New Maxim XJ750 (to the forum anyhow)

Hey all! Names Ben - how goes it? I am the owner of a 1982 yamaha maxim XJ750. I purchased the motorcycle from its previous owner 3 years ago this month. The bike had 2,349 miles on it, and I paid 500 bucks + trade for a moped for it. He bought it brand new back then for his wife. Long story even longer, she left him and it sat from late 80s till about 5 years ago. He had the carbs gone through and changed the oil with royal purple ever 4 monthes.

Its my first motorcycle, and it is (out of the bikes ive rode now) on of the quickest and most comfortable bikes Ive ever rode! Since I purchased it, Ive done the following:

-Regular oil changes (valvoline full synthetic.)
-New battery
-New rear tire
-New fork seals
-New plugs (every year)

I only run 93oct or higher fuel in it, and always make time to run/ride it. Bike currently has 17,436 miles on it as of riding into work this morning. I would like to replace the factory coils on it and see about some sort of spin on oil filter adaptor for it. Other than that, I plan to put many more miles on it -Ben

 

Welcome!

Be sure to post up some pictures!

Around this time, checking your valve shims/clearances should be high on your priority list. They should be checked(and re-shimmed if necessary) every 5,000 miles.

You will also want to check the rear brake shoes for delamination, as the pads can separate from the carrier, jamming up, and causing the rear wheel to lock up. -not good-

Lastly, i see you wrote that you use full synthetic oil?

How does that work?

Generally our bikes do not like the synthetic stuff and most experience starter clutch and a lot of slipping issues due to having a wet clutch.

Castrol 4T is easily found and works great.

 

I will post pictures if I have time tonight. As far as the synthetic oil goes, I did notice a little slippage/flareing @ WOT after a few hours of riding (to and from northern IN to Chicago IL.) I normally used the Mobil 1 full synthetic 4T, but this spring they were out so I switched to the valvoline full synthetic. I also use a little bit (maybe 1/4 bottle) of ZDDPlus additive and prolong additives in the bike as well. I didnt know how well the bike would respond to it, but if those 2 products let me put 243K on my turbo maxima and almost 200K on my Buick Grand National motors (and with me beating the living tar out of them both) then they couldnt hurt in the bike right? I have been getting a little squeaking from the rear brake when applied, was going to tear it down this winter and see about replaceing all the rear brake stuff anyhow. As far as the valve shim deal, not quite sure how that works. Like I said, this is my first motorcycle and Im trying to learn as much as possible about it. Definatley a whole nother animal compared to Turbo V6s and SBC... -Ben

 

The engine probably likes that oil, and maybe even the additives. Your clutch doesn't. That clutch is old-school. BigFitz has a nice how-to about valve adjustment, search for him in the "authored by" search box.

 

Didnt find the valve adjustment/shim posts. Is there a better option for clutches on these bikes then? With 17K Im sure it will be needing one here in the not-so-distant-future. I was also wondering about any performance gains for the bikes (I E 4-1 exhausts, rejet carbs, etc) for a bit extra power/top end. Also, Id heard that theres a 6 speed transmission option for the Maxim XJ bikes - is this true? Would help out A LOT on the highway - which is mainly where I ride my bike. Thanks for all the info guys! -Ben

 

Welcome and don't put off the valves. If (when) they get too tight you will ruin the valves and your fun.

Valve shim walk through is here.

In my opinion unless the exhaust it rotted away leave it stock. These bikes have a very unique sound that I for one enjoy.

Rejetting can be a black art but isn't hard to do. Tuning it can be.

At only 17k your clutch shouldn't be worn out from normal wear but possibly the plates may be oil 'saturated' (if that's the correct term) from sitting as long as it had.

The 550's had the 6 speed gear box. You're stuck with the 5 speed unless you're a mechanical genius and have very deep pockets.

And your brake lines are good for 4 years.

 

I do love the way the bike sounds, but I wasnt sure just how restrictive the exhaust is VS say a 4-1 setup. I R CaRb iLiTeRaTe so I wouldnt be jetting/tweaking anything carb-related. Has anyone taken the Seca turbo stuff and put them on say a Maxim 750 without a major revamp needed - or are these bikes not compatible like this? Seeing a lot on here, and its laceing me with ideas.... -Ben

 

Welcome.

