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Way rich jetting and still 3-4k stumble?

Old 09-08-2007, 08:58 AM
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Way rich jetting and still 3-4k stumble?

My new to me Hawk has a K&N filter and full Micron exhaust. Trying to hold a steady rpm at normal cruising range produces the 'lean' feeling stumble. I just pulled the carbs and found 190/195 mains, 45S pilots, needles in next to richest setting. I spent 3 hours last night reading everyones jetting threads and that setting sounds like it should be wayyyy too rich. Any guesses as to what the problem could be? Can you get a rich stumble?
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Old 09-08-2007, 12:41 PM
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Sounds like you have the Dynojet kit installed & jetted for the K&N filter. (because of the #45 stock size pilot jets - FactoryPro kits came with #50 pilot jets)
Dynojet suggested running those size main jets with the K&N
Stock filter was the 180/185 jets....as I recall.
I've heard of a several S'hawk owners having your problem running a K&N

You might try # 48 pilot jets
the 2500-3500RPM range is right at the transition area between the idle circuit & main jet/needle

My S'hawk had a stock air filter, 180/185 mains, needles on the 3rd clip, #48 pilot jets & worked great with no stumble

Visit http://factorypro.com/ > product support > CV carb tuning > high RPM engines

More on Keihin Carbs& how they work: (not specific to the Superhawk)
http://www.gadgetjq.com/keihin_carb.htm/

http://www.sudco.com/keihin.html
http://www.carbparts.com/keihin/need..._your_carb.htm

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Old 09-08-2007, 01:02 PM
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Great info!! Thanks CNI Dawg!!
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Old 09-08-2007, 01:23 PM
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Assuming it is a Dynojet kit, you could go to their website and download the pdf of the instructions for the VTR jet kit. It is kit #1185.

Given your filter and exhaust, what Dynojet recommends would be 190f/195r and needles fifth groove from top and pilot screws 2.5 turns out.

Sounds like that is how it is set on your bike. Still might be a bit rich for your individual bike, but you might want to check the resistance reading of the throttle position sensor and make sure carbs are in sync before you start changing jets and needle position.
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Old 09-08-2007, 02:10 PM
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drop the clip to the 5th slot on the needle

Mine did the same thing and that cured all
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Old 09-08-2007, 03:24 PM
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I haven't set my tps yet. One piece of info I left out...front plug is nice and brown, rear is white. My first thought was a vac leak but I tried the WD40 test and not even a slight rise in idle was detected. The seat of the pants dyno tells me it's rich everywhere else - it just has that 'wet' exhaust note and it's not crisp. But I am by no means used to a v-twin, so I can't judge things with much authority. I will also add that the problem isn't just at 3-4k, I just noticed it there the most because that's cruising rpm for the most part. No matter where you try to hold a steady throttle it's notchy. Whack it open though and it's right there with no hesitation.

I rode an '03 GSXR1000 last night and it felt like it had an electric motor. I told the guy it was a big 2-wheeled sewing machine!

Josh, so you have the clip in the richest position? Is there supposed to be a washer under the clip (both my carbs had one)? Man, that just doesn't seem right to have to run it that rich. That is off the charts richer than stock!
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Old 09-08-2007, 03:47 PM
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If that rear plug is white it is running too hot. Needs to be a little more on the rich side. Also syncing the carbs might be a good idea. Your idea of checking for an air leak is excellent - make sure you've checked all of it thoroughly. I messed an engine up pretty bad by missing one a while back. Bring out the inspection mirror and go for it. Make sure you push the rubber around as your looking. What may be nothing at an idle is vibrating open under road conditions.
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Old 09-08-2007, 03:51 PM
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there was a shim, but i think i put it on top of the clip. With the K&N you gotta have it in the 5th notch.

