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Author Topic: (Pics) Sr250 blown up. (Thoughts, options, etc.)  (Read 292 times)

Offline mkb423

  • Posts: 15
(Pics) Sr250 blown up. (Thoughts, options, etc.)
« on: Aug 12, 2017, 10:23:26 »
Hey guys! First off my name is Michael and I'm from the hills of Tennessee. I recently bought an 80s model sr250 "bobber" project for $300. And after many attempts to get it to fire, I decided to tear the motor apart. (Side note: this is my first motor tear down/ rebuild ; I'm not very educated in engines  however I'm trying to build this bike by myself and learn as I go.) after the tear down I found that the piston ring was broke. The cylinder sleeve was scratched and the piston was damaged as well. I'm not sure what my next move will be but I'm trying to make sure I understand/know all my options before picking a route to take... that's where you guys come in!! I was told by a friend that I could "hone" the sleeve, "sand" the piston and buy oversized rings. Is that possible? Seems like a temporary fix? Can I bore the the sleeve I have now and put a tad bit bigger piston in it? Or is the best to replace the piston, sleeve and rings all together?


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Offline mkb423

  • Posts: 15
Re: (Pics) Sr250 blown up. (Thoughts, options, etc.)
« Reply #1 on: Aug 12, 2017, 10:25:53 »
Hey guys! First off my name is Michael and I'm from the hills of Tennessee. I recently bought an 80s model sr250 "bobber" project for $300. And after many attempts to get it to fire, I decided to tear the motor apart. (Side note: this is my first motor tear down/ rebuild ; I'm not very educated in engines  however I'm trying to build this bike by myself and learn as I go.) after the tear down I found that the piston ring was broke. The cylinder sleeve was scratched and the piston was damaged as well. I'm not sure what my next move will be but I'm trying to make sure I understand/know all my options before picking a route to take... that's where you guys come in!! I was told by a friend that I could "hone" the sleeve, "sand" the piston and buy oversized rings. Is that possible? Seems like a temporary fix? Can I bore the the sleeve I have now and put a tad bit bigger piston in it? Or is the best to replace the piston, sleeve and rings all together?


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Offline mkb423

  • Posts: 15
Re: (Pics) Sr250 blown up. (Thoughts, options, etc.)
« Reply #2 on: Aug 12, 2017, 10:28:00 »



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Offline advCo

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Re: (Pics) Sr250 blown up. (Thoughts, options, etc.)
« Reply #3 on: Aug 12, 2017, 10:33:57 »
That piston looks junked. Bring it to an automotive machine shop, have it measured and get the next size up piston and ring set, and send it out to get bored to the next size. That damage is way past honing.


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Offline mkb423

  • Posts: 15
(Pics) Sr250 blown up. (Thoughts, options, etc.)
« Reply #4 on: Aug 12, 2017, 10:45:34 »
That piston looks junked. Bring it to an automotive machine shop, have it measured and get the next size up piston and ring set, and send it out to get bored to the next size. That damage is way past honing.


Ok, thanks for the info. Another question if I may,  if I do the slightly bore The cam, what other parts, if any, will I need to change to make it run smooth. Valves? Cam? Jets?


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« Last Edit: Aug 12, 2017, 10:59:30 by mkb423 »

Offline advCo

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Re: (Pics) Sr250 blown up. (Thoughts, options, etc.)
« Reply #5 on: Aug 12, 2017, 10:49:25 »
To check the valves for sealing, I like to tilt the head on its side (so intake or exhaust is pointing straight up) and pour some gasoline in. Give it a few minutes and make sure no gas seeps through the valves to the combustion chamber. Repeat on exhaust valve. If fuel leaks you will likely need new valve seats cut. Do yourself a favor and replace the valve seals while you have it apart.

If you go up to the next size bore you probably won't have to jet but depends on many factors that you won't be able to tell until the bike is running


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"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0
82 GS550L - Tracker-ish - http://www.dotheton.com/forum/index.php?topic=67229.0 - Sold
74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
73 Suzuki RV125 -http://www.dotheton.com/forum/index.php?topic=73875.0