Big Bore Kits for Harley

Question I have a 1994 Dyna Wide Glide I’m customizing this winter. I want to rebuild the 1340 Evo engine. I’ve been looking at big bore kits for Harley, a friend of mine has an 06 deuce he put a big bore kit in it. His stock engine should’ve been 14th cc I think. Would the jugs and pistons work on my 1340 evo? I appreciate your time and input on this. Thanks, Paul

Answer Paul, there are big bore kits offered for your Evolution motor. The kits usually require that your crank cases be honed to accept the larger cylinders. That makes the job a bit more involved than your buddy’s Twin Cam kit.

S&S offers their classic Sidewinder package. Check that out.


A big bore kit is not the only way to gain significant horsepower.
Consider Screamin Eagle heads with a more aggressive cam.
A Thunderheader, or Supertrapp exhaust also aids a performance package/combination.

Choose a cam that reflects your riding style.



The Evo has been around for three decades now. People have figured out a lot of different combinations for creating more horsepower. Do your homework. Search on line to see what others have done. Read reviews of kits & combinations that have been tried. Find something that fits your budget.
Don’t rule out Nitrous. That is a lot of fun too!
https://www.mpsracing.com/products/NOS/no01o.asp
https://www.revperf.com/product_info.php?cPath=25_34_131&products_id=373

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14 Responses to “Big Bore Kits for Harley”

  1. TheMaddYooper

    I had to go back and look. I just got this discussion in Apr of 19. The comments are from 2015. Any way the first thing I ask myself and anyone else wanting to do a build is how much money do you want to spend? Then how much can you afford to spend? These are questions that the individual needs to answer for themselves. After that is how do you ride? If you don't or can't answer those questions it is way to easy for the average guy to get in over his head and end up with a very expensive law ornament. Having said all of that I like S&S products I have never been disappointed with them. Nitrous is horse power smart. It isn't combustible it produces power by rapid thermal expansion. So you get power without additional heat. Always a plus. One last thing, I don't believe in cutting corners. It costs more to dothese things but in the long haul you will be better served. Have fun I know you will.

  2. robert cunningham

    I had my '98 dyna rebuilt a year ago and added domed pistons for more compression. big mistake. It pings under load, especially when hot. I live in AZ it's always hot. I have a S & S 520 cam in it right now. I'm considering a 85" kit and more cam. I would appreciate your input. thanks, robert

  3. Wayne shelton

    I. Have. A. 2012 wideglide. 103cub inch. Can. I. Change out. The. Stock carb. An put. On. S&S. In. It's. Replacement? Thanks. Bro

  4. Jerry

    I've got an anniversary ultra classic. I'm going to put a big bore kit, 6 speed xmsn and high performance pipes in her. Are there any other components I should buy to go along with this upgrade?

  5. Andrew T

    Hi Keith. That oil burp is no big deal. We refer to it as morning sickness. During the riding season, and when your bike is running it typically has 1/3 of a quart or so circulating through it at any given time. When your ride is shut down for extended period of time (ie; winter). Oil from the reservoir can settle from the tank into the motor caseing. When you fire things up for the 1st time of the season some of this excess oil simply burps out the vent tube of the engine. Next fall, check the oil level on the dip stick when you store the old girl. Then before firing her up in the spring, check the oil level. You will notice a difference. After you fire up the motor, check the level again. You should notice that the oil has come back to the reservoir. Except of course what has burped out. This is also partially why you want to run a motor with a remote oil reservoir prior to changing the oil. So there is no excess oil trapped anywhere in the system, the correct amount of oil is in the engine, and the reservoir. Hope this helps.

  6. keith

    Chuck I have a 1981 FX stroked and big bored to 93" using all S&S parts, After sitting over winter when I start oil is coming out the vent hose that come's out of the S&S oil pump? Any ideals?

  7. Jarry

    What do you think is better for all around riding, no racing or high rpm's, a remap from Harley, or an after market cobra F.I. Computer kit for a 103 engine, circa 2013 or 2015, along with pipes and free flowing air filter.

  8. Richard

    Back in 1988 I used a Sputhe Big Bore Kit. Turned a stock 80" into a 95.5" and with a 4 5/8" STROKE 107". You really have to cut the cases to fit these cylinders. Would I do it again, NO! The best bang for the the buck I've seen over the years is a 4 5/8" stroke with stock cylinders 89".

  9. Salvador

    How can I adjust the low iddle on my 1997 heritage

  10. Andrew T

    Hi again Chuck. I realized a typo. The needle for the carb was from a "1989 Sporty". The reason is the diameter, and taper of that needle provide improved fuel delivery during the throttle range. You will get the same result from "Thunderjet Kit" however you will most likely find a dramatic drop in your fuel economy.