4th gear speed
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
RE: 4th gear speed
SK......Your XL produces it's maximum horse power at 6200 rpm. I think the tach reading you are getting is correct. 4500 rpm with an indicated speed of 90 mph sounds about right. You have 1700 rpms remaining before you reach red line. Very rough extrapolation gives you a top speed potential of 124 mph at 6200 rpms.
Now, the top speed of a Sportster with standard gearing is around 110 to 115 mph. With your gearing that might increase to 124 mph providing you can reach 6200 rpm. Here is where I think you will encounter a problem. I would be very surprised to learn that you can turn 6200 rpm using that 3.11:1 gear. If you care to test this out, be sure there are no authorities close by. It's still raining around here, so I cannot get my machine out yet.
Now, the top speed of a Sportster with standard gearing is around 110 to 115 mph. With your gearing that might increase to 124 mph providing you can reach 6200 rpm. Here is where I think you will encounter a problem. I would be very surprised to learn that you can turn 6200 rpm using that 3.11:1 gear. If you care to test this out, be sure there are no authorities close by. It's still raining around here, so I cannot get my machine out yet.
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Elite HDF Member
Joined: Mar 2005
Posts: 4,092
Likes: 1
From: St. Petersburg Florida
RE: 4th gear speed
If my tach reading is correct, then there is a problem with my carb or engine because it can not idle below much below 1500rpm without dying.
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
RE: 4th gear speed
Hey SK.......Yes, an engine should idle nice at 900 to 1000 rpms. Below that it will start to falter and die. The only way I could think of to test your tach yourself would involve making an attachment that would allow you to connect the tach with an electric motor having a given, known rpm speed such as a 1/2 horse 1750 or 3600 rpm motor.
I still have not been able to get out on the road, but this weekend I will do so and give those readings off my machine so that you can compare.
Question: When you put the 16 inch tire on the rear I was wondering if the circumference of the 16 inch was equal to the circumference of the original 18 inch that came on the machine? I assume your speedometer drive is off the transmission, as mine is. Any difference in wheel size will certainly affect your speedometer accuracy. I will get back to you with the numbers.
I still have not been able to get out on the road, but this weekend I will do so and give those readings off my machine so that you can compare.
Question: When you put the 16 inch tire on the rear I was wondering if the circumference of the 16 inch was equal to the circumference of the original 18 inch that came on the machine? I assume your speedometer drive is off the transmission, as mine is. Any difference in wheel size will certainly affect your speedometer accuracy. I will get back to you with the numbers.
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Elite HDF Member
Joined: Mar 2005
Posts: 4,092
Likes: 1
From: St. Petersburg Florida
RE: 4th gear speed
My Speedometer drive is off the front wheel. I tested it out against the police radar speed signs that are put out from time to time. My speedo reads a little high at lower speeds but is dead on at 60MPH. So using 60MPH as a definate confirmed known speed, my tach in 4th gear reads 3000RPM. When my gear ratio was 24t front and 48T rear it read 3300RPM at 60MPH.
Cruiser
Joined: May 2005
Posts: 199
Likes: 0
From: Sanford, North Carolina
RE: 4th gear speed
hey there sk. i run a 21 tooth sprocket at the tranny output shaft and a 47 tooth at the rear wheel. pretty good highway speeds but i cant really read the tach at high speeds. but i did read the speedo at 115 once with a little left to go!
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
RE: 4th gear speed
SK......Rain finally stopped and I got out. Here is what resulted:
3rd gear at 45 mph= 3500 rpms
4th gear at 50 mph= 3600 rpms
4th gear at 60 mph= 4300 rpms
4th gear at 70 mph= 5300 rpms
This is what my Sportster indicated on the tach and speedometer. I do not know how correct they are, and I did not want to come up on a cop to have it verified. At 70 I was passing everybody on the freeway though, so I assume that I was doing an honest 70, maybe a bit more perhaps.
