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Post by roketajam on Mar 30, 2012 9:10:29 GMT -5
Lance Charming 50cc was idling one day and just died (like it flooded out). It turned over but engine did not attempt to fire. Troubleshooting:
1. Gas flow to carburetor is good.
2. Sparkplug grounded to engine is sparking.
3. Tried starter fluid into intake manifold and sparkplug hole and no change.
4. Checked and adjusted intake and exhaust valves. Set to various thickness; 0003", 0004, 0005, etc. and no change.
5. Bought compression kit. Tested with throttle wide open and read 60 psi.
6. Injected teaspoon of oil into sparkplug hole to attempt to coat rings to get compression up, but no change noticed in compression.
Okay, I think I have convinced myself that I have an actual engine problem, even though there is less than 1000 miles, no noise from engine or anything unusual going on prior to it just dying all of the sudden. I guess next step would be to take off the head and check piston for crack/wear or anything unusual on top end.
I would appreciate any advice on things to be aware of or things to look for specifically, since this is the first time diving into the engine. Not an engine guy, but I can learn.
Appreciate any advice.
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Post by terrilee on Mar 30, 2012 9:18:28 GMT -5
i am NOT a mech
but i think ur rings are goneanother fallen hero Attachments:
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Post by ericrockstar on Mar 30, 2012 9:38:28 GMT -5
.004 & .005
Maybe .0004 may not be enough. Compression seem a bit low.
Is the spark good and strong and blue?
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Post by Stash on Mar 30, 2012 9:40:55 GMT -5
I would say definitely rings/piston. Ive had the same issue recently and it gave me fits. make sure the gaskets are good and the head and cylinder are bolted down tight.
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Post by roketajam on Mar 30, 2012 10:35:09 GMT -5
Thanks guys. Yeah .0004 is typo, should be .004 & .005. Good information on gaskets and tightening bolts. Appreciate it. Any specifics on how to tell if piston or rings are bad?
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Post by Stash on Mar 30, 2012 10:48:33 GMT -5
Other than pulling the cylinder off and looking, Im not sure. If you take the piston off though its pretty obvious. I would bet one is stuck.
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Post by Pony66 on Mar 30, 2012 10:49:17 GMT -5
Thanks guys. Yeah .0004 is typo, should be .004 & .005. Good information on gaskets and tightening bolts. Appreciate it. Any specifics on how to tell if piston or rings are bad? It should be .05mm. If gap is too large the valve will not open. Can you smell gas in your oil? You may have a blown piston ring or broken valve or dislodged valve seat. |
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Post by justbuggin on Mar 30, 2012 10:51:27 GMT -5
just that when you pull the head make sure you have it at top dead center with the two little holes inline with the valve cover gasket surface with the big hole up mark the chain and sproket so when putting back together you will be able to get the timing back in the right spot
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Post by roketajam on Mar 30, 2012 12:36:00 GMT -5
Stash--Just to clarify, what might be stuck after taking the piston off?
Pony--Can the ring be bad without being broken. Would I just look for wear?
justbuggin--Good information. I'll make sure to set at TDC before cracking it open.
Question: So loosening the brackets holding the camshaft, will I be able to tilt the sproket to get the timing chain off?
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Post by terrilee on Mar 30, 2012 13:26:55 GMT -5
Question: So loosening the brackets holding the camshaft, will I be able to tilt the sproket to get the timing chain off?
get some paint or something like it
mark the tooth and place on the cam chain
so u can put it back on the right way
ifna u dont, wow u will have fun |
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Post by timber on Mar 30, 2012 13:47:58 GMT -5
Could be any number of things, but rings, a small hole in the piston, or even a crack in the cylinder wall make perfect sense.
I think if the valves are good, you should be able to turn the engine over by hand and when you feel it starting to resist turning during the compression stroke, stop and see if that pressure goes away rapidly or slowly, or at all.
Hard to describe in text, but if everything is good- valves, seats, rings etc, that compression you are making should "hold" for a time, how much time I can't say, but let's call it "X" to represent seconds and minutes.
If anything is worn or leaking, that compression will decompress rapidly and turning the flywheel will suddenly become easy as there's no pressure against it once it leaks out of the cylinder.
If when new/normal you found it took 15 seconds to lose the pressure, and then one day it takes 3 seconds, then you can easily tell there has been a substantial change there.
You won't have a number in PSI but this method is similar and as you are doing this by hand, you might even be able to HEAR where the leak is.
You can open the dipstick and also determine if the pressure is leaking into the crankcase.
Would be a good idea to get a "baseline" of how long the pressure "stays" in the cylinder.
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Post by wile on Mar 30, 2012 13:49:33 GMT -5
 Wile |
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Post by roketajam on Mar 30, 2012 15:04:42 GMT -5
Terrilee, \\-olf and Wile, thanks for the great tips. Will do.
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Post by meitianman on Mar 31, 2012 0:26:09 GMT -5
easy junkyard way to tell if the rings are bad is to put a few cc's of oil in the cylinder and turn the engine over by hand a few times without the plug in and recheck the compression. if the rings are bad that will make the compression go back up for a very short time. use thicker oil if you have it.
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Post by timber on Mar 31, 2012 9:40:11 GMT -5
easy junkyard way to tell if the rings are bad is to put a few cc's of oil in the cylinder and turn the engine over by He already tried that; |
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