hwr
Scoot Member
Posts: 73
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Post by hwr on Nov 5, 2018 7:35:06 GMT -5
Howdy,
Ive had my little minarelli clone with a ported polini sport 70 for around 1000 km and the little end bearing is rooted. Pretty frustating, but i deserve it... using the polini brand bearings did not lend well while the bike was ripping at ~10k rpm.
What brands have people used as replacements? im happy to spend the money on superior quality bearings to avoid such regular rebuilds?
If someone has upgraded their 12mm gudgeon polini sport 70 little end bearing hit me up
Cheers
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Post by Jwhood on Nov 5, 2018 7:49:59 GMT -5
I've been running a Corsa for 4000 miles and haven't threw a wristpin bearing that's pretty impressive,wiseco make great wristpin bearings,not sure of the part number though
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Post by ryan_ott on Nov 5, 2018 8:21:20 GMT -5
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Post by fugaziiv on Nov 5, 2018 9:28:37 GMT -5
Polini is some of the best stuff you can buy...
Matt
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Post by 90GTVert on Nov 6, 2018 5:08:18 GMT -5
I use Wiseco bearings as detailed in the link that Ryan provided. I have blown apart more wrist pin bearings than I would like and recently found that using the stuff that comes with Taiwan BBKs could be a bad idea. The bearings from Taiwan kits that I had were thinner in spots than what I got from Wiseco. Having an intact version of the wrist pin bearing that destroyed my last cylinder around and a Wiseco B1042, I took a look at them side by side. Looks like the Taiwan bearing gets really thin in the center and the Wiseco doesn't. Taiwan bearing on left, Wiseco on right in all pics.
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Post by aeroxbud on Nov 6, 2018 5:17:12 GMT -5
Polini is some of the best stuff you can buy... Matt I have Polini bearings all through the slider engine. Never had a problem before. I have found the stage 6 stuff good in the past.
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hwr
Scoot Member
Posts: 73
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Post by hwr on Nov 6, 2018 9:18:45 GMT -5
You've made a liar our of me haha, turns out the little end bearing came with the naraku crank.
Reminds me:
@90gtvert, you used a naraku stock replacement crank in one of your builds, are u using the wiseco bearing you mentioned?
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Post by fugaziiv on Nov 6, 2018 10:13:29 GMT -5
Polini is some of the best stuff you can buy... Matt I have Polini bearings all through the slider engine. Never had a problem before. I have found the stage 6 stuff good in the past. Since the Stage 6 kits are manufactured for S6 by a different company that just like Polini happens to be Italian, that makes sense. Matt
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Post by 90GTVert on Nov 6, 2018 14:46:05 GMT -5
@90gtvert, you used a naraku stock replacement crank in one of your builds, are u using the wiseco bearing you mentioned? Honestly can't recall what's in there now. Prob either Naraku or Wiseco. The bearings that I've had blow apart were all stock replacements or from Taiwan made BBKs like HOCA and Motoritech. Not sure if what Naraku sends is the same stuff or not.
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Post by fugaziiv on Nov 6, 2018 14:56:08 GMT -5
@90gtvert, you used a naraku stock replacement crank in one of your builds, are u using the wiseco bearing you mentioned? Honestly can't recall what's in there now. Prob either Naraku or Wiseco. The bearings that I've had blow apart were all stock replacements or from Taiwan made BBKs like HOCA and Motoritech. Not sure if what Naraku sends is the same stuff or not. Naraku sources the same bearings as HOCA/SSPG/TAIDA... as do all of the Taiwanese kits for the most part. Matt
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hwr
Scoot Member
Posts: 73
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Post by hwr on Nov 7, 2018 6:49:15 GMT -5
So pulled the engine down today.
The small end bearing is only 12.6mm wide and so is the conrod small end. wil running a wider wrist pin bearing cause issues if its exposed on either side of the conrod?
The wrist pin had worn a groove where the bearing sits to the extent that the pin was difficult to move. Luckily the needles where still inplace for the most part, the cylinder head begs to differ, some slight damage
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Post by jackrides on Nov 7, 2018 14:27:09 GMT -5
Reverting to old motorcycle tech, some conrods have holes or slots thru the bearing surfaces to access oil spray. I would put a very small radius on these edges to lessen stress on that area of the needles. Higher rpm increases stress a lot.
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hwr
Scoot Member
Posts: 73
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Post by hwr on Nov 8, 2018 5:09:28 GMT -5
I bring photos: Also does anyone know if you can use a longer wrist pin bearing than the conrod!! Buggered Needle Bearing Buggered Gudgeon Pin And
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Post by kkzxxx on Nov 8, 2018 10:40:17 GMT -5
Sure you can, actually why use anything smaller? Ive had the same small end bearing for the last 16k kms, it is wide enough that I had to file the piston about 1mm for it to fit.
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Post by ryan_ott on Nov 8, 2018 11:29:12 GMT -5
I’d use a bearing that the rollers are at least as wide as the rod end.
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