Dyno jet installation with K&N

Drill holes in slide
190/195 mains
New needles with clip in 5th position
shroter springs
Leave piolets alone

When i installed mine i didnt read the directions completely the first time and it ran like ****. The very last part of the instructions said that if using a k&n filter you must put the clip in the 5th positioin and not the 4th on the needle.
I had a nasty mid range stumble like your describing so i took the carbs out again and re read the instructions and realized what i did wrong. Runs like a top now
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Old 09-08-2007, 04:11 PM
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Driven;

Assuming they are Dynojet needles, they have six grooves. If you have one groove showing between the e-clip and the tip of the needle, you are in the fifth groove from the top already.

Per the Dynojet instructions, your jets and needle position are spot on for a K&N with a Micron full system.

If one plug is white, I'd check that carb's diaphram for a tear or hole and make sure the O-ring between that carb and the airbox is intact and fitted properly.

Also the syptoms of an out of spec tps include unevenness at steady state throttle and with small changes in throttle position.

PS Needles clipped 5th groove from the top is only one more than Dynojet specifies (4th from top) for a VTR with stock airfilter and cans.
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Old 09-08-2007, 07:50 PM
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sometimes we cant see the forest through the trees. . . hell, i do this all the time.

anyways, if one plug is white, you have a vacuum leak. period. your settings are very rich and you shouldnt have ANY stumble when on 190/195, 5th - 6th ring, stock 45s... regardless of brand of pipes and filter. i have really open MIG pipes with a k&n and i am on 5th ring, 180/185 and stock 45s and not a problem. if one plug is white, you have a leak. . . if not in your carb boot maybe manifold or somethin else. i had the same issues. got a new 30$ boot and it was a done deal. i tried one time using hose clamps, but the band was wider than the rubber boot's groove to fit the band, and it cut it open. dumb idea. be sure to hand tighten the boot clamps. i use an 8mm socket with 2 6" 3/8" extension arms, and i put em all together and can tighten the boots with a final half turn by hand with the tank on! works great. but i never use the socket driver to turn the 8mm socket, just my hands. i found the rubber boot with actually bevel out away from the carb throat if tightened too much. well, good luck. just my 3 cents
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Old 09-08-2007, 09:18 PM
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I'm also convinced the jetting is fine. I also agree that either it's getting extra air from somewhere or not enough fuel. I'm hoping the latter as trying to find vac leaks is a nightmare. Couple of causes for not enough fuel may be a clogged jet or float level too low.

So is WD40 the preferred method for finding air leaks? Will carb cleaner work just as well?

I'm gonna have to leave it parked until I figure this out - lean conditions can cause major damage.
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Old 09-08-2007, 09:39 PM
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driven;

I think Cleveland is right- the first place to look for an air leak is the booty between carb and manifold. I would just pull it and look it over real good. Next to check would be carb to airbox mating.
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Old 09-09-2007, 12:08 AM
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Driven... WD40 is probably fine, don't use carb cleaner it is too harsh, I use starting fluid and get good indication. be sure to use small squirts with a good pause in between, and use the red tube to pinpoint the area in question
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Old 09-09-2007, 12:44 AM
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Hey Driven,

have you pulled the snorkle out of the front of the air box yet?? I have the same stumble at 3-4k. I have the dynojet jet kit and erion pipes with a K&N filter. After i pulled out the snorkle the problem went away on my bike. I do not know if this will work for you but it did on my bike

Dennis
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Old 09-09-2007, 07:28 AM
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If you're carbs have been removed and reinstalled by someone inexperienced with the VTR then the carbs may not be completely seated. There is a trick to it. First, some type of light lubricant such as silicone spray aids greatly. Secondly, you need to install the rear carb first, then once you can get the front carb in you have to press down pretty hard until you feel them seat. There will be no doubt when they are in correctly. You should look to see if the boots are even all the way around the carb throats.
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Old 09-09-2007, 01:20 PM
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Originally Posted by Hawkrider View Post
If you're carbs have been removed and reinstalled by someone inexperienced with the VTR then the carbs may not be completely seated. There is a trick to it. First, some type of light lubricant such as silicone spray aids greatly. Secondly, you need to install the rear carb first, then once you can get the front carb in you have to press down pretty hard until you feel them seat. There will be no doubt when they are in correctly. You should look to see if the boots are even all the way around the carb throats.
I definitely felt it 'seat' but did not use the method you suggested. It did not appear perfectly even all the way around like the front though. I will pull the carbs and reinstall them per your instructions. 2 questions though...

