High end clanking noise

  • Thread starter Keepthedrivetommy
  • Start date


Hi all,
I was having this problem last october when it started going really down hill and causing major power problems. So I want to make sure that it doesnt happen again. you can refer to the original thread I created, http://www.motoredbikes.com/showthread.php?t=6955&highlight=diagram.
Ok so, I would get my bike up to top speed, 32, and then when I let off the throttle, I would hear this metal on metal clanking noise. I knew it wasnt good. so I looked at some other threads, and found that the wrist pin bushing or even the wrist pin might be shot. It turned out my piston was burned up from too lean of a fuel mixture. So I replaced the piston, cheacked the bushing and wrist pin, and both were fine, no cracks. And boom, my engine was back to life.
But now it is starting to get a little warmer, I can get my bike up to full speed again, but the metal on metal noise is still there. I have power, and the bike runs beautifully and Im using one of those oil mixtures that can be used for any air-cooled 2 stroke between 20:1 and 50:1. But the same problem is present when I get to my top rpm and let off the throttle, there is that horrible clanking noise. It lasts 2-3 seconds until the bike slows down a little.
So I know its not the wrist pin/bushing, last time I checked they were fine. Im using an appropriate fuel mixture, because this oil is appropriate for all ratios. I can't think of what the problem might be?
Any ideas gents?

Also, Im curious. Here is an example. Augi bought that sale/deal motor kit from daxa couple months back to review it. It was the 60 or 65, but he took the kit, and standard 26 in wheel bike, put em together and within 2 days, he was pulling 37 no prob. I have a 26 in wheel bike, same engine but the 70 instead, and have never been able to go over 34 without feeling like the engine's rpm's might rip it apart if I keep it at that speed for another 2 seconds. Other people say they can go 40 downhill...don't the rpms get RIDICULOUSLY HIGH AND LOUD at that speed. Might there be something seriously wrong with my bike that I have never been able to approach those speeds, even if the wind was at my back and I was going downhill, without feeling like my engine was going to explode?

PS...Im sure the simplest answer to my problem is to buy the titan...thank you to anyone who was thinking of saying that, but that answer is ruled out due to obviousness, if thats a word.
The oil can be run at various mixtures. What mixture are you actually running? How does your sparkplug read?
Dunno if this helps but i had the same metal to metal contact noise when throttling down or off....it turned out to be the larger gear cog on the right hand side slightly rubbing on the actual inside of the casing.I ground the inside of the casing so it cleared.......problem solved.
fetor, did you only get the noise when at higher rpms, and only when letting off the throttle...or the noise was constant? And what do you mean ground? You sanded away some metal? The bottle said to mix the entire bottle with 10 gallons on gas.
That's right...only at higher revs and ONLY when i decelerated.It had me tricked for awhile cos i thought it was piston related.
"Ground" means i purchased a small grinding wheel and attached it to my drill then proceeded to take away a small section from the inside of the aluminium cover....IF that's your problem it'll stand out like dogs balls cos you'll see the scrape marks.
thanks alot fetor, im going to check that out, but it definitely sounds like the same exact problem. Ill let you know
I'm glad I found this thread. Just finished my first build a few days ago. I've been taking it easy - only riding for about 15 minutes and not going too fast. I rode a lot yesterday though - about two hours. The first half of my ride - everything sounded great. Then this noise started to appear and got louder over time. It is a high-pitched shrieking sound. I can't quite explain but it just sound like a really bad "rhrhedededdeedededededeeeedeeddeeee" me sound. In my mind I picture the piston scraping against something inside the engine each time it goes up and down. That is what it sounds like to me.

The big clue is - when I have the clutch pulled in the sound immediately disappears. As soon as I let the clutch out, even before I start to throttle the shrieking begins. This awful noise is so loud it begins to cover up the sound of my engine. My problem seems a little different than those in these similar posts - simply because the sound begins when releasing the clutch.
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Well here's a little update -

I made a SLIGHT...SLIIIIIIIGHHHHT adjustment to the little metal arm on the engine that the clutch lever operates. The little metal arm that swings open and closed when you operate the clutch... Anyway, I unscrewed the little screw for the spring and just screwed it back in..maybe letting off the slightest bit of tension. This possibly combined with simply riding seemed to cause the noise to go away. I don't really know what fixed it but it seems to have just disappeared over time. I'm wondering if things just needed to break in by themselves a little. Anyway I can't be more happy with my bike right now - it is FLYINGGGGGGGGG. I don't have a speedometer but I have to believe that I'm getting 25-30 EASILY (66cc and I only weigh about 140lbs).

God I love motorbikes - the really are the most incredible land-vehicle man has ever made.
I can easily keep up with street traffic on 90% of the roads.
I get to move to the front of the line at red lights.
I can go about 100 miles per gallon
If I run out of gas, I can still get to where I need to go
Very cheap to purchase
Fun to build
Cheap to maintain
Almost everyone I pass by can't keep their eyes off of this "weird" thing they've never seen before :)