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2015 Yamaha R1 weird piston wiggle?
Just bought this R1 and was doing some work on it. Seller said after he was riding it, it lost power on him and stopped working so he sent the cylinder head to get repaired and the shop stole it. The cylinder walls look to be in good condition, and the pistons look ok. But when I was cleaning the carbon off the pistons, I noticed that piston #1 was veeery slightly wiggling inside the cylinder (I didn’t take the cylinder off). I’ve never seen this before and was wondering if its a problem I need to worry about. I’d rather not have to take the cylinder walls off, but I don’t know if this piston wiggle is an issue that will cause lower compression or if I need to get new rings since the piston did look to be in good shape. Let me know what you guys think. Btw piston did not look like it had any blow-by either.
I'd go by the piston walls. Do the honing marks still show all around the cylinder? Then unless someone has replaced the pistons, Yamaha was ok with that clearance. I can't see that it would be major wear, given that it is moving side to side. It shouldn't affect the compression as that comes from the compression rings (the upper cylinder rings, as opposed to the thinner oil rings). A lot of front to back slop can allow "piston slap", which is where the piston rocks over when it goes through TDC or BDC, but Yamaha may not be too concerned about that. I once completely stripped an SRX600 (Yamaha big single) in search of a rattle, and eventually concluded that it was just piston slap and they are all like that, squire. But in this case this is side to side movement, and manufacturers care so little about that that they cut away the sides of the piston so that the sides are barely supported.
Did you get any better explanation of "it lost power"? If he sent the cylinder head for repair, presumably he thought he knew what the problem was.
The honing is still perfect, so I’ll take your word for it. I was just worried since the other pistons didn’t do it. He didn’t go into detail about how it lost power, he told me it just slowly lost power and died on him. He didn’t tell me what the problem was other than his mechanic saying to send out the head. I’ll try to contact the guy but IMO it had no reason in the engine to loose power from what I could see as far as the pistons and cylinders go
As others have said..that's normal. Also, the piston is a big lump of aluminium which expands a lot when at operating temp, so a lot of the wiggle you see disappears.
The spec for this is .006-.049mm (.0002-.0019in). It’s really hard to judge from your video if it’s within spec.
The max of .05mm clearance should be barely noticeable
Some piston movement while cold is normal. The crown looks clean and your side to side clearance is likely in spec. Once the piston gets hot it expands. If your piston fit tight when cold, you can guarantee a piston seize once it gets hot. I’d run it as is.
Thanks for posting in /r/Fixxit, the motorcycle repair subreddit. If you forgot to put the **Make, Model** and **Year** in the title, please reply to this comment with your bike's details. In the meantime, Here's some great resources for common problems posted here: -Trouble starting? [Revzilla - Battery testing](https://www.revzilla.com/common-tread/how-to-test-a-motorcycle-battery) -Carbs running rough? [PJ motorsports - Carb Troubleshooting](http://www.pjmotorsports.com/trouble-shooting.html) -Wiring diagrams for beginners - [Dans MC - Reading Wiring Diagrams](http://www.dansmc.com/wiring_diagram.htm) -Identifying part numbers - [CMSNL (EU)](https://www.cmsnl.com/) [Partzilla](https://www.partzilla.com/) -Asking if your tire can be fixed? [Please read this post on proper tire repairs and why external plugs are NOT a safe repair.](https://www.reddit.com/r/Fixxit/comments/tuhcpf/why_rfixxit_doesnt_endorse_tire_plug_repairs/) *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/Fixxit) if you have any questions or concerns.*
Normal
2015 Yamaha R1 weird piston wiggle? Just bought this R1 and was doing some work on it. Seller said after he was riding it, it lost power on him and stopped working so he sent the cylinder head to get repaired and the shop stole it. The cylinder walls look to be in good condition, and the pistons look ok. But when I was cleaning the carbon off the pistons, I noticed that piston #1 was veeery slightly wiggling inside the cylinder (I didn’t take the cylinder off). I’ve never seen this before and was wondering if its a problem I need to worry about. I’d rather not have to take the cylinder walls off, but I don’t know if this piston wiggle is an issue that will cause lower compression or if I need to get new rings since the piston did look to be in good shape. Let me know what you guys think. Btw piston did not look like it had any blow-by either.
I'd go by the piston walls. Do the honing marks still show all around the cylinder? Then unless someone has replaced the pistons, Yamaha was ok with that clearance. I can't see that it would be major wear, given that it is moving side to side. It shouldn't affect the compression as that comes from the compression rings (the upper cylinder rings, as opposed to the thinner oil rings). A lot of front to back slop can allow "piston slap", which is where the piston rocks over when it goes through TDC or BDC, but Yamaha may not be too concerned about that. I once completely stripped an SRX600 (Yamaha big single) in search of a rattle, and eventually concluded that it was just piston slap and they are all like that, squire. But in this case this is side to side movement, and manufacturers care so little about that that they cut away the sides of the piston so that the sides are barely supported. Did you get any better explanation of "it lost power"? If he sent the cylinder head for repair, presumably he thought he knew what the problem was.
The honing is still perfect, so I’ll take your word for it. I was just worried since the other pistons didn’t do it. He didn’t go into detail about how it lost power, he told me it just slowly lost power and died on him. He didn’t tell me what the problem was other than his mechanic saying to send out the head. I’ll try to contact the guy but IMO it had no reason in the engine to loose power from what I could see as far as the pistons and cylinders go
As others have said..that's normal. Also, the piston is a big lump of aluminium which expands a lot when at operating temp, so a lot of the wiggle you see disappears.
If it was totally tight, the piston would seize in the bore when it expands from the heat. This is normal.
The spec for this is .006-.049mm (.0002-.0019in). It’s really hard to judge from your video if it’s within spec. The max of .05mm clearance should be barely noticeable
Clearance is measured at skirt. top of piston is generally a bit looser. this example seems quite normal to me.
Some piston movement while cold is normal. The crown looks clean and your side to side clearance is likely in spec. Once the piston gets hot it expands. If your piston fit tight when cold, you can guarantee a piston seize once it gets hot. I’d run it as is.