1. I have sprayed wd40 all the way around the boot at the carb side and engine side and no rise in rpm, so I have doubts about it leaking there. I did the test at idle. Is it recommended to perform this test at say 1/4 throttle as well? Perhaps the greater vacuum signal from the higher rpm will cause it to leak when there is no leak at idle? The bike idles perfectly.

2. When installing the carbs, is it done as one big assembly with them 'linked' or do you leave the link bar loose when installing the carbs and then tighten afterwards?

Thanx!
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Old 09-09-2007, 09:46 PM
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Engine vacuum is higher at idle than any other time. Guess you've never sync'ed your own carbs, eh?

You should NEVER loosen the carbs from each other. Install them as one assembly. If you've loosened them then a carb sync is imperative.
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Old 09-10-2007, 04:59 AM
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Nope, never done it. I have not separated the carbs, it was just a thought. I am pulling them off again and checking the float levels as well as cleaning all accessible ports. The bike did sit for a while before I got it. I really don't think it's a vac leak, especially if vac is higher at idle. The bike idles perfectly. I'm hoping to find a clogged pilot.
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Old 09-10-2007, 07:51 AM
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keep in mind elevation too.
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Old 09-10-2007, 02:06 PM
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I HAVE THE EXACT SAME PROBLEM, ONLY I KNOW THAT MY BIKE IS RUNNING RICH, WHEN BLUE FLAMES COME OUT OF THE EXHAUST, ABOUT 6-8" I'LL ASSUME IT'S RUNNING RICH, BUT IT LOOKS SO COOL AT NIGHT THAT I'VE LEARNED TO LIVE WITH A LITTLE STUMBLE @ 3300 RPM. USUALLY BY JUST GOING FASTER. I STILL GET ABOUT 35MPG, AND SCARE THE HELL OUT OF OTHER RIDERS!!!!!!! P.S. VANCE AND HINES EXHAUST SOUNDS FRIGGN AWESOME!
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Old 09-10-2007, 05:01 PM
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I think if you're blue flaming that's better than black chugging. The point is to be about the same on both cylinders and not have one rich and one lean.
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Old 09-11-2007, 06:29 AM
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I'll be digging into it tonight. Any other suggestions besides what was mentioned above? I'd like to get this squared away as I have decided not to keep the bike and would like it to be problem free before selling it to someone. This is literally the only flaw it has. It's a great machine, I just should have never rode my buddie's GSXR1000...
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Old 09-11-2007, 10:18 AM
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FYI I called Dynojet's tech service and they told me to go to the last clip on the needle. That seems excessive to me, but I'll try it as it's far easier than removing the carbs. Is there any harm in having the rear needle one step richer than the front? Greg?
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Old 09-11-2007, 12:42 PM
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although it may cure some stumble, both jet needles should be at the same level. the only time the air fuel mix needs to be richer in the rear cylinder is at idle, when it is impacted by heat the most..sitting still. hence, you only need to make the air/mix screw in the rear 1/4 out(richer) more than the front. again. i wouldnt worry about jetting issues. your already very rich for your setup. if one plug is white , and the other dark tan or black, then the white cylinder is running way too lean, and it automatically makes me think vacuum leak. just cant tell ya where if you checked the air box connection, snorkles are plugged, holes are plugged, and your manifold boot seems sealed. very weird. keep us posted. just my opinion, but worry about all the screws and holes and snorkels first. somethins funky on that rear intake.
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Old 09-11-2007, 01:10 PM
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What snorkles and holes are you referring to? The rubber boots that sit above the 2 pcv type filters inside the airbox?

