Dynoed earlier this week, first time.
Main jet selection for a flatslide is not all that complicated to get close using seat of the pants in the fields out back IMO. I was within two sizes of where I belonged, although weather and humidity itself can cause that much of a variance, but the needle is another story.

My advice to anybody running an aftermarket carb, is to go to the Dyno. Two needle clip grooves and two main jet sizes lean was costing me 11HP at 5Krpm. There was a definite dip in the HP and TQ curves that coincided with a huge hump in the A/F ratio meter, that was costing me bigtime acceleration in the midrange. While tweeking the mainjet only got me another 2HP on top, it combined with the raising of the needle (dropping of clip) to iron out the huge dip in the midrange for a gain of 11HP at 5K.

I started at 160 main, 2nd groove from top on needle. Ended up on 165 main, 4th groove from top on needle. Needle setting is indeed very crutial, I never dreamed it could have had such an impact.

FYI - If you raise the needle for midrange, the low end richens up too, so pilot and idle mix are effected and must be retuned. I had to drop the pilot several sizes as a result of richening the needle.


* This post is by no means a suggestion for anybody's needle setting - from what i am told by a couple dyno guru's, some people need the 2nd, some the 3rd, and some the 4th and 5th groove. It all depends on intake setup, porting, etc. I am just sharing how important it is, and how much you have to lose or gain. We are all always talking about peek numbers, but to my knowledge I cannot recall such a conversation on needle settings before so i thought I would share.

 

Good information Chris but what I'm finding is that everyones set up and modifications seem to be so wide and varied that one really can't get solid information on a setup.....it's all subject to too many variables....... [img]i/expressions/face-icon-small-disgusted.gif[/img]

 

HT,

what was your final #s? can you post any pics? also what air/ fuel ratio reading was you at?


good info!

 

My point exactly Scoundrel - we should all just go to the Dyno, it really is that easy.

We all spend hundreds and sometimes thousands for all these mods, but rarely spend the extra mesely $100 to get it all tuned right. Since tuning can cost or gain as much HP as any mod that exists, Dyno tuning seems to the cheapest source of HP there is. Not to mention just knowing you are just right with your mixture for fuel ecomony as well as HP.


Sam, I tuned for power and not economy, some will say that 14.7:1 is the right A/F ratio but I made best power slightly rich in the 13's and that's where I left it. Once I get the charts scanned I will post them, no shame, no pride, just sharing. On this raining humid day wearing 22" knobbies on the dyno rollers I got 48.6HP @ 7K and 41.8#torque @ 5.7K. Some may say its low, others high, but the well tuned curve is what I was there for and the HP curves intersects and takes off right where the torque curve just begins to drop at 5.7K carrying on to the peek HP at 7K and I am now a happy camper.

Its kinda funny really, a while back i was being told on another post that the A1/A2 cams were lazy until they peek at an rpm much higher than practical or usable. I find 7K very usable, and very practical. I'm very impressed with their curve actually, and I do believe it is as good a curve as I've seen.

 

If I could find a Dyno in my area I'd go.......[img]i/expressions/face-icon-small-sad.gif[/img]
All the performance shops around here say there's no need for a Dyno but when I ask them if they have a Dyno I find the answer to there opinion......No Dyno.

 

hightower, did u try anything richer than 165 main, clip 4th position?

 

yes I went to a 170 main, a/f ratio went down of course, and I lost .6hp and .5# of torque. we made 3 pulls for each change I made and took their averages. did not try the 5th groove on the dyno as the a/f ratio on the 4th groove matched the a/f ratio of the top end with the main jet that yielded the best power. my lesson I learned here is that it doesn't hurt as much being a bit rich as it does being a bit lean, the 160 main was costing me 3hp from the 165, where the 170 was only costing me .6hp.

 

holy crap chris! 11hp is insane.... I am fearing the tm45, because sure I will know what optimum settings are on the day I dyno, but everytime we travel to the badlands/silver lake/LS-utah and then also everytime the temp changes, wont that give the opportunity to screw with a/f significantly?

How did you find your dyno? dynojet.com dosnt seem to be very helpful, because the two closest to me are non existent lol.

I wouldnt mind dropping 100 on some runs at all, the experience, the tuning, and knowing my peak hp/tq numbers would be great.

Was it 100 for an hour? Do they limit the # of runs in the hour? How many total runs were you able to make? If it is 100 for an hour, that seems like a barain to me!

 

once the carb is tuned and the needle is where it belongs the only thing that would need changed for varying conditions such as altitude or weather changes is the main jet and the easy to acces idle mix screw, everything the needle meters comes thru the mainjet so if you decrease the mainjet you decrease the fuel flow that the needle meters. and its so easy to swap a main in a TM on a DS that you've got it made way better than anybody else, way better off than the raptor riders, and the banshees, etc. I've been traveling with the TM for 3 years now and everywhere I have ever been from sea level to 10K time after time I've had it easier than everybody else in my party. Even at Walden Colorado I'm yanking wheelies up the tree shoots coming outa the woods. All I ever do is drop one main size for every 1500 feet I rise and it stays in pretty good tune, better than most.

indiana, illinois, michigan - we're all the same altitude, I never change my TM riding in each of these places.

You gotta just call the bike shops around you and ask them if they have dyno, I called around Indy and there are several here, any decent size city with a variety of bike shops otta have at least one I would hope. Even if you gotta drive a while to get to it, make a day of it and have fun. Bigwaynster drove 3 hours one way to Indy to dyno with us, its worth it.

some shops charge by the hour, some charge by the pull. the one I went to charges $25 to put the bike on it and make the first pull, then $10 per pull there after no matter how long it takes to tune between pulls.

 

great info HT,
if you don't mind what pipe are you running for this run. Ive notice a big reading difference in my air/fuel ratio meter readings on my going from 18 supertrapp disks to a full open. my readings went from .875 to .950 to .720 to .850 so it leaned out quite a bit. I haven't had time to mess w/ it to much yet but the meter is money well spent. a dyno would be better but I think the meter is the next best thing.
Sam