1982 Maxim XJ750 Are These Problems?

Well, my bike, xj750 maxim may or may not have a few problems, I was wondering if an owner or PO of one can tell me if this is normal since im new to bikes in general:

1.) Most of the time I have to use the choke to get her started, which is normal, but she stays in the 1000-1500 rev range, after about 1-3 minutes, the bike starts high revving to 2700-3000 rpm's and stays around there with the choke on.

2.) No matter what, I cant get past 75 mph, even going down hill, and I have a 750cc engine, so I dont know if thats normal. (I read a post of a guy hitting 90+ with a 700cc but he might of had a turbo or something) Also, I HAVE to keep the choke on while im on the freeway or I wont be able to go past 60 mph.

3.) At higher revs (6000+), it feels like like its misfiring. It doesnt misfire as much with the choke on. I dont know how a motorcycle is supposed to act at high revs, maybe its normal.

4.) If I pull the throttle all the way down, the bike actually goes slower. Not sure if thats supposed to happen or what, but I have to barely turn the throttle in order to accelerate faster.


What Ive noticed is that my plug on the far left (if im looking at the bike from behind) is always caked with black stuff on the tip, and trace amounts on the screw part. Also, my Battery warning light is always going on when I first start my cycle, it stays on for about 5-8 minutes, then goes off and sporadically turns on and off for minutes at a time. I checked my battery and its fully charged.


Any input would be great, you guys have helped me so much in my last post and I totally appreciate it.

Thanks!

 

Hey crimsonlung. The higher RPM with choke on is perfectly normal, as long as it comes back down to idle when you disengage the choke (which is actually an enrichment circuit).

A well-tuned 750 should be able to go over 100MPH... No turbo. The black spark plug indicates that #4 cylinder is running too rich, which is probably why the bike doesn't run so well... What do the rest of the plugs look like?

what, if any, work has been done to the bike, as far as you know?

 

Although it sounds like you have one plug that is too rich, you are getting starved for fuel (ie: your points #2 & #3).

So, like the rest of us, you'll have to thoroughly clean your carbs. I'm sure there will be tons of technical help chiming in, but it isn't nearly as scary as it sounds. Go slow, you'll learn a lot, and your machine will happily take you to over 100 mph (should you choose to go that fast) once you're done.

They're great bikes. The carbs need attention, but it is sooo worth it.

And about the 100 mph thing, I found a scary statistic last week : 80+% of motorcycle deaths are riders of less than 2 years experience. Aim to be a 20+ year rider like some of the folks here.

 

Another thought I've had about 100mph on my Maxim is that the bike IS 26 years old. It seems like it's in very good shape but why take that chance. I graduated the year this bike was made, and as Toby Keith says, "I ain't as good as I once was" and I'd hate to find out the hard way that my bike isn't either. I've had it over 80 though and that was enough for me.

mikeg

 

The stock speedometer on it only goes to 80mph max, so it can still go to 100?

The rest of the plugs have a little bit of crud on it, but not as bad as that one on the left.

Custom work Im not sure, but 4 my pipes are running into what looks like a single custom pipe on the right side, I dont know how the stock bike looks.

 

Well, the only thing I worry about is if a tire popped while I was going fast, but other then that, I feel confident I wont eat it on this bike. It just feels so sturdy and handles like a dream. I wont ever do any crazy stuff like standing up on my seat or popping wheelies (Which I dont even know if you can do on a XJ HAHAHA) But I am young (24) and I started on a 250cc and hated how I couldnt keep up on the freeway, got this 750cc next and I was thoroughly impressed at its power, but now, I want to try a 1000cc+, I guess I was just born with a lead foot.

 

I dont mind cleaning the carbs myself, one thing I am worried about, when I take things apart, I usually cant put it back together if its deep in there, do I have to unscrew alot of things? Also, I heard that I have 4 carbs, is this true?

 

Yep, you have 4 carbs. They likely need completely torn apart & cleaned, but it is not hard... you just have to be (a) organized (b) patient (c) thorough. The hardest part is getting the rack off the bike... well, ok, maybe getting the rack back on the bike... but actually cleaning them is a breeze.

