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Anyone dyno their bikes to get a good read on A/F?

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Excuse my ignorance as I am still learning so much. Some of you guys have been like a virtual pit crew and I really appreciate all the feedback. I know it probably is frustrating seeing the same topics and questions over and over. I did research on the matter and I don't think I want to invest in a A/F meter as I might be changing the exhaust out (depending on results) and I don't know any welders. I have reached out to a few dyno tuners that do carb'd bikes but they are all 1.5 hours away. I haven't heard back but I can imagine they wouldn't sit and wait while I tore the bike apart to change jetting without it costing me my remaining arm and leg (good ol' aluminum frame WR450). 

 

Some mods came with the bike, some I did myself, but the list is:

 

2007 WR450f - stock exhaust with GYTR "high flow" baffle and the intake opened up

JD jet kit with 165 MJ, MAJ occluded from factory, 45 PJ, stock PAJ, red needle and 4th clip

AIS delete kit

Powerbowl 2 with stiffer AP spring - 1.5 turns out

Dynatek CDI with 3rd map advanced (TPS plugged in)

Stock cams

Valves are in spec but on the tight end. All wearable parts on the carb have been replaced. 

 

The bike runs fine. It starts easy and idle is consistent. I had a hard time getting the PJ dialed in because I still have the ACV installed in the factory configuration. The bike feels great on the low end with lots of power and no hesitation although it can be a bit touchy on the throttle. My mid-top end feels like it is lacking in power. I was at a 168 MJ and tried going up to a 170 MJ but noticed a flat spot up top and I could smell the fuel. I tried a 165 and it felt better but the occasional pop on decel now. My head is spinning with all the variables in jetting that I wanted to get an A/F reading to get answers. Am I barking up the wrong tree and just noticing the limitations of a stock exhaust? The bike just rips up until it hits higher revs at WOT.

 

KRAN, if you are reading this, I owe you a round if we ever find ourselves in the same watering hole. 

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I've never A/F ratio via dyno tuned any of my bikes for one simple reason; Dynomometers are designed for measuring peak hp at wide open throttle using a fixed load.  This is not anything like what you experience when riding off road. In fact, closed to partially open throttle is the most common condition when riding. 

Having said that, I have  followed dozens of threads where bike owners have added A/F ratio meters on their bikes and read along as they have analyzed their jetting using 'real world' riding condtions.  They usually come to the same conclusions that the 'tuner's come to, and I have been copying that info.

I use seat of the pants tuning. 

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^^^ This.

Very, very few shops have an actual brake dyno. Almost all are drum inertia ones designed to measure only peak power.

I do use a wide band on bikes to check jetting. Specific testing is done (steady state throttle on an even grade to induce a 'controlled load') to ensure useful and repeatable data.

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3 hours ago, THE KRAN said:

Having said that, I have  followed dozens of threads where bike owners have added A/F ratio meters on their bikes and read along as they have analyzed their jetting using 'real world' riding condtions.  They usually come to the same conclusions that the 'tuner's come to, and I have been copying that info.

I use seat of the pants tuning. 

It seems that most everyone that had installed an A/F meter has a configuration much different than mine (exhaust, cams, filters). I know that different bikes will run differently at different temperatures too. I would love a wideband O2 sensor but thats just not in the cards for me. I guess I'm just overwhelmed by how many factors you consider for each change and the subsequent effect it has.

I am stuck thinking about changing the exhaust, cams, or modifying the carb to open up the MAJ at this point. I am only wanting this because of how the bike feels on the top end. It could also just be the fact that this is my first thumper and that's just the way it is. I don't have anything to really compare it to.

Do you two have any thoughts on where I should look to for improvement? How do the numbers look at 500-1000' elv. with temps between 70-90 currently.

Edited by Nixinus
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Howe 'opened' is the airbox? A 165 main should be plenty big enough unless you removed the entire top. A carb depends on some air flow resistance to draw in fuel. The stronger the resistance, the greater the vacuum signal and the greater the ability to draw in fuel. Main jet size does not correlate to power output. I bet I could tweak your intake to need a 180 main (power will not change) or as small as a 155 and the power would still remain unchanged. An engine is a pump. You need to get air AND fuel in, burned and exhausted as best as possible for maximum power.

Perfect jetting for a a particular air density and pretty close jetting on a 4S make darned near the same power, maybe a few percentage points difference. So if your bike makes 50hp PEAK, jetting might vary that by .2hp. Nothing except to a top tier pro.

Trust me, you are probably not using all the power the bike makes. Only the top A level and pros do. The rest of the real world use at best, 70% power of a stock bike. They just think they need more power.

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I completely agree with you. I tried to avoid phrasing that suggests I think the bike is not powerful enough or that I somehow needed more ponies for my put-put around town. The bike is PLENTY powerful. I am really enjoying everything I have learned about bikes starting with my first streetbike. I am self taught with the help of books and forums so this is more of a continuing education. Throughout all the years I have always just set my carbs up with a kit and never touched them again. 

I have two circles cut out the top of the airbox, about 2-2.5" diameter. All the jetting changes have given the low end some snap and excellent throttle response. The mid-top end feels like it plateaus early. I don't know if that's physical limitations of the setup I have or a setting I can change (i.e. jetting).

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If you were lean, the bike would sound 'dry' and it would simply fall flat on it' face until rpms dropped. If it were too rich, ir would sound 'wet', having a "blatty" tone. It would misfire at WOT.

Some seat of the pants tuners find these two extremes, find the mid point and go just a bit rich of the mid point. That often works.

James Dean basically does that, but to get expected results, you must follow his instructions to a 'T'. If he said do X to the air box, do X, do not fall in to the trap is if a little is good, more is better.

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On 8/23/2017 at 10:34 AM, Nixinus said:

I completely agree with you. I tried to avoid phrasing that suggests I think the bike is not powerful enough or that I somehow needed more ponies for my put-put around town. The bike is PLENTY powerful. I am really enjoying everything I have learned about bikes starting with my first streetbike. I am self taught with the help of books and forums so this is more of a continuing education. Throughout all the years I have always just set my carbs up with a kit and never touched them again. 

I have two circles cut out the top of the airbox, about 2-2.5" diameter. All the jetting changes have given the low end some snap and excellent throttle response. The mid-top end feels like it plateaus early. I don't know if that's physical limitations of the setup I have or a setting I can change (i.e. jetting).

By the way to derestrict a WR450 you are supposed to unscrew the binocular snorkel on the top of the air box and remove it completely.  

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6 hours ago, stevethe said:

By the way to derestrict a WR450 you are supposed to unscrew the binocular snorkel on the top of the air box and remove it completely.  

The snorkel is out and two circles have also been cut out of the airbox by the previous owner. JD seemed to think that was ok as he referred me to the std. jetting described in the kit.

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1 minute ago, Nixinus said:

The snorkel is out and two circles have also been cut out of the airbox by the previous owner. JD seemed to think that was ok as he referred me to the std. jetting described in the kit.

Should be fine. I cut everything out of the top of my air box and drilled four 1" holes on both sides. But mine has a built motor. 

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1 minute ago, stevethe said:

Should be fine. I cut everything out of the top of my air box and drilled four 1" holes on both sides. But mine has a built motor. 

Yea, and I am still running the stock exhaust with an bigger insert. 

 

I got a pretty good idea of things from your responses. The bike runs fine now so I will just run it. When it comes times to rebuild the motor I will look into performance matching the engine/exhaust/intake.

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