New Ride: 1981 Yamaha XJ650 Maxim

A deal too good to pass up... So I didn't. This gem was a solid little garage find from one of our fine serviceman at Ft. Bragg. (Thank God for him and all the other men and women defending and serving our country.) He wanted to sell it quickly and inexpensively because he was deploying and it had already been sitting for over two years. Of course, the bike had the normal problems from sitting, plus a few more. Gummed carbs, dead battery, non-working brakes, and a thick protective layer of dust. Besides slightly tweaked original handlebars, the bike was straight and cosmetically fine. The paint was hazed a bit and the chrome needed polishing, but all is to be expected. On a difficulty scale, from mothballed to road-ready, the middle-sized XJ looked to be about a 5 on a scale of 1 to 10.
This was my first 650 4 cyl. from Yamaha of this era. I was curious how it would perform. The 1981 Yamaha XJ550 Seca I had was impressively quick and spirited. I'm not a big fan of the "psuedo-cruisers" that the big 4 started producing in the early-eighties style wise, but most of the time they still went down the road well.
More to come...

A Rant Against "Customizing" Your Motorcycle.

Well, right off the bat, I want to warn my loyal readers that this post may offend some of you... Of course, this isn't my intent, but enough is enough, this needs to be said.

DO NOT CUSTOMIZE YOUR JAPANESE OR EUROPEAN MOTORCYCLE! In almost every instance, "customization" is more akin to "bastardization" and should be considered a crime against humanity.

It doesn't matter whether the motorcycle is old or new, a cruiser, standard, or sportbike. The compulsion that many owners feel to "improve" their bikes needs to be resisted. A 15" extended swing-arm on a lowered Hayabusa not only looks foolish, but it destroys the handling and all but renders the machine useless. Removing the shocks and welding in "struts" on that 1971 CB750 does not make it any more cool. Either does removing the fenders and lighting. And your bike is certainly not cooler if, shocker here, you give it a flat-black rattle-can paint job accomplished without any masking tape. You all have seen the Craigslist ads advertising "custom paint" or "one-of-a-kind bobber/chopper", etc. You know, the ones that are being sold for the same price as an original unmolested bike. Every time I see an advertisement with the word "custom" in the description I immediately get sick to my stomach. Especially with older/collectible bikes. It really hurts me deep down inside.

Okay, okay... I'm being a bit ridiculous. There are some tastefully and well-done customized bikes out there. Some even that I would love to call my own. The reality of it is though, more often than not, the "customizer" lacks the skills, tools, and/or knowledge to do anything more than destroy the motorcycle. And even when the "builder" is able to pull off what he's trying to do, beauty really is in the eye of the beholder.

IF YOU CANNOT RESIST THE URGE TO "MODIFY" YOUR CLASSIC MOTORCYCLE, PLEASE, PLEASE, PLEASE KEEP READING...

1) First of all, I'd ask you one more time to reconsider. Try to appreciate the character of the motorcycle as it was intended to be. An old Honda CB, Yamaha XS, or Triumph Twin in basically unmolested yet functional condition is pretty rare these days already. If you come across a nice one, keep please consider leaving it that way. They are MUCH more likely to appreciate in value than a modified bike as well. In fact, if it's really nice, you probably could finance your entire project by selling it and buying a rougher one.

2) If you must mess with it, try to do it in a way that it is reversible. Many things, like handlebars, seats, racks, exhausts, electronic ignitions, etc., are bolt on items and can be added or swapped without otherwise damaging the bike. Put the removed parts in a box in storage, or sell them to somebody looking to breath new life into their bike, and at least nothing is lost. If you're painting body work or gas tanks, even if you think it's in lousy shape, PLEASE check to see what similar ones are going for on Ebay type sites. Some years, styles, etc., in original paint, even if only in fair condition are worth a mint and VERY desirable to some. Consider selling your parts and getting ones in worse shape if you're going to be repainting them anyway.

