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AFR testing stock and near stock - Shocker!!

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In the interest of providing the group with what I hope to be clear information (AFR meter data) on the most common basic mods (while I wait for my DJ lit from ProCycle:), I put the bike back to pure stock for a baseline. Except for the header weld grind which I can’t reverse. In MX_Rob’s epic needle comparison thread, :moon: he at one point did back to back AFR runs with the un-ground pipe and then with the header weld ground down, and saw no impact on the AFR readings so I don’t think this should skew the data.

So the baseline I started testing with today is a completely stock air box with the snorkel installed and stock main jet (MK 140), and NO shim. The bike is a 2008 DR650. Geared one tooth down on the CS Sprocket, and I am at 65’ ASL. (East side of Orlando FL). This was a new experience for me because I pulled the snorkel out and started playing with the jets the day I got it.

Interesting! The Suzuki engineers knew what they were doing. They just didn’t have the same goals you and I may have. In almost all cruise conditions, the meter is showing at or near 14.7. Sometimes flickering a little higher and sometimes a little lower but averaging right on Stoicimetric. At WOT I was seeing low to mid 13’s. So for from a passing EPA regs and max MPG, they hit it right on the nose. But, if I snap open the throttle; I get the big bog I have heard so much about. The AFR jumps to the red and reads 17-18-19 for just a second or so. Very annoying. The front wheel is hard to lift even in first. If I bounce it and catch it just right it will come up a little but not very impressive. Cruise feels a little rough and “lumpy” but not too bad. If I pull on a little choke, it smooths out. So far this is about what I was expecting. But stand by!;)

The next step was to pull out the snorkel and leave the jet and needle stock. I was expecting to see everything get leaner and the bog to get much worse. WRONG!!:worthy: It got richer!! Bog all but disappeared!!:busted::jawdrop:

This can’t be, I MUST have screwed up something, so back in with the snorkel. Same results as before. Back out with the snorkel, just 3 minutes to pull the seat and the snorkel so identical conditions. But again it got richer! *** is going on here?? :confused:I put the snorkel back in and went for a long ride, stopped pulled the snorkel and rode back home. Same results.

There must be some vortex, or fluid flow kind of magic at play here with the snorkel that I have no idea about. Time warp, worm hole, alternate universe, I just don’t know.:thumbsup: But the plane fact is that the jetting is wonderful, if a little on the rich side with stock jet and needle and no snorkel. WOT drops to the 12.5 – 13.1 range. Cruise at every speed I tried is around 13.5. Front wheel comes right up in first gear with just quick twist of the wrist. A very slight bog sometimes but nowhere near what it was with the snorkel in. Going up in the main or shimming the needle would seem to be the logical thing to do, but from what my meter is telling me it is exactly the wrong thing to do!:smirk:

Interesting that ProCycle said he had to go DOWN on the main when tuning on the dyno with just the snorkel removed to get max power. I didn’t understand that at the time but now it makes more sense. Rchill said he was running with snorkel pulled and stock jets and when he put the snorkel back in, it didn’t seem to run good. Now I think I know why, he was use to the much better running no snorkel and stock jets setup so putting the snorkel back in made it run worse.

So if I haven’t missed anything or made any gross errors, the good news is that for stock air box and needle setups, just yank that snorkel out and you have a much a much stronger and better running bike.;) No need to change the jetting! But don’t throw away the snorkel. Save it for when you want to take a trip and get max mileage. Just snap it back in. No jetting change needed.

I did experiment with the needle shimmed at both .030 and .040, and the snorkel out. As expected (for once!) they made the mixture just a little richer. Not much difference between .030 and .040 and both a bit too rich but ran well. They don’t seem to hurt anything but will reduce MPG a little. So I wondered if I could uncover one of my 1” holes to lean it out a little. NOT.:confused: It got way too lean. Cruise AFR went to 15-16. I didn’t even get off the block before turning around.

I am going to run with the stock jets until I get the DJ kit and then start opening up those air holes again!! I want to see how big I can go on the air box with the DJ needle and jets. Need to get that front wheel up in second gear anytime I want!:p

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Gauge only, the only data logging is in my head. Not a real reliable system given my advanced age!:thumbsup:

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Interesting that ProCycle said he had to go DOWN on the main when tuning on the dyno with just the snorkel removed to get max power. I didn’t understand that at the time but now it makes more sense.

That was strictly jetting for max power not for AFR numbers.

So if I haven’t missed anything or made any gross errors, the good news is that for stock air box and needle setups, just yank that snorkel out and you have a much a much stronger and better running bike.:thumbsup: No need to change the jetting!

Most riders will not be that lucky. The more common result of pulling the snorkel and doing nothing else will be a bike that runs so poorly in the midrange as to be nearly unrideable.

