Damaged Spark plug
 

About 30 miles into my 35 mile commute home from work today my Storm stopped running and would not restart. After pulling out the plug, I found it to be very damaged. Has anyone ever seen anything like this before or know how it can be caused? If I am lucky the metal either blew out the exhaust or is in the bottom of my oil pan but I am assuming a piston ring job may be in order.

Was there a crash or something? That plug looks really chewed up top to bottom?

If the plug is that damaged, I would say the piston and cylinder head are also screwed.

No noticeable sound. Just a loss of power.

That ain't good.:ohno: Pull the head and see what damage was done. I,m wondering if you had a screw or something in the air box it sucked in through the carb? Check the carb and see if screws or even if the butterfly choke valve is still there.

It's my opinion this should be covered under warranty.

The last time I saw that it was a dropped exhaust valve head that turned sideways and shut down the engine quick. There was no rev down. He was buzzing along then immediate silence. The valve head was embedded in the piston. When we sorted it out after cooling, we tried to start it and nothing. It made no funny noises or anything. Sounded just like it was out of fuel when we tried to start it. I could see the valve in the piston by rotating the engine with the kickstart and looking down the plug hole. My eyes were better 25 years ago.

HOLY SMOKE that is bad.

I bought one of these a while back and you will be able to do a cursory inspection without removing the head. It has 5 little LED lights on it and works great. You can get them cheaper on ebay but have to wait longer for shipping.

https://www.amazon.com/DZT1968%C2%AE...70_&dpSrc=srch

A alloy piston is not going to do that sort of damage to a steel plug...
so my thought is something steel has gone though the motor..
start looking for missing bolts/nuts etc on the intake side of the motor..

Maybe it's still in there......the piston won't be a pretty sight... might pay to lift the head...


...

"LG" (蓝光牌) is made by 重庆市南迪火花塞制造有限公司. That company located at the SAME city as bike/ small engine "hub" which very few retails in bike shop/ parts house. ;) Nobody want that shite ruin their biz...
Infamous "torch" http://english.torchsparkplug.com/about.aspat at least is soild . For those short of ¥ = so-so product from Hebei/ Zhejiang ...

I am thinking it may have melted and possibly melted through the piston.
Will find out when I open it. Wishing I had that endoscope.

Tom, you can pop the valve cover off and slowly turn the engine over by hand (or with the kicker). If both valves actuate properly, you'll know the damage wasn't the result of a dropped valve.
I'm with HB; my guess is the plug grenaded.

Look like my piston melted. Exhaust valve is gone.

OMG! That's something I've never seen, It's completely obliterated. Thats looks like something that should be covered. Have you contacted the seller?

Yes, I sent Don at apscusa.com an email last week. He called me on the phone and promised to cover all the parts. He asked that I open it up first and take some pictures. I emailed him yesterday evening so I hope to hear back on Monday. Don says they have parts at 8 different locations around the country.
He also told be he would work with a professional shop for the parts If I want to bring it someplace for repair.

I did call a shop in my area. http://www.procyclevt.com/. I was politely told that it was not personal to me but they refuse to work on a Chinese, or any 'off brand' bike. He mentioned an bad customer experience but I assume there is some animosity considering he charges thousands more for used bikes.

In actuality, this only took a few minutes to tear down and seeing that I won't need to split the case, it's going to be quick to repair.

Good luck with it and glad to see Don getting after it. Hopefully you get the parts in quick, Aluminum melts at 1220' F, is there any concern of other damage than the topend, possibly aluminum chunks un the case?

Bad Rectifier? I have no idea what caused this.

I have no experience with a meltdown like this either, hopefully it can just get a afew new part and be ok.

I'd say a valve dropped and caused total meltdown, hope you get it covered under warranty indeed. That would require just get a new complete engine. Too much debris cycled around the oil vanes by now.

Yep, dropped exhaust valve as I suspected. If the engine was running lean, the exhaust valve could have overheated and popped. If not, it was a bad valve to begin with.

Looks like it got hot. really hot. Is your carb stock?
running too lean can do this.

You may want to fatten it up.

