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2 stroke piston and cylinder scratches by the exhaust port???


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Bike is up-jetted to correct jetting, air filter is fairly clean, bike has only got 1200 miles since its most recent top end rebuild recommended is every 6000 miles on this 125 2 stroke road bike, top end  was done at garage, always warmed up and ridden nicely. seems to have deep to severe scratches on the piston and cylinder bit, seems to be where the exhaust port is and on that general side. could do with some help on understanding the possible issue so i can stop it from happening again.

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106103789_1213970408947260_7648919231595096031_n.jpg

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3 minutes ago, Jack Kay said:

Bike is up-jetted to correct jetting, air filter is fairly clean, bike has only got 1200 miles since its most recent top end rebuild recommended is every 6000 miles on this 125 2 stroke road bike, top end  was done at garage, always warmed up and ridden nicely. seems to have deep to severe scratches on the piston and cylinder bit, seems to be where the exhaust port is and on that general side. could do with some help on understanding the possible issue so i can stop it from happening again.

106310324_322834998729739_6736915346950653217_n (1).jpg

106103789_1213970408947260_7648919231595096031_n.jpg

Thats one crispy critter. If its a Wiesco piston, you are supposed to drill two holes up on the front of the skirt for lubing up. Molten metal! Yeahhhhh!!!!!image.png.fb71dd51a65f84e3afadd4137ba9c411.png

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yep looking now on eBay and its a Wössner piston, but that has no holes like you said, so might be due to that?

update:

might even be a vertex piston either way they both dont have 2 small holes like you said

Edited by Jack Kay
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Just now, Jack Kay said:

yep looking now on eBay and its a Wössner piston, but that was has no holes like you said, so might be due to that?

Jack, im not sure about wossner pistons. I know for a fact, that you have to drill 2 vertical holes in the front skirt of a wiesco piston so it will lube up for the front of the cylinders exhaust ports. Thats the hot side of the cylinder, hey its the exhaust port. Intake is a wee bit cooler. Bro, I use OEM pistons on my CR's, so I dont have to bother with drilling. I had a wiesco,but never used it...

 

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11 minutes ago, Jack Kay said:

will just get a piston with these holes then 🙂

Um, Jack, bruh, you will have to mark and drill em yourself, I dont think they sell em, pre drilled. Find a table vise, a shop rag and a nice drill, Carbide drill bits work best. You have to make sure your holes match up with the center of the exhaust ports. Slap that rag covered puppy in a vice, drill em out like bubba says in the video, clean up all metal fragments, then install it in a freshly re-coated cylinder. Teach a man to fish, and he will become a fisher man. Now Git er' done! Hoss!image.png.3a5e99c6ac170d061be62d9c36a4b7a4.png

Edited by M E T A L A C I D
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9 hours ago, M E T A L A C I D said:

Um, Jack, bruh, you will have to mark and drill em yourself, I dont think they sell em, pre drilled. Find a table vise, a shop rag and a nice drill, Carbide drill bits work best. You have to make sure your holes match up with the center of the exhaust ports. Slap that rag covered puppy in a vice, drill em out like bubba says in the video, clean up all metal fragments, then install it in a freshly re-coated cylinder. Teach a man to fish, and he will become a fisher man. Now Git er' done! Hoss!image.png.3a5e99c6ac170d061be62d9c36a4b7a4.png

umm yes they do found some right now that are pre drilled

p08-pistone-stampato-grafitato-accessori-ricambi-husqvarna-sms-sm-wre-cr-wr-125-2t.jpg

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1 hour ago, Jack Kay said:

umm yes they do found some right now that are pre drilled

p08-pistone-stampato-grafitato-accessori-ricambi-husqvarna-sms-sm-wre-cr-wr-125-2t.jpg

Ok, Hoss, y'all in biznezz! Clean up or replate that cylinder and go git at it! Note: racing motor assembly lube goes a long way at getting the initial start up clean safe. Lube up everything in site, hit those small end bearings. Note, assembly burns off quickly and is replaced by the proper 2-t lube you put in the engine's fuel, Git er done! Cowboy!🤠

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Is the nikasil chipped off on the exhaust port bridge?  I've overlooked that before and toasted fresh top end in no time.  I'm sure those holes are a good thing to have in piston, but the score lines up with the bridge, making me think nikasil is gone partially.  I cant quite see it in your picture though.