Your plugs sounds like they are a little rich, if they are all black & carboned up a bit.. but that might be due to running it on the choke/enrichment circuit. Follow Rick's Old School Carb Cleaning guide in the How-To section. The group will then direct you to set your pilot screws 2.5 turns out from the bottom, run it, and then take good clear digital pictures of your plug tips & tell you where to tweak from there. You couldn't ask for more...

 

Chacal has a great post on carb cleaning with all the recommended tools and replacement parts to have on hand BEFORE you start. I recommend reading this post. The job is not hard but it is time consuming. He has all the parts and tools at prices that are a lot less than other places I have looked. Look for this post in the forum. http://www.xjbikes.com/Forums/viewtopic ... =next.html

It's a ways down the page.
Posted: Sat Jan 05, 2008 5:42 pm Post subject: Re: Idling at 3000 rpm (he asks sheepishly).

By the time you get to the 4th carb, it'll be a snap.

Best of luck and take time to do it right.

 

The stock speedometer on it only goes to 80mph max, so it can still go to 100?
[/quote]

With the gearing you have, you should be able to hit 130MPH if your motor is in tip top shape. Of course you'd never know based on your 85MPH speedo.

Even though the speedo will only READ to 85, the bike can certainly go much faster. I've got the same bike and some years ago before the tear down and re-build, i had it up past 120. I know this because I passed my friend who was doing 120 at the time.

I wouldn't recommend it as it's really not safe, but hey, I was invincible when I was 17, right?

 

Yeah I remember those days my Honda 750 would run 120, & I have driven 2 Peterbilts & 1 International that would go over 100. I am not sure which was the most hair raising 2 wheels over 100 or 80,000 lbs over 100 mph. Now that I am almost 52, 70-75 is enough for me on the street or highway
keep the rubber side down and the wind in your hair

 

Yeah I remember those days my Honda 750 would run 120, & I have driven 2 Peterbilts & 1 International that would go over 100. I am not sure which was the most hair raising 2 wheels over 100 or 80,000 lbs over 100 mph. Now that I am almost 52, 70-75 is enough for me on the street or highway
keep the rubber side down and the wind in your hair

 

Yeah I remember those days my Honda 750 would run 120, & I have driven 2 Peterbilts & 1 International that would go over 100. I am not sure which was the most hair raising 2 wheels over 100 or 80,000 lbs over 100 mph. Now that I am almost 52, 70-75 is enough for me on the street or highway
keep the rubber side down and the wind in your hair

 

Yeah I remember those days my Honda 750 would run 120, & I have driven 2 Peterbilts & 1 International that would go over 100. I am not sure which was the most hair raising 2 wheels over 100 or 80,000 lbs over 100 mph. Now that I am almost 52, 70-75 is enough for me on the street or highway
keep the rubber side down and the wind in your hair

 

As others have said, it looks like you have a mixed bag of difficulties. Could be that the enrichment valve on your #1 cylinder carb is not seating properly when you take the choke off. Could be 1 or more carbs need cleaned and the idle mix screw(s) readjusted. Could be that the carbs need all the above AND a good sync. Could also be that the rubber manifolds connecting the carbs to the head are cracked and leaking excess air (spray some WD40 on them to see if the engine RPMs change).
RE: battery warning light - is the sensor in the correct battery cell? The gauge is calibrated to read a certain voltage level as "good"; if the sensor is in the wrong cell the voltage will be off.

 

lmao. Thats the very first bike I bought. and I have to say it is so very possible to do 120 mph and even more if it is tuned and running right!

And I also have to say yes it is also very possible to do a wheelie with an XJ (I was 18 at that time). However I highly discourage it!!!
That is most definatley NOT how you want to treat that bike!
oh and one more thing.
It is great to be a confident rider no doubt. But don't you ever lose respect for that powerful machine. and never never NEVER ride like you wont go down. once you think that you have masterd riding and think you have it licked and you wont go down. YOU WILL and Hard!

there will always be some F%$# Tard not watching for you (or not careing that you are there).
or there will be some lose gravel you didnt expect when you thought you could go that fast around a corner and try to drag you knee on the ground.

I have went down myself and I have seen some of the most expeienced (aged) riders go down over people in cars or gravel and rocks.

I am sorry if I sound like I am being hard on you but this goes for everyone out there that does or will ever ride...

I want to be able to give you a biker wave someday as we pass each other.
Repect the bike and its power and it will do the same.

Happy Riding!