Red Line too easy?

[XJkid]

Not being a racer, I am not sure what would/could happen at red line. I understand that the engine could grenade, but my XJ can get there so easily, I wonder if red line is a no-go, or just a guide line. I don't plan on spending much time there, but if Galaxy can get there with no effort, is it safe to be there?

[DiverRay]

Some people here like to run the engine up, and some like me only do it now and then. The XS engine was so overbuilt that RC Engineering drag raced one for the year WITHOUT tearing it down below the jugs! So yeah, they will hold up, but then they are now 40 years old, so it would be ok to hit it now and then, but don't try to run it that high all the time. And yes, in lower gears you CAN go well beyond the red line....

[3Phase]

If it was safe it'd be called, "Greenline."

XJ1100
Peak HP == 95 HP @ 8,000 RPM
Peak Torque == 65 ft-lb @ 6,500 RPM

Somewhere after 6,000 RPM, the torque starts to drop as the engine begins to lose its lunch and has to fight harder and harder to make power. Running above peak torque for a long time burns more fuel that creates more heat to make less useful power that increases engine wear. As the cylinders heat up, more fuel will blow past the piston rings, washing the oil off the cylinder walls and contaminating the engine oil.

Do it!

[hamjam]

in the time spent on an XS11 i discovered they really like 5000rpm and are very comfortable there

[IanDMacDonald]

in the time spent on an XS11 i discovered they really like 5000rpm and are very comfortable there

I'd hope so, as that's where mine is 75% of riding (highway).

[BA80]

Can't count how many times mine has been completely off the scale. You really can't trust these tachs anyway.

I generally just go by feel.

[3Phase]

I don't plan on spending much time there....

Kid! It depends on the mechanical condition of your engine and drive train.
Man, I feel like I'm channeling Arlo Guthrie's Officer Obie.

Any engine may seem to run fine and make excellent power but it can have, for example, a damaged connecting rod bearing as my XJ11 engine did when I checked it. If we tell you, "Yeah, it's alright, go for it!" and you lunch the engine when you zip out on the highway to play with the big trucks you're a dead man.

Normally, excursions up around redline are safe if you know for a fact the engine is good because you or a qualified mechanic checked it and you're not just assuming it's good because, "It ain't broke yet!"

Continuous operation at or near redline is not safe so just because it'll do it, don't run down to Walmart for tube socks and beef jerky at eight grand in 1st gear.

[Bonz]

I haven't heard anyone say the valve train could be a problem past redline. Those are some big old valves in that head with 40 year old Springs. I'm not saying don't do it, because I'll run mine up to redline every so often but the acceleration tapers off in my opinion after 7000 rpm, just past the torque Peak. Sure, it's still accelerates but there isn't anything my 80SG gets used for that 7,500 RPM won't suffice.

It does nothing for me pushing it hard when I can pull in the garage and hop on a ZRX 1200 with 145 horses at the rear wheel in its modified form with an 11,500 RPM redline that carries peak horsepower up to 10,500 RPM. It has the XS covered in peak torque at the rear wheel by the time it is passing through 2,300 rpm versus the Yamaha Factory spec of 66 ft lb at the crankshaft at 6,500 rpm.

Sorry, I wax poetic on the ZRX too much. However I think it's a great bike that guys could consider as a second bike. They can be picked up for not alot of money and they modify to your heart's content. They are incredibly easy to maintain with much longer valve adjustment intervals and oil change intervals. Wiping down and lubing a chain every 300 to 500 miles is no big deal. In truth it can be stretched longer if on the road. In reality, with longer valve adjustment intervals and oil change intervals, you're doing those half as often so lubing a chain is a few minute job that you could spend 5 minutes doing 20 times which is less time than an extra valve adjustment and oil change you'd be doing on the XS in the same time frame.

[BA80]

With the stock final drive it's almost impossible NOT to hit red line in 1st and 2nd when you are on the XS hard. It can be real jumpy. One of the main reasons I opted for the 850 FD. Much smoother operation.

