When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
When i e-mailed this company asking why their are very little in the way of high performance bolt on engine kits for the HD M8 114 engine this was their response and I must say it sounds very interesting to me.
We offer a 124" bolt on big bore kit for the M8 107" engines (with 4-3/8" stroke) and 127" bolt on big bore kit for the M8 114/117" engines (with 4.5" stroke). Our 127" kits will be available the middle of October. If you are interested in our 127" kit, I would recommend placing an order soon, as more than 50% of the first run have already pre sold. The black granite kits may be a little later in October as we are just starting of those cylinders.
This is a stock 107ci jug. 114/117ci is probably pushing the outer limits of the lower cylinder skirt. In my world I would not bore that cylinder to 117ci. And 120ci and above without welding up the crank and boring the cases to maintain a thicker cylinder wall. That's a thin cylinder wall to begin with for the displacement. And air cooled at that. I don't care what wonder metal HD claims to use. Mine will live it's life as a 107ci or there about. I bet we see a bunch of busted cylinder skirts and twisted cranks in the near future.
You're saying in essence the crankcase is being pushed to its limits by larger cylinders/pistons replacements? I not being that mechanical oriented often wondered why this wasn't more of an issue with performance upgrade kits such as these bolt ons. Ditto with the trans too, correct?
117 on the 107 cylinders is fine provided you prep the cylinders properly before boring. The 114 cylinder starts with a bigger bore and thicker liner so you can go 124 with those. There are some people trying to push them larger but IMHO your asking for trouble. You then move into the ones that are being re sleeved with a larger liner and boring the cases. We have a set prototype 4.250 bore cylinders we have been working on as do others but to go that big, head work is a must, due to sealing area issues. Then you get aftermarket cranks that are 4.625" stroke as well so getting 131 cu in (4.250 x 4.625) in stock cases is coming soon. Others are playing with 4.375" bore as well, so getting 131 to 150 cu in is happening right now.
Man. This stuff is akin to when the smartphones first hit. Six months down the road and they're obsolete. 131/150 cu in? The later being Leading Edge I assume?
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Slideshow: The bar-and-shield logo shows up on far more than motorcycles, some of the company's most unexpected products have nothing to do with riding.
Slideshow: From the troubled AMF years to modern misfires, these bikes earned reputations for reliability issues, questionable engineering, or disappointing performance.
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Slideshow: The Swiss custom shop has taken a Harley Softail and stretched it into something so long and low that it looks closer to a rolling sculpture than a conventional motorcycle.
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Slideshow: A standard cruiser becomes an intricate metal canvas in the hands of a Swiss custom house known for pushing Harley-Davidson platforms far beyond their factory brief.
Slideshow: Harley-Davidson's challenges aren't abstract; they show up in dropping shipments, shrinking dealer traffic, and strategic decisions that aren't yet translating into growth.
Revolution Performance
