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  1. #1
    Senior Member cmorris's Avatar
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    big bore

    i about to begin another journey restoring another one on my 250r trike. i wanted to get some info from some of you seasoned guys.what is best big bore to go with. i know everyone has a different opinion, however, i want to do a big bore build and would like to see what has been the most all around power. i appreciate all the input

  2. #2
    Senior Member douglas's Avatar
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    give led a call he's been involved with 250r's for 40 years. his reputation is second to none

  3. #3
    Senior Member acecarlos's Avatar
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    Quote Originally Posted by cmorris View Post
    i about to begin another journey restoring another one on my 250r trike. i wanted to get some info from some of you seasoned guys.what is best big bore to go with. I know everyone has a different opinion, however, i want to do a big bore build and would like to see what has been the most all around power. i appreciate all the input
    The question is "what is best big bore to go with", not who is your favorite builder, everyone has their choice. To answer the question directly:

    Hate to say it, however; a budget will dictate the BB CC playing field. Let's assume "budget" was not a concern, then the next question would be what do you want the engine for, what do you expect and is it going in a Trike or Quad....last and MOST important IMO is "reliability" vs all out Performance.

    The most favorite BB's engines are in the 350-363/370 range for both Trikes and Quads. Followed by Puma's in the 431CC range, and last Saber's in the 500 to 561CC range. For general riding, woods, duner, mx and TT; 350, 363/370's are the pick for most, reason being Cost (Budget), Power and Reliability. In a Quad they are a Beast, in a Trike they are a Beast on Steroids, most can't utilize all the power a 350 or 363/370 puts out. Step into the Puma world at 431CC, and you will get hurt if you don't respect the Power these engines make. Their are also limiting factors to a Puma or Saber in a Trike; such as Pipe Chamber size gets to be to Large and kick starting to clear the Pipe on a Trike...not an issue on a Quad.

    David Ham, Ben Webb, Jeff Carrelli, Cody Smith just to name a few BDT Racers that in 2018 have won most if not all Races they entered across the US in Trike & Quad 250R's racing 350CC to 363CC engines against in some cases much larger 2 stroke displacements...so point is a 350 to 370CC will put out as much HP as you could possibly need. David Ham alone WON 5 series Championships in 2018 across AZ & CA on his BDT363 Trike.
    Jeff has won the FL Nationals & series for years on a BDT350CC. Cody has won the NEEDT Pinelake 2 Stroke Nationals on a TRX250R for the past two years 2017 & 2018. Ben Webb is the Hole Shot King after only racing Trikes for a short 2 years...again point being all on 350-3563CC engines.

    Also; the Bigger you go, the more maintenance you need to keep up with. 363/370's piston life is greater than Puma 431 piston life and much greater than Saber piston life. Reliability is very good on 350-363/370's, good on Puma 431's and less on Sabers 500/561CC...as long as the complete engine is built like new, 100% bottom end included, the bottom end's & cylinders last very well into years of use for all BB's.

    Expect 363/370's to put out 62-65HP, 431 Puma's 72-74HP, and Sabers up to 561CC in the 82-84HP area....all of these as MX or Woods, Duner builds (not Drag) with matched setups; Pipes, Intake, IGN and Fuel. Last....run nothing but Race Fuel on your BB engines, and a New CR250R IGN is almost a "must have"....

    Carlos
    Last edited by acecarlos; 01-02-2019 at 12:26 PM.
    Big_Mike and cmorris like this.