3) If you're going to be cutting or welding, you're probably not still reading this anyway. If you are, and you're set on it, make sure what you're doing is SAFE and STRAIGHT. I've seen some dangerous looking chopped/bobbed bikes being ridden by young kids with their first bike they thought was cool or got for a "deal". Remember, you may find somebody foolish enough to part with their money for your bike down the road. Please be responsible about it.

4) Wow, I can't believe you're still reading this... Last thing: If you do decide to paint ANYTHING on your bike, either take the part off, or spend the extra 10 minutes masking it off properly. Nothing looks worse than a crappy paint job, and very few things are more difficult to "fix" than over-spray where it shouldn't be.

Harbor Freight lights the way.

I needed a timing light... And since I don't know anybody with one to loan, I had to bite the bullet and buy one that I'll probably only ever use once every 2 years.

Where do you go for a "single-use" or disposable tool? Harbor-Freight Tools my friends. Say what you want to about the quality of their Chinese-made plastic "hurry up and use it before it falls apart" tools, the price is right if you only plan on needing it once. I'm pretty sure I only dropped $7.99 on the "Chicago Electric" timing light, and while looks like it was appropriately priced, it did the job asked of it.

The procedure for checking the timing according to the Haynes workshop manual from my "library" said to first check the timing at idle 800-1000rpm, and then the advance at 4000rpm. If you recall, I had rotated the backing plate of the Dyna ignition pulse coils into the fully retarded position in order to help cure the spark-knocking.

So I've got the light hooked up properly and I'm about ready to summons the big KZ to life. Man... if this thing is correctly timed, it's going to really suck. Do I keep retarding the timing even at the expense of power? Well, I'd have to do something... It's not rideable the way it is. The plugs, appear to indicate a rich condition if anything... A compression test showed between 115 and 123psi on all four cylinders which really doesn't seem that high. Are the combustion chambers really so poorly designed that 120psi is too much? I really don't want to tear this engine down... ENOUGH ALREADY, just check the timing!

What did I find? The timing was still WAY TOO far advanced. I would guestimate about 7 degrees too far advanced even with the backing plate rotated all the way retarded! Wow... At first I thought the plate may have been installed backwards and because of the positioning of the pulse coils relative to the rotor it would be too far advanced if installed improperly. After spending more than a half hour messing with the ultra-tiny nuts and bolts used to fasten the coils to the backing plate, I flipped the mounting plate over. Folks, I should do a little more measuring next time... My assumption that the backing plate was backwards was such a good explanation to me that I just went ahead and did it without really looking or measuring to see if was the case. ANYWAY, I was wrong. The plate wasn't even close when flipped around.

Since everything else was fixed in position (rotor is fixed relative to the crankshaft) the next thing was to enlarge the adjustment slots to allow me to further retard the timing. It turned out to be a 45 minute job with an old-fashioned chainsaw round-file, but a simple one. After a few tries, I removed enough material to set the timing properly.

The fix was easy enough, but why did I have to do it in the first place? Was it just an incorrectly machined backing plate from Dyna? A plate from a different motorcycle that happened to fit properly otherwise? I'm not really sure, and at this point it doesn't really matter.

BUT, it does raise some red flags about the history of the bike. Although, according to the previous owner, it wasn't his "trusted friend and shop" that installed the electronic ignition, the bike had over $5k in receipts for engine work in the previous 5 years. Including two times where the top-end was removed and once for crank bearings. Did the shop never check the timing? And further, how could any actual mechanic ride this bike without immediately noticing and at least indicating to the owner that something was awry? Especially, since the shop seemed to be quite willing to dive deep into the motor, a timing issue shouldn't have been outside their ability. I don't think it's possible... Something about the story doesn't add up. When I consider that the 29mm smoothbore carbs disappeared after being removed when the shop claimed they were "worn out", I wonder how much of the engine work was actually done. Was any of it done? Boy, I really wish I could have gotten the name of that shop...

KZ1000: More disappointment.

