The Yamaha Road Star Warrior Forum

I've had High Compression pistons installed and now my tank goes on reserve at 110 kilometers or 70 miles! It shouldn't be that bad should it??

 Thanks anyone for any info on this,

Bobby Boy

I have just installed pistons, cams etc ..Speedstar kit  and on a day with mixed driving got 109 miles before fuel light...better than ever ! Is your bike running very rich ? You may have to lean it out some with your PCIII or ecu.  For reference I'm about 240 lbs and that is with no faring.

Any chance that you are reading miles instead of kilometers?  Just asking?

only if the person who put the pistons in screwed something up,  Compresion ratio should not change oyur fuel map

It doesn't usually take too long for the new piston rings to wear-in so maybe your mileage will jump up in a few days.

You can check your exhaust and your plugs to see if their color and condition indicate running rich.

If you use the PC3USB and installed the accelerator pump function, disable it.

http://www.powercommander.com/powercommander_iii_usb/powercommander_general_downloads.aspx

Thanks for that idea, but my speedo is in kilometers. Also, now my top end is not quite 180 kms/hr! Before the upgrade I was doing 190 with some left over! Shouldn't I be able to reach the same speed, at least, and at a lower rpm?!

Thanks Arizona,

I haven't thought about checking the plugs yet as I keep taking the bike back to let them do it.

My latest top end speed also is barley 180 kms/hr! I was able to make 190 before the upgrade with some left over!

Bobby

I get better mileage since I've fitted HC pistons. I did have it re-dynoed though. As for top end I now hit the rev limiter in top even quicker than before and the accelleration is much stronger.

Was gearing changed?  Yes, you should be able to reach the same speed, but it would be at the same RPM, not a lower RPM.  Racers often install shorter gears for better accelleration.  The shorter gears will often cause cruising fuel economy to suffer, as well as, top speed.

If you're red-lining the tach at 180 kms/hr now where you used to hit 190kms/hr with space to go.  Either you're missing an upshift, your gears were shortened, a smaller drive pulley installed, or a larger sprocket was installed.