 

Here they are - the long awaited pics!

 

Howdy Ben, I'm Steve from Las Vegas, I have the same bike as you, have had mine for over a year now, have not ridden it at all, I'm restoring mine. Here is some info for you on what I've found with mine at 19K, found stuck rings on #4 piston, inside of the engine was as clean as a hospital, the clutch is in excellent shape, but I am going to replace the friction disks, bolts, amd springs. I'm going to install tapered roller bearing in the steering head; in case you didn't know the stock bearings are un-caged ball bearings. I decided to do a resto job because I discovered a crack in my frame, so I stripped it down and got it welded and now I'm waiting for money to build up so I can get it powder coated. I envy you on your prize, I wouldn't do a thing to it except get those valves checked, and the rear brake. Don't know how often this condition occurs, have never had it happen to me, but better be safe than sorry.

 

Thanks for the info Steve! Yeah, I cant do much with mine till winter - as its my daily driver right now. As soon as winter hits, I plan on doing quite a bit (or at least as much as budget allows for) to the bike. Planning a road trip to Florida this fall - should be a blast on the bike! -Ben

 

Good luck on your trip Ben. Watch out for them bugs!

 

I like those 3 point case guards, the one thing I really need for my bike. That air box doesn't look like it's from a 750 Maxim, they don't have chrome on the sides like that. Maybe somebody customized it a little, but nice looking bike!

 

I was thinking the same thing..me likey. Could you post a close up pic of the airbox cover area?

Very sweet looking ride by the way.

 

Im not sure about the airbox, I always wondered that myself. The crome pieces and the blacked out exhaust header I havent seen on another XJ750 like mine. The previous owner had said that it had all the Midnight Special options on a regular XJ750, but I dont know enough about the midnight special (or these bikes in general) to know if he's correct or not. I'll take some more detailed photos if I get a chance to sunday. Thanks guys! -Ben

 

Heres pics of the airbox as requested. The Model number of it is shown in the 2nd pic



Thanks -Ben

 

Hello fellow '82 Maxim owner and welcome from Denver!

Those look like trim pieces for the airbox off of Midnight Special, though i may be mistaken, but that's what it looks like.

Massimo

 

Actually, if the trim is just Chrome plated then they came from a 650 Maxim. If they are gold, then it would be from a Midnight Maxim. But the pic looks like it's just Chrome.

 

They are screwed into the airbox if thats what you mean. I was told they were a Midnight Special option, but I dont know enough about the midnight special options to say if it is or not... it may very well be an option from a different bike. Turned over 17,600 ridin into work this morning.... -Ben

 

Howdy Ben, the Midnight Maxim "option" was the WHOLE bike as a separate model. It was black and featured gold colored trim and accents all over the thing to make it look cool. It was also had black Chrome on the exhaust pipes and mufflers. What you have is, as you have found out, not stock for our bikes (XJ750Maxim). But since these trim pieces are inter-changable this is why you have what you have. In fact I have decided that the look of your trim is preferable to the stock trim, so I'm going to buy 650 trim for my bike.

 

If I recall, I looked into that when I realized the other bikes had chrome there. I don't think it's that easy, the 650 chrome won't just go the 750 box. I believe the 750's airbox is shaped slightly different where that trim is. My theory is that this bike has a 650's WHOLE air box instead of a 750's. But I could be wrong.

 

Here are the links for the valve adjustment by Fitz
AIRHEAD VALVE ADJUSTMENT with Pics
AIRHEAD VALVE ADJUSTMENT Part 2: The Tool vs. ZipTie -w/pics

You can find most of the maintenance write ups in the FAQ suggestion section.

Those airbox covers are from the 650 Maxim. They will directly replace the black plastic covers that came stock on the 750 Maxims

To give you a reference for the Midnight Maxim (and to just show it off 8) )



The 750 Midnight Maxim was available only in 83, and was black with gold plated accent on the side covers, grab bar, swing arm covers, carb hats, headlight ring, and fork badge. The bike also has gold paint accents on the footpegs, final drive, brake plate, and wheels. The oil pump covers on my bike are aftermarket.

The 650 Midnight Maxim was available only in 81, and carried the same black/gold color scheme to also include the airbox side trim.