So as we left off last time, I was complaining about the bike feeling too flat on top end. Essentially, what happened was the previous owner's shop switched a set of sweet Mikuni Smoothbore 29mm carbs out for a set of stock 26mm round slides. They also transferred the main jets: 120s... All else equal, a larger bore carb will require larger main jets to flow the same amount of fuel. So when the "shop" transferred the carbs over, the 120 mains were likely all they had in stock and was "convenient". Insert rant about how too often people get taken advantage of because of their lack of familiarity with things... I'd love to have a few choice words with the turkeys who were "helping" out the previous owner as a "friend." ANYWAY... This bike, with APE pod filters, 117.5 mains and 20 pilots ended up being pretty darn close according to the SOTP (Seat of the pants) dyno.

But this SOTP dyno run came after much fuss with the ignition timing... The KZ snapped crackeled and popped even on 93 octane fuel far worse than any bike I'd riddent to date. As previously mentioned, the KZ had a Dyna electronic ignition installed on it eliminating the points system. The Dyna set up was pretty straight foward and simple looking, with a slotted backing plate to adjust the static timing just like the original equipment points set up. Upon intial inspection, it was adjusted right in the middle of the adjustment range. I didn't have a timing light at the time so I just eyeballed it and retarded static timing a few degrees. Still spark knocking. A few more degrees... No improvement... All the way to "fully retarded"? There may have been some slight amount of improvement, but it still wasn't cutting the mustard. I double checked the mechanical advance unit to make sure that it was working properly and wasn't stuck in the fully advanced position. Everything looked correct.

Is this is just the way this thing is going to behave with the big-bore/high compression pistons? What's the point of carrying around the weight of a liter bike if you can't even use the mid-range punch? The KZ650 was vastly superior to it's big brother when motoring down the road because of the nagging pre-ignition problems. I was disgusted with the Big KZ.

Time to buy a timing light...

KZ1000: First Ride and Further Inspection.

Beautiful... With about 45 minutes into the carbs, the bikes running and idling fine. It's time for a ride, but after a quick inspection of all the major systems. Brakes? Check. Lights? Check. Tire Pressure? Add some air, Check... and so on down the list. Good... Everything looks fine. We're ready to ride. It's 10pm already and the Kerker is not a neighbor's best friend so it's fortunate that we don't have many.

Snapping the throttle open, the bike revs up pretty well and doesn't hesitate or stumble, with just a little wisp of black smoke coming from the exhaust. Is it black or is it blue? It's dark out and the only "fresh" gas I had kicking around was 2-stroke pre-mix... Maybe it's set up right? "This thing should be a monster," I think to myself. High compression, big bore, high-lift, free flowing old school muscle... Okay, GO already!

The very first thing I notice after throwing a leg of her and maneuvering out of the driveway was how heavy it is. Compared to my 1978 KZ650B, the 1000 is a tank. Actually, it's more comparable to it's GL1200 stable mate than the 650 in the mass department. At somewhere close to 600lbs full of fuel, it's definitely not light, but the long-ish Suzuki GS swing arm exaggerates it's heft in the driveway for sure.

We're riding now... The front tire has taken a set from sitting so long to it's dancing around a bit, but it's more annoying than unsettling. Being a bit unsure about what type of monster I have here I didn't want to unleash the beast on cold tires so I put a few miles on before going WFO. Cruising down the road at 55mph the engine is turning just over 3000rpm and it has decent but not overwhelming power when rolling on the throttle. Unfortunately, this bike, like it's smaller brother KZ650, is a premium fuel only bike. If I open it up too much at low RPM with 87 octane it pings and knocks like a Jamaican metal drum convention during an earthquake. I sure hope premium fuel solves that so I don't have to retard the timing... roll-on power is what this bike is supposed to be all about. Because the pinging is so prevalent, I can't really get a good feel for the KZ's real-world road power. I guess I'll just have to see how it spins out tonight...

