Wiseco piston weight difference.

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graham heise
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Wiseco piston weight difference.

#1 Post by graham heise » Sat Sep 22, 2018 10:14 pm

I have 2 wiseco rz350 pistons. They are the same size 65mm and same part numbers are stamped on the top. 513m06500. The only difference is one i had as a spare bought 7-8 years ago , the other was recently purchased. The old piston weight with rings is 203.5 grams. The new piston is 209 grams. Thats a 5.5 gram difference. I am assuming the mix of alloy may have changed over production runs as they look identical. I am thinking of removing enough materail from the heavier piston to get the weights to match. Good idea or not? Thinking of filling the bottom of the skirt to remove material. Has anyone done this? Open to advice on this. Other option is to buy another new piston? ImageImage

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tacky1
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Re: Wiseco piston weight difference.

#2 Post by tacky1 » Sat Sep 22, 2018 10:17 pm

Absolutely Graham, File it all the way around the skirt to get them even,
It doesn't matter really where on the bottom as I remove the little bridge on the skirt to make the pistons work in an LC and never had any probs.
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JonW
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Re: Wiseco piston weight difference.

#3 Post by JonW » Sun Sep 23, 2018 1:43 am

Yes, take those tangs off if this if for an LC as for elsewhere Id see how much weight the tang removes, that will give yo an idea of just how much you will need to remove and if you think its a good idea etc.
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
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waltmil
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Re: Wiseco piston weight difference.

#4 Post by waltmil » Sun Sep 23, 2018 5:50 am

Have you weighed just the rings?
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graham heise
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Re: Wiseco piston weight difference.

#5 Post by graham heise » Sun Sep 23, 2018 6:21 am

waltmil wrote:Have you weighed just the rings?
no i haven't. I doubt they weigh 5.5 grams themselves. i will check them. I'm going to go ahead and remove the weight across the entire piston base. This is for an rz engine.
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waltmil
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Re: Wiseco piston weight difference.

#6 Post by waltmil » Sun Sep 23, 2018 10:20 am

That was just a thought. It is possible that Wiseco may have added some material to an area that may have experienced failure, piston pin boss, crown?
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Re: Wiseco piston weight difference.

#7 Post by brrrappp » Sun Sep 23, 2018 12:21 pm

There is probably an engineer of two on this board that could give a better opinion on this. But I think you have to consider buying a matched pair if your bike is a keeper.
I understand the desire to have the lighter pistons. That could be a few hundred RPM difference. But you have to wonder if there was a change in alloy or if thickness was added for reliability in the newer version. If it is a different thickness or alloy, I would expect different heat dissipation. One piston running hotter than the other could cause jetting issues.
Why not sell both of those on eBay and buy a matched and balanced set?
Do you have a stock piston laying around to compare the weight? That might be kind of interesting to know as well.

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Re: Wiseco piston weight difference.

#8 Post by MK » Sun Sep 23, 2018 12:48 pm

As an engineer being forced by emergency to use a Prox and a Wiseco of 0,5 mm different size:
There were not "more" vibrations than before. Just in a slightly different rpm range.

With this knowledge i can say: save the work and use "as is".

Btw: The different weight is not due to "different alloy". It's simply different dimensions like wall thickness.

For the pea pickers: If you disassemble a crank, put the webs on a scale and tell me if they were within 5 grams,
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Marrcel
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Re: Wiseco piston weight difference.

#9 Post by Marrcel » Sun Sep 23, 2018 5:36 pm

64,25 wisecos weighs 196g with rings
prox 207g yamaha 203g over here.
Are you shore they are the same brand?

graham heise
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Re: Wiseco piston weight difference.

#10 Post by graham heise » Mon Sep 24, 2018 12:13 am

Marrcel wrote:64,25 wisecos weighs 196g with rings
prox 207g yamaha 203g over here.
Are you shore they are the same brand?
As to my original post. Same brand, same size, same part number on top. I was surprised to find a weight difference in what i thought should have been identical.

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JonW
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Re: Wiseco piston weight difference.

#11 Post by JonW » Mon Sep 24, 2018 5:26 am

The old Wiseco company was known as 'Seize-co', perhaps youve one of the older and less good units there :/
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

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Re: Wiseco piston weight difference.

#12 Post by silverstrom » Mon Sep 24, 2018 6:06 pm

I think 'seize-co' is a misnomer. The majority of Wiseco issues were due to inappropriate bore clearances and improper warm up before riding. These days the details concerning forged pistons are widely known and more care is taken.

hondaror
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Re: Wiseco piston weight difference.

#13 Post by hondaror » Thu Sep 27, 2018 11:09 pm

Also, the way they make the pistons have changed over the years. Clearance requirements as well. The newer stuff is better.
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Marrcel
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Re: Wiseco piston weight difference.

#14 Post by Marrcel » Thu Jan 03, 2019 5:32 am

Sorry guys i misted this thread.
New stuf is better. Ok but how do you know?
Is the newer lighter or heavier?

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Re: Wiseco piston weight difference.

#15 Post by Bare » Thu Jan 03, 2019 5:45 pm

You don't imo. Lotsa faith based assumptions I suspect.

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