What did you do to your Yamaha today?

I was going home from work a few years back, and, after being passed by several sports bikes on my 1150GS, I realised it was biker night in Whitby (Dracula not Ontario)
I kept a few behind me on a twisty uphill dual cabbageway, but the GSXR that flew past on the final straight didn`t know about the car park exit at the top (blind brow). He T Boned a fiesta just before I got there. He was conscious and breathing (just about), his race leathers were all that was holding him together, and the air ambulance was called.
I kinda went off racing after that.

 

A little maturity goes a long way.

 

You may be interested in the valley in the torque from 4-7K from a Cycle Guide article, June 1981.

 

That is a VERY interesting piece of the puzzle and I thank you for sharing it. I'm curious as to what is causing or contributing to this "torque valley" in the XJ being it's right in the middle of the highway operating band. From the little I've gathered with the camera it appears to be a function of the needle taper coming up to the shoulder of the needle body itself where the taper becomes more aggressive and I'm tempted to locate a set of "police" needles to confirm this.
What I did do was take my 750 SECA for a good interstate run Monday afternoon after swapping in the modified aftermarket emulsion tubes on the #122 mains to see how things panned out. The original plan of mixed city/highway riding got nixed so I took the opportunity to really run the bike. Unfortunately that torque valley really shows itself on the interstate from about 65 to 80 and twisting beyond the 1/2 throttle gets almost nothing, I had to drop down a gear several times just to make passes one time reaching the century mark and this is when the bike felt really good. The downside to all this is the lack of MPGs and the best I could muster under this was 28. Honestly I don't know if this is better or worse being the bike was designed & tuned during the Reagan admin for emissions and the prevailing 55 MPH limits so I'm curious as to what others are experiencing with their 750 XJ's. I suppose I could get high 40's to low 50's running at 55-60 MPH at the risk of being flattened by some overbearing SUV. According to an older Cycle World article from June of '81 this is about what they found during their tests.
In retrospect it's no worse than some of my past machines be it the 1980 CBX I wrecked or V45 Magna as they too were tuned under the Reagan administration, the CBX was an excellent cruiser and had many camping trips on the book while the V45 was a commuter with a nervous disposition and really difficult to get at carburetors. Maybe I need to keep my expectations in check after all the SECA sounds like an angry b*tch above the 7000 mark and will happily go beyond the 9500 mark passing another sport bike. In short it's fun and maybe that's what I should focus on.

Now down to the emulsion tubes the motor had a slightly better feel off the line, streetable best describes this but get into that torque funk it's almost as bad as the stock pieces with the OE #120 mains but without the breakup. I may make a few more mods to both the tubes and swapping around the jets but seeing what that article says I'm not sure how much more is going to help short of fuel injection or going with a different carburetor. Swapping in my #126 mains this early wednesday and changing the oil, weather guesser is threatening us with breezy warm temps so maybe I can get a few miles on the saddle and see how this works out. If nothing else I can piss off my neighbors.

 

Couple of points to consider:

a) starting in the late 70's and then getting progressively more stringent into the 80's, emissions regs (expecially CO) were getting more restrictive and the manufacturer's response was to lean the engines out throughout the rpm range, but especially at idle and off-idle speeds. It got so bad that Yamaha actually issued a dealer bulletin that says (paraphrasing): "if a customer complains about poor off-idle performance (acceleration for normal street use), yank those mixture screw plugs out and richen up the pilot mixture screws a bit." So much for those EPA regs........

b) for street bikes, the most important bit of "performance" for a typical rider is the torque response at lower rpm's....in other words, off-idle to mid-range......the typiral "city driving" mode with a lot of stop-and-go riding. You don't want a bike that is sluggish at off-idle or mid-range, as this is frustrating for the typical owner (who then goes and adds pod filters to improve performance, or bigger jets and shims the needles, all of which tends to further decrease lower-rpms performance as those sort of changes move the torque and horsepower maps further up-and-to-the-right of the rpm curve.......).

So you can see the tug-of-war here: lean it out to meet emissions regs, and then figure out how to deal with the off-idle / mid-range performance issues that leaning it out creates (this problems still exists today, which is why almost all auto manufacturers do some type of "cheating" on emissions certification testing, and sometimes get caught).

In reality, a few simple changes to these era bikes will create a much better user experience, and this usually involves richening the pilot fuel circuit (larger jets and/or mixture screw position adjustments) and basically leaving the main fuel circuit alone (or increasing the jet size by 1 "size"). For wringing even more performance out of any given size engine, the choices are basically to move the torque/horsepower further up the rpm scale (which then makes it sluggish at off-idle and mid-range rpms), or, as the saying goes, there's no substitute for cubic inches (or millimeters, as the case may be).

