Recall that I already posted that my first fill-up after the gearing change showed 40.4 mpg.

Today, the 2nd fill-up after the gearing change showed 41.2 mpg.

Both of these are with me still doing more unintended fun acceleration than I usually do, just because it's so darn easy now.

So, I think we can conclude that the gearing change does not reduce mpg.

There is a lot of significance to this.

Normally, when you make a gearing change like this that improves acceleration and throttle response so much, your mpg declines.

The exception is when the vehicle is significantly mis-geared from the factory, usually for emissions and/or noise reasons, to be "legal" where sold. When this situation occurs, (i.e. no mpg loss upon re-gearing), it verifies that the factory gearing was indeed WAY off of optimal for performance.

So, what we have here is indirect proof of the assertion that LA_Dog and I have been making all along: Harleys are currently way mis-geared from the factory in order to meet emisisons and noise constraints, and one of the very best bang for the buck mods is re-gearing. Thank goodness it is not wildly expensive to do, and that the parts are available via both HD itself and from the aftermarket. We are fortunate.

I have had this occur before, on a truck - a 2004 Chevrolet SSR retro pickup. That vehicle was geared not only for emissions and noise, but also was stuck with the gearing used on GM's other SUVs, because for a low volume vehicle like the SSR, it made no sense for GM to pay the costs, and delay market introduction, in order to do the required testing to have the chassis certified in a new configuration, so GM simply plopped the SSR body onto a Chevy Trailblazer already-certified chassis.

I re-geared that vehicle from 3.73 to 4.54 rear axle, a 22% gearing change - going on DOUBLE the change we are making in going from 32/66 to 30/70. The engine rpm at 60 mph of course went up by 22%, but was STILL barely around 2100 rpm! The mpg drop was hard to measure outside of a controlled track environment, because it was so small, but amounted to about 4 to 5%. It was that modest because the factory gearing was that much off the performance ideal. By the way, the 0 to 60 time dropped by 0.8 second, and the quarter mile time by almost a full second. With no other mods. (Later mods dropped the quarter mile much more, so that the final version was around 3.5 seconds quicker in the 1/4 mile, but that's a long and different forum story)

Jim G

 

Jim, in your specific case this may be true. But as I mentioned I am planning to exchange the inner primary cover anyway for a chromed one. So swapping the front pulley could be done during that process mitigating the overall labor costs.

As for the lower belt guard pls keep in mind that I'm running the chromed one and not the cheap plastic thingy that comes stock. So cutting this in shape as Brian did with yours will be nearly impossible. The modification of the mounting point is a rather small issue compared to this, I agree.

 

30 and 70 tooth pulleys ordered.


Who has done this without replacing any of the original seals? I know some are good for a few times. Just curious.

 

Yes, I didn't see that you are running the chrome lower guard. Cutting that would indeed necessitate a stripping and rechroming job on top of the mods to the guard. Sounds costly.]

It would probably be easier and less costly to make a brand new guard shaped similar to my modded one, and either paint it or chrome it, or make it out of aluminum or stainless steel.

Jim G

 

Jim- good post above on the reported mpg, as well as conclusions on lame factory gearing off the showroom floor. that's really the main point of this entire pulley mod- get back what HD took away from us on all 2007-up bikes. basically after this mod our bikes are going to run / perform like pre-2007 bikes that already came with a shorter, more performance optimized final ratio.

another nice benefit- no re-tuning of bike required. also significant because any other type of performance mod that puts more power to the wheel does require it.

 

Going 2 teeth down on the front is equivalent to going four teeth larger on the rear -so yes generally 6% improvement.

since we know a 32/70 will fit the axle slot with stock belt, ideally you have the same amount (at least .61") of rearward slot travel when dropping the front pulley to a 30t. I'd like to see 3/4" of available rear slot travel to ensure enough margin for belt tighten plus alignment.

All I can say is - it will be close with 30/66. I do see the logic of doing the front pulley when you have the primary off- makes sense. but considering the minimal work involved at that point to also change the rear pulley, why not do both at once while the bike is already apart and on the lift? surely you'll get a better deal on overall labor? even if no better deal, you'd have it all done in one shot.

 

Jim I added a link to your post on page 1, post 1 - Your summary findings will be of good help to anyone else reading up on this mod. thanks very much!

 

Thanks, LA_Dog. Yes, my findings being right in the first posting is much better than a reader having to wade through hundreds of posts to find them. Great idea, and thanks again for doing it - and the tons of other work you have done to make this thread helpful to other riders.

Jim G

 

cool- good luck with the install and hope all goes smoothly. me personally I always change the primary seals. just extra insurance and not something I want to have to take back off if there is a small leak or weeping. inspection cover gaskets, i re-use those all the time.

 

They told me I need 5/16 spacer so maybe you can add that if someone else wanna buy a 1" pulley.
Like I told you the other day, the new CVO has a 1" pulley too, but with a stock 1" belt instead of the stock 20mm I have on my bike. So if I have to buy a new belt I'll try to go for the 1" but I hope I'll be able to use the old stock belt saving a few $ for other upgrades