On old VW automobile air-cooled engines a dropped exhaust valve was a frequent problem. If an exhaust valve was adjusted too tight, then when the engine got hot and the metal expanded, the gap between the end of the valve and the rocker arm would disappear entirely. Then when it got even hotter the valve would not be able to fully close; the hot valve would not even contact the cylinder head. Since the metal of the valve did not contact the metal of the head (did not seat with it) it could not dissipate its heat to the head. While this was happening more hot exhaust gases would rush around the now slightly always open valve and get it hotter still, until it would get so hot it would eventually break off and fall into the cylinder causing destruction. Maybe that was the cause here.

Yes, Stock.

Could be, however there was the recommended gap.

Could have been too lean. The intake was still there because the air/fuel coming from the carb cooled it. The exhaust valve over heated along with the piston.



The new or repaired engine could do the same thing without adjusting the jets in my opinion.

Could be the timing was too advanced also, that will burn/melt thru a piston also.

The stock carb on the Bashan Storm has a 105 main jet in it so I'd be surprised if the carb was too lean.

The damage to the piston is more than just a dropped valve. It got really hot. Lean mixture is the most likely reason.

If it was so lean that the engine melted down, wouldn't the engine have stalled or bogged down with the choke off? Usually super-lean engines won't run unless they're choked (or they bog badly when the choke is off).

Normally I would agree but timing is locked in on most motorcycle engines.

that baby had been running hot for a while.

It probably lacked power at top end. He stated he was 30 miles in his commute. He could have been running wide open for a long time. I am sure this is how the bike was ridden for quite a while. When you look up the cause for a melted piston you will see lean fuel mixture is a likely cause. If it was my bike I would up the main jet to a 110 and the pilot to a 25. A little rich is much better than a little lean. It cools the valves.

What size pilot jet comes stock in a Mikuni VM26 carb? I haven't changed mine out but have the main jet at #120. Is the 25 pilot jet a "sweet spot" when running a #120 main jet?

I am not sure what comes in the mikuni. I think 20. but again not sure. The main jet would the one to worry about here because at wide open throttle that is the one delivering the gas. If your 120 works and up to 1/4 throttle is good. you should be all set. I am running a 27.5 and a 115 in a mikuni. I have the exhaust and modified the air box. I am at 400 feet. Different places need different jets. Elevation and air temp all play in to the mixture.

My ride takes me from 200 ft to 1872 ft. Going home is mostly downhill. Where it failed was on the flats closer to home. Almost wide freaking open but not all the way.

Vermont ain't flat... :-)

Out here in WNY 500-600 ft. elevation is about average...it's mostly flat where I ride. I did order a #25 pilot jet (genuine Mikuni) online just in case I find that I need it. I also modified the air box, installed the performance exhaust, and jetted with a #120 main jet. Seems to run well in all throttle ranges, at least with the current hot weather we're having (mid 80s and humid daily). I rode the Hawk a few miles on the #110 (after the pipe upgrade) and it ran fine but upon inspecting the spark plug it was definitely running a little lean. Doubt it was lean enough to melt the engine down but better to err on the rich side than too lean.

I'll be avoiding those Wingsmoto main jets in the future and will stick to Mikuni brand - the Wingsmoto jets don't thread in so well.

Please see diagram. Main jet (120) is above 3/4 throttle.



http://4.bp.blogspot.com/-k8EnLdp-Ef...jet_usage1.jpg

Where do you think the fuel comes from when using the throttle valve and needle jet? I think it comes from both the pilot jet and the main jet. Both need to be sized correctly.

Yes. The needle meters the flow from the main through the carb. A thinner needle or raising the needle equals more fuel from the main sooner. It is the transition from the pilot jet to the main. Yes, they both need to be sized correctly.

The main jet does not play a direct role in fueling until right around the 3/4 throtte mark. You would be surprised at how big of a difference in main jet you can run and not be aware of the difference below that point. The main jet is the total fuel level that passes through the needle jet (emulsion tube), but the needle restricts flow through the needle jet as low as 1/8th throttle through 5/8 throttle, thus rendering the main jet size itself more or less inert until the passage restriction of the needle has opened up an area at least equal to the area of the main jet at the emulsion holes.

You could put a 110 and a 120 main jet in the same carb, on the same bike, and never know the diffrence until you go beyond 5/8 throttle, and definitely once you reach 3/4.