The anticipation is killing me: GO WFO! The 7750 redline comes and goes pretty rapidly in 1st gear. Then again in second, and in third. Brakes... Legal again... Okay, yeah, it's faster than the KZ650 and KZ750. But I'm not blown away by it. In fact, to be honest, I'm disappointed with how flat it feels up top. It pulls well, it goes good, but not like I feel it should considering all the work that's been done to it. After a few backroad runs, my best seat of the pants guess would be about 85-90 rear wheel horsepower. Whoopee. Isn't a stocker supposed to be in the 80s? Definitely nothing like a stock Suzuki Bandit 1200 (115-ish rwhp) or even a Buell S1W Lightning(94rwhp). I'm not 100% convinced that I won't have more fun on the nimble little 650 even without the grunt. Is there something wrong with this bike?

Maybe... Did you catch what's up with it? Although I haven't tested my theory yet, there are a few hints in this post and the last one. It has to do with the PO's friend switching over the carbs. And it's not that the pilot jets are too lean... (cue Jeopardy theme)

Kawasaki KZ1000: The next big thing.

It seems that I've become a Kawasaki guy as of late... A quick look into the garage shows 5 Kaws, 1 Honda, 2 Yamahas, 1 Suzuki, and 2 Triumphs. I've always have been partial to the first generation of Honda SOHC fours as being overall great motorcycles, Kawasaki's four banger offerings of the mid to late 70's have been growing on me like fungus. This particular bike, a 1980 KZ1000 LTD is my latest craigslist find and a gem (to me) at that! I'd consider it to be a mild "period-custom" with a lot of pretty neat hop-up mods that were likely done in the early 80's. Some of the goodies include: 1054cc big bore kit, Corbin Gunfight and Lady seat, Dyna Electronic ignition and coils, Suzuki GS aluminum swingarm, alloy wheels laced up to the stock hubs, Progressive rear shocks, K&N superbike bars, a halogen headlight conversion, welded and gusseted frame, and many chrome doo-dads on the engine and footpegs, etc. NICE... While I'll normally prefer restoring a bike back to stock, period mods that don't drastically change the character of the bike (improvements...) aren't all that objectionable to me. As my first experience with a big Kawasaki four cylinder, I wasn't quite sure what to expect from it. The engine was rated at around 84hp stock (I assume this to be crankshaft hp) according to a few different websites I saw.

When picking up the bike, the previous owner said that the carbs would need to be cleaned in order to get the old girl up and running. I peered into the fuel tank to check it's condition and the gas smelled as if it were as old as the bike itself so I expected the fuel bowls to be covered in a think green slime. That was not the case. PO had his "shop," a trusted friend, recently put a new set of carbs on the bike as the old units, according to this friend, were badly worn out so they would not idle or run correctly at low speed. Of course, the shop didn't return the 29mm smoothbore Mikunis after fitting the "new" used set of stock 26mm carbs on the bike (which he charged $300 for). Can you say red flag? I think the PO got taken for a ride and his carbs stolen... But I can only speculate. Anyhow, the "friend" did put a 117.5 main jet (vs. 102 stock) to compensate for the individual pod air filters (darn it...), big bore kit, Kerker exhaust, and high lift cams that were installed. But no changes were made to the pilot jets. We'll see how well that works. I replaced the needle valves, blew the carbs out, and refitted them to the bike. The low speed screws were set at 3 turns out. A few strokes at the kicker with fresh fuel in the bowls brought the old girl roaring to life.

Next: Further Inspection and First Ride.

Air intakes and performance exhaust systems.

So the big question in my mind was how the 1982 Kawasaki KZ 750 LTD would perform with the individual pod filters. It was the "hot set-up" "back in the day" to have an individual K&N air filter or velocity stacks fixed directly to the carburetors in order to offer the least restriction and maximize flow and power. Well, maybe that was true back in the 50's and 60's, but that's because the engineering behind those earlier machines was no where near the level that even bikes of the 70's and 80's had. 

