60mph top speed?

I got an '81 XJ 650 Maxim a few months ago, so that's fun. But after reading some posts on here it seems that the max speed is significantly less than it should be.

In 5th gear, I can easily get it up to about 55. After that though it seems the redline/power drop is around 58mph. There is no tach on the bike so I don't know the exact engine speed. I can't really think of a good reason that I'd be getting shorted so much on the top speed. Any ideas?

 

Unless your clutch is slipping (which it could be) you aren't anywhere close to readline in 5th going 60. How many miles? Have you adjusted the cable? replaced the clutch?

Are you sure you're going 60, and that your speedo is accurate?

Do you know what redline is? It's 9500 rpm Do you know what that sounds like?

You could have mixture issues at the top end. Any intake mods? Pod air filters? Any other mods besides the lack of a tach?

Have you checked your valve spec or compression? Cleaned the carbs? Are you sure you're running on all four cylinders?

How long have you been riding the bike, and what did the previous owner (PO) tell you? How much of it do you believe?

 

There are pod filters, hasn't been rejetted. Would that make that much of a difference?

The carbs are clean, but I haven't checked compression or valve spec.

The clutch doesn't feel like it's slipping. And the speedo is accurate, according to various radar signs that've been posted in my area.

As far as the redline, when I bought the bike there was no tach so I am not fully sure of what the 9500RPM redline sounds/feels like. But there is a definite power drop around 57 or 58, and the engine starts vibrating in a way that i can't imagine being good.

 

Your pods with no re-jet could be contributing to the problem. My bike has a "vibration zone" from about 4000 to 4500 rpm, then above that it's smooth as glass. Maybe you're hitting the same vibration zone and you're mistaking that for the red line.

 

I should probably get a tach and be sure.

 

Yes, pod filters without any other intake changes will make your bike run lean. That's a fact. Tuning for pods is a whole other discussion, and you should search the website for advice on that, it's not cut and dry and there is no formula, only experimentation. Is the exhaust stock?

Since you're new here (post wise), welcome to the site. What maintenance have you done on the motorcycle and how many miles does it have? You want to make sure it's safe to ride over 60 (or at all) wrt brakes, bearings, and tires.

You should check your valve clearances and compression. You could burn a valve if they are out of spec, and if your compression is bad nothing you do short of tearing down the engine will fix your running issues.

Getting a set of stock gauges definitely helps with tuning although it's not required.

 

Thanks.

The exhaust is (i assume) stock 4-2.

I did an oil/filter change a few hundred miles ago. The odometer reads around 7k but I have a hard time believing that. The previous owner didn't have the odometer on the bike when he sold it to me.

There is an oil leak that I plan on looking at more over the winter.

I rebuilt the front caliper so both front and rear brakes are in good working order. Tires are good. Haven't noticed any bearing issues.

I will need to borrow the compression gauge from a friend to check the compression, but that shouldn't be a problem.

 

The big problem with pods seem to be that it causes air flow to become extremely turbulent, which these carbs don't deal well with. That, combined with perhaps low compression and very dirty carbs, might be what you're dealing with.

Are you sure it's firing on all four cylinders? Ride it and get it warmed up, and then spit on all four headers. If any of them evaporate significantly slower than the others, you aren't firing on it.

I believe it has been reported by some that pods might be significantly more usable if, instead of being put directly onto the carbs, they have airbox boots put between the carbs and pods--that allows turbulence to be smoothed out. (The best option is to get a stock airbox and get your bike back to stock setup--pods are a bit of a nightmare on this one.)

No matter what, though, I'm sure you need to have your carbs cleaned. Sounds like your main jets are completely stopped up.

And unless you're Bigfitz and have a perfectly tuned bike to the 9's, the XJ engine has a vibration zone. On the 650, that's usually between 4.8 and 5.2 on the tach. The better in tune the bike is, the less noticeable it is. And 58mph should be right around that zone, so that matches perfectly.

(You are going to get an entirely new bike when you just do the basic maintenance. Prepare to be blown away.)

Good luck.

(Edit: by the way, I've got some spare airbox boots if you want them. Sell 'em for $20+shipping. Try and confirm what I wrote, as I only remember reading that somewhere in passing some time ago, never put or seen pods on this bike myself.)

 

CHECK YOUR VALVE CLEARANCES.

Out of spec valves will throw off compression test results; and you can't properly set up your carbs until they're IN SPEC.

And I'm not the only XJ owner whose bike is properly tuned and thus, smooth.

 

anyone have a good tutorial on getting valves to spec anywhere? or should i just be searching around?

 

The guy who just responded to you, bigfitz52 wrote a How-to on that (and many more very important topics). Look for it in the FAQ Suggestions.

Also, get a shop manual. The how to is great because all of the high quality pictures will instill a sense of confidence your first time, but a proper shop manual is a must for maintaining these old bikes.

 

I filmed the process of adjusting valve clearances, among other things. Unfortunately, I put off the editing process for a while, and my laptop was just stolen... And I literally just sold my bike 20 minutes ago.

Though she's cute, and I did get a date out of it. Maybe there'll be a video yet.

 

Here's what you're looking for: http://xjbikes.com/Forums/viewtopic/t=1 ... art=0.html

 

Now assuming you get everything checked out FIRST (valves, clean the carbs, compression, firing on all four) you CAN figure out what the powerband of your bike is without a tach. Assuming you clutch doesn't slip, of course.

ONLY ONCE EVERYTHING CHECKS OUT, you should easily be able to hit 40mph in first gear and 60 in second BEFORE you hit redline. If the bike can't handle these speeds in these gears, post the results (example: bike gets to 30mph in first and stops pulling).

 

Is it safe to just pull throttle until it stops accelerating?

 

As I said, ONCE you know everything else is in order (valves, compression, clean carbs) and you know it will stop / handle properly (brakes, suspension, brake lines, tires), then yes. These bikes are very solid.

Besides, they don't really get FUN until you hit the poweband, which doesn't start until 7k rpm. If you are doing 60 in 5th gear, you are only flirting with 5k rpm.

Yamaha spec on the bike is 'cruising at 5k rpms'. This is just over halfway to redline - the bike should happily continue to pull, as you are aware.

Remember this is a small bore engine designed with a high redline. The bike, when properly tuned, will love doing 70-80mph in 5th gear, which is somewhere around 7-7.5k rpms.

 

Second on the question of "do you know what 9500 rpm sounds like?" You ain't at redline until you think the bike is about to explode into tiny liddle bits and you feel like there are demons shrieking in your ears.

 

if thats how your bike sounds at redline then you gotta fix something, lol.

9.5k is a beautiful sound to my ears