The midnight special was an XS model available in 250/650/750/850/1100 sizes. Once again in the black/gold color scheme, but with little if any parts interchangeability with the XJ models


Ghost

 

Well, hmm, wonder what I was thinking of, I'd swear this minor "mod" had been discussed and rejected before, but now I don't see the thread. If that's the case I'm with LVSteve, I'm getting those chrome ones

 

They look like they just bolt to the stock airbox with 2 screws on each side. Should be a fairly interchangeable part I would think?

MiGhost, Awesome bike! I like the backrest/storage for the passenger. If I decide to (and by that I mean when I do) get another bike, I will be looking for something like that for my long distance trips -Ben

 

I'm not too comfortable with (or even have half the tools) to do the valve adjustment thing. I know my carbs are gettin pretty bad (2,800RPM idle after warm-up ) so I think that If I can find someone locally (or within a resonable distance) I may have them go through the carbs and check the valves out allright. Is there a conversion kit to make it so you can use blade fuses instead of the factory goofy lookin connections? Ive read that these bikes have electrical issues later in their lives, so just wanting to be prepared.... -Ben

 

You need a service manual, and you're going to need some tools and to "get comfortable" with the whole valve adjustment thing.

Valve clearance checks are not a one-time proposition; it needs to be done every 5000 miles.

XJ4Ever has fusebox retrofit kits.

 

Well, I can say that its probably never been done then - as I have never done it, and the previous owner didnt put enough miles on it to even warrent doing one. Why do they need to be done/checked so often - poor design or ??? There a fix or replacement so you dont have to worry/check it so much? Like I said, I'll prolly have it done in the spring when the carbs are off getting rebuilt. Thanks for the info though guys! -Ben

 

Hi Ben here's the story about the valves; The camshaft is placed just above the valves, there is a large cylindrical bore cut into the head for the "bucket" which rests directly on the end of the valve, a disk of very hard steel called a "shim" fits into a recess in the top of the bucket and the cam lobe comes into contact with the shim, after the valve closes, there is a gap between the cam and shim which needs to be maintained, and these shims come in a variety of different thicknesses to accomplish that. The reason engineers designed it this way was to eliminate push rods, rocker arms, etc; it saves weight and allows for a more compact design. The down side of this design is that as the engine wears, the clearance between the cam and shim decreases, and if this clearance check is neglected long enough the valves won't close all the way. this leads to inefficient operation and in the case of the exhaust valves, damage from over heating. The 5000 miles that Fitz mentioned is what Yamaha specified as the recommended limit, however this is by no means " A MUST DO NOW BEFORE ANY MORE MILES GO BY" thing. The wear is very gradual, just keep it the back of your mind as you rack up the miles. But in your case as you have been putting the miles on I advise you to get the valves checked. Hope this clears it up for you.

 

It makes sense to me, it just seems wierd that they wear that quick that you need to check them every 5000miles. I could see maybe every 40-50K take a peek and make sure everythings kosher, but 5k? 0.o Thats maybe 300 hours on the engine clock? Idk, just seems like it should have more longevity than that.... >_> -Ben

 

Ben, Ben, Ben, it looks like you wrote the last post without reading what I wrote, maybe it's my fault for using too many words.

Imagine if you will, the environment of the exhaust valve and seat, hot, with some pressure(when the valve contacts the seat), Carbon, HEY THAT'S WHAT DIAMONDS ARE MADE OF! now I'm not saying that diamonds are made in your engine, but the Carbon that you scrape off the combustion chamber IS abrasive.

Even though the seat and valve face are hardened steel, as the miles pass by the valve seat is going to recede into the head and this is why you have to check for decreased clearance. Any way the check is fairly painless, all you need for tools is feeler gauges, 19mm open end wrench, 5mm Allen wrench, and a Phillips screwdriver. Oh, and lets not forget a shop manual.

Of course, I agree that 5k is a bit excessive, but consider other factors such as the type of gasoline you use, the efficiency of your air filter, and how rich the mixture is that is going into your cylinders. Here is another tail to think about, I owned a 1997 Toyota Tacoma which has the same "shim over bucket" design as our bikes, I put over 400k on that truck doing delivery driving. I NEVER TOOK IT IN TO TOYOTA FOR A VALVE ADJUSTMENT, the cost was too prohibitive to me, but nothing happened to the valves and I can't tell you why. Part 2, I also owned a 1990 Toyota PU with a V6 engine, same valve design, at 250k I burnt an exhaust valve, checking the valve clearance was even more expensive for this engine.

