Me again,
I am about to regear this 88 flhtp. (Rubber mount police bike) I've gotten such good advice here I thought I would run this by you.
This bike runs well and puts 60-65hp to the ground. It has a mild cam and carb, better muffler. It is a dedicated hack with raked trees.
Back sprocket is shot anyway. Needs to go.
Right now it has 2.94 gear ratio 32/61. This is not stock. It is the international ratio for bikes sold in Europe.(autobahn)
This is way too high for driving with the hack as we found out. It diminished the ride quality as 5th was only useful at 70 and above.
With a passenger in the mountains 4th could be used but often 3rd was required.
American bikes came with a 14% higher 3.37 ratio. 32/70
I am leaning towards a even higher 3.6 ratio 30/70 which will make 5th gear rpm the same as 4th gear rpm now.
I ran the numbers and this is how it lays out.
what I have: (HDI)
2.94 ratio 32/61 tooth
RPM Calculator
MPH 1 2 3 4 5
5 ---- ---- ---- ---- ----
15 1905 1299 ---- ---- ----
25 3175 2166 1568 1205 ----
35 4445 3032 2195 1687 1372
45 5715 3898 2822 2169 1764
55 ---- 4764 3449 2652 2156
65 ---- 5630 4076 3134 2548
75 ---- 6497 4703 3616 2940
85 ---- ---- 5331 4098 3332
95 ---- ---- 5958 4580 3724
105 ---- ---- ---- 5062 4115
115 ---- ---- ---- 5544 4507
125 ---- ---- ---- 6026 4899
what you would have owned if you had an average american bike of this year:
3.37 ratio 32/70
RPM Calculator
MPH 1 2 3 4 5
5 ---- ---- ---- ---- ----
15 2183 1489 1078 ---- ----
25 3639 2482 1797 1382 1123
35 5095 3475 2516 1934 1572
45 ---- 4468 3235 2487 2022
55 ---- 5461 3954 3039 2471
65 ---- 6454 4672 3592 2920
75 ---- ---- 5391 4145 3370
85 ---- ---- 6110 4697 3819
95 ---- ---- ---- 5250 4268
105 ---- ---- ---- 5802 4717
115 ---- ---- ---- 6355 5167
125 ---- ---- ---- ---- 5616
What I am about to buy:
3.60 ratio 30/70
RPM Calculator
MPH 1 2 3 4 5
5 ---- ---- ---- ---- ----
15 2333 1591 1152 ---- ----
25 3888 2652 1920 1476 1200
35 5443 3712 2688 2066 1680
45 ---- 4773 3456 2656 2160
55 ---- ---- 4223 3247 2640
65 ---- ---- 4991 3837 3120
75 ---- ---- ---- 4427 3600
85 ---- ---- ---- 5018 4079
95 ---- ---- ---- ---- 4559
105 ---- ---- ---- ---- 5039
Some of you have owned, do own, or have delt with customers with hacks of this style and weight. (this an early california hack)
We live in the mountains. It seems there is always a 5000 ft pass between us and where we want to go. We also travel a good deal and will be taking a couple of 3000 mile trips this summer. I weigh 200lbs and I am usually in the hack because I am injured at the moment.
I'm thinking what I have is roughly equal in weight and frontal area to a HD hack.
If you a hack like this how is it with the factory gearing?
Did you change it already or would you like to? Should I go even higher?
What about gas milage? How much affect will this have?
Right now we have to run in 3rd and 4th most of the time and I am thinking we get in the mid thirties but I haven't checked it.
Lastly my wife seldom rides above 75, 80 if threatened by severe weather.
These parts are expensive and I would like to get it right
the first time.
Thanks for your help,
Joe
replacing all three as a set is a good idea in the first place
your speedo will end up off [is probably off now actually]
it appears that the ratio you are looking at is about right
you might want to consider a smaller engine sprocket and go to stock rear belt & pullyes - that way all the belt drive parts wont have any adjustment issues or questions
get the high load stock drive belt for the 88's
several mfg make smaller primary engine sprockets - baker comes to mind - there is a thread going currently where the discussion of smaller engine sprockets takes place. its actually simpler than the belt pully swaps.
to
Karata also has motor ssprockets in different tooth sizes.
I would add a late style primary chain adjuster at this time.
Lonnie
I'm not sure how high a gear ratio to go with. With the very low ratio that is on the bike presently I can tell that it needs to be changed. But how much I am not sure.
I don't want to go so high as to make it a gas hog. If is possible to do that.
We were down in Tucson last month and were able to test the hack and gearing out. But the gearing was so far off from where it needs to be, that we just know that we need to change it, but not how much.
Originally written by fastjoe on 2/7/2008 5:46 PM
I'm not sure how high a gear ratio to go with. With the very low ratio that is on the bike presently I can tell that it needs to be changed. But how much I am not sure.
I don't want to go so high as to make it a gas hog. If is possible to do that.
We were down in Tucson last month and were able to test the hack and gearing out. But the gearing was so far off from where it needs to be, that we just know that we need to change it, but not how much.
3.60:1 may be a tad low even in the mountains. (high numerical = low ratio) 3.37:1 would be ideal IMHO. As you say, change the real srockets to 32/70 with a new belt and you will have it. The primary is probably already 24/37 teeth so you can leave it. That's my story and I'm stickin' to it!
I just ordered the parts to change it to 3.37.
Seems like the way to go.
Thanks for the help!!
Joe
Originally written by fastjoe on 2/14/2008 1:27 AM
I just ordered the parts to change it to 3.37.
Seems like the way to go.
Thanks for the help!!
Joe
You'll be glad you did! The only issue now is changing the rear belt and pulleys. The shaft for the swing arm has to come out to remove the swingarm. The service manual covers it nicely.
Happy Trails.
