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Old October 8th, 2010, 08:56 PM   #81
JMcDonald
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Ooooooooh ok I gotcha!! Thanks .
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Old November 24th, 2010, 05:00 PM   #82
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I got my new exhaust put on, and i had to make some modifications to the mufflers to quiet it down, and ended up possibly reducing flow more than I anticipated. It performed worse when i drove it with the same jet settings, so i went up (to 115) thinking it must have been lean, and it was even worse. Going down (to 110) helped some but the top end still seems worse than it was with the 112s and stock exhaust.

After getting still-poor results with the 110 jets, I swapped the stock exhaust back in place and it is about the same top-end performance! I will do a highway run on the way home tonight to see if its any better with the 110s vs the 112s, but it doesnt really feel any different up top.

Conversely, after tuning the low end a bit with the new exhaust, it pulled better than ever at low throttle openings, so i cant figure out why the top end is so lacking.


I might try to drill out the "DB killer" i welded in to see if it was a flow restriction that is causing my problems. Id be willing to deal with more noise if it gets me the performance for which Im hoping. If the low-end response i mentioned before is indicative of what could be had throughout the powerband, I definitely want that.
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*edit*

The top speed is lower with the 110s than the 112s?!?! Tonight my speedo barely went over 100 when in the same distance I could usually approach 105 when I've had the 112s in for the past few weeks. This is just with nothing but a pod filter, so the 112 should have been way rich. What is going on?

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Old November 26th, 2010, 11:33 AM   #83
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Cut out the cores of my mufflers to open flow as much as possible. Now the exhaust consists of dual 1.5" pipes with mufflers using ~2.25"ID cores.

Changing nothing, I swapped it on and found the low-end to be very nice again, but the top-end waning. It pulls more slowly and tops out at about 90mph, whereas with the same setup like I said before it would . I didn't mess with the needle height, but I didn't think needle height affected top-end WOT power, and that is definitely down. Also, going larger on the jets made things worse

I am completely out of ideas. Does anyone have any suggestions? It pops and sputters when engine-braking, but I think that is due to the mixture screws being a little rich, no? Why is the top-end so poor when I know the exhaust is capable of flowing well, and I have tried all the jets from 110-115 with no results (with 115 being the worst and 112 and 110 being about the same)?
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Old November 26th, 2010, 07:19 PM   #84
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try 108s and see if the top end improves.

have you removed the kleen system? that usually gets rid of the popping on decel.
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Old November 26th, 2010, 09:48 PM   #85
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Yes I did get rid of the Clear Air system, though I wonder if it might be leaking a little, allowing fresh air into the exhaust system anyways. I guess I am just surprised that 110s would be too rich with this setup, but I know every bike is different. Frustratingly enough, my FP kit only came with 110 through 115 :-/ . So I guess I'll need to find a 108 set somewhere? I will also try playing with the needles some this weekend.
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Old November 26th, 2010, 09:50 PM   #86
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http://jetsrus.com/
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Old November 26th, 2010, 10:26 PM   #87
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Thanks for the link and quick responses. I went ahead and order the 102, 105, and 108 jet sizes just to cover all my bases. I figured I'd be annoyed if later on I ended up wanting something smaller than 108 and had to pay like $11 with the shipping just for one $3 parts pouch. Plus if I decide I want to go back closer to stock, I'll have some room to adjust.

Hopefully this helps.

Quick question. Has anyone compared performance of the OEM needles and aftermarket ones? Is there a noticable difference?
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Old November 27th, 2010, 12:09 AM   #88
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the stock needles are much leaner than the aftermarket ones.

also, the stock needles are not identical and differ left and right. they can be made to work with proper shimming, but to get things perfect, aftermarket needles work better.

check out the difference in taper between the stock and factory pro needles.
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Old November 27th, 2010, 07:23 AM   #89
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Ah gotcha. So the richer mixture at milder throttle openingd gives better performance?

Kelly, are you surprised that 110s would be too rich? I am wondering if the lack of a smooth transition between the ~1" exhaust ports and ~1.37" pipe id is cauing enough turbulance to reduce flow? I might have to work on that.
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Old November 27th, 2010, 11:59 AM   #90
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best performance is gained when the fuel/air mixture is closet to ideal for any given rpm point. stock jetting (on a stock bike) is lean on the bottom/midrange and rich on the top.

once you start making changes to intake/exhaust, you need to keep searching for the best combination of main, needle and pilot jets that provides the closest to that perfect air/fuel ratio.

add the fact that you are working with an exhaust with no R&D time on a dyno and my feeling is that the design of the pipe may be providing you with less power than a pipe from one of the major manufacturers. Pipe design is a blend of mechanical principles and black magic. It's not as simple as making something yourself and expecting the same results as a company that has invested time and effort to produce a product which provides the engine to make as much power as it's capable of.

