Low end torque upgrades sprocket?big bore?
Stellar HDF Member
Joined: Feb 2013
Posts: 3,072
Likes: 1,727
From: Dallas, Texas
2007 Dyna FXDB, 98,000 miles - SE-255 cams, EFI to CV-40 conversion, V&H slipon's, baffles removed and DK Custom Torque Thunder baffles in it. Just treated it to an AMS BIG TORQUE PORK 105 kit (KB Forged 10:1 pistons. Still breaking it in, but all I can say is WOW!!!!! TONS of low end torque . . . TONS of mid-range torque! VERY HAPPY with the combination.
Road Master
Joined: Jul 2016
Posts: 919
Likes: 245
I changed out the front sprocket on my last bike (Liter bike), and it was night and day different in how hard it launched. One of the best, and cheapest, mods I ever did.
Downside is you're trading top end speed. So on the freeway you're RPMs will be up a little higher to do the same speed. Also messed with the speedo but I'm not sure how it is with Harleys so verify that.
Those guy who manage to get their Harleys to do a 90 degree wheelie, it's in the gearing not the engine. I would start with the sprockets, they're a lot less expensive. Look into different combinations to get the ratio you're looking for. If you find you don't like it you can just swap it back.
BTW since we're on it if I recall you want to be sure you buy new bolts and a high quality sprocket, lot of torque going through those, don't cut corners on it. Wasn't too long ago someone ripped their rear sprocket in half on here.
Downside is you're trading top end speed. So on the freeway you're RPMs will be up a little higher to do the same speed. Also messed with the speedo but I'm not sure how it is with Harleys so verify that.
Those guy who manage to get their Harleys to do a 90 degree wheelie, it's in the gearing not the engine. I would start with the sprockets, they're a lot less expensive. Look into different combinations to get the ratio you're looking for. If you find you don't like it you can just swap it back.
BTW since we're on it if I recall you want to be sure you buy new bolts and a high quality sprocket, lot of torque going through those, don't cut corners on it. Wasn't too long ago someone ripped their rear sprocket in half on here.
Grand HDF Member
Joined: Jun 2013
Posts: 4,998
Likes: 875
From: Iowa
If you only want some more grab on the low end and do mostly highway riding and want good mpg then do the final drive, the .030 gasket, and have the heads cleaned up with the combustion chambers measured then mill them to measure 84 cc. That'll get you to 9.49:1
If you want the 10:1 aggressive riding that drinks gas, then I'd do the 107 big bore with 3cc domed pistons, the final drive, the 0.030 gasket, and have the heads cleaned up with the combustion chambers measured then mill them to measure 86 cc. That'll get you to 10:1
If you want the 10:1 aggressive riding that drinks gas, then I'd do the 107 big bore with 3cc domed pistons, the final drive, the 0.030 gasket, and have the heads cleaned up with the combustion chambers measured then mill them to measure 86 cc. That'll get you to 10:1
If you only want some more grab on the low end and do mostly highway riding and want good mpg then do the final drive, the .030 gasket, and have the heads cleaned up with the combustion chambers measured then mill them to measure 84 cc. That'll get you to 9.49:1 corrected compression. That is the suggested max compression.
If you want the 10:1 aggressive riding that drinks gas, then I'd do the 107 big bore with 3cc domed pistons, the final drive, the 0.030 gasket, and have the heads cleaned up with the combustion chambers measured then mill them to measure 86 cc and add compression releases. That'll get you to 10:1 corrected compression which is drag racing level and past the suggested level from the manufacturer.
Also, be aware that if you up the compression with either of these you will have to do clutch work as well to handle the torque.
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