XJ650 Maxim making odd noise when hot

I've noticed when my '82 650 Maxim gets fairly hot, usually when I have been riding for 45 minutes - 1 hour it starts to sound a bit different from the exhaust, and make a kind of harsh sound when under load, like when it's pulling up through a gear. It's a bit hard to explain, there is no obvious backfiring or loss of performance, it just has kind of a harsh sound to it when it's hot, and it returns to normal every time I start it cold. It also seems like there is a bit more noise from the top end, like valvetrain noise when it is that hot, but that could be just me? Could it just need a valve adjustment? Just found it odd that performance doesn't seem to change when this happens

 

I just found something in another thread that may be helpful, it seems i've been shifting this bike a bit too low in rev range, i've been making regular upshifts around 5K RPM where people are saying to shift around 7K. Have I just been making the engine work too hard by shifting too soon, causing it to run too hot?

 

I wouldn't say that 5k is too low to shift, but it certainly likes to go higher in the rpm range. These engines love to wind up.

When is the last time you changed your oil?

 

first off check the valve shim clearences .
what are you basing getting hot on? are you using a temp gun?
7 to 9 k shifts are ok but hardly the norm unless you just like to wind it up. shift points depend on what speed you are looking to get to , a rhythmatic thing
if I shifted at 7 to 9 k I would end up going over 75 to 95+ mph with the final shift
just make sure you do not lug the motor

750 shift points

550 shift points


edit to correct pic

 

I usually shift around 5. Check to see if either of your heat shields are loose.

 

What does it matter when you shift??? You need to follow what XJ550H says , good chance you have tight valves , and agree did you use a heat gun ..or are you basing it all on feel? Remember a clappy valve is a happy valve , when they stop making noise is when bad things happen. These bikes are cooled 2 ways by the cooling fins and the oil , so yes these engines have some noise to them .

 

5th to 6th....??.....is that a euro model thing ??

Never knew I had a 6th gear.....

 

My first bike was a Kawasaki KZ400.
It had a 6th gear and I still find myself trying to find it. Habits did hard.

 

If you have to ask "could it need a valve adjustment" - checking valve clearances is probably the place to start. Even if you have never done it, you can do it. I was very intimidated the first time, now, thanks to the information and experts on this site, while a nuisance, it is easy as pie to check every spring.

The first time I checked mine, it had been 20k since the last adjustment, and a couple were really tight. Glad I checked!

And yes, it got noisier on the top end after bringing them all back into spec.

I also recommend buying a cheap infrared heat gun. I got one on the auction site for about $10 shipped. It came from Hong Kong, infrared is misspelled, and the directions are in cryptic English, but it is accurate enough for this use.

 

If you have a 650 or bigger, you don't. But if you have a 550 like some do, then you have a 6th gear.

 

I have been looking for that 6th gear now for 35 + yrs.

So, it is not there.

Now I can give my foot a rest searching for it all this time......

 

The XJ 550's have 6 gears and a chain drive, the rest of the bikes with shaft drive have 5 gears.t up to us some how
Yamaha had to make it up to us some how


my error on the upload had 2 pics of same thing

 

Now I am really disappointed I don't have 6th gear...I could have gone that much faster....

 

Actually looking at these shift points, I find hard to believe that I would shift a such low miles/hour points......they seem very low & unrealistic to me......

I am in 5th gear at 37 mph........hard to imagine that

 

5th gear at 37mph is not right at all, on my 650 I'm at 35mph, 5K RPM in 2nd gear

 

125 is too slow for you?

Seriously though; 6th would be an overdrive (keeping the stock ratios in mind). I'd be nice for fuel economy (50+ MPG sounds good), but wouldn't provide more top speed. The top speed is pretty much limited by a combination of horespower and aerodynamics. Put a stock XJ drivetrain in a streamliner and she'll likely flirt with or exceed 200 MPH.

The recommended shift points are to maximize fuel economy without putting undue stress on the drivetrain (by shifting too soon).

 

Last changed the oil about 3.5K miles ago, I'm sure could probably use one again soon. I'm basing the temp on feel I do not have a temp gun but I do need to get one. I'll check my valve clearances to see if that is the issue, maybe it's normal for these engine, maybe I'm just crazy? I'm still really learning the finer details about these bikes, I don't have any point of reference as my 650 Maxim is my first motorcycle

 

Another item that can cause hot running is a lean mixture or floats not set correct...what do the tips of plugs look like?

 

Again, they just seem so low ..that's all.....I just can't see myself in 5th at only 37 mph.....in most situations, I am either in 3rd or 4th at that speed...

 

I do not think yamaha would endorse shifting at redline but you can, there is no right or wrong shift points , unless you shift so soon the motor starts lugging.
I actualy looked at my tach yesterday when shifting and found I was shifting around 5 k.

 

Thats seems to be where I shift as well.
Assuming my tachometer is even remotely accurate.

 

I'm in 4th around town most of the time; 35-40 MPH.

 

I shift at around 5k when riding "sedately", 7k normally. But... To be fair, I tend to ride my 750 pretty hard, as she's just so happy from 5.5-7k. I can't get past how quickly the bike goes from "This is nice." to "Weeeeee!" At 5.5+

Shifting at those ranges gets you going really fast in a hurry.