I commute with my bike to work...almost everyday..but not in the snow. I would like to be able to cruise more comfortable at 60mph or so, and not have my tach at 6000-6500. How can I do this without sacrificing power? Very limited budget.

 

Personal opinion and least costly, unless there are vibrations at that level that bother you, put some black tape over the tach face so seeing it won't bother you anymore. The engine is built to rev that high without problem and is probably in a good part of the powerband at that. You might be surprised to learn that a lot of engines rev fairly high at highway speeds. My Zephyr 550 will rev around 5500 at 65 or so. I don't worry about the rpm except at 4000 and 6000 rpm where there is an annoying buzz for a few hundred rpm (mentioned in the media road tests back in 90).

Otherwise the cheapest way is to go to the biggest front sprocket you can put on the engine. If at the biggest, the next lowest price change is to go to a three to seven tooth smaller rear sprocket.

I have an excel spread sheet I made up to do tire comparisons based on OD or circumference to find rpm at speed, but it has other possibilities and will work with up to six speeds. You key in the primary gearing tooth count, each gear tooth count, final drive tooth count, and tire diameter or circumference, then check speeds at different rpm and with different final drive tooth counts. PM me if you want me to attach a copy to an email.

 

[QUOTE=klx678;491865]Personal opinion and least costly, unless there are vibrations at that level that bother you, put some black tape over the tach face so seeing it won't bother you anymore. The engine is built to rev that high without problem and is probably in a good part of the powerband at that.



wow, it just seems like I am going to hurt it, I am not used to revving a 4 cycle like that. Is it okay to rev that high for long periods of time..say 15 minutes or so?

 

[QUOTE=10thmountainman;491866]hours thats not even a high rev in my opinion

 

i've had mine at 8K+ for the better part or an hour many many times...

 

I agree that 6000rpm for sustained periods isn't going to cause a problem. A smaller rear sprocket will help lower cruising rpm in theory, but in practice, the little 250 just doesn't have the horsepower to keep you at speed once you start climbing a hill or hit a headwind.
Horsepower peak is at ~8500 rpm, and in top gear, you need every one of those ponies.
I went with a smaller front sprocket. It *raises* cruising rpm, but it also helps keep me nearer the power peak on the highway without downshifting.

 

by how much did your RPMs go up at cruise speeds when you did this?

 

One tooth change up front = 7% rpm change (at the same speed)
14 -> 13 +7%
14 -> 15 -7%

 

If you have hilly terrian & put the 15 on, you will be shifting between 5 & 6th a lot, or maybe 4,5,&6th.

 

so basically if I cruise at 6000, my speed is about 60mph. If I drop to a 13 my RPMs would rise to about 6420 but I would accelerate quicker. On the other hand if I go up to a 15, my RPMs would drop to about 5588 but I would have slower acceleration.

Would adding a slip-on and rejetting get back the loss in acceleration?
Should I even be worried about the RPMs in the first place? A couple members are thinking I shouldn't be.
Would adding a slip-on give me the same feel a 13 would ?