Bike redlines at 55mph in 6th gear.

dburrows6735

dburrows6735

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Hey guys and girls,

I have an 81' XS 400 special II. I bought it about a month ago and have been wrenching away to get it running. It runs fine except at high speeds. When I get to 6th gear at about 55mph my rpm's are at 7 and the bike lacks power to go any faster. It is not sputtering or missing, its firing correctly, I think. I can give more throttle but the really doesn’t want to go any faster. Also at this speed I hear a metal on metal slapping sound. I tightened the drive chain to a 3/4 spec and thought that would rid me of the problem but it is still lurking. So I really have two problems and don't know if they are linked.

Any suggestions? Clutch slipping (too much oil)? Timing, plugs? Small bike and this is as fast as I can go?

Thanks for any help.

David
 
Definitely not as fast as they'll go, same model as mine and I've been able to peg the speedo on I94; that was with the tach reading ~7.5k. Methinks they are related :D, but it COULD be something weird like the wrong sprockets on 'her.
 
It really did not seem like she has been opened up to change out any hardware. I had to remove the alternator plate to put a new starter in it about a week ago and everything seemed original. Any way I can check to see if they are stock?
 
It's probably not them, but you can check by counting the number of teeth on them. I think the ratio for them is in one of the books, but maybe someone else knows offhand. Far as I know, the only way they would be off by that much is if the PO replaced the front with one WAY too small and the rear with one way too big, just sayin'. Sorry if I'm not much help.
 
I would suspect a slipping clutch. What oil are you using? I just did a friends worn clutch a few days ago. When I test rode before the job it slipped worse as the rpms went up; i.e. no top end and the engine just keeps revving but the bike doesn't go any faster.
 
I'm using yamalube 20-50. Im not sure on volume per spec's, so I put in 4 quarts. My manual is in the mail some where so I could not reference that. The "specialist" guy at the parts shop told me to run that weight and volume. Sound ok?
 
The yama-lube sounds fine but not 4 quarts. My 79 holds around 2 1/2 get the bike on a flat level spot and on the center stand and just set the dip stick on the threads to get a reading. This could be your problem also could hurt the bike a lot!!!!!!
 
Cool, thanks. Now that I think about it I think I only put in three quarts, because I thought 4 was way to much.(I have a terrible memory). Im assuming that a 1/2 - 3/4 of a quart would cause the same slipping?

Ill drain it tomorrow and check and get back to you guys.

Thanks for the help!

I love this site!
 
4 quarts sounds like way too much; the case on my engine says 2300 cc. Completely dry I think the engine takes 3 liters.
 
@thiliiyr, a lot of things dont work on my bike including the speedo (any tips?). Between riding buddies and those handy speed trap auto guns I have my bike speed vs. rpms down.

@Houghmade, it says 2300ccs on my crank case, soooo Im a moron I should of known it means 2.3Q. I'm new to all of this.

Sorry to make this look like twitter Im just trying to reply to you both in one post.
 
Does the '81 have a glass reticule on the engine to check oil instead of a dipstick? You said the dipstick is missing? Did it snap off the cap? Usually if you lose the stick you've gone and lost the cap with it.

Have you pulled the speedo cable and assembly off the bike? You could try lubing the hell out of the cable; the manual recommends motor oil for cables, but 20w50 is really thick stuff.
 
I have a glass reticlue. It is showing all oil (glass totally covered). There are no real units of measure on the viewing glass, is it suposed to be half covered or what? I still have the cap it just looks like someone pried the dip stick off.
 
Do you have a center stand? Usually there are dashed marks next to those windows to show low and full, but if it doesn't have the marks fill it at least half way while the bike is on the center stand. If you don't have a center stand have someone sit on the bike and hold it upright for you on a level surface like a garage (improvise if necessary). Anywhere between half and just below the top of the little window is probably fine :)
 

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