So use your best judgement, and talk to others with lots of experience to determine when you really need to check your clearances

 

The rear package is the yamaha tour deluxe package that was available for the 750/920 virago, and the 650/750 Maxim. The fairing is the X-1 fairing. Good luck finding one. I have had this package for over a year, and it has been the only one that I have have seen available.

I may have missed it in one of the earlier posts, but if you put your location in your signature (member options/my account/ profile information). You might find a member close to you that might be willing to help you on your bike.

Our resident parts supplier Chacal carries a kit to upgrade the fuse box. You can locate the parts catalog by clicking the XJ4ever banner at the top of every page. The parts catalog is the 5th entry down. Also take the time to read through the other entries. There is a large amount of valuable information in them.

Ghost

 

I will try to make it easier to understand.

If you run your bike at average speed you will be running somewhere around 5500 rpms. In 5000 miles you will clock approx 100 hrs at an average of 50mph. In that 100 hrs you will have turned approx 33,000,000 rpms. Yes, That is 33 million. Given that it takes 2 rpms to complete one cycle in the four stroke engine. That is 16.500,000 times that the valves open, and close.

That is a whole lot of valves slamming into those valve seats. This tends to wear the seats in causing the clearance at the camshaft to decrease. If the clearance on the cams are not maintained you will evetually get to the point that the valves will not close completely.

By the time you get to the point of the valves not closing. You have run the bike enough that the slight loss of power from one or two valves may be unoticable to you. In the mean time those valves are not getting enough time on the valve seat to transfer the heat to the head, and eventually get warpped, or burnt. At which point you are well past an easy repair/maintenance to keep the bike running.

Some where along the line you stop riding because the bike just does not run right, and not being able to figure out the problem the bike gets left to sit, parted out, or junked. You would be amazed at how many times a new member comes along with a poor running, or non running bike, and as soon as the valve clearances are set, and the carbs are cleaned/rebuilt. The bike starts running like new again.

If you can floss your teeth, You have the ability to check, and adjust the valve clearances. Fitz's write ups walk you thorugh it every step of the way.

Carbs, and tunning are also covered just as well.

Ghost

 

I get all of what you guys are saying, it just seems excessive to check it that closely. I know my bike isnt running right between the plug wires starting to ark (discovered that the other night just how bad they were getting) and the carbs are probably in dire need of cleaning/adjusting (2300-2600rpm idle after warm up - dont even need the choke at all on a 61* day.) Located in northern Indiana, Im not sure if there are any members that are close by. I've heard theres a guy in the next town over that works on older bikes, but he mainly only works on older kawaisakis and suzukis. So maybe a yamaha wouldnt be too much of a streatch? 0.o -Ben

 

It never ceases to amaze me what people will go through to rather than check and adjust their valves. Rationalization, argue with the specified intervals, theorize about why it's not necessary, a disgruntled old fat dude said they were ok--- anything to talk themselves out of doing it. We've even had members SELL their bike rather than adjust the valves.

Here's the deal: the valves pound themselves into the head, tightening up the clearances. This happens primarily in the first few thousand miles of the motor's life. The initial adjustment, at 3000 miles, was the most important. The subsequent checks every 5000 miles thereafter are equally important; however-- if properly attended to from the beginning, the subsequent checks will usually be only that-- checks. What usually happens is that on their first adjustment, a majority of them will be tight; likely all of them if it wasn't done at 3K. The next time, if done on schedule, maybe one or two (the ones that were "close" on the previous check) might need re-shimming. Then, as the miles pile up, you'll find that often none of them need to be re-shimmed, or maybe one here, one there.

But if they've been completely NEGLECTED (common) then you have to get "caught up." As stated above, if neglected long enough bad things WILL happen.

Keep in mind that the people giving you this advice are speaking from experience; not just quoting "the book."