All-in-all, for that era and for the target buyers, these bikes were a pretty good compromise for the typical owner.

 

You're right it's been quite the tug-of-war despite the compromises, unfortunately the tech wasn't there when the bike was made the last part of 1980 and I have to adjust my expectations accordingly. Right now I'm working on dropping my #126 mains back in and checking/wet-setting the floats, I have #42's on the pilot side and have them all balanced within one inch Hg on 2.5 turns of the fine thread needle. Around my small town and on the rural highways it's well mannered and quick with a crisp throttle so I'm thinking this is about as good as it gets. The #126 mains seem to work well with the 4-into-1 Kerker Pro Sport exhaust and our ethanol laced gasoline, going to dump a jug of 100LL AvGas in and see how that goes. Looking like thursday is going to be the day as I don't feel like bucking a 25 MPH head wind.

For that era... I was going into the 5th grade when this bike rolled down the assy line and soft rock dominated my radio. How things have changed.

 

I'm sorry, but I can't see Yamaha letting a bike go into production with a simple carb related issue giving that torque trough. Far more likely it's to do with the exhaust system they "had" to use, or this and a combination of this and lack of suitably mapped ignition. By mapped I mean one that can add advance, then retard at higher rpm, or more throttle to reduce pinking. You want to fix the trough - get a mappable ecu, four into one, and put the bike on the dyno - you might also need some jets and needles though.

 

I should add: given what the desired riding performance was supposed to be (from Yamaha's perspective and understanding of "the market"......who would be buying these bikes, what did they expect, what does our advertising promise and promote, etc.), the design of the engine system then follows from all of that ---- so it's not just the carb jetting that is taken into consideration, it's also things like: carb type and size (venturi diameter, etc.), cylinder head design, camshaft lift and timings, compression ratio, and as mentioned above, ignition timing "mapping", etc.

The point being, the carb jetting is just a small part of a bigger puzzle, but of course since the carb jetting (and air intake system) is one of the easiest thing(s) to monkey around with, that is where most of the effort goes (and with predictable results).

Or as Chief Brody said to Captain Quint in "Jaws": I think we're going to need a bigger bike.......

 

I can heartily recomend a Vmax, but then people further tune them.
The XJ900 must be worth a look too, given we are an XJ forum - same engine as the 650/750, stiffer frame (slightly longer, which is possibly a negative), looks good too. Not forgetting the XJturbo... But of course, we know someone turbo-ing a 900...

 

FWIW, Regan was in office less than a month when mine rolled off the line in February of '81. And I was celebrating my 7th birthday.

 

Well Raegan might have had something to do with covering over the idle mixture screws on US machines, but I would suggest nothing else, and certainly not elsewhere in the world.
I once had a mini (A series) engine on the dyno, I was setting the ign advance on a mapped system. Normally you limit full throttle ignition timing to around 32 degrees. At 4000 ish (I could check, I would still have copies of the map), I added timing, in 2 degree steps, more and more, up and up went the torque. In the end I had 42 degrees of timing in there! I had to back it off to saner levels due to the load sites either side needing less, but it was an eye opener.

 

Mine is a late Carter bike, having been built in May of 1980.

Yesterday I (finally!) finished the muffler replacement. I ran into a string of annoying problems: on Monday, my cheap "titanium coated" drill bits burned themselves into oblivion drilling 10mm holes in the mild steel stock I had bought to make brackets, and my attempt to just push it through led to the drill burning out. Sigh. Yesterday I borrowed a drill and bit set from a friend, then got sidetracked by the fact that the right muffler (the one that will have to come off at every tire change) had practically welded itself to the adapter I put on the collector outlet. Much measuring and fiddling and trimming followed, and I finally figured out the Harley Sportster muff's inlet narrows down a bit just back of the slotted clamping portion. I solved this by putting a "go no further" mark on the pipe and cutting the hanger bracket accordingly.

Fiddling and trimming the adapters on the collector gave me the opportunity to pull the system off and re-install with nice new gaskets. I did not replace the head pipes with the spares I found in the box o' parts, because while they were shinier than the originals they were also more beat-up. I probably should have wire-wheeled the rust off the originals and then painted them with high-temp paint, but that's a project for another winter. Summer's just about here and it's time to wrap up the wrenching season and get into riding (though I still have to install the "performance" cam in the Himalayan).

Getting things lined up was tricky. When I first put the mufflers on the ends of the pipes, the welded-on mounting tabs (which were perpendicular to the surface of the muffler) aligned with the middle of the muffler/passenger-peg mount casting. Hmm. I rotated the mufflers until the bend in the mounting tab lined up with the back of the muffler hanger rubber (green line in the photo). This had the tab sticking up at about a one o'clock position (red lines) as seen from behind. A little quality time with vise and hammer fixed that, leaving the tab in the correct vertical orientation:



On to hanger fabrication, which involved some CAD tools:


"CAD" standing for "Cardboard Aided Design"

And a little trial and error:


Notch required to clear passenger peg bolt. No idea why it's only needed on the right side.

