Looking for more speed from a sprocket

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cutlass400

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I'm lookin for more top end speed from my 82 xs400sh and was wondering which sprockets people have tried and how much MPH they gained. I don't mind sacrificing low end for some more speed. Also are these bikes safe at higher speeds (over 75-80 mph).
 
XS400 Maxim(mono shock rear) here.. I hit 75 or 80 at least once a day when commuting. No head shake, no wobbles, changes lanes and swerves nicely... but that may be the monoshock?? Considering its a 30 year old bike this thing handles amazingly.
 
You can also change the primary sprocket and achieve the same results for a cheaper price,and change it back and forth easier for different uses,such as highway and street use. The front teeth equal about 3 teeth on the rear and don't require as much chain adjustment as the rear. lha
 
I would say 75 -85 MPH is reaching the upper most 'comfortable' limits of these bikes. I haven't changed the sprockets on my bike but have thought about it. I enjoy the 'torquey' feeling and understand these bikes were made for higher rpms. My bike smooths out @ 7000 rpms and I dont go any faster than 85 MPH( at least not yet...maybe 'do the ton' one day). I think I will leave it as it is for now. Pretty sure you can run your bike 75-85 MPH no problems.Enjoy & be careful.
 
If you want to cruise at higher speeds get a bigger bike. The XS400 was not really designed to run 100 mph all day long.
And if you did run that fast for long it will tire you out much faster than a larger heavier bike.
When I want to travel fast and far I ride the Harley. It handles the high speeds much better.
Leo
 
I've never had any issues running at WOT for extended periods of time. With the right equipment (i.e. seat and grips) you won't get too tired either. I've toyed with the idea of going one up on the front though.
 
I have a '77 XS400 and have gotten to 105 before and it seemed pretty smooth considering it's age. I did notice that when I dropped my front forks through the yokes a couple inches I would get a death wobble sometimes. Needless to say I returned them to their original height.
 
cutlass400 said:
I'm lookin for more top end speed from my 82 xs400sh and was wondering which sprockets people have tried and how much MPH they gained.
Click to expand...
I'm looking into the same thing. There's quite a bit elsewhere on this Forum.
Check out these 2 threads for others' input:

http://www.xs400.com/forum/showthread.php?t=4982
http://www.xs400.com/forum/showthread.php?t=7592&page=2
 
Like I've told people before,the easiest way to change the gear ratio of any bike is the primary sprocket. Usually you can change it,adjust the slack,and have it ready in about 30 minutes,and they don't cost nearly as much to have an extra or two on hand. On my Dt400 dirt bike,I have a 14,15,and 16 tooth sprocket for changing ratio quickly. lha
 
There is one thing to remember on adjusting sprocket changes, you can go too far.
Your bike has alimited amount of HP. This HP can only pull a certain ratio before you start to lose top speed. Do I now just what your bikes max ratio is? No. All bikes will vary some.
You can gear your bike high enough to go a possible 125 mph if you have a long enough place to get there. Like the Bonneville Salt Flats. Where you have very long straight ways to get high top speeds.
On the roads you normally drive you might get a 1/2 mile straight. Those gears for ten mile runs won't reach very high in 1/2 mile.
You need to figure out the perfomance you need verus the performance the XS400 can give. Smaller bikes can't give you easily abtainable high speeds of larger heavier bikes.
If you can't be content with the abilities of your XS400 then maybe you should get a larger bike.
Now If you want a few lower rpms at highway speeds then swapping the sprockets is a good way to do it.
I have tried several different sprocket combos and have found that two or three off the rear is about the most you need. More and you lose to much low speed performance.
Makes them a bit of a dog around town.
Leo
 
If you google motorcycle gear ratios to speed you will find many charts that you put in the ratios of your bike, primary, transmission and final drive and tire size, they tell your speed at different rpms.
You can swap numbers around on the sprocket sizes and see the speeds you will get.
These figures are just on paper, your results will vary on your bike.
On my bike the charts say I should get 127 mph at redline in high gear. I doubt it can pull those gears that fast with the power the bike has but runs at much less rpms at highway speeds.
 
XSLeo said:
I have ... found that two or three off the rear is about the most you need. More and ... Makes them a bit of a dog around town.
Leo
Click to expand...
Sounds right. We've determined that since my dohc Maxim only has a 5 spd, Yamaha has already reduced the rear sprocket down to 35T (from 39?) to keep the rpm at 6,000 at 60 mph. My only option appears to be to increase the front from 16 - 17T.

Several guys with the lower powered SOHC have been able to reduce their 60 mph to as low as 4800 and still be satisfied with low speed performance. So I should be okay losing 500-600 rpm at 60.
Presently, I can cruise down the town's main street at the speed limit in 4th gear and, without downshifting, can accelerate adequately enough to keep up with any car. So with a 17T front, I might be able to choose 3rd instead of 4th to cruise through town. Likely at a slightly higher rpm - which, if anything, will mean quicker acceleration without a downshift. So it should improve driveability on 2 fronts.
 
all 82's are 6 speed? mines stock... I dont got much power left in 6th I get 130kph (strait line no hills).

stock sprockets Goes just as fast in 5th

K&N and mufflers and one jet up on mains should help a bit.
 
domains said:
all 82's are 6 speed? ... Goes just as fast in 5th
Click to expand...

I don't want more top speed - I haven't been over 105 kph (65) yet and may never. But I want less buzz at 98 (60). Yamaha made 3 different engine/tranny combos:

The sohc "Special" with 6 spd. tranny - 27 hp (per Bikez)
The dohc "SECA" with 6 speed tranny - 38 hp (per xsrider)
The dohc "Maxim" with 5 spd. tranny - 38 hp (per motorbikes.be)

I have a Maxim - a way for Yamaha to offer the dohc engine at a lower price point than the SECA?
 
bentwrench said:
are you sure your speedo is working right? That speed seems too low with the sprocket's you're currently running...
Click to expand...
I've wondered that. All I know is that the readings are consistent. I took note again today. At 80 kph (50), the tac reads half a hair under 5,000. At 100 kph (62) it's a full hair over 6,000 rpm.

One or both of the gauges could be off, or maybe the new tires I inherited are not factory specs. If the rolling circumference of the front tire is larger than spec (while the rear is not) the speedo would read low. If the rear tire were smaller (while the front is not) the tac would read high.

I'm going to find and install a 17T front since, regardless of whether something or other is off spec, I want to loose the 500 rpms.
 
My bike, a 1977, hits 80mph in fourth gear but will not hold that speed in fifth. I thought it was because I am a bigger guy. I weigh 275 pounds and I thought the bike just didn't have the power.
 

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