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Hey jaeger22; you have seemed to set my heart at ease about the 'getting a leaner running engine with the snorkel removed'. I've only read that one must shim the needle with pulling the snorkel. I don't even know how to shim the needle, but with your experience with running the stock needle and jet as I do, it gets richer? Good!, I guess. I only know with the snorkel out and totally stock BST-40, is has great pull at higher MPH, feeling it mostly going from 65 -75 or 80 MPH. I think your CS sprocket might make for the easier pulling of the front wheel. Not sure. Thanks for all your work and input on the DR with your AFR meter. Most of us don't, won't, or can't do that type of research on our bikes. I do hope that your work has assured me that just pulling the snorkel out and leaving everything else stock will do no harm to the engine. As I've said prior, it DOES run fantastic bone stock with only the snorkel removed. I ain't changing nothing!:thumbsup: Runs great with only that simple easy to do mod that I learned of here at TT. Thanks again for you input and research on the DR with your AFR.

rc

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That was strictly jetting for max power not for AFR numbers.

Yes, I totally understand that. I was surprised when you first said that because I expected the removal of the snorkel to drive it very lean, too lean for max power. But I see from my readings today that it didn't go way lean.

Most riders will not be that lucky. The more common result of pulling the snorkel and doing nothing else will be a bike that runs so poorly in the midrange as to be nearly unrideable.

That is what I expected to see on my bike. And I didn't think that my bike could be that different from the others in stock form. You have a good point in that I am looking at a sample size of one and making general assumptions. From what RC said above, it looks like he has a bike that does about the same thing as mine. Maybe some do and some don't but I would expect identical setups to act very close to the same. I know you have a lot more experience, :worthy:have you actually seen stock bikes or ones with identical mods act that differently?

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have you actually seen stock bikes or ones with identical mods act that differently?

Yes. My own. When I first got it and started playing around trying to make it run properly. Just removing the snorkel made it run horribly. Not even remotely driveable :thumbsup: Shimming the needle .030" and installing a 135 main jet fixed it right up and gained almost 3hp over bone stock.

From all the DRs I've seen here and all the others I've read about on the various forums I believe there is quite a bit of variation between individual bikes. Folks with the same mods end up with different jetting setups. Some riders with stock bikes report getting 60 mpg while others report never getting better than low 40s.

When stock, my bike made 34 HP on my dyno. When a local long time customer of ours bought a DR and brought it over for testing it clicked off 37hp in totally stock form.

It's my guess that there are a lot of production variations that affect compression height and cam timing. Suzuki specs tell us that the stock motor has 9.5:1 compression but the ones I've measured were closer to 8.7:1. Dave Searle at Motorcycle Consumer News measured his at 8.8:1. On my '99 motor the base gasket surface is out of parallel with the crank bore by about .005". If Suzuki is that sloppy with all the 'non critical' tolerances in the motor it's easy to see how some bikes would run differently that others.

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Wow! I had no idea there was that much variation.:thumbsup: Looks like I will have to avoid making generations based on my results and just report what I find.:confused: With the proviso, YMMV. I do think it would be worth trying the bike after pulling the snorkel before adding the shim, just to see. On the other hand, the shim does not hurt much even on mine. Just a bit rich.

Maybe the ideal path is to try both and see which seems to work best, both for mileage and power.

Thanks for your insight ProCycle!

John

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Yeah, the variations point out the need to actually do the work of testing and tuning which you have jumped into with both feet :confused:

And yes, pull the snorkel and see how it works first before doing any thing else. I have read reports of riders doing just that and being quite happy with how their bike runs. There are also a few who shimmed the needle and left the snorkel in with good results.

test, tune, test, tune, test, tune, test, tune, test, tune, test, tune, test, tune, test, tune, test, tune, test, tune, test, tune, test, tune, :thumbsup: in that order!

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Yes. My own. When I first got it and started playing around trying to make it run properly. Just removing the snorkel made it run horribly. Not even remotely driveable :thumbsup: Shimming the needle .030" and installing a 135 main jet fixed it right up and gained almost 3hp over bone stock.

From all the DRs I've seen here and all the others I've read about on the various forums I believe there is quite a bit of variation between individual bikes. Folks with the same mods end up with different jetting setups. Some riders with stock bikes report getting 60 mpg while others report never getting better than low 40s.

When stock, my bike made 34 HP on my dyno. When a local long time customer of ours bought a DR and brought it over for testing it clicked off 37hp in totally stock form.

It's my guess that there are a lot of production variations that affect compression height and cam timing. Suzuki specs tell us that the stock motor has 9.5:1 compression but the ones I've measured were closer to 8.7:1. Dave Searle at Motorcycle Consumer News measured his at 8.8:1. On my '99 motor the base gasket surface is out of parallel with the crank bore by about .005". If Suzuki is that sloppy with all the 'non critical' tolerances in the motor it's easy to see how some bikes would run differently that others.

I read that series on the DR in MCN (blueprinting...all the way to the bigger piston) very good read. I am not into the big piston stuff, but the work to return the compression to the designed ratio, that sounds like a project that will yield real results w/o comprimising engine life. I guess it makes sense. The engine was designed to handle 9.5 to 1, so all the parts are spec'd so that is the max you can get but all the tolerances are stacked so they will give 9.5 or less. with the way that works out most bikes will have less as Jeff mentioned

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