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Discussion in 'Thumpers' started by bmwhd, Dec 2, 2005.
73 mpg (70 mile daily round trip commute).
WOW :eek1 I hope others are getting similar results!
Ron has things very well sorted out
I get between 50 and 55 mpg with the 351, but that's more gross throttle mismanagement than anything.
My mileage has been pretty bad; 35-45 ish but I know that my jetting has been way off! The good news is, I'm getting close to 30,000 miles (50,000 km) with no mechanical problems and still my same slacker maintenance schedule!
I want to get it dialed in but haven't been able to... here are my issues:
1. Normally I wouldn't mess with it. I'd take it to someone who really, really knew their stuff and have them dial it in for me on a dyno. Here in Malaysia I don't know that there is anyone that can do that. Everyone is an expert at fixing something broken so that it will go BUT no one understands the desire to "fine tune" something that runs pretty ok but we know could be better! (The rear brake was completely out on my KTM once and I brought it into one of the higher end shops to fix it, left the bike and took a loaner and came back that evening. They said it was done, but when I got on it, the rear brake was still completely out so I yelled at them. The mechinic put his arm around me, walked back to the bike with me, squeezed the front brake lever a few times and said, "This is also a brake and it is working fine. That back pedal just controls the rear brake but you can stop just fine with this one. Go ahead and bring it back in when they are both out!")
2. If I was doing it myself I copy other smarter guys numbers from the forum here, but the problem is on this forum I haven't come across anyone with similar weather to what we have here and the same set up I have. (Everyday 89-99F/75-99% humidity; 351, BBBB (Bill Blue Big Bore) BB 33mm carb bored to 34mm, bb/barker full system pipe.
3. No jets in stock in the coutry.
ouch.......do you foul plugs?
Jetting isn't really rocket science. I've had a mental block with regard to carburetors for years, but since all three of my bikes have 'em, I've had no choice but to learn.
I've found that Dynojet's recommendations in their kit are pretty much spot-on. I have a Twin-Air filter and KLX300 pipe/muffler and use a DJ124 main jet, the stock 35 pilot, and the DJ needle in the middle position. AF screw is 2-1/2 turns out. The bike runs like a top and gets good mileage as long as I'm not wringing the piss out of it on the freeway.
I'm not sure what to recommend with the TM33/34, but I would suggest ordering up some main jets and a couple of pilot jets.. have somebody here get 'em and ship 'em if you have to.. they're not expensive. They you can experiment. Yeah, taking the carb on and off to rejet is a pain, but if you spend an afternoon doing it, it'll be well worth it. You can even get the thing off and on the bike with the bike hot; it's not that hard.
A while back I found an online jetting calculator.. I'm trying to find it again, but so far no luck. The thing is, there is very little change over elevation and temperature/humidity. Just get it running good on a given day and it'll probably be just fine... certainly better than you're getting now.
If you need help getting stuff, PM me. I'd be happy to order it and ship it to you if you have Paypal. :)
Thanks Rob! I really appreciate it
How about humidity... anyone know if that makes a difference?
no need to go to the 40 pilot the stock 35 is more then enuff
Yes, humid air will have less oxygen than the same volume of dry air, so you need to go leaner. How much? You'll have to experiment to determine that.
FWIW, I found the Dynojet recommendations too rich. I ended up going with the Stage 1 jetting (stock snorkel and exhaust), but one size smaller on the main jet. I had to call DJ to get the smaller main, as the kit contained jets in two-step increments.
I think you're probably right.......and our humidity here ain't too low either
Humidity has very little affect on jetting if It did your bike would be underpowered on really humid days and that just ain't the case. Sure it will have an effect as well as temp. but neither will affect it like serious elevation changes will. I have never changed jets cause it's cold out or it's really humid today and the bike runs the same for all I can tell in all conditions.
I saw this in the Cycle Gear catalog today. Will it work on the stock carb?
Easily adjust the air/fuel mixture on your Kehin carbs with this convenient Air Fuel Mixture Screw from Trackside.
Features and Benefits
CNC machined from billet aluminum
Anodized finish for durability
Easy grip and turn design requires no tools for adjustments anytime
Numbered 1-4 for easy adjustment
Includes spring, two washers and o-ring
Designed to resist backing out due to vibrations
Fits Kehin FCR carbs
I don't believe so; this is for the FCR carb, which is a totally different carb than our stock CVK carb. There IS one that fits it; I forget who makes it (even though I have it -- a friend ordered it for me). Somebody will likely post about it.
Kouba makes a fuel screw for our KLX right here is little 'ol Boise.
Carls Cycle, the local dealer, sells the part http://www.carlscycle.com/catalog_detail.asp?cat=2448
That's it! That's the one I have.
Ya, I've seen that one before too. I was just thinking for $10 I'd pick one up at the store. It's not a priority by any means.
Some guys use a little screw bit and get in the stock screw for adjustment. I've found the Kouba T-handle to be helpful when dialing in a pilot jet (tried the #38 with 250 and 351 both and found it to be large, went back to the #35 both times), and when riding up to high elevations when a little leaning in the pilot circuit makes a nice difference. I ride a lot of elevation change here (can go 4,000 ft to around 10,000 in a day). Quick and easy. Dan888 showed how he marked the screw and carb with a sharpie when seated, which makes it easy for dialing back and forth. I put a big line on one side of the screw, and a thinner dashed line on other side (180 degrees) to show the "half" mark. I look at it occasionally and its easy to tell if its backing out on its own (never has). I know...pics...but I don't have one.
got mine from www.factorypro.com for $17
Factory Pro Tuning
179 Paul Drive
San Rafael, CA 94903
</BIG></BIG></B>Toll Free US and Canada)
(415) 491-5920 Voice
fax 415 492-8803
Replying to my own post...
With the weather starting to warm up here in the dez (we're in the low 100's now) I noticed my bike became a bit rich at idle and at the off-idle transition. An 1/8 turn in on the mixture screw got it back to the sweet spot. At the last fill up (same commute) I got 74.5 mpg. BTW, I don't ride trying for high mpg's, I just ride.