 

Heed Fitz warning Ben, we're just trying to help you to avoid more expensive repairs. As I was removing my valves for the restoration job I'm doing, I found some problems, a broken valve guide, now I've got to take the head to a machine shop to have the guide replaced and the seat ground. I could get a replacement head off Ebay for less than what a machine shop would charge, but I'll have to find out what the cost difference would be first.

With all of the predatory motorcycle mechanics out there, it's a good thing that XJbikes is here for all of us riders, so it's up to you Ben, listen to our advice or you may be forced into the loving arms of one of "those " mechanics.

 

I get what you're saying, and thanks for the continued support. I more than likely will not be doing much of the work myself - as I am #1 Bike illiterate #2 Carbeurator illiterate and #3 Valve Shim Illiterate. http://www.gnttype.org/maint/turbox.html thats mainly what I work on - a very far cry from the yamaha 750. I couldnt tell you what the inside of that motor looks like cause in the 7 years Ive owned them, the most I had to do was pop the valve cover off to change out a rocker shaft ( too much boost+stock rockershaft/pushrods+bigger cam.) I wasnt on here trying to pick a fight or start an argument, I was just trying to figure out if A. why it was such a short interval to have the shims checked and B. if there was a remedy for the poor design. I'm sorry if I offended any of you or made enemies - that was not my intention. I just want to enjoy my bike well into the 40-50-60K I see people get out of these bikes with ease. Thanks -Ben

 

Although I've tinkered with cars for years, I was bike illiterate, carburetor illiterate (to this day I seriously have to look up how to spell that word every time I use it) and valve shim illiterate before I bought and began recommissioning my XJ this past winter. If you've had experience popping valve covers off before, believe me, you can check your valve clearances and replace your shims as needed!

It's a painfully simply job as long as you have the right tools (which aren't expensive), a clear head and patience; put aside a few hours when you can and just do it... and then in 5k miles when it's recommended that you check again, having done the process once before, you'll be able to do it again in a hour flat.

In the end, you'll be that much more familiar with YOUR bike if you do this and what other work you can yourself, and you won't be flushing cash down the drain in the process. Take it from someone who just recently got his first bike on the road after working at it over more than half a year: it's REALLY satisfying to be able to take your bike out knowing it's safe, reliable, you did all the work and if/when something goes wrong you'll know how to fix it yourself!

Edit: I forgot to mention: that's an awesome looking ride you've got there!

 

Hi Ben, I didn't get in any way offended by your past texts, it just seemed to me that we were not explaining to you adequately enough as to why the engineers suggested that the valve be check at that interval. I hope you now understand that, and BigFitz nailed it in his post about the initial check needing to be done at the 5k mark. So good luck and thanks for sharing the pics of your bike.

 

Initial was to have been done at 3000. Thereafter every 5000.

It's not due to "poor design" it's inherent in the metallurgy and materials that were in use in the early '80s combined with a high-revving motor with what would by today's standards be some pretty big valves. It's an early design.

The XJs are from that interesting era that spelled the end of traditional, "old-school" engineering and the beginning of computer-designed, more effecient and lightweight components. Four (or even five) small valves (per cylinder) do a lot less hammering than two larger ones.

As far as being "valve shim illiterate" here's a reading assignment for you: http://xjbikes.com/Forums/viewtopic/t=14827.html and Part Deux: http://xjbikes.com/Forums/viewtopic/t=29209.html.

If you want to get 40K+ miles out of an XJ motor, you HAVE to properly maintain it. Ignore it, and you won't get past the mid-twenties, if that. Most XJ bikes with completely ignored valves don't even make it to 20K without cooking something.

 

Yes, but usually when I pop a valve cover off, this is whats waiting to greet me underneath it:


Stock 3.8 out of a Buick Grand National. Far cry from pulling the gas tank, adjusting anything. Trust me, I love nothing more than tinkering and messing with stuff and feeling proud and accomplished when I figure something out/fix something. But, in the case of this bike, Im in over my head and I dont feel comfortable having/trusting myself to do the needed work to keep it on the road. I will either A. Try to get ahold of the guy in the next town over who works on older bikes or B. take it to the Yamaha dealer and have them do the work. If I screw something up in a car, its one thing: but screw something up on 2 wheels with me going 70+MPH.... :0 Thanks for the compliments and support though guys! -Ben