I hope this helps you make the comparison to the readings you are getting.........piniongear
3rd gear at 45 mph= 3500 rpms
4th gear at 50 mph= 3600 rpms
4th gear at 60 mph= 4300 rpms
4th gear at 70 mph= 5300 rpms
This is what my Sportster indicated on the tach and speedometer. I do not know how correct they are, and I did not want to come up on a cop to have it verified. At 70 I was passing everybody on the freeway though, so I assume that I was doing an honest 70, maybe a bit more perhaps.
I hope this helps you make the comparison to the readings you are getting.........piniongear
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Elite HDF Member
Joined: Mar 2005
Posts: 4,092
Likes: 1
From: St. Petersburg Florida
RE: 4th gear speed
Ok, so here is the difference between our two bikes:
.............................Piniongear 24T front 51T rear...........................Skjold 24T front 43T rear
3rd gear at 45 mph= 3500 rpms.............................................. ......3000rpm
4th gear at 50 mph= 3600 rpms.............................................. ......2500rpm
4th gear at 60 mph= 4300 rpms.............................................. ......3000rpm
4th gear at 70 mph= 5300 rpms.............................................. ......3500rpm
.............................Piniongear 24T front 51T rear...........................Skjold 24T front 43T rear
3rd gear at 45 mph= 3500 rpms.............................................. ......3000rpm
4th gear at 50 mph= 3600 rpms.............................................. ......2500rpm
4th gear at 60 mph= 4300 rpms.............................................. ......3000rpm
4th gear at 70 mph= 5300 rpms.............................................. ......3500rpm
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
RE: 4th gear speed
SK......Interesting comparsion. I cannot determine why the inconsistancy between the different speeds. In 4th yours jumps an even 500 rpms for each 10 mph increase and mine is 700 rpms and 1000 rpms. You have a much stronger machine though. My bike could never pull that high of gear ratio, as it is taxed running the 24T presently on it.
You definitly have a faster machine, regardless of the tach issue. My engine is 883 cc and yours is 1000 cc. The extra displacement may give yours some torque advantage, I don't know. My engine hits it's maximum horsepower at 6800 rpms and yours peaks at 6200 rpms, so that is a difference.
You definitly have a faster machine, regardless of the tach issue. My engine is 883 cc and yours is 1000 cc. The extra displacement may give yours some torque advantage, I don't know. My engine hits it's maximum horsepower at 6800 rpms and yours peaks at 6200 rpms, so that is a difference.
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Elite HDF Member
Joined: Mar 2005
Posts: 4,092
Likes: 1
From: St. Petersburg Florida
RE: 4th gear speed
Well my bike has been completely stripped to the frame and the engine ripped apart. It seems that I have a few upgraded goodies like performance cams and upgraded S&S rods. I also have .020 overbore pistons giving me a tad extra displacement. That might have also contributed to the extra umff that is pulling that extended grear ratio. I will be restoring my bike from the frame up. I will post details in another thread. I definately will be adding the Andrews wide ration 2.66 1st gear set in the rebuild to compensate for my 3.11 to 1 gear ratio so I am not burning the clutch so much on take-off.
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
RE: 4th gear speed
SKJ.......All right! You have the project started. I am interested in seeing it progress. Keep us updated on how it goes and post a photo from time to time. When I did my rebuild I made some photo record of it as I went along, and later I was glad that I did.
Did I understand you correctly in that you discovered some 'performance items' in the bike, or did you mean you will be adding S&S rods and performance cams?
The .020 overbore along with the fact that is is a 61 cubic inch displacement must account for the high gear you can pull. Still....That is a really high gear in my view. OK, good luck with it and congrats on pulling it apart.
Did I understand you correctly in that you discovered some 'performance items' in the bike, or did you mean you will be adding S&S rods and performance cams?
The .020 overbore along with the fact that is is a 61 cubic inch displacement must account for the high gear you can pull. Still....That is a really high gear in my view. OK, good luck with it and congrats on pulling it apart.