OK, the latest issue with my 78 JC Penney Pinto with about 7000 miles. It's making a sort of random pinging noise. It's not loud or steady, just sort of a "ding da-ding ding" that I hear mostly at idle.
If I crouch down to the level of the engine, I can hear it more on the right side (the side that the clutch cover is on) than the left.
The engine starts right up and runs well, goes about 25, idles fine. Clutch seems to work OK. Any ideas? Thanks!
try a higher octane fuel?
check your piston were the wrist pin goes thru i had the same prob that i ignored and BOOM i was out a very mint newport
The piston, hmm. What would I be looking for, exactly?
bump
By the way, for anyone not familiar with these, the Pinto has a Puch E50 engine, same as a Puch Maxi 1-speed.
OK, here's the latest: I took off the head and cylinder. Everything looks really good, no carbon, rings look great, wrist pin clips are in right. Took off magneto cover and looked at the flywheel, it doesn't seem loose.
I'm stumped. Anybody have any ideas what the pinging noise could be? Something to do with the clutch maybe?
Are you running 93 octane gas, (like patfark said)?
Um, no. I always thought high-octane gas was to prevent valve pinging, and since 2-cycle engines don't have valves, I didn't think it would help.
But help me out, maybe I'm not understanding something.
Don't tell me I missed the easiest possible thing to do...
if you have another head gasket handy you could do a pretty simple test .. add another layer of head gasket.
This will lower your compression ratio. If the pinging stops or decreases, you've narrowed the search down to a few things..
too much timing advance, low octane fuel, too high compression ratio, too lean an air:fuel mixture, etc.. ....all things involving too much heat in the space above the piston.
_ding da-ding ding that I hear mostly at idle_
no way is it preiginition if you're hearing it at idle .. if heard anywhere it would be heard when lugging up a hill.... So forget the head gasket thing..
Keep looking for a mechanical thing. I havent read all this thread yet .. Do you have an expansion chamber installed (a performance pipe) . Those ding-a-ling normally.
Any exhaust or muffler can make a ringing sound.. an exhaust leak may sound like a ping... and internal baffles can come loose and rattle around too.
A constant noise might be most noticable at idle just because there's less engine noise and no road or wind noise at idle.
Grab your piston. And pull it up and down (or in and out depending on how your working on the motor)while it is at top dead center. does it move slightly. It shouldn't. If it does you need to replace the wristpin bushing. It is a common problem with these motors. And causes that exact type of noise.
Brian, from looking at the shop manual not easy w/h several special tools, have you found a simple way?
I'll try that piston test, that may be the problem. I'm looking to see whether the piston itself moves un and down on the connecting rod, correct? And it shouldn't move AT ALL?
To answer joew's question, I don't have a performance pipe (yet).
One other thing, does it really help to use high-octane gas on mopeds? I would have never thought it would make a difference in such old, low-tech engines.
piston pin clearance is tiny .. the pin should slip smoothly into the piston boss holes with only mild hand pressure. The piston may rock sideways slightly but there should be no up-and-down movement between piston and connecting rod.
here's one way to test slop in the bearings ..
remove the head.
turn the crankshaft so the piston rises to Top Dead Center and only very slightly past TDC.. (the object is to "stretch" the crank / rod / piston chain.)
Now pound on the piston's crown with the heel of your hand, or with a padded hammer, or a soft rubber mallet.. something completely silent.
If you hear a slight "click" sound, you've got at least some extra slop in bearing clearances somewhere down below ..
repeat the test a few times.. an obvious CLICK everytime you try it is reason for concern.
OK, tried a couple things. I have the whole cylinder off, so I just gave the crank arm a few good tugs. Didn't seem to be any play (whew).
Tried the same thing with the piston and it DID move, though again, I had to give it a pretty good tug.
So, I think I've got a bad wrist pin bushing. Can anyone give me a brief description of how to replace one?
Thanks for all the help, by the way.
it's best to measure things before deciding on a cure .. and if the pin/pin bushings really are gone, it may be from a lack of lubrication, and you'd probably wanna measure other things.. all other things.
Why buy parts for an engine that needs new parts all the way down to, and including, the crank.
OK. I'm new to all this, so any pointers on what else I should look for? Like I said, I have the cylinder off, but I'd be a little reluctant to crack the whole bottom end open.
And again, any pointers on replacing a wrist pin bushing would be appreciated. As I mentioned, the piston (but not connecting rod) did move slightly when I gave it a good yank, so it seems like it may need replacing.
if you want to do this yourself you need the manufacturer's specs.. they should be in the manual. Acceptable tolerance will be + or - a few thousandths.
get a set of telescopic gauges and a caliper to measure the bushing bore and pin diameter.
or just take the parts to a shop and let them measure.
If you find lots of wear and if this happened suddenly, theres a good chance more stuff got toasted.. Splitting the case is a chore.. so buy a new engine? Trade work for money if you prefer.
But all this is premature and speculative .. measure the piston / pin / little end connecting rod clearances and move on from there. You can them make informed decisions..
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