another newbie question

I recently acquired an 83 xj750m. According to a Yamaha related web sight the vin # shows this to be the midnight edition. But a previous owner has repainted (poorly) the side covers and gas tank. What sets the midnight apart from a regular xj750 ? Also i read where they are suseptible to engine failure starting at 40,000. miles. Mine has 39,500. should i be worried? What do i need to do to prevent engine failure? Thanks in advance for any help

Norm

 

Midnight is mostly just a paint scheme.. More black than usual (engine, headlight bucket), and gold trim here and there.

As for XJ engines falling apart at 40K.... well, I guess you can make any engine fall apart at 40K (or much earlier) if you try hard enough. Sand in the crank works good for that... Also, if you never change the oil, I guarantee that it will not live very long.

Ok, seriously though... These motors are built quite well. Check valve clearances and change the oil frequently, and your Max will last a good long time, way past the 40K mark. My 750 just rolled over 50K, which is quite a bit for an air-cooled engine, but some folks on this forum have clocked way more than that.

 

If the midnight is all black then mine is not a midnight. The motor and exhaust have never been black. I checked the numbers on the frame and the engine and they match.
Here is where i got the 40k worry. Total Motorcycle Websight.
Their review:

UMG Says: Heavy, awkward four that was a bit off the pace but lasted for reasonable mileages. Camchain and tensioner usually went first, followed by the valves and pistons. Mileages varied greatly, although few managed more than 75 thou and most were in trouble by 40k.

UBG Says: Heavy, awkward and bigger capacity custom version of XJ650 which lasted for reasonable mileages. Camchain and tensioner went first, followed by the valves and pistons. Shaft-drive eases maintenance. Over-complicated digital dashboard can cause problems.

Not trying to be argumentative, just trying to figure out what i need to do to prevent above.

 

The best recommendation is to get your hands on a factory service manual. Then go through the "maintenance" section, item by item, LEAVING NOTHING OUT. Nothing. Do them all.

Then ride your bike.

 

Hey NORM, Welcome !!
There are a few chain guides that will dis-integrate STARTING at 40K, and definitely by 60+K. Preventing this is the dreaded case-split along with major overhaul, OR, run this engine and keep an eye out for a low mile $200 motor. I'm at 43K and have a 20K spare already.

These are heavy compared to WHAT 1985 "cruiser"??

Post-up your frame VIN and you'll get detailed info here.

 

how much does an older XJ weight? mine is a lean 480lbs

 

My 82 XJ750 Maxim weights about 493lbs.

 

Oh God! I am at 48k and in the hands of previous owners. At least there is no smoke or odd engine noises - apart from the clutch bearing - so hopefully shes had regular oil changes.

UK bikes seem to be of generally higher mileages, so the chances of finding a low miles xj600 engine are slim.

And welcome!!!

 

My vin # JYA22R007DA003965

 

http://www.xjbikes.com/Forums/viewtopic/t=14577.html

According to this ^ ^ ^
JYA. . . Japan Yamaha
22R. . . 1983 USA Maxim
007. . . a check digit
D. . . . 1983
A. . . . Japan assembly plant
003965. . . if the #'s started at 000101 then it's the 3864 th bike.