was design for at high temps it's possible for the gap to close tight. Very seldom happens that I know of with stock motors. Here's just one site that explains what and why you have to adjust ring gap. Piston Ring End Gap Recommendations or go over to Wisco, SpeedPro, TRW or any piston manufacturer for their recommendations.
OK, Grey, you win. I have deleted my posts, never should have said anything. I should know better than to argue and fight with people on the internet.
Just want to say thanks for the replies. They did not take the engine apart, they did a compression test on it. So I went ahead and took it apart and found that both pistons had good rings and the clearance was within specs. I cleaned everything, replaced o-rings and gaskets and now I have a new problem. The carburetor wont fit back on. It seems the insulators don't line back up. Just not sure what I'm doing wrong, I'm thinking maybe I should of left this problem bike alone.
Actually Grey...I do quite a bit of engine work. Matter of fact, since Jan 1, I've done top ends on two late model high performance snowmobiles, not to mention cutting valve seats on a Rincon head. Tomorrow I tear a Honda EU1000 generator down that's consuming oil excessively. Just for the record, I didn't say use a smaller piston to vary ring end gap...I said use a looser piston to cylinder fit. As in the variable being bore size, not piston. If it's a cast iron sleeve and CAN be bored, you go an extra thousandths or two and thereby increase the ring end gap. The problem with filing rings is most modern offerings come with various types of coatings that are very easily flaked or chipped...and just aren't intended to be subject to machining. Now maybe rebuilding a V8 for the dragstrip is different. I think the fit of the ring to piston is of great importance, as is the ring end gap. I check both every time. Every so often you get a 'dud' piston where the ring landing is too tight...I've also seen pistons that looked fine but the landings were wore to the point of rings being too loose (I'm talkin' up and down play here). Sometimes pistons have been updated or changed and the rings that have been sent are for the 'older' style. Of course there's always the chance to install them upside down. If you want good results you'll pay close attention to that kinda stuff, contrary to 'doesn't matter'. I wouldn't use Wiseco specs to fit Honda pistons and rings...nor would I use Honda specs to fit a Wiseco. Wiseco's are forged...and a totally different piston altogether with completely different expansion characteristics. Ever measured a Wiseco piston at the top? They're actually egg shaped.
