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What piston do I have?

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While gathering parts to rebuild my '86 XR600R, I picked up a new old stock OEM piston and ring set from eBay. They were still in the Honda boxes with the part numbers on them. The number match the parts fiche for my bike. My engine had a Wiseco piston in it. When I started putting things back together with the new parts, I found that the wrist pin was too short for the piston. I thought that the Wiseco pin was simply shorter for their pistons, it's clear that the bottom of their piston is narrower where the pin fits.

A member from here has put a stock pin in the mail for me so I'll have the right one to put it back together.

However, while searching around looking at parts etc., I see that Wiseco claims their wrist pins will fit their pistons as well as the OEM Honda piston. They say it should be 2.5" long, which the pin I have is. So I started looking a little closer, and my Honda piston looks a little different than the two I can find pictures of online.

Notable, the bottom of the skirt on mine is flat, while there are angles cut in the ones online. The bottom of the piston on the sides below the pin is also shaped a little different. They both also look narrower where the pin fits than mine. My piston fits a stock bore cylinder perfectly, I know it's the right 97mm bore. I put it on the rod with the short pin I have, and the skirt does not hit the crank, it will fit fine if I can get the right pin. I'm kinda worried that the pin that's in the mail will be the same length as the Wiseco pin I have. If so that's gonna suck! :ride:

Here's a few pictures of my stock piston, as well as the two I found online of other stock pistons to compare. The last one of my piston shows just how short the in is, it's slipped all the way against the clip on the other end.

Can someone identify this piston, or verify that the OEM pin is longer than the Wiseco pin, same length? If I had known I'd run into this problem I would have bought a stock size Wiseco piston to go back in. I should have known better than the rush it and try to save some cash... Oh well... :ride:

These are pictures of the OEM piston I have, part number 13101-MK2-043

1-1.jpg

2-1.jpg

3-1.jpg

See how the wrist pin is too short?

4-1.jpg

These are picture of other OEM pistons I found online. Note how the skirt is different than mine, and they look narrower where the pin fits.

5.jpg

6.jpg

Any ideas?

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While gathering parts to rebuild my '86 XR600R, I picked up a new old stock OEM piston and ring set from eBay. They were still in the Honda boxes with the part numbers on them. The number match the parts fiche for my bike. My engine had a Wiseco piston in it. When I started putting things back together with the new parts, I found that the wrist pin was too short for the piston. I thought that the Wiseco pin was simply shorter for their pistons, it's clear that the bottom of their piston is narrower where the pin fits.

A member from here has put a stock pin in the mail for me so I'll have the right one to put it back together.

However, while searching around looking at parts etc., I see that Wiseco claims their wrist pins will fit their pistons as well as the OEM Honda piston. They say it should be 2.5" long, which the pin I have is. So I started looking a little closer, and my Honda piston looks a little different than the two I can find pictures of online.

Notable, the bottom of the skirt on mine is flat, while there are angles cut in the ones online. The bottom of the piston on the sides below the pin is also shaped a little different. They both also look narrower where the pin fits than mine. My piston fits a stock bore cylinder perfectly, I know it's the right 97mm bore. I put it on the rod with the short pin I have, and the skirt does not hit the crank, it will fit fine if I can get the right pin. I'm kinda worried that the pin that's in the mail will be the same length as the Wiseco pin I have. If so that's gonna suck! :ride:

Here's a few pictures of my stock piston, as well as the two I found online of other stock pistons to compare. The last one of my piston shows just how short the in is, it's slipped all the way against the clip on the other end.

Can someone identify this piston, or verify that the OEM pin is longer than the Wiseco pin, same length? If I had known I'd run into this problem I would have bought a stock size Wiseco piston to go back in. I should have known better than the rush it and try to save some cash... Oh well... :ride:

These are pictures of the OEM piston I have, part number 13101-MK2-043

1-1.jpg

2-1.jpg

3-1.jpg

See how the wrist pin is too short?

4-1.jpg

These are picture of other OEM pistons I found online. Note how the skirt is different than mine, and they look narrower where the pin fits.

5.jpg

6.jpg

Any ideas?

Keith,,,,,,,,,you been drinkin again:moon:

Just kiddin,,,measure the pin hole in that piston you have,from the inside of one lock groove to the other inside of the lock groove.........i`ll post a pic of where i mean in a minute:thumbsup:

Brian

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:ride: Not drinking, just been up all night, couldn't sleep!

Groove to groove in the Honda piston is a hair under 79mm. Wiseco is a hair over 62mm.

I should have thought to ask you to measure the pin before you sent it. :ride: Might have saved us some trouble!

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:ride: Not drinking, just been up all night, couldn't sleep!

Groove to groove in the Honda piston is a hair under 79mm. Wiseco is a hair over 62mm.

I should have thought to ask you to measure the pin before you sent it. :ride: Might have saved us some trouble!

I`s gonna have to slap ya,,only a little:thumbsup: but it`s gonna happen:moon:

100_2944.jpg

Measure from the arrow(inside edge of the lock groove) to the same place through on the other side,,should be arround 70mm i think..

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Nope, right at 78~79mm... This just confuses me more! lol

Ok, next question...

What would happen if I cut two spacers off my used pin to center up the good on in the piston? If the pin you sent me is 70mm, that will put it under the walls on the piston. I can't imagine anything unusually good would happen, but sure would hate for something bad to! :ride:

I'm almost ready to run a hone through the cylinder until the Wiseco piston fits and be done with it... :ride:

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Nope, right at 78~79mm... This just confuses me more! lol

Ok, next question...

What would happen if I cut two spacers off my used pin to center up the good on in the piston? If the pin you sent me is 70mm, that will put it under the walls on the piston. I can't imagine anything unusually good would happen, but sure would hate for something bad to! :lol:

I'm almost ready to run a hone through the cylinder until the Wiseco piston fits and be done with it... :ride:

Well for one,if the wiseco is bigger than the bore you have,,then you have to bore it,,,runnin a hone through it to do anything more than give a good cross-hatch pattern will cause an out of round out of taper cylinder...you cannot control a hone to take off exactly the same material all the way arround and top to bottom.........you`ll basically ruin the cylinder........don`t do it...

4mm side to side play,,,,,,,,,don`t think you`re gonna like what it`ll do,,the pin can`t walk that much side to side i think,,,,could be wrong,but i doubt it:banghead::ride:

So basically i wasted 7 bucks i`m thinking:banghead:

Brian

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I just double checked the distance from the pin to the top of the piston, started thinking that maybe that's not even the same, but thankfully it is. So I think at this point I'm going to take the longer pin you've sent, and however short it is, I'll split that and cut two spacers off my old Wiseco pin, and put it together with a spacer on each end of the pin. That will keep it centered in the piston. It should be long enough to fit the stronger parts of the piston, and should be ok. As long as I can get the side to side play right it should work. Emphasis on should... :ride:

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Does the piston have a part number on it or did you get the number off of the box? Is there a chance that the box is correct, but the part inside has been swapped at some point?

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That's what I'm thinking. The number is on the box, no numbers on the piston. The box was old and opened before.

Even if that's the case, how many motors did they make with a 24mm piston pin, 97mm bore, same piston height, etc.? If I can figure out what this piston is I'll just get a pin to fit it. It'll be a lot cheaper than buying yet another piston...

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