Low Compression
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  1. #1
    Junior Member mzunno2's Avatar
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    Low Compression

    what's up guys, I just picked up this 86 250r. The compression is pretty low. it reads about 115-120 cold. My question is do you guys think that when the compression is that low the cylinder is toast or do you think I will be ok to bore/hone it out and get a piston in there still safe enough to run pump gas. I don't have too much experience with these bikes and this will be my first top end rebuild. obviously I won't know what condition the cylinder is in until I tear it down.
    Any input and advice is greatly appreciated.
    Thanks guys

  2. #2
    Senior Member etccb's Avatar
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    You wont know for sure if that cylinder can be fixed or is worth fixing until you tear it down.

  3. #3
    Supporting Vendor acecarlos's Avatar
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    Quote Originally Posted by mzunno2 View Post
    what's up guys, I just picked up this 86 250r. The compression is pretty low. it reads about 115-120 cold. My question is do you guys think that when the compression is that low the cylinder is toast or do you think I will be ok to bore/hone it out and get a piston in there still safe enough to run pump gas. I don't have too much experience with these bikes and this will be my first top end rebuild. obviously I won't know what condition the cylinder is in until I tear it down.
    Any input and advice is greatly appreciated.
    Thanks guys
    OEM Honda cylinders are very reliable, almost 'bullet' proof and still the best overall option for the 250R....thats the good news IMO.

    More than likely your rings or piston are worn out, or the rings can be stuck or binding in the groves, as well as the bore out of round or worn. Usually going to the next bore size, honing and new Piston & Rings, upper end gasket kit refurbishes the OEM cylinder back to like New.

    As suggested; take the top end apart, fully inspect cylinder with an accurate Bore Gauge, Bore, Hone as needed to new size. If stock head, and squish heights; expect compression to rise to 165-175 lbs after fresh top end. 165/175 lbs is more than safe for Pump Gas, keep away from Ethanol Based Fuels.

    Carlos
    Last edited by acecarlos; 01-28-2019 at 03:17 PM.
    BDT WURKS RACING....WWW.BDTMOTORSPORTS.COM ON EBAY TRY 250RTRIKES...OR CALL 909-466-9152...BDT IS THE HOME OF THE 250R....LARGEST NEW AND USED PARTS INVENTORY IN STOCK...."SIMPLY THE BEST"

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  5. #4
    Junior Member mzunno2's Avatar
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    Quote Originally Posted by acecarlos View Post
    OEM Honda cylinders are very reliable, almost 'bullet' proof and still the best overall option for the 250R....thats the good news IMO.

    More than likely your rings or piston are worn out, or the rings can be stuck or binding in the groves, as well as the bore out of round or worn. Usually going to the next bore size, honing and new Piston & Rings, upper end gasket kit refurbishes the OEM cylinder back to like New.

    As suggested; take the top end apart, fully inspect cylinder with an accurate Bore Gauge, Bore, Hone as needed to new size. If stock head, and squish heights; expect compression to rise to 165-175 lbs after fresh top end. 165/175 lbs is more than safe for Pump Gas, keep away from Ethanol Based Fuels.

    Carlos
    Awesome info. Thanks alot. that's what im hoping for. Any recommendations on where I can send it to be bored out?

  6. #5
    Senior Member UshouldaBOUGHTaHONDA's Avatar
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    For just a bore/hone check with a local engine shop, a trusted mechanic should be able to direct you somewhere local too. I’m sure guys will chime in on other places to ship it to if that’s your only option. What’s your location? Someone may know somewhere close to ya.... if you are sending it out you may want to explore porting options & get it all done! I’m sure local guys can port too but I’d want to leave it up to someone like BDT or another reputable 250r builder!
    1987 TRX250R
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    FTZ Fat Boy with ESR centermount exhaust

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    Junior Member mzunno2's Avatar
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    Im located in Long Island NY. if I do have to send it out I will most likely explore all those options and have a port job done as well. How do I get in contact with BDT or other reputable 250r builders if I do opt to send it out? thanks for the help !!

  8. #7
    Senior Member SandSlinger's Avatar
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    If you have a local Napa machine shop there in New York they can bore it out for yah. I've had em do banshees and blasters for me with zero issues. It was fairly cheap to, just make sure u give em your new piston with cylinder. Its a option if you don't wanna ship out west.

  9. #8
    Junior Member mzunno2's Avatar
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    okk cool thanks man!

  10. #9
    Senior Member american opel's Avatar
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    imo make sure you take it to a shop that does 2stroke cylinders.dont just take it anywhere.

  11. #10
    Supporting Vendor acecarlos's Avatar
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    Quote Originally Posted by american opel View Post
    imo make sure you take it to a shop that does 2stroke cylinders.dont just take it anywhere.
    Absolutely correct...!

    Quote Originally Posted by mzunno2 View Post
    Im located in Long Island NY. if I do have to send it out I will most likely explore all those options and have a port job done as well. How do I get in contact with BDT or other reputable 250r builders if I do opt to send it out? thanks for the help !!
    Please don't just send it to any machine shop or shop that does not work on 2 strokes, specifically Honda 250R's....you won't get the 'Best' work for your cylinder. Lot's of good 2 stroke 250R shops around, you have a lot of options, if interested in BDT here is BDT contact information:

    BDT Motorsports
    8760 Helms Ave
    Rancho Cucamonga, CA 91730
    909-466-9152
    USA

    Carlos
    BDT WURKS RACING....WWW.BDTMOTORSPORTS.COM ON EBAY TRY 250RTRIKES...OR CALL 909-466-9152...BDT IS THE HOME OF THE 250R....LARGEST NEW AND USED PARTS INVENTORY IN STOCK...."SIMPLY THE BEST"


 
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