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Am I reading this right, recommended top end rebuild 6,000 miles on a 125 2 stroke screamer? No way. The piston rings are good for 25 hrs, says so right on the box. But most people do a top end at 100 hrs or so. It's ok with me, you can go your 6,000 miles. I do mine at about 100 hrs also, and that's about 1000 miles and don't have that problem.

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10 hours ago, Knutco11 said:

Is the nikasil chipped off on the exhaust port bridge?  I've overlooked that before and toasted fresh top end in no time.  I'm sure those holes are a good thing to have in piston, but the score lines up with the bridge, making me think nikasil is gone partially.  I cant quite see it in your picture though.

Nikky is gone because of blast furnace overheating, this ol boy says this bike is for the street, I just bet this sum b, revved its guts out showing off to his buddies or something. Hey I did it back in the day. Time for a re-coat, as I said earlier. Drill those holes man!

7fc1e349c3826cc13b6f8667ec201be5.jpg

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Doesn't really matter what happened I suppose, cylinder is toast, replace it.  But if I could count, I'd tell ya how many times I have seen the nikasil flake off on that spot, and score the piston exactly like is shown.  I'll bet it's not an effect, but actually the cause.  That bridge on the exhaust is a very high maintenance thing.  Think of how much heat is getting thrown past that bridge 24/7.  It's a very failure prone thing, and I'm just saying it is also easy to over look.  Just my 2 cents, have a good one!

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16 minutes ago, Knutco11 said:

Doesn't really matter what happened I suppose, cylinder is toast, replace it.  But if I could count, I'd tell ya how many times I have seen the nikasil flake off on that spot, and score the piston exactly like is shown.  I'll bet it's not an effect, but actually the cause.  That bridge on the exhaust is a very high maintenance thing.  Think of how much heat is getting thrown past that bridge 24/7.  It's a very failure prone thing, and I'm just saying it is also easy to over look.  Just my 2 cents, have a good one!

Nickasil sucks, the old school cylinders are the best. Production and money are probably why they did this change over, while nicky is probably longer lasting, I prefer old school cylinders, you get more options.

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1 hour ago, M E T A L A C I D said:

Nickasil sucks, the old school cylinders are the best. Production and money are probably why they did this change over, while nicky is probably longer lasting, I prefer old school cylinders, you get more options.

I think they went away from it because in two or three hard races the top end would be egg shaped.  Cast iron alone just isn't enough with modern hp levels in these small engines, especially 2 stroke.  I agree the options are nice, but your never gonna be able to put 3 or 5 standard size pistons in a cast iron cylinder without the cylinder getting majorly out of round.  Nikasil is good stuff overall, just doesn't hold up very well in spots like exhaust bridge ports.  Probably why Husqvarna put those holes in the piston in relation to the bridge on the port...

 

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And bridge ports were failure prone on non nikasil cylinders too.  Instead of chipping, the whole bridge would crack on the top or bottom, probably from too much heat and expansion/contraction of the metal.  The sleeve and or whole cylinder would then be junk.  Nikasil is not cheap to do, so I doubt the factory's started doing it to save money.  They were likely spending more on the process.

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4 hours ago, Knutco11 said:

And bridge ports were failure prone on non nikasil cylinders too.  Instead of chipping, the whole bridge would crack on the top or bottom, probably from too much heat and expansion/contraction of the metal.  The sleeve and or whole cylinder would then be junk.  Nikasil is not cheap to do, so I doubt the factory's started doing it to save money.  They were likely spending more on the process.

Sounds like a winner, although, my 84 CR-500R, never had any issues, and I checked it periodically according to schedule, nary a chip or scratch. Good bike, goood bike...

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