to that end, you need to keep searching for the main jet size that will allow the engine to run in the sweet spot. gl... you're doing the R&D that most (some???) pipe companies go through before they release their product to market.
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Old November 27th, 2010, 03:54 PM   #91
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Quote:
Originally Posted by kkim View Post
best performance is gained when the fuel/air mixture is closet to ideal for any given rpm point. stock jetting (on a stock bike) is lean on the bottom/midrange and rich on the top.

once you start making changes to intake/exhaust, you need to keep searching for the best combination of main, needle and pilot jets that provides the closest to that perfect air/fuel ratio.
Oh I understand all this . I am mostly surprised that it needs less fuel up top than I was expecting.

Quote:
Originally Posted by kkim View Post
add the fact that you are working with an exhaust with no R&D time on a dyno and my feeling is that the design of the pipe may be providing you with less power than a pipe from one of the major manufacturers. Pipe design is a blend of mechanical principles and black magic. It's not as simple as making something yourself and expecting the same results as a company that has invested time and effort to produce a product which provides the engine to make as much power as it's capable of.
I am used to turbo performance in which case the best exhaust system is no exhaust system, and the next best one is the biggest one. In those cases, a 4" pipe is a 4" pipe and it doesn't matter if you made it in your backyard for $100 or spent $1500 on a professionally-made one. I guess I don't have a feel for how much exhaust gas velocity affects scavenging, and how much scavenging affects performance at different RPM ranges. With this exhaust, I actually expected a hit to the bottom range due to decreased exhaust ags velocity, and more power up top due to the reduction in backpressure. That my results are the opposite makes me wonder if these effects really aren't that significant, and if there is something else at work.

Perhaps there is an issue of higher-than-expected turbulance at the header inlet. I had previously considered that the system could be too large in diameter and thus maybe could not create significant exhaust gas velocity for scavenging even at peak flow. But, after seeing the increased torque and snappiness at low throttle openings and at the low RPM range (where ideal scavenging would typically show the largest gains), I am beginning to wonder if that is a small factor in this.


Question on fuel tuning:
Ok, so as you go from rich to ideal, the engine will continually pick up more torque through the range range, correct? If you go past ideal, into the "lean" range, will power also begin to wane predictably, or will hesitation and stuttering be the immediate next step once a mixture is leaned beyond the ratio for maximum power?
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Old November 27th, 2010, 03:59 PM   #92
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this is the best tutorial on seat of the pants carb tuning for the 250 ninja that I have found.

http://faq.ninja250.org/wiki/How_to_...ng#Carb_Tuning
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Old November 27th, 2010, 05:13 PM   #93
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Aah thanks for that reminder. I read that page when first looking into mods and forgot all about it!
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Old November 27th, 2010, 07:27 PM   #94
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My question was no really answered in that article, though. So, in your experience, how does a bike that is slightly too lean on the main jets feel? Does it just get less powerful, or do the obvious symptoms (missing, stuttering, etc) show up as soon as the mixture goes beyond stoic?

Thanks.
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Old November 27th, 2010, 08:31 PM   #95
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4 strokes are much more forgiving when it comes to jetting and agree as you approach "best" jetting, it can become confusing if you're too rich or lean.

When you are close to ideal and can't decide on main jets, here are 2 aids that I have used.

to test if the bike is too rich, run it up in a higher gear (4th or 5th) wide open and as you are at WOT, back off the throttle a bit and see if the bike picks up revs. If it picks up revs, your too rich at WOT and need to go down in jetting a step.

to test for lean condition, do the same thing and while at WOT, turn the choke on. If the bike responds with more revs and picks up power, the jets you have are too lean and you need to go up a step.

dunno what wasn't answered in that article... seems pretty straight forward to me.

Example:

~Start from stock.

~#105=Way too lean. Bike won't rev past 6K RPMs.

~#108=Bike revs to redline, but sputters at high RPMs.

~#110=Bike pulls hard to redline.

~#114=Bike bogs at high RPMs.

~Go back one size to #110s.

Symptoms:

LEAN = Stuttering. Runs better when bike is hot. White plugs.

RICH = Bogging. Runs better when bike is cold. Black plugs.
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Old November 27th, 2010, 08:40 PM   #96
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Like you said, as you get closer to stoic it becomes less obvious. I was curious what lied between "stuttering" and stoic, but from your description and advice it does sound like there is something between what is listed in the example you quoted.

