Greetings,

What will happen to the power & drivability of my 1990 Softail Springer (FXSTS) if I go from a 70 tooth to a 65 tooth pulley? It is a stage one build with only a V&H exhaust and a cone filter. I understand that I will loose a little take off power and gain a little on the top end by going from a larger pulley to a smaller pulley. But how much? What are people's experience with this? How much acceleration loss will I have? How much will my RPMs drop at 70mph?

I bought a real nice solid 65 tooth pulley off of eBay for $60. Please understand the only reason I bought it was for looks. I don't like the looks of the stupid black pulley that is on it now. I would have never bought it, but I thought I had a 65 tooth pulley. I went out last night and counted the teeth on the pulley.


I am more than happy with the gear ratio of the 70 tooth, but I am concerned that I will not be satisfied with the higher gear ratio when I go to a 65 tooth pulley.


Any comments, suggestions, or experience would be greatly appreciated!


*I searched the forum and I can only find info about going from a 65 to a 70 tooth

 

Will I have to get a new, shorter belt? It looks like my belt is pretty close to being all the way back? I did not remove the covers to check to make sure...

 

Hard to say whether you would like it or not...you would have to try it and see. 93 down bikes have a lower geared primary...so you would wind up with gearing similar to what a 94 up bike has stock. 70 tooth bikes had a 132 tooth belt and 65 tooth bikes had a 130 tooth belt...so it is very likely you will have to change the belt.


http://community.jpcycles.com/articl...e-pulleys.aspx

http://www.harley-davidsonforums.com...oth-count.html

 

I bought my 1990 Glide new, which came with a 61T rear pulley as stock, because it was an International spec model. I have since installed a stock US 70T one (with longer belt)! Why? because the original gearing was very long/tall and IMHO hurt rideability. I now have a 107" engine and feel no need to change my gearing. Your stage 1 doesn't add anything to your performance that needs any change IMHO.

You can use the tooth counts of the two pulleys to analyse the change the 65T will give. Your torque to the rear wheel will be reduced 65/70 = 93% of stock gearing, which will probably counter any small improvements your stage 1 gives you. Yes, you will need a shorter belt.

As for top end gain, it is unlikely there will be any. Our bikes are very over-geared as stock, to help them meet EPA regulations (or equivalent in the case of my bike when new). At 5,000rpm your bike has a theoretical speed of 128mph. Changing to a 65T will increase that to 70/65 x 128 = 138mph, however it is unlikely to be able to do either of those, as it doesn't have the power available to do those speeds!

Your gearing will be changed in the same way, so the rpm at a given road speed in top gear will be reduced to 93% of what it is at present. If you currently cruise at say 3,000rpm then engine speed will be reduced to 3,000 x 93/100 = 2,790rpm.

 

so what your really trying to say he needs a lot more HP for that pulley swap if not he will be greatly disappointed

 

My 1988 is all stock in that area. On the interstate the RPM's are generally higher than I would prefer. At 70 the RPM's are about 3300. I'm guessing that at about 100 MPH I'm probably pulling redline. I don't know for sure as I have never had this bike that fast and have no plans too. I have had two Goldwings in the past and when it comes to jetting down the interstate they will spoil you. They don't breath all that hard at 120. For everything else the Harley is better.

 

It does depend what shimaze wants of his bike and there is a risk he may be disappointed with the reduced performance he gets. A lot more torque would certainly work better with raised gearing. I happen to think our bikes have high enough gearing as stock and to raise it even further doesn't do anything useful IMHO.

With my S&S 107" I have over 100/100 and the gearing is just fine! I get to use all the extra performance my investment paid for. If I could afford a low CR 124" I would start with the same gearing as I have at present, on the same principle. I had a TC88 for several years and changed the gearing on that from a 25T compensator to a 21T. Now that really woke up that bike! 19% extra torque was almost free.

 

Do a Google search on "70 tooth harley chrome pulley cover".



If it's just about cosmetics get one of these.

 

^^What he said.

 

I appreciate the hearsay evidence & expert testimony presented. Based on the opinions expressed herein, I motion the court to suppress the 65 tooth pulley idea and demand the 70 tooth remain in place with no further intervention.


Thanks, Shimaze