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General Category >> Rubber Side Down! >> Bike won't go past 75m even with sprocket change.
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Message started by StuckinTexas on 10/10/17 at 13:36:56

Title: Bike won't go past 75m even with sprocket change.
Post by StuckinTexas on 10/10/17 at 13:36:56

So I have a 2004 Savage with a Screamin Eagle exhaust and K and N drop in air filter and I just recently swapped out my belt drive for a chain with 43 tooth in the back and 17 in the front and I still can't get past 75. I think before the swap I got up to 83 before but I'm not sure if it was 73. My idle mixture screw plug has been drilled out but I'm not sure if the bike has been jetted or not from the previous owner who did the mods on the bike. What can I do to increase the top speed on the bike?

Title: Re: Bike won't go past 75m even with sprocket chan
Post by Gary_in_NJ on 10/10/17 at 13:45:51

How many miles on the engine? Have you done a compression test?

Unless you are trying to ride at max speed at idle, the idle mixture will do nothing to effect operations at or near WOT. What jets do you have installed and what position is the needle?

Title: Re: Bike won't go past 75m even with sprocket chan
Post by kiwi rider 89 on 10/10/17 at 14:28:22

have you factored in the fact your speedo might be inaccurate now?
I'm riding a stock 89 LS 400 chain driven with 17-48 sprockets and I'm getting just over 125 kph (77mph) my speedo is out by round 5%
reads 100kph but doing 110kph ish

Title: Re: Bike won't go past 75m even with sprocket chan
Post by kiwi rider 89 on 10/10/17 at 14:34:11

have a look at this calculator for gearing
http://www.sprocketcalculator.com/
stock i had a 17-50 sprockets

Title: Re: Bike won't go past 75m even with sprocket chan
Post by justin_o_guy2 on 10/10/17 at 14:44:15

How big are you?
Got a windscreen?
Bags?
Drag bars or buckhorns?
And what size rear tire?
How it's jetted matters.
Speedo is driven by the transmission.
Designed to Report the speeds that a given RPM in a given gear would create using the OEM gearing and the rear tire circumference. They usually report a higher than accurate speed. By replacing the tire with a taller sidewall they are pretty close. Changing the front sprocket diameter to rear sprocket diameter ratio and you get higher speeds without the speedometer knowing about it.
The low horsepower motor can only shove so much stuff down the road at speed. We do some gearing change not for speed, but to decrease the RPM at highway speeds.

Title: Re: Bike won't go past 75m even with sprocket chan
Post by kiwi rider 89 on 10/10/17 at 14:51:06

that's why I did the change to mine so i'd have a little more usable rpm at 100 when passing cars

Title: Re: Bike won't go past 75m even with sprocket chan
Post by Serowbot on 10/10/17 at 15:28:53

Remember, your speedo doesn't run off the front wheel like most bikes,...
It will read the same at any given rpm/gear, regardless of gearing...

Title: Re: Bike won't go past 75m even with sprocket chan
Post by Ruttly on 10/10/17 at 18:19:59

With gearing like that you need more power or a perfect running engine.

Title: Re: Bike won't go past 75m even with sprocket chan
Post by pg on 10/10/17 at 18:48:35

0B2C2D3B3331360C3D20392B580 wrote:

Although that sprocket combination will allow for relaxed cruising, the engine isn't strong enough to push it on the high end. If you like the chain, I would try a 16 T counter sprocket. That will raise the rpms but you will see a significant amount of performance on the top end.

Best regards,

Title: Re: Bike won't go past 75m even with sprocket chan
Post by Ruttly on 10/10/17 at 19:45:16

I would do the opposite even if it costs more. 18/48or49or50 the smaller counters make the gears too short your always shifting , you won't even feel a difference between 4th & 5th , it doesn't allow you to use the powerband or torque of the big single and rear 43 a stock engine has a tough time pulling.
Get a GPS so you can get a accurate speed.

Title: Re: Bike won't go past 75m even with sprocket chan
Post by Dave on 10/11/17 at 03:42:04

Yep......use a GPS or PhoneApp to check speed, as your speedometer doesn't read correctly once you start fiddling with the final drive ratio (pulleys or sprockets). The stock 23/68 gearing is 2.9565, your current 17/43 gearing has a ratio of 2.5294. That is a change of 16% - so ignoring any speedometer error you may have........a speedometer reading of 70 mph will now be a ground speed of 81.2 mph.

And.........with the current gearing you have it is very likely the engine can't wind up enough to get your top speed in high gear. The 25/65 gearing I have on my bike has a ratio of 2.6000. I have a modified engine and I can't get to my top speed in high gear - and neither will you. If I want to go "full speed ahead" I have to do it in 4th gear - but the taller gearing allows for very nice highway cruising in 5th gear, as my engine is only turning about 4,000 rpm at 70 mph.

Title: Re: Bike won't go past 75m even with sprocket chan
Post by StuckinTexas on 10/12/17 at 15:34:41

Quote:

Yeah. I'm using an app called strava it has gps. Mines off by 10 mph over 50 mph. On bike it reads 65 mph which gps shows my top speed at 75 mph.

Quote:

reads 100kph but doing 110kph ish
Posted by: Gary_in_NJ Posted on: 10/10/17 at 13:45:51
How many miles on the engine? Have you done a compression test?

Unless you are trying to ride at max speed at idle, the idle mixture will do nothing to effect operations at or near WOT. What jets do you have installed and what position is the needle?

Almost 15k. Had it at 13k 1 year ago. I haven't cracked open the carb. Its been running good ever since I got it.
I've just been messing with the idle screw around low rpm and backfiring.
Read the screw will help a tad to the main jet. Just feeling it out and seeing what difference does it make and practicing before the jets I ordered from here come in.