Thanks for the pointers. I will utilize them tomorrow.
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Old November 28th, 2010, 03:25 AM   #97
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My brother in law pulled apart his zzr250 the other day and I decided to have a look at what main jet sizes these bikes run considering they are almost the same bike mechanically. Well I was not expecting to see a 105 main jet on a stock bike. I'm guessing it would be a Keihin jet too. So my question is why can't we run these in our bikes? Is it because of the cats in our bikes could clog up due to over fueling? I recently purchased a dynojet kit for my stock 250r and put in the 96's and the bike pullls to red line alot better than before. going off the jet size chart the 105 Keihin is the same as 102 dynojet and seems like alot to me on a stock bike. What do you all think?
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Old November 28th, 2010, 07:24 AM   #98
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Is the zzr250 the one that makes like 10hp more than the 250r? If so,that would explain it for sure.
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Old November 28th, 2010, 09:24 AM   #99
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I did about 5 miles strait today at WOT on 4th (at about 11-11.5k RPM and 88mph due to the strong headwind), playing with the choke and throttle while watching the speedo to see if I could figure out any correlations. I never got any conclusive evidence, because everytime I would see a change and think I did something, I would realize I was actually going slightly up or downhill.

So, I finally just pulled one of the plugs after coming strait home (about a mile total after getting off the highway).

I used to read plugs on dirtbikes and RC engines, but those were both two-strokes and thus should be exposed to more oil and such so I am not sure if the lean-rich scale is supposed to be different on 4-strokes. Even still, I was surprised to see how clean and white it all looked (both the insulator and surrounding metal). In my experience, pulling a plug like this from a 2-stroke meant it was running dangerously lean.


Comparing it with the dansmc spark plug chart ( http://www.dansmc.com/spark_plugs/sp...s_catalog.html ), it looks like its on the lean side. If pic #14 is ideal, mine looks to be closest to maybe #24. But, those plugs all look a lot dirtier than mine, so it is hard to make a direct comparison. Basically, on my plug the insulator looks a lot whiter / greyer than it should, and the surrounding metal has effectively no carbon deposits and has a greyish "dusty"-looking layer.

The plug has about 4000mi on it. This is with full exhaust, Pod filter, and 110 FP main jets with the needle clip in the middle position.


What does it look like to you guys?

Thanks.




*edit*


And I think my temporary seal for the kleen system (where that cap bolts to the head) is leaking, which would give me the pops and backfires, no? I might play with the jetting again today and I'll check that while I'm in there. If I have the time, I might just make a flat cap instead of re-using the stock one, if possible.
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File Type: jpg exhaust_intake_110main_sparkplug.jpg (86.0 KB, 6 views)
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Old November 28th, 2010, 03:37 PM   #100
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Welp, i guess ill just wait til the new jets come in. I tried the 112 mains again (I hadnt tried them since i removed the cores of my mufflers), and it would barely rev to redline and would even sputter some getting there (interestingly enough, making it feel lean). I let it idle for about 10 minutes while putting it back together, and rode for about 15 miles. I came back and pulled the same plug as before and the insulator now has a bit of a brown hue and the end of the threaded portion has a little bit of carbon buildup, as if just starting to get toward stoic. But why is it now running worse?
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*edit*

Here is the new plug pic (same plug though). Comparitively, it still looks lean compared to the pics on that webpage, but you can see the insulator getting a little brown and the surrounding metal starting to get some carbon deposits. But, like I said, performance was terrible.


Thanks in advance for any advice or pointers or whatever .
Attached Images
File Type: jpg exhaust_intake_112main_sparkplugs.jpg (49.8 KB, 4 views)
File Type: jpg exhaust_intake_112main_sparkplugs_2.jpg (62.0 KB, 4 views)

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Old November 29th, 2010, 07:00 AM   #101
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Am I reading these plugs correctly?


I found another page that, while providing way more detail and complexity than I was looking for, still is pointing to a lean WOT condition indicated by a white insulator:
http://www.4secondsflat.com/Spark_plug_reading.html


So, either I am still reading the plugs terribly wrong, or there is some other issue making WOT, top-end performance suffer when the mains are richened up. I'd like some input if possible on that.


But, I am waiting on the smaller mains to arrive and will see where I am at with those.
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Old November 30th, 2010, 07:43 AM   #102
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Not sure if everyone is tired of the topic, or if everyone just hates me, but I didn't expect after two days my many relevant questions and desires for clarification would still be left ignored :-/ .
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Old November 30th, 2010, 07:52 AM   #103
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Not sure if everyone is tired of the topic, or if everyone just hates me, but I didn't expect after two days my many relevant questions and desires for clarification would still be left ignored :-/ .
Give it a day or so. The forum has been slow since the Thanksgiving holiday started. I'm sure everyone will be back in the routine in a couple days and you'll see some answers.
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Old November 30th, 2010, 08:27 AM   #104
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Have you adjust your mixture screws? I did'nt see in your post that you said anything aout it.(I may have missed it). Your set up is the same as mine. I have a 110 in mine with my mixture screws backed out 2.5 turns.
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Old November 30th, 2010, 09:25 AM   #105
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Yeah with all of the main jet setups i have been able to get the low end quite crisp with the mixture screws. But, those should affeft WOT, top-end operation I dont think. I guess the main questions I have are whether or not I am reading the plugs correctly, and if so, why I might be having the opposite effects when adjusting fueling to compensate. I am guessing once I try the 108 main (or even 105), I might get some powerband back and will probably be ready to leave it alone. I just want to know if I am completely understanding the plug reading wrong, or if there might be some other problem.