And, of course, a bit of persuasion to match the alignment of the hanger bolt (straight east-west) with that of the muffler (splayed out a bit).


Always important to note which side gets hit.

Everything lined up, mufflers slipped into position, clamps tightened, everything felt solid. Roll the bike outside, start the engine, got a nice smooth purr punctuated by a loud pop-pop-pop that seemed to be coming from the front of the bike. Yeah... I had tightened the headpipe-to-head nuts on cylinders 2, 3, and 4, but cylinder 1's nuts were still finger tight. Oops. Quick tightening, and the bike sounded good. A little quieter than with the original pipes, but not as much as I had expected.

Took the bike for a ~70-mile ride, hit some bumpy gravel roads, checked tightness when I got home. All good. The bike sounded pretty much the same as with the original rusted-out pipes, perhaps a bit quieter. It also seemed to run a bit better, with less of a flat spot around 6000 rpm. I suspect the rusted-out mufflers were a little less restrictive than this already-lean engine wanted, and a bit of back pressure made it run better. The "butt dyno" also suggests a bit more low-end grunt than before (again, to be expected from a bit more back pressure).

I neglected to take a photo of the bike with the new mufflers (too busy enjoying riding it), but will post one after my next ride. All in all I am pretty happy with the results of this project. All that remains is to decide whether to have the hanger brackets I made welded to the mufflers, or leave them bolted in place. And install some kind of rubber baby-buggy bumpers where the centerstand and side stand hit the mufflers.

I am still debating whether to take the Maxim on the Hügellandschaft Adventure Ride (two days of gravel and dirt roads around Galena, IL) next weekend. I think it's more than up to the job (after all, I did put "dual-sport/ADV" tires on it), but I still need to install a mounting and power supply for the navigation system if I'm doing that. The alternative is my Himalayan... but if I take that bike, I will need to install the "performance" camshaft that bumps it from 24.5 to about 28 horsepower ("performance" is relative). Decisions, decisions...

 

As promised... a couple photos of the new mufflers on the bike:



The Harley parts are now the shiniest things on the bike!



I was out having fun on pavement-free roads this afternoon, getting ready for the Hügellandschaft Adventure Ride next weekend, when I spotted major leakage around the right fork seal. Nuts. My temporary repair was a little more temporary than I had hoped. Well, it got me to the Crud Run. I have a replacement set of forks, but they are going to require a bit of assembly and installation work, and at this point I have run out of time. So, next year. I hadn't yet figured out how to mount and power my navigation system either, nor do I have the slightest idea how to load my heavy camping kit on this bike, so probably a good idea to wait anyway.

But boy, those mufflers look cool!

 

Dude they DO look cool and if I didn't know any better (being I'm not the brightest bulb) I'd say they were stock.

NAV system mounting; maybe what I have going will help with the ideas. I run an older Garmin Nuvi 1450 in a RAM cradle mounted where the YAMAHA filler used to be, the mounting holes were the exact distance as the head and I used some spacers to jack it up. Power comes from a bucking regulator board avail from Amazon and it's set to 5.1V output powered by ignition on. I normally use the Garmin for a speedometer but the breadcrumbs have helped a time or two. Only drawback to all this is the mount obscures the key some, where I'm at it's not a problem but the key comes out when I'm in the city.
Going to blast and VHT paint my exhaust this weekend if the weather cooperates.

 

I have a standard RAM ball mounted in the same place. It’s convenient for sure.

 

They do, just like they belong there.

 

Spent the weekend blasting & painting my pipes and muffler, went with a silicone based high-temp paint that's used on injection press barrels. Got four layers down.


Yes I did, earplugs in and 25 miles around the loop with several times beyond 9000 RPM. Was never liked much by my neighbors.

 

So today I now have 3000 of my own miles on the SECA since it was resurrected, 39,021 miles on the clock right at the intersection of hwy 107 & Memory Ln by Ryders Saloon in Henriette... couldn't have planned this one better myself.

 

Perfecto. Reminded me I'm getting close to a milestone as well. Sitting at work, I'm 49 miles away from 40k. Ride home is 26. Hope I remember to watch for the roll-over on the following ride.

Got the bike in 1995 with 11.5k miles on it. Average annual mileage is really distorted due to about 15 total years of downtime out of that 29 years.

 

Didn't have my phone with to snap a couple of pix, I will when I reach that 10,000 mile point however. Today it's all about adding to that bug collection on the headlights!