[Bonz]

I agree with you Greg. Having my current SG with the FD mod and riding the "new to me" SG with the stock FD, the stock FD makes on/off throttle transitions herky-jerky, especially at low speed. It's part the carburetors and just the way it goes. However combined with the stock short FD gearing, the combination gives that jerkiness.

[3Phase]

He did not ask if redline could be done, he said, "Galaxy can get there with no effort."

He asked if redline was safe and the only correct answer is: "No, it is not safe unless you know the condition of the engine and drivetrain."

Anything else is a guess and by definition is not safe.

Now, why someone would ask if it was safe to redline the engine in a motorcycle that, rain or shine, can run well over 100 mph with only a few square inches of rubber on the road is a better question but I don't really need to know the answer.


Bonz, I'm biased for KZ-wasakis. I miss my '81 KZ750 like you wouldn't believe, or maybe you got your believer fixed and you know exactly what I mean.

[Bonz]

Yeah, I really like Kawasaki's. I guess they have a bit more rough-and-tumble image from when I was growing up compared to the other brands. They sure stack up performance-wise although maybe fit-and-finish wise they aren't quite the level of others.

In redline discussion, why isn't the valve train mentioned when it comes to redline durability ? I would suspect issues with the top end before the bottom end, but apparently no?

[3Phase]

I can only go with my experience with these engines.

For me, the XS11 valve train has been bullet-proof, I haven't even tweaked anything related to the valves while running the engine. I bent a couple of valves on my first cylinder head through my own stupidity but I haven't repeated that learning experience.

The valves do affect the torque decrease after ~6,500 RPM that I mentioned after peak torque but I'm not The Professor and I'm not stranded on an island so I didn't explicitly mention Volumetric Efficiency and Pumping Loss either.

The biggest problem I have seen in three out of the four engines I was using or tried to use is bearings.

'80G: Some moron ganked the #1 and #4 connecting rod journals with the rod bolts and destroyed the crank and the bearings. I had to replace the crankshaft and all of the bearing shells.

'81LH: I bought the crank and case to replace the one in my '80G. I had to use and fit the '81LH crank to my '80G case when I discovered the main bearing shells were bad in the lower case half of the '81 engine because it had been scored by something at the factory before assembly and was scrap.

'79SF: No bearing problems at all.
#3 cylinder wall was rusted out from sitting for ten years in the salt air in Lompoc with an open valve so I bought a good set of used jugs and pistons.

'82J: #2 connecting rod journal and bearing damaged by who-knows-what. The rod bearing has been replaced and the journal polished by hand. I'm still praying for this engine and I for darn sure don't redline it!


Out of four engines, the only one that was safe to redline the day I bought it was my '79 Special, "Bush," but I couldn't have said that without guessing until I split the case and checked the engine myself.


Yeah, I miss my Kawasakis. I don't buy motorcycles to look at them, I ride them and Kawasaki's fit and finish was more than good enough for my KZ750 and my KZ440 LTD.

[Bonz]

Definitely, the riding is why we do it!

[XJkid]

[QUOTE=3Phase;499310]
Now, why someone would ask if it was safe to redline the engine in a motorcycle that, rain or shine, can run well over 100 mph with only a few square inches of rubber on the road is a better question but I don't really need to know the answer. [QUOTE]

That is the allure!

Now that my speedo is working again, although it is only an 80 mph, I was doing some simple math to determine top speed. Some spex I read said 133mph for the XJ. Looking at rpm vs. mph on the lower end of the scale, it would seem the top speed would be a little higher, but then there is higher wind resistance at top speed, so maybe it is correct.

My main concern being "at speed" would be wheel bearings. A catastrophic failure "at speed" would be catastrophic indeed!! I have attempted to check and re-grease the front bearings, but that is seemingly impossible. I could not get enough of the edge of the race to get it out.

On the final drive note, I have been thinking about doing the swap, but I am concerned about having trouble coming off the line, especially if my wife were with me. Does take-off smooth out, or do you need to bring up the "R's" and let out the clutch slower?