First Yammy, need mo' powa!!

Hey, just joined the ranks. I just bought my first yammy, its a '81 xj650. I was looking for a bobber project and i talked the guy down to $525 so i snatched it. In town it does ok, but on the highway i realized this puppy does not like to go much 70mph, it will but screaming the whole time. I NEED MORE POWER!!
how can i sqeeze some more hp out of this thing? I found a MAC 4-1 but not much more. I just want to be able to go 70 without the bike sounding like its gonna blow.
Also i hear you have to tinker with the jets alot on these bikes, any truth. My other bike is a Harley so this is way out of my zone. thanks.

 

If it is tuned right that 650 should get at least 100mph unless you weigh 300#. Time for a tune up, carb clean and sync, new plugs. Is it stock of has it been modified with pod filters and exhaust?

 

its completely stock from what i can see. 100mph! the speedo only goes up to like 85mph. i am planning on changing all the fluids, plugs and filters and seeing how that affects it, payday is on friday tho.

 

I'm 212 and my 650 will do 100 mph. Doesn't take all that long to get there either.

Loren

 

the only way your going to get more power would be to swap to a 750 motor they dont make any performance parts for the xj 550 650 and 750 unfortunately. you might get a few more ponys with a 4 into 1 and jet it right with a k&n in the airbox but thats about it i lucked out i paid 500 for my maxim x wich is in a whole different league then the regular xjs performance wise. something isnt right if its having a hard time crusing at 70 mph

 

More like 115 if you wring it all the way out.
You didn't say, but if it's the Maxim 650,(a 16 inch rear tire) you can buy a 18 inch rim and gain about 8% "overdrive" to help calm the revs a little. You've got some work to do.

Welcome to the site - rear brake check !!

 

hmm, maybe i will just have to crank it and see. it just screams at 70 and sounds like its gonna blow, maybe im just used to that at 140 on the harley. Another question, what are some safe rev limits? it sounds loud but rpms arent at redline.

 

140 on your Harley? Some folks around here don't think Harleys can go fast. I may have opened a big can of worms with that! Welcome to the site and hope you can work out the issues.

 

"Cruising" RPM for an XJ motor is 5000rpm; they do run at 5000-6000 on the highway. You can't go by the sound, these are high-revving motors and it sounds like you're used to the opposite. Remember the 10K redline...

Properly tuned though, 100mph should be no problem, and as alluded to by others, they get there quick.

 

My 83 XJ650 Maxim has found the 100 mark a few times. does it pretty easily, too. You have a 9500 redline, and you're gonna be going waaaay over 100 to get there! these bikes will scream like the dickens, but they LIVE for the 5-6000 range. Here's where you're just getting into the power band, too. It WILL be a completely different sound than what you're used to. I' going through the exact opposite--I just finished a two-year rebuild of a 99 Intruder 1500. I'm still learning the feel and sound of a big-bore v-twin. Just doesn't sound right.... sounds like a couple of cylinders are missing. Oh, wait.....a couple of cylinders are missing--there's only two.

Funny, I must be getting more used to it, cuz I rode my 650 maxim last night and kept trying to shift but it wouldn't go. I had to count several times to make sure that was getting all the way to 5th gear. LOL

Dave Fox

 

Careful here. Harleys, like most modern day motorcycles, will go fast but they typically don't go fast quickly! A GoldWing will do 100 mph but an R1 or R6 will get there MUCH quicker!

 

if it is 8% that makes a big difference 7k would be a tad under 6500. big change from a harley that turns about 3k or so at 60

 

My '04 1200 sporty can go 120 easy, 140+ given the road is long and straight enough. But this is a sporty i spent the last 6 years building too.

I guess i will just have to get used to reving it higher and make this kitty scream instead of purr like im used to. still gonna need a little extra power though.

 

i hear what you are saying about the screaming at 70mph at 6K

Ive been asking around trying to find out if the xj1100 final drive will bolt on and change the gearing down a bit.

 

maybe the harley was on the back of a very fast tow truck

 

cold blooded.

 

Well, your Harley churns low RPMs @ 60-70 as it has tons of torque
The XJ high reving motor will pin the 85mph speedo in 2nd or 3rd gear on my 750
I top out around 115-120mph

Performance engine parts are not accessible on the market for these scooters...sorry

Best performance at reasonable cost is to do the following

Obtain a 750 Motor(if you do go sans airbox you WILL be doing YEARS of tuning)
Get some cleaned up carbs or parts for your current set up
The 18" rear wheel is a great idea as well.

AND start reducing weight, lol
The reduction of weight will get you up to speed quicker and will make your 500-600 lb bike a bit lighter

 

Well, you do know that this engine is meant to be ridden like a two stroke...

It's a real screamer and (when new) was tested to over 125mph!! You really have to rev them - 9,500rpm is where this motor produces peak power.

It was viewed as a negative at the time, but Yamaha wanted to beat the Z650 in the top speed stakes. So they made this lovely tourer into an intractable rev-monster - noticed that giant hole at 6000 yet?

You've either got to pootle along under 5000 and take in the scenery, or forget all the mechanical sympathy you've learned over the years and just hammer it!

Nige

 

Just sell that one and get an 1100cc, FJ or XJ. Because you can't beat CC's.

 

I forget what the exact years are but every vehicle in the US in the early 80's pinned the speedo at 85mph and has a big standout number for 55mph. It was some BS legislation at the time (i was in diapers, this is knowledge the sages have handed down)

I dunno what the gearing on a 650 is like but I know in top gear my 750 (w 18' wheel) does about 11 or 12 mph per 1k of rpms. So when I coax it up to redline in 5th I'm doing around a buck twenty. I've gotten her doing 110 up a 6% grade.

As others have said, with an old bike like that it needs to be recommissioned properly to make it closer to new. It's got plenty of power if you free up it's true potential.

"Sitting kills bikes, maintenance tip #1: RIDE IT"
-MB-

 

I like having the lower speedo... it makes it less likely that I'll do something really dumb on it. Hell, that's why I ride a 550 in the first place.

 

Believe me if you take the time and tune the bike you will be suprised at what it can do.

Thoroughly clean carbs, synch carbs, colortune and re synch carbs.

The difference between a fouled plug and a properly burning fuel mixture will be night and day on the bike.

This really isn't alot to do on a bike from the 80's.

Hit the throttle on an xj650 thats properly tuned and it will definitely throw you back and I'm no light weight.

 

I don't think anyone mentioned this, but a larger front and smaller rear sprocket will lower revs as well. Acceleration will suffer, but the same is true with using a larger rear wheel.

 

Full fluid and filter change, new plugs, valve clearances checked & shimmed and a proper carb balance would be where I would start. Know where you're too before you set off making too many changes. If your motor is down on stock power, trying to regain it by tuning is like ripping up $20 bills in the shower.
Stokie

P.S. Try rev'ing the nuts off of it right up through all the gears and only change up when you feel the 'pull' start to tail off - ignore the noise it makes. That may give you a better idea of it's top end.

 

XJ650's have no chain They are shaft drive.

 

Know the power of the dark side young Skywalker.

 

I commute on my 750 daily, 70 MPH is about 5500 RPM and it regularly sees 100+ MPH with no problem passing trucks. Something is wrong with your bike good luck they are great bikes.

 

Great bikes but something seems wrong on yours or ur just being too gentle with it.... get on her!!!