Quote:

by: justin_o_guy2 Posted on: 10/10/17 at 14:44:15
How big are you?
Got a windscreen?
Bags?
Drag bars or buckhorns?
And what size rear tire?
How it's jetted matters.
Speedo is driven by the transmission.
Designed to Report the speeds that a given RPM in a given gear would create using the OEM gearing and the rear tire circumference. They usually report a higher than accurate speed. By replacing the tire with a taller sidewall they are pretty close. Changing the front sprocket diameter to rear sprocket diameter ratio and you get higher speeds without the speedometer knowing about it.
The low horsepower motor can only shove so much stuff down the road at speed. We do some gearing change not for speed, but to decrease the RPM at highway speeds.

6th 190lbs. No bags on right now. No windscreen either.
Drag bars. Stock tires. Its actually a 17/41. I've read some on here ride at 80-90 mph. I just wanna get up to 70-80 and hold it there.
It hiccups for a sec at 75 and then I back off at to 70.

Quote:

Posted by: Dave Posted on: Yesterday at 03:42:04
Yep......use a GPS or PhoneApp to check speed, as your speedometer doesn't read correctly once you start fiddling with the final drive ratio (pulleys or sprockets). The stock 23/68 gearing is 2.9565, your current 17/43 gearing has a ratio of 2.5294. That is a change of 16% - so ignoring any speedometer error you may have........a speedometer reading of 70 mph will now be a ground speed of 81.2 mph.

And.........with the current gearing you have it is very likely the engine can't wind up enough to get your top speed in high gear. The 25/65 gearing I have on my bike has a ratio of 2.6000. I have a modified engine and I can't get to my top speed in high gear - and neither will you. If I want to go "full speed ahead" I have to do it in 4th gear - but the taller gearing allows for very nice highway cruising in 5th gear, as my engine is only turning about 4,000 rpm at 70 mph.

That's sounds like it could be that and I don't like it haha.
I really should open up the carb and go up a size little by by little. This bike came from Illinois and then Ohio before that so I wanna assume that the main jet is on the smaller said because of the weather. What a jet kit that's tuned well get me another 5-10 mph?

Thanks to all of you that replied :thumbs up:

Title: Re: Bike won't go past 75m even with sprocket chan
Post by batman on 10/12/17 at 17:59:19

Stuckin texas, The only thing that will increase your top speed is if your motor makes more horse power,changing to your lower drive ratio harms your chance of that being possible .A stock motor produces 29 hp at 5400 rpm at 85mph(about) but your bike is trying to do it with a little more hp ,I would estimate with your muffler, a well tuned carb an low resistance air filter you would make about 31 hp,which would raise a stock bike's speed to about 87-88at 5600rpm with STOCK gearing.With your gearing your bike going 85mph has a reduced motor speed (by 14.5%) of 4960 rpm and is therefore only making about 24.5 of it's 31 hp and 4.5 hp less than a stock motor and stock gearing ie .It won't ever get there! Lower gearing such as you have saves gas, and has enough power, at more reasonable speeds like 55-65 but will not make your bike faster. rejetting your carb won't produce anything close to 5-10 hp ,maybe 1.

Title: Re: Bike won't go past 75m even with sprocket chan
Post by justin_o_guy2 on 10/12/17 at 18:24:31

4C5355524F4879497941535F14260 wrote:

I didn't type the questions out of curiosity.

Title: Re: Bike won't go past 75m even with sprocket chan
Post by mpescatori on 10/13/17 at 00:10:14

Stuckintexas.

A GPS phone app will require a phone stand to clamp onto the bars.

For that kind of money you might as well buy a $10 bicycle speedo and use the front wheel to determine speed.

http://https://i5.walmartimages.com/asr/47998bf6-b98f-444a-bb48-a7ff0db198b1_1.c1289544c879b4eeaad392634fa4d154.jpeg?odnHeight=450&odnWidth=450&odnBg=FFFFFF

Waterproof Digital LCD Cycle Bicycle Bike Computer Odometer Speedometer Cycling

https://www.walmart.com/ip/Waterproof-Digital-LCD-Cycle-Bicycle-Bike-Computer-Odometer-Speedometer-Cycling/153760173

I concur with most explaining how longer gearing will NOT give more speed - only better mpg...
...unless you convert the bike into a "Bonneville Salt Flats" monster... ;)

Texas' quickest Ind...Savage ?

http://2.bp.blogspot.com/-KGCOjmGdIRQ/Tlvl37Y9DEI/AAAAAAAAVaA/UN8mrOwB4WA/s400/suzuki_tempter.jpg

http://bikes-and-nuts.blogspot.it/2011/08/suzuki-tempter.html

:D

Title: Re: Bike won't go past 75m even with sprocket chan
Post by batman on 10/13/17 at 08:00:54

Stuckin Texes, the best fix for your plight would be to change your front sprocket to a 15 ,that would give you a 15:43 ratio of 2,866 ,allow use of your present chain,and allow you to reach normal high speeds(80's),and save 1-2 mpg. Speedometer error (3.25% ) could be ignored , as they generally read high with the stock rear tire anyway.

Title: Re: Bike won't go past 75m even with sprocket chan
Post by cygnet on 10/15/17 at 09:24:27

I have the kaw front pulley on mine, I can get 145 kph any time as long as there are no big hills and the winds arn't blowing 60k. Everyone is right we just don't the HP to go faster you can only get so much out of 31hp, in fact I'm impressed how well it does on such little power a highway bike it ain't .

Title: Re: Bike won't go past 75m even with sprocket chan
Post by justin_o_guy2 on 10/15/17 at 09:28:48

He hasn't responded to the questions that would allow us to make a reasonable guess as to how fast it could go. If it's dragging a half sheet of plywood down the road, it's not gonna break the sound barrier.