Most people know that an exhaust system can greatly affect how a motorcycle performs. That's why when you open up the catalog of any big parts house (Dennis Kirk for example) you'll see pages and pages of aftermarket/high performance exhaust systems for just about any bike out there.  Of course some people want a different exhaust for their bike for aesthetic reasons or because they buy into the old mantra of "loud pipes save lives". (This is a subject best left for another day...) But the industry has traditionally been focused on increasing performance over the stock systems. 

Exhaust tuning is a very complex science that uses many different principals to help evacuate the spent gases from the cylinders of the engine and keep fresh unspent air/fuel mixture in. On single cylinder engines (or engines where each cylinder has a completely seperate header and muffler system) header pipe diameter and total length are two of the largest variables. Remember that the air moving through the engine does not do so in a constant pressure, steady state way. As the exhaust valve opens, the gasses are still burning and highly pressurized as they begin to move out of the cylinder and into the exhaust port and system. There are two distinct energy waves or "pulses" moving into the exhaust at this point: The exhaust gases themselves have kinetic energy moving into the pipe, and the sound wave. The oversimplified version is that the length, shape, and diameter of the exhaust can be designed so that these pulses (and their negative "reflections" sent back to towards the engine when the pulse reaches the end of the exhaust system) can be used to draw more exhaust out of the cylinder when the exhaust valve first opens and "stuff" the fresh air/fuel mixture back into the engine when the intake valve begins to open (especially critical as valve "overlap" increases with longer duration cam timing). When you add in the additional variables of multiple pulses from multiple cylinders in 2-1, 4-1, and 4-2-1 exhausts, it becomes an extroadinarily complex task to maximize power  (I'll go into more detail at a later date in another post).  Also, since the speed of the "pulse" of exhaust gases varies with engine RPM, the exhaust system will be most effective at a certain RPM and less effective at all others.  By manipulating length, diameter, etc., a tuner can design a system to work at a desired RPM.

I thought you were talking about Pod air-filters?

Yeah, yeah... I know... Stick with me though. A well designed air intake system works in a similar way as a well tuned exhaust.  The suction from the engine created by the intake valve opening is essentially a "negative" version of the pulse seen at the exhaust side. The intake tract length is one variable that can be manipulated in order create a "stuffing" effect (literally creating a positive pressure of air into the cylinder).  These energy pulses created by the opening and closing of the intake valves cause a starting and stopping of the flow of air into the engine. This vibration behaves in the same manner as a sound wave which is why the volume of the air intake system and airbox plays an important role in creating the "stuffing" effect.  Think of it in terms of a musical instrument... An acoustic guitar has a hollow ressonance chamber to help amplify the vibrations (sound)  from the strings. The resulting higher "volume" in the case of a motorcycle engine is how large the "stuffing" effect is at the intake of the motor. As with the exhaust system, the volume of the intake system and the length of the intake tract affect the  RPM where the intake system performs optimally.

So that means we can design the exhaust and the intake to work best at peak RPM and we'll have a killer machine right?

Well, with the good comes the bad... These systems will have an RPM range where they work best, but the flip side, is that there is also an RPM range where they will do exactly the opposite of what we want them to do. Remember, we're dealing with waves here... they have peaks and they have troughs. When the peaks line up with eachother, they resonate and amplify their effect, which is what happens at their optimal RPM: In our example, the exhaust is "pulling" it's hardest when the intake valve first opens or the intake system is "pushing" it's hardest when the intake valve first opens. When a peak lines up with a trough, they energy wave will end up cancelling each other out: The exhaust and intake systems are function in essentially atmosphereic pressure. When a trough lines up with a trough, the bad effects are amplified: the exhaust is "pushing" the gases back into the cylinder when the valve first opens and the intake is "pulling" the air out of the cylider when the valve first opens.  There will be an engine RPM where the worst case scenario occurs and power output will drop off dramatically. Of course there are countless ways to combat the severity of the problem, including staggering the optimal RPM range of the intake and exhaust systems, but it still will exist in some form(dynamic intake and exhaust tuning is a recent engineering accomplishment). 

To be continued...