Maximum sustained safe cruising RPM?

[79xs]

I'm pretty new to the XS650, but have a bunch of experience with antique bikes. I recently got a 1979 XS650, which is my 'new' daily driver. Its mostly stock, and only has 2,900 original miles, and I am the second owner.

When going down the highway around 70 mph, the bike is cruising at about 5,100 RPM. I think the bike has stock gearing (based on counting teeth and the previous owner telling me so).

I'm pretty young, so I dont mind the vibrations, I just dont want to hurt my motor. This seems like a lot of revs for a 30 year old bike. This would destroy one of my old Harleys or BMW R75 in no time flat...

I ride with my girlfriend on the back pretty often, so I do not want to gear it down more than 1 or 2 teeth on the rear sprocket... in fear of the bike being too slow around town with her on the back.

Is it safe to run these motors at 5,000 RPM for 30 minutes or more when going down the highway??

 

[XSLeo]

Your old Harley had a redline of 5000 rpms, big twin anyway. I don't know about the Beemer. The redline on the XS650 is 7500. So 5000 rpms is well with in the redline. I'm not sure just what the rpms were but I spent 5+ hours at 80-85 mph with no problems. I think the bike handled it better than I did.
Riding two up the stock set up should be fine. You might try a 32 rear. This will drop the rpms about 200 at 60 maybe a bit more at 70.
The 32 will take a bit more clutch to get moving but once up to 5 or 10 mph it will be fine.
Leo

 

[azman857]

I just installed new sprockets (stock 17 front and 32 rear) and new chain. The 32 rear did take away some acceleration off the line and cruising, but it's no slug. Like XSLeo says once your going your OK. I weigh in at 250-260lb so I'm no lightweight.

 

[hamamatsu]

I have spent many 350 to 400 mile days on my XS650H riding with my son-in-law and his 1200 Bandit. Needless to say the old XS650 had to run hard to keep up with the Bandit. The only problem I encountered was double vision on my part. You should be ok, just keep good oil in the bike and change it often...it's cheap insurance.

 

[Hairyblackdude]

I never had an issue with my bike until I started riding it to work.. A good 20-30 mins straight of 55-60 mph cruising.. I felt like I was KILLING the bike.. Id always try to shift into the non existant 6th gear..

Dropped the rear sprocket down to a 30 tooth.. It was a little silly how much smaller the new sprocket was compared to the stocker, but after using it-- What a difference !!

Probably the best thing I did for my bike.. I can cruise at 75-80 mph comfortably without getting vibrated to death or feel like the engine is killing it to stay at that speed.. This translates thru all the gears, I can do 45 down the blvd in 3rd gear without making alot of noise.

It also lets me cruise around a parking lot in 1st gear without having to work the clutch so the bike doesnt lurch when I give it gas etc..

On stock gearing, alot of times in parking lots or shopping centers, I found my speed to be too fast for 1st & too slow for 2nd.. New gearing is awesome & in my opinion one of the best things you can do for these beasts!!

I didnt really notice any difference in acceleration- but Im not one to really crank it either.. I only do it when my friend on his Z1000 rides with me- trying to keep up !!

 

[79xs]

I also "feel" like I'm killing my engine, especially since its a 31 year old bike.

BUT, I'm not sure if cruising at 5,000 rpm for extended periods is ACTUALLY bad for these bikes.

It seems silly to me that Yamaha's most popular bike for 20 years was not designed to be ridden on the highway the way it was built at the factory...

So, is 5,000 for 30 mins actually hurting my motor, or is it just hurting me??

 

[blackbetty]

I was honestly nervous to take mine on the highway at all.....you get moving and that engine felt like the head was gonna pop in your lap.

I am rebuilding it now so hopefully things will be a little better; I have it geared 17/32.

 

[pumps]

You're not hurting it. Like has been said you're no where near the redline. It's a 360 degree parallel twin and it's gonna vibrate. Nature of the beast. There are a few things you can do to minimize it. Make sure your dampers on your bars and footpegs are in good condition. Carbs tuned and in sync. Some guys put stuff inside the bars. It's the only motorcycle I have had that will go backwards on the center stand when revved. There's probably more that I have forgotten.

 

[xHolepunchx]

Not saying that my results should reflect anyone else's, but I picked up a slightly leaky motor from a '78, unknown mileage, not rebuilt, but freshened up pretty good before dropping it in my bike. I did about 4000 miles on it this summer. With the exception of having to change/top off the oil often. Almost all of my riding is at 70-80 mph on the highway sometimes for 2-3 hours at a time. I weigh 215lbs and sometimes ride 2 up with my girl. Ive learned to believe that it's not going to explode under me, makes the rides that much more enjoyable.

 

[XSLeo]

A bit of highway use is probably good for the old girl. Gets the crud blowed out.
Unless you suspect engine trouble high speeds won't hurt it.
I have found that having the bike in good tune and the carbs synced will help vibes the most.
Leo