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I can't fathom an automotive machine shop that's not eager to bore the engine. That's their bread and butter, at least with cages.
 
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Discussion Starter · #23 ·
I can't fathom an automotive machine shop that's not eager to bore the engine. That's their bread and butter, at least with cages.
The ones I talked to said their machines can't bore something that small. I may have found a solution though: I found a guy on eBay who makes copper gaskets for the 250 CNC machine from copper. He said he can make a custom 57.4mm gasket for me. So I might buy that Chinese big bore kit after all.
 

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Discussion Starter · #25 ·
The egg roll 280cc bore kit is on its way! I'll let you all know if the cylinder crumbles in my hands when I get it lol. I just got done marinating everything in oven cleaner, so I'm gonna inspect the valves today.
 

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Discussion Starter · #26 ·
I found something to ride in the meantime--I traded my two best RC cars for a 96 CBR600F3. 0-60 in about 3 seconds! Riding this is a very, very different experience to say the least.

Tire Wheel Fuel tank Automotive fuel system Vehicle
 

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1985, 86 CMX250C, 81 CM200T, 74 CL360, Invisible to cages, treat them accordingly. Avoids Road RAGE!
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Be very careful please! Like you said, a much different ride!
 
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Almost bought a SV650, but found the steering too "twitchy". As you will discover, if you haven't already, the handling is much different on a sport bike. Don't let it get away from you.
 
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Discussion Starter · #29 ·
Very true, the handling feels bizarre to me. To turn it feels like I have to counter steer a ton. When I first got on I thought the foot peg and shifter were missing or something, and then I looked like a foot and a half back of where I expected it to be and saw it. I'm trying to grip with my legs and not use my wrists, it's easier said than done. I don't plan on going over 55. I just want to bomb around the country roads and maybe commute to work. If I do anything foolish, I'm sure that my wife will find out somehow and punish me!
 

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Discussion Starter · #30 ·
Hopefully intake valve 14711-152-000 (kit from Amazon) and intake valve 14711-399-000 (only intake valve listed on Partzilla for 87 250) are the same thing, because I installed the former. I used my calipers, and they seem identical. Lapped the valves (easy) and reinstalled the valves (very hard). I also ported the intake and exhaust.

Friday, the big bore kit comes! Wish me luck!

I'm debating whether to use the big bore kit gasket (crappy, thin piece of aluminum sandwiched between plasticy material--the same one on eBay with extra holes in the gasket), or custom order a 57.4mm bore machined out of copper.
 

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Hopefully intake valve 14711-152-000 (kit from Amazon) and intake valve 14711-399-000 (only intake valve listed on Partzilla for 87 250) are the same thing, because I installed the former. I used my calipers, and they seem identical.
did you bother comparing length or diamater of stem or valve seat width??
the 2nd gen intake valve had a slightly thinner valve seat width, otherwise both valves are the same

14711-152-000 was engineered for the Honda XL75 1977 to 1979 though is was used on a few 80cc and 100cc bikes in later years..
I'm not saying it won't work, but feel you are a bit impetuous..

If the old valves didn't leak as you indicated, cleaning and lapping should be all that was needed..
 
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Discussion Starter · #32 ·
did you bother comparing length or diamater of stem or valve seat width??
the 2nd gen intake valve had a slightly thinner valve seat width, otherwise both valves are the same

14711-152-000 was engineered for the Honda XL75 1977 to 1979 though is was used on a few 80cc and 100cc bikes in later years..
I'm not saying it won't work, but feel you are a bit impetuous..

If the old valves didn't leak as you indicated, cleaning and lapping should be all that was needed..
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Discussion Starter · #33 ·
Just got the fortune cookie big bore kit in the mail today. I'm going to try and install as much as I can after I put the kids to bed. Wish me luck!
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Automotive design Bicycle part Automotive exterior Rim Gas
 

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Discussion Starter · #34 ·
Not good. Smushed a side rail getting the cylinder on, so used a 52mm side rail which didn't really fit. Oh well. Tried again and crushed the wavy wiper ring. Cut a small piece off and reinstalled it. I'm already feeling like things are not going well at this point. Then, the big bore kit cylinder gasket is a piece of garbage and doesn't have holes big enough for the dowels. Used my drill bit to widen the holes and the cheap gasket folds and crumples and leaves sharp pieces sticking up on the holes. I put it on anyways. Everything is limping along. I try to torque the head bolts to 17ft lbs (204in lbs) and SNAP!

I don't know what to do besides just buying a new engine at this point. I don't think I can fix this. It's half past midnight and I'm pissed and hopeless.
 

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1985, 86 CMX250C, 81 CM200T, 74 CL360, Invisible to cages, treat them accordingly. Avoids Road RAGE!
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Another engine would probably be less time consuming. A 2nd generation engine is easier to find & will fit, but the electrical wiring is slightly different. Personally I'd try to stick with a 1st gen if you do bite that bullet. More power!!!
 
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Discussion Starter · #36 ·
In case anyone is on the fence, I would NOT recommend the Chinese big bore kit:

Gas Bicycle part Auto part Font Tool

Automotive tire Automotive lighting Motor vehicle Audio equipment Eyewear

Automotive lighting Automotive tire Bumper Tints and shades Automotive exterior


If it is because I put the 52 mm side rail on, then this all could be my fault. But I could not for the life of me get the pistons out of the cylinder. I started off tapping gently and then moved all the way up to a giant donkey Kong hammer and 4-ft pry bar. I'm pretty sure I destroyed all the bearings inside the crankcase. I hit that pry bar under the cylinder so hard that the engine lifted off the ground.

Now I have 300lbs of paper weights. Awesome 👍.

Price of your used bike: $300
Price of bobbing out your bike: $1000
Price of your mechanical parts: $600
Your bike now being worth $25 in scrap metal: PRICELESS!

My life is nothing more than a cautionary tale to others, full of folly, idiocy, and gratuitous suffering. Heed my word fellow rebels! Do not bob-out these classic beauties; the curse will come upon you, and you will be left taking the bus or driving your cage.
 

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1985, 86 CMX250C, 81 CM200T, 74 CL360, Invisible to cages, treat them accordingly. Avoids Road RAGE!
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At least you definitely kept your sense of humor about it. I laugh at myself more often as time goes on. Not because I haven't learned, but because of what I've forgotten.
I too feel for your woes.
 
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Discussion Starter · #39 ·
I can't believe I'm asking this....... but is it possible to do an entire rebuild, down to the crankcase bearings? I see main bearings for sale, but no rod bearings even listed as a part. Are the rod bearings not replaceable? I'm pretty sure I destroyed every bearing in that crankcase when I beat on it like the "high striker" carnival game with the sledge and bell (not to mention the drill bit that broke off on the cam tensioner hole and fell into the abyss). I literally hit the cylinder as hard as I could with my giant sledgehammer until it broke off--do you think the lower end is toast?

The prices of used engines are insane, so that's out (plus being broke). I have a long Ohio winter where I can rebuild this puppy.
 

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1985, 86 CMX250C, 81 CM200T, 74 CL360, Invisible to cages, treat them accordingly. Avoids Road RAGE!
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Sounds to me like a rebuild isn't really going to be that probable. :whistle:
I bought my "parts bike", that is now my everyday rider, for $200. Perhaps you can find something similar???? Hope, Hope, hope!
 
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