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  5. #4
    Super Moderator Big_Mike's Avatar
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    cmorris what are you looking to do with your setup? The application will most certainly determine what is best for you. How big of a big bore are you looking to go? My ESR 420 cylinder built by BDT is a MONSTER! Its got all the complimenting parts (big carb, race gas, wurks exhaust) and I would say that motor is pushing 70+HP! When I build the next one it will definitely be a CP 431 Puma but right now my motor is so reliable and crazy FAST! I am only riding maybe twice a month and the motor is still fresh but the time will come when this one tires out and that's when I am pulling the trigger on the Puma. I once considered the Saber but that to me seems more geared for all out drag racing which I do not do. Like Carlos mentioned any cylinder can be setup how you choose. If your looking to be under 350cc's I would look at the ESR cylinders and have a reputable shop build it to your specs and make sure you give them as much information as possible like your riding style, where you ride, tire size etc, gas type etc..

    If you are looking to go BIG, 363,370,431+ I would seriously consider the CP cylinder line!
    1986 Honda FourTrax 250R
    BDT Puma coming soon..

  6. #5
    Senior Member cmorris's Avatar
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    i have an amazing builder that i have much respect and does an amazing job. big mike was was wanting to build a big bore for my trike for mx i have heard so much good things about the 363 or 370. i like ripping through the woods and enjoy riding but would like some more power to keep up with my friends that have banshees.i hate tailing them because i am a die hard 250r man. i appreciate all you guys chiming in and all your help. i think i will be going for what my builder recommended i want to try the 370 with the cr ignition. i really appreciate all you guys. i honestly was just wanting to see what you experienced guys thought about the different big bores.i hope you all have a great day and thanks again
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  7. #6
    Senior Member etccb's Avatar
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    There are a couple of different configurations to get that 370 that you want. In the ESR cylinder there have been 81mm bore stock stroke and the popular 4 mil stroked 350 cyl being used for 363 or called 370 builds racing and playing in the woods. There is recognized quality, durability, performance as well as value in the ESR cylinder and it is used by most builders in many different configurations including many of those results referenced up above in this thread. The ESR cylinder is a good back bone for whomever you have build it if you don't have it built by ESR or yourself. Good luck.
    Last edited by etccb; 01-03-2019 at 07:54 AM.

  8. #7
    Senior Member cmorris's Avatar
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    thanks a lot buddy and thanks for responding

  9. #8
    Senior Member Burns350R's Avatar
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    The 81mm bore stock stroke 370 is by far my favorite engine. Makes more low end/mid power than my 363 +4 stroker motor. And the same or better on top.
    (MX) TRX 363R 02- Laeger Narrow Frame/CR500 Link,Motowoz, Roll Design +4, RPM +4 axle, LED 363 +4 Stroker, 38 A/S carb,Rath Signature Series,CCP

    (XC) TRX 370R 86- Stock frame(gusseted),No link rear, JD MGC +2 Arms, Motowoz shocks, RPM XC Axle, LED 370, 38 A/S carb, Rath Signature Series

  10. #9
    Senior Member cmorris's Avatar
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    Quote Originally Posted by Burns350R View Post
    The 81mm bore stock stroke 370 is by far my favorite engine. Makes more low end/mid power than my 363 +4 stroker motor. And the same or better on top.
    thanks burns sounds like im headed in the right direction then curious to see how it handle in the trike

  11. #10
    Super Moderator Big_Mike's Avatar
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    My first ESR motor was a 350 big bore stock stroke, ESR 5 pipe, 39mm PWK, race gas motor fully assembled by ESR and that was the first motor to scare me on a quad! This was around 2002 and that motor was bonkers and very reliable it had well over 50 hard hours on it and that motor only met its fate when my brother accidentally put straight 87 octane lawnmower gas in with no pre-mix! I still have the piston on my work bench! My motor prior to that was the original oem cylinder/motor with a mild port job by a local Kawasaki mechanic and I thought that was fast, until I went into the big bore territory! What a difference!

    I had a twist throttle on the R when I put that 350 big bore in my bike and that's when I had 2 friends on separate occasions completely destroy my OEM plastics because they both flipped over because of the power that motor had and that twist throttle made for a violent ride if you weren't a seasoned rider.
    1986 Honda FourTrax 250R
    BDT Puma coming soon..


 
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