What is the SOHC 38hp XS400 0-60 time?

[stemloop]

Currently my 81 xs400 Special is in the shop. It seems like it might need substantial repairs, possibly a top-end rebuild. The mechanic was talking down how much I'd want to invest in it, saying, "You know, it's an old bike, small engine, people don't really want those, you wouldn't want to take it on the highway, etc." My take is (1) dude, your shop is focused on old bikes; yes I realize it's not a Norton but it's still a pretty cool bike (2) It's no less powerful- or actually more powerful- than modern 250-300cc sportbikes. In fact, it can do a 14.3 quarter mile time (http://www.motorcyclespecs.co.za/model/yamaha/yamaha_xs400 77.htm). Mine has the electric start removed but is otherwise no lighter than stock; I'm wondering what the 0-60 time is as well since I have more familiarity with that number.

Using calculators designed for cars (http://www.autosnout.com/Car-Quarter-Mile-Calculator.php, http://www.060calculator.com/) I'm getting a 0-60 time of 5-6 seconds- which is pretty quick I think!

(Note the first calculator that estimates 6 s 0-60 also produces a 1/4 mile time of 14.6 s, which is pretty close to the 14.3 s claimed by the website)

 

[xschris]

Most stock xs400's (391cc) make more around the 32-35 hp. The dyno test for the xs360 (358cc) was 27hp. The 400 does have a better cam but with only 33cc's difference in size 5-8hp is more believable. I did talk to a old yamaha mechanic and he said he remembers a guy put an 80's xs400 on his drag bike dyno back when it was new and it was around that area. Your 0-60 time will also depend on your weight as well as the bikes. Plus your ability to make fast shifts. My 80 that weighs under 300lbs ( lots of aluminum and titanium bolts and removed everything that I don't need to keep it street legal and safe) Is way faster that the other two stock xs400's I have the are closer to 400lbs.

 

[stemloop]

Most stock xs400's (391cc) make more around the 32-35 hp. The dyno test for the xs360 (358cc) was 27hp. The 400 does have a better cam but with only 33cc's difference in size 5-8hp is more believable. I did talk to a old yamaha mechanic and he said he remembers a guy put an 80's xs400 on his drag bike dyno back when it was new and it was around that area. Your 0-60 time will also depend on your weight as well as the bikes. Plus your ability to make fast shifts. My 80 that weighs under 300lbs ( lots of aluminum and titanium bolts and removed everything that I don't need to keep it street legal and safe) Is way faster that the other two stock xs400's I have the are closer to 400lbs.

Thanks for the reply.

First Id say if you are determining xs400 hp based on xs360 dyno, obviously you have to keep in mind 38 hp is quoted at the crank! So you can't really add like that. Also, those calculators are for flywheel and not dyno hp. I just want an estimate of what the bike is capable of stock, obviously such quoted times are somewhat of an upper limit using expert riders/drivers, so if you want a number relevant for comparison , you'd want something that was acquired using equivalent skill.