Honda Discussions about Honda ATVs.

250x big bore

  #11  
Old 03-05-2011, 08:30 AM
Trailblazer
Join Date: May 2008
Location: Middletown Ohio
Posts: 94
Likes: 0
Received 0 Likes on 0 Posts
Default

Thats what I said a shorter stroke will rev faster, . A 250x with a 80mm piston will be around 288cc , a 300ex is a 282 cc motor . Both are around the same cc's but both will have different power curves . The 250x would have more torque but the 300ex would rev faster . Because Honda stroked the crank instead of installing a larger piston .

ok i think the question of big bore 350X's is one of the most popular. it seems like people always ask how big to go and what kits are out there. while this is not a 100% complete list as there will always be a engine builder doing his own thing. it is rather extensive. first i will give the basic displacements. then i will discuse options and differances

piston...................68mm crank (stock).............74mm (6mm)stroker



81mm (stock)................350.4cc.................... ....381.3cc
81.5mm ........................354.7cc................... .....386cc
82mm............................359.1cc........... .............390.7cc
83mm............................367.9cc........... .............400.3cc
84mm............................376.8cc........... .............410cc
84.5mm.........................381.3cc............ ............414.9cc
85mm............................385.8cc........... .............419.9cc
85.5mm.........................390.4cc............ ............424.8cc
86mm............................394.9cc........... .............429.9cc
87mm............................404.2cc........... .............439.9cc
89mm............................423cc............. ..............460.3cc
89.5mm.........................427.8cc............ ............465.5cc
90mm............................432.5cc........... .............470.7cc
90.93mm.......................441.5cc............. ...........480.5cc
92mm............................452cc............. ..............491.9cc
95mm............................481.9cc........... .............524.5cc


as you can see thier are many different sizes to choose from.

one other thing you may notice is there are two ways to achieve the same displacement. however although they will be the same cc and have the same peak H.P. they would be completely different in there charecteristics. let me explain by using the stock 81mm piston with a 6mm stroker that achieves 381.3cc vs just boring the cylinder for a 84.5mm piston to get the exact same displacement.

the 81mm/74mm bore/stroke combo is a more "square" design. by that i mean the bore and stroke are closer to the same size as the 84.5mm/68mm bigger bore set up. what does all that mean? a squarer motor will produce quicker and more revs and have a broader H.P. range. meaning it will produce more H.P. at the lower RPMs then the 84.5mm bore only motor. this translates into a more usable powerband with the bore/stroke combo. wereas the bore only will have a slower reving powerband.

this is why all the new four strokes have faster reving motors then the older designs. this produces a better "race" motor. before four strokes were mostly trail bikes/quads and a slower reving motor was more desirable for "play" use.
 
  #12  
Old 03-05-2011, 09:01 AM
Weekend Warrior
Thread Starter
Join Date: Nov 2008
Posts: 17
Likes: 0
Received 0 Likes on 0 Posts
Default

My goal is not really to out run a 300ex,thats just what I was trying to use for comparison..

My 250x is jetted, k&n filter and crappy full cobra exhaust.. we also have a 300ex with pipe,jets and filter...

Now the 300ex seems WAY better down low(torque) but my 250x seems to be a little better up top..

The 300ex revs through the power band really fast..

I have 2 250x bikes and just to want to have some fun with one..
 
  #13  
Old 03-05-2011, 09:30 AM
Trailblazer
Join Date: May 2008
Location: Middletown Ohio
Posts: 94
Likes: 0
Received 0 Likes on 0 Posts
Default

O.K. I didnt know you had both bikes I thought you were trying to outrun your buddy. You see the difference then. I still think the bigborekit would be slower but you never know . Depending on how much you want to spend a 350x motor is a very fun option. I bought mine for $500 on craigs list . If your 250x motor runs good you can sell it and put the money towards a 350x . Mine will run with a 400ex and out runs most 300ex ,s . I say most because I got outrun last year . But a 350x /250x will be faster than say a 330ex
But I also like the 250x motor they are fun bikes and the 250x has reverse . Good luck with your bike if you buy the bigbore kit post the results and let us know how it rides
 
  #14  
Old 03-05-2011, 04:52 PM
Weekend Warrior
Thread Starter
Join Date: Nov 2008
Posts: 17
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks for all the advice.. I think I will just take the money I was gonna spend on the big bore and put it into a 350x fund..Now if I can just find a 350x at a good price..
 
  #15  
Old 03-05-2011, 05:44 PM
Pro Rider
Join Date: Aug 2008
Posts: 1,317
Likes: 0
Received 0 Likes on 0 Posts
Default

Sounds like a good plan. And a fun project. Good luck.
 
  #16  
Old 03-11-2011, 07:04 AM
Trailblazer
Join Date: Nov 2007
Posts: 73
Likes: 0
Received 0 Likes on 0 Posts
Default

The 350x project is a great one. I did this swap three years ago rode it for two and sold it last year. I totally regret selling it. I had the 86 with 6 spd transmission. This thing would walk away from STOCK 400exs (notice I put stock) A custom exhaust, 450r muffler, 400ex carb and a uni filter was all I had on it too. If you need any help with building it, Im sure I can find my old notes on what i did. It was a blast to ride. 350x rear swingarm 300ex frame 400ex front shocks, it was a great heinz 57 quad
 
  #17  
Old 09-05-2016, 08:42 PM
Weekend Warrior
Join Date: Sep 2016
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
Default

I got a 1987 Honda TRX250X how do I or what is a cheap way to get more speed
 
  #18  
Old 09-05-2016, 08:51 PM
Weekend Warrior
Join Date: Sep 2016
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
Default

I have an 87 honda trx250x that I don't get to go faster but with a cheaper way
 
  #19  
Old 04-19-2019, 02:42 AM
Weekend Warrior
Join Date: Apr 2019
Posts: 1
Likes: 0
Received 0 Likes on 0 Posts
Default Will will 330cc big bore kit fit on 1987 honda 250x

will 330cc big bore kit fit on 1987 honda 250x
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Quadzilla Heritage
Classifieds, Garage Sale & Swap Shop
0
09-25-2015 01:39 PM
XxS0ccerstarxX
Polaris
1
09-24-2015 05:38 PM
XxS0ccerstarxX
Honda
4
09-24-2015 02:02 PM
XxS0ccerstarxX
Suzuki
1
09-22-2015 08:07 AM
Huntingdeer
Performance Mods and Project Quads
1
08-23-2015 12:06 AM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 

Thread Tools
Search this Thread
Quick Reply: 250x big bore


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: