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After a fresh replate by millennium technologies (they had access to this new piston for sizing), a new wiseco piston with proper exhaust bridge holes drilled, new wrist pin and bearing, and new power valves, my 2001 rm125 has a rattling sound coming from the engine. This bike is seriously testing me. It hasn’t given back what I’ve put into it in the slightest. Someone please help me diagnose this noise. I have a video of it running in this YouTube link: https://youtube.com/shorts/sBJHr1Bg7iQ?feature=share

I have freshly rebuild my top end on my 2009 yzf250, new intake valves piston and rings, cam chain. I put it all back together ran mint, but after starting it up for about the 3Rd time a loud knocking noise from the engine appears, the bike is still running fine although a very obvious loud knocking noise. valves are all inspect aswel. note, the knocking id only at one certain compression stroke its past TDC its a short stroke but quite a difficult one, never had even put it in gear so i dont think it is the trans. i also ripped out the cams a couple times thinking that was the problem and once i put it together it ran mint for about 4 seconds then knocking came back. I originally thought it was the exhaust cam decompression sticking but after inspection was not making the nosie. I took the flywheel off and checked if I had put it wrong, but no. have just tore apart the clutch side cover and all teeth are fine. I am at a point where I don't know what to do next. please any advice is much appreciated.

Hello. I'm not sure if this is the right section of this forum, "engineering and technology" was the most relevant section I could find. Intro: So my dad and I are working on a project, I'm currently 16 and want to start training riding a dirt bike. So we put months into putting a Lifan 110cc 4 stroke enduro engine in a Yamaha yz 80 (97) that was missing only a engine. From reading forums I gathered that Lifan engines (if made after 2010~) are pretty good, for being a China engine that is. We are starting to finish the project, with only a few things missing. I tested the bike for the first time two days ago, and it didn't seem to have any issues. It sounded healthy, I guess. My dad has been working with stuff like this his entire life, and I trust in his abilities, but regarding this issue I thought I might as well seek answers from forums. Issue: So the bike ran very well for the first two days. It started on a few kicks, sounded healthy and ran well. But I was unaware of the whole "breaking in" process of using a new engine. We did stuff that websites and forums have claimed to "not be healthy for the engine". For example, we revved it in neutral a few times, didn't shift at all (since I'm new to riding I stayed on the first gear), we didn't let the engine get hot before riding, as well as not letting it cool down before being started. In my defense, I don't know much about all of this, I simply trust what my dad tells me. When I started it today after checking the oil and fuel I heard a rattling noise. It seems to come from somewhere around the cylinder. The rattling noise can be heard when rolling the bike with the engine off as well, but not constantly. The second time I started it today to see if the noise remained, it didn't rattle for about 20~ seconds, but then it started again. I heard that it might have something to do with the clutch, but it doesn't seem like it since pulling the clutch in and out, both slow and fast doesn't affect it. My dad said "It's a new engine, I wouldn't worry about it since there shouldn't be any issues". I'm very skeptical about that. I've heard it might be the piston rings that have suffered because of our recklessness. I haven't checked if the noise is still there when actually riding it, but I would guess it is. ALSO: The bike hasn't been driven for that long at all. I would say I've tried riding it for around 0.6~ miles. Did these very short sessions damage the engine in any way? What do you think about this, do I have any reason to worry? Also, sorry if my writing is bad. I'm from Sweden, and English isn't my primary language. I appreciate any information regarding this issue. Too long, didn't read: Rattling from around cylinder, barely been driven (0.6 miles), didn't occur the first two times, lifan 110cc 4 stroke enduro engine. Edit: This has now been fixed. The spark plug was loose. If anyone else is hearing this noise from their engine, it might be worth checking if the spark plug is loose for you as well.

I just finished rebuilding the bottom end of my 2002 yz426f. About three months ago, the connecting rod snapped while I was riding it in the trails, and then damaged the crankcase and a transmission gear. I replaced the gear, cases, and the rod. I just got it started up, and, once the bike warmed up, It started making a very loud rattling noise that sounded like it was coming from the top end. I checked the valves, and they are in spec. The camshaft bearings appear to be free-turning. The cam chain has plenty of tension, and the cams are in time. Any ideas as to why it would be rattling?

Hello guys. I have been reading the forum for a long time and this is my first post. I have a DRZ S and after reading many posts here and feeling confident enough, I bought a used fcr mx 39 and installed it. The bikes runs pretty well and pulls hard with the exception of when opening and closing the throttle from and to idle. On openings from idle , no matter how smoothly i operate the throttle the bike behaves very abruptly. It has like a 0.5 sec delay and then after feeling that someone gave the bike a strong kick, power is delivered as it should. On throttle closing the situation is the same as power cuts off instantly Other symptoms are: When the bike doesnt operate throttle is smooth ,but when it's on its more resistant and feels notchy during the initial opening (around 1/8) If I set the idle to the recommended rpms ( by ear) it hangs and I have to blip the throttle in order for the rpms to drop. Slide does this rattling sound especially when cold. I have tried adjusting fuel and idle screw, checked for leaks, valveds and for cable binding with no result. I ended up opening the top of the carb to raise the needle and took notice of two things.Firstly the vacuum plate was worn from friction (seal seemed fine) and secondly the slide had excessive free play due to the grooves that had been created on the internal of the carb body from the slide rollers. I concluded that all my problems were possibly a result of uncontrollable air flow during idle and small throttle openings, creating a lean condition. Raising the needle helped a bit but didnt solve the problem. So the questions are: Is my assumption right about what may cause this situation? Has anyone tried filling those grooves with some kind of resin or jb weld succesfully as a temporary fix? Thanks and sorry for the bad english Specs: drz s -09, bb Athena, kn filter, 3x3, stock muffler carb specs: fcr mx 39, 155mj, 45pj, emn needle 4rth clip

Okay so I have a 2008 KX250F its making a rattling noise from the engine, left side. It doesn't do it right when it starts up but as it warms up it gets louder and louder. I can't hear it over the exhaust when I rev it though so I'm not sure if it stops when I rev or it just simply isnt loud enough for me to hear. I recently took my bike to ridenow and they suspect its the cam chain or the tensioner however I didn't have the money for the to check it out so now I have it back at home. I took off the cylinder head cover today and checked the cam chain to see if it was loose, its in spec. However I'm not sure what I would be looking for in the tensioner to see if its bad or not so I didn't mess with that. If you guys could give me some input on anything else it'd might be and what I would be looking for when looking at tensioner that'd be greatly appreciated, thanks.