I know all indications point to vac leak, but the wd40 test has yielded nothing. Is there a better way to find a leak? Would starting fluid work better? I have sprayed all around both ends of the boot including the barb for the petcock vac hose, all around the carb to airbox, basically everywhere I can think of. I didn't like the idea of offset needles either. I'm still wondering about a possible low float level as it would explain a decent idle but problems as the motor calls for more fuel. But then again it doesn't hiccup in the least when abruptly twisting on it. Also wondered if somehow the flow from the tank itself isn't what it should be on the side feeding the rear carb? I don't know. I can think of several things but the bottom line is that it's getting too much air or not enough fuel. I'm afraid to ride it until this is fixed.

Last edited by driven; 09-11-2007 at 01:24 PM.
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Old 09-11-2007, 01:49 PM
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Originally Posted by ClevelandSuperhawkRumble View Post
although it may cure some stumble, both jet needles should be at the same level. the only time the air fuel mix needs to be richer in the rear cylinder is at idle, when it is impacted by heat the most..sitting still. hence, you only need to make the air/mix screw in the rear 1/4 out(richer) more than the front. .
Well I have to disagree with you on your statements.
First- the rear cyl. always needs to run richer than the front, that's why it has a larger main jet.
Second- the temp. difference is greater at speed as the front cyl. gets addional air cooling, that is why the pilot jets are the same size.
Third- while a whole clip difference is quite a bit, the HRC jet kit has you add one more shim (.5mm or .020") to the rear needle, which would be close to 1/2 a clip slot.
I do agree with you on checking everything else first and stagering the jetting is the last thing to play with but it can be a good thing.
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Old 09-11-2007, 01:54 PM
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8541 - your right, all circuits in the rear cyl are to some degree impacted more so than the front by heat, but to turn a plug tan/dark in the front and ghost white in the rear?....well, we have another issue more severe on our hands.

Driven - on my setup, i have only 3 hoses that are functional coming from air box, and both are on the pvc type connectors. if you were sitting on the bike like you were riding it but looking down into the open airbox, it would be the upper left large hose and the lower right large hose. then i connect the little hose in the lower right as well (breather from rear of carb) . your float bowl theory is valid, but unlikely. see how thats the only thing i could think of as a last resort, ide check it out. any others with float bowl symptoms and solutions?

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Old 09-11-2007, 02:01 PM
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Originally Posted by ClevelandSuperhawkRumble View Post
on my setup, i have only 3 hoses that are functional coming from air box, and both are on the pvc type connectors. if you were sitting on the bike like you were riding it but looking down into the open airbox, it would be the upper left large hose and the lower right large hose. then i connect the little hose in the lower right as well (breather from rear of carb) . your float bowl theory is valid, but unlikely. see how thats the only thing i could think of as a last resort, ide check it out. any others with float bowl symptoms and solutions?
You should have four hoses, 2 from the the crank case breathers (the large hoses 1 ft & 1 rear that go to the plastic bottle inside the airbox) and 2 from the carb slides (the small hoses deliver filtered air to the back side if the slide diaphrams so when they move they don't suck in dirt which could destory the slides and possibly the carbs.)

Well now that you added more to your post.... I agree that he has a major problem and I also don't believe it's jetting related, I just wanted to point out that the rear needs more fuel as it always runs hotter and that you can stagger the needles with no ill effects.

Last edited by 8541Hawk; 09-11-2007 at 02:04 PM.
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Old 09-11-2007, 04:10 PM
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I know this is way too obvious, but have you checked to see that your K&N is properly oiled (not too much oil, nor too dry).. I'd hate for it to be something this simple.
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Old 09-11-2007, 08:21 PM
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Well, pilots were clear, floats were right on spec, carb boot has no holes, rips, etc, carb to box seal is fine, yada yada yada. I am at a loss. It still runs exactly the same. I haven't synced the carbs or set the tps. However I don't see how that will change anything unless advance is happening too soon. That should affect both cylinders though, not just the rear.

I will try moving the rear needle to the last clip, but I feel like that's just masking some other issue I'm missing. At this point if it makes the stumble go away and ends the dangerous lean issue I'll dance a jig. I really want to like this thing but so far it's been a big disappointment. I suppose last resort would be to return everything to stock and see what happens. I might have about 6 weeks of riding left. Clock is dwindling and so is my patience!
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