My shop is in an over-sized two-car garage attached to my home. My work is a calling, in the theological sense of the word. Ethical and moral questions arise every day – they are hard, sharp, unambiguous and unavoidable.

So I get this note from a guy in the Andes …

Posted: November 30th, 2011 | Author: Administrator | Filed under: Engine, Fuel & Air, Motorcycle Repair | No Comments »

… and this is what it said. But to make sense you should go to the end of this post and read back up. I’m too damn lazy to rearrange it for you. And please do visit Matt’s blog. He’s an extraordinary man – too smart to be fearless – but he is. I do believe the man loves living too much to be afraid of dying.

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Matt,

RE XT500 – yes, more power – lots – but also more size and weight – lots too. I’ve become a bit of a crank about weight in my cranky old age. Big power is big stupid fun but the additional mass needed to keep it all more or less in line is not fun – but still stupid. See? I told you I am a crank.

My first bike was a Hodaka Ace 100 – a 100cc. 2-stroke street-legal enduro bike. It made modest power but weighed just under 200 lb. In real off-road/no-road riding, one’s rate of progress is mostly terrain and traction-limited – not power-limited. So big power is worse than useless – you can’t use it but it still comes with all that extra size and mass. Stupid. Of course, the more nearly your course of travel resembles a road, the more you can put big power to the ground.

This winter I am building myself a hot-rod to my liking – 300 lb. & 40 rear-wheel hp. (approx.). A former customer had an XR650-L that he seized due to letting it run out of oil. Usually, the damage is worst at the extremities of the pressurized oil supply – the head (cams and valves). But in this case the piston seized hard enough to break off a big chunk of the piston skirt on the intake side. The cam journals got hot – cooked oil on the adjacent castings – but they did not score or seize so the rest should be fine. When I autopsied the corpse and gave him my estimate for a resurrection, he asked for some time to think it over. After a few months I ended up with it in lieu of. And not much of a bargain at that. But I have an earlier-gen XR600R frame which is smaller and lighter and I’ve got the new higher-compression over-size piston/rings/etc. and boring the cyl. and renewing the valve faces/seats will be under $200. Say another $1k for a CBR600 front and rear end tacked onto the XR frame. Make it $800 for cables, tires and widgets and what-not. I’m leaning toward a monochrome/bare metal aesthetic – no paint, no plating – everything fine-bead blasted to a dull satin luster and clear-coated – powder or epoxy. All fasteners of silicone-bronze. The tank a longitudinal stack of three aluminum alloy tubes approx. 6″ dia. w/ends slash-cut/tapered and capped at each end. A repro-tractor seat cast in aluminum – yes, they are available for around $60 intended as a decorator item and often used as seats on bar stools in the den – I guess. Seat rigged as a springer with those cool mini coil-over shocks. No fenders. I have no idea what it will really turn out to be – I tend to make things up as I go along. But you get the gist – a light-weight thug.

Yes, opening up the airbox can only help.

Cheers,

Chris


i meant drz400…. typo there at the end.

thanks chris!

you can see pictures of the whole journey (11 months on the road so far) at www.spokecount.com. one of the best posts is called ‘’san blas
panama to capurgana colombia.”

i ordered a carb kit from keintech, but getting it delivered down here
has been an issue. i will take the carb apart and see what i find. i
seem to recall somebody on the ADVrider forum mentioning the
adjustable needle. i just put in a brand new air filter and applied
the recommended 2-stroke oil. do you think opening up the airbox
would assist any?

i am glad to hear the shop is coming together! i take it existential
MC is doing well! any more custom projects going on?

i ALMOST bought an XT500, but balked at the last minute for the
simple, reliable dr200. but i am already missing the extra umph of my
drz200 on the long mountain climbs when there are 10 trucks to pass.

and to clarify, i don’t recall ever claiming that the unicycle trip
was fun… :)

cheers,
matt


Matt,
An adventure indeed – but that’s what I’d expect from a loon who thinks a 2k mi. off-road unicycle trip is fun.

You are almost certainly experiencing oxygen starvation – or, rather, your
engine is. The carb is jetted for sea level or thereabouts and the stock
jetting usually work pretty well up to about 3k ft./1k m. elev. It’s the
main jet that is most in play at full throttle – and the stocker is
flowing
too much fuel for the available oxy at your higher elevations making the
engine run too rich – you will be fouling plugs soon if you haven’t
already. So lean out the pilot mixture – screw it out if the pilot screw
is upstream of the throttle slide and in if it is downstream – and lean out
the mid-range by lowering the needle. I can’t recall if your needle has the
grooves and a clip that makes it adjustable. If so, put the clip in the
highest groove – lowering the needle. If your needle is not adjustable
you will need a smaller needle jet. If you are having problems now at 3k m., it
will be undriveable at 5k. And even if/when you have the jetting sorted, the engine will be making significantly less power – less fuel/air = less power. Make sure your air filter is clean clean clean. If it is at all occluded,that will exacerbate the rich condition. Please do add me to the list if you are sending out periodic reports. You would barely recognize the shop these days – fully insulated, well- lit, two real table lifts, floor to ceiling shelving, three workbench spaces, organized and humming.

Cheers,
Chris


hey chris!
i hope you are doing great. i have cooked up quite the adventure. i bough a 2003 suzuki DR200 with 6000 miles on it in medellin, colombia. i am headed south fast to ushuaia, argentina, then back north slowly. now here’s my issue. when i am running between 50 and 60mph in 5th gear, i am getting some power loss. it is especially noticeable when i jam on the throttle to pass, climbing, or when a wind gust hits me. the bike ran great at about 1500m and now i am between 2 and 3000m going up to 5000m in peru, any suggestions? drill out the mixture screw, as it might be too lean? or could it be some other issue? just wonder your thoughts.

cheers,
matt



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