Thanks.
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Old November 30th, 2010, 10:48 AM   #106
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the plugs look pretty close to optimum. how are you testing them? WOT and chop or just pulling them after you ride?

the danger is going too lean, of course... be sure to check for aluminum balling on the insulator.

btw, you should be reading the base ring, not the insulator color.
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Old November 30th, 2010, 12:39 PM   #107
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The first time I checked, it was strait after a 5-mile ride at a constant WOT when I was playing with the choke settings and minor adjustments of throttle from WOT. Got off the highway, rode the half mile home, and pulled the plugs. The second time was after about 15 miles of just generally assertive riding.

By the base ring, you just mean the flat, circular end of the threaded portion? If that is the case, would you say it looked better in the first pic (with the 110s), and worse with the soot buildup after switching to the 112 mains? If that is the case (with any soot being bad), then things are starting to make sense that I just need smaller jets.


Reading through the database, it is starting to make me wonder how FP ever thought 115 mains would have been necessary, heh. Seems 108-112 would have been far more universal?
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Old November 30th, 2010, 01:08 PM   #108
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I have an uphill stretch of road behind my house that I can pin the throttle WOT and ride a mile or so to my house when I test jetting. The best way is to WOT, chop the throttle, kill the engine with the kill switch and then remove the plugs right there for the most accurate reading.

Based on my testing on a 4 stroke dual purpose bike, you are looking for a grey color on the base ring (yes, the flat area that the electrode is welded to). The trick is to get as close to a grey color w/o going too lean (white) and melting the electrode.

For street applications (as opposed to race conditions) you want to stay on a bit richer side than at optimum, so based on your pictures, you're getting pretty close.

Signs that you are getting close to a too lean condition are very small aluminum balls (sometimes almost microscopic) on the electrode. If you get that, you know you're a step to lean and need to back off (go richer) the mains one step.

That's to isolate the mains. From there, you start playing with the needle clip position/s and finally the mixture screws settings. Remember, if you change the main jets, the other settings can change, so it's always better to select the main jets first and work your way down to the mixture screw settings.

Also, you should check the carb sync when you get to the mixture screw settings.
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Old November 30th, 2010, 03:23 PM   #109
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Hmm thanks for that info! That all makes much more sense now. It is sounding like maybe going to the 108 mains might be a step in the right direction, then.

Thanks again for the clarifications! I will report what I find in the next few days. The jets should come in tomorrow but i wont have them in for a while. I think I might put in the #40 pilot jet since even with the 110s it was a hair over 3 turns, so it would likely need more from the pilot jet with the smaller mains, right? And am I correct in understanding the guideline to be go to a larger pilot if the mixture screws are more than 3 turns out?
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Old November 30th, 2010, 03:40 PM   #110
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am I correct in understanding the guideline to be go to a larger pilot if the mixture screws are more than 3 turns out?
that's correct, but I would wait till you get the mains sorted, then the needle clip settings and then worry about the pilots. moving the clip position on the needles has a small affect on the pilot circuit.

if you find you need the 108s, you may need to compensate by going richer with the needle clip position, which will in turn richen the pilot circuit, which is why they recommend you start from top and work your way down, otherwise, you're pretty much guessing.

btw, if you have access to a good dyno shop in your area, you might want to consider taking the bike there to sort the jetting. your custom pipe may be giving you some results that are not common with an exhaust designed specifically for the 250 ninja.
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Old November 30th, 2010, 04:10 PM   #111
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Ah I was just figuring if I have to pull it apart again I might as well put in the larger pilots since it *should* still be within its tuning range, but you are right that this was largely an assumption, and that hasnt been helping me much with this project so ill just wait on that :P .

I dont think I will be able to budget dyno tuning into the project, but after getting things largely settled I might try to do a few runs to see how the curve looks and what the AFRs look like.

Thanks again for the help.
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Old December 4th, 2010, 05:00 PM   #112
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Everything from 112 to 105 on the mains gives the same top speed of around 95mph (i.e. no change in power from stock with the snorkel removed). With the 105s, it sounded cleanest up top, but part-throttle response was worse than stock (especially around 3-5k) due to being lean. The needles were already on the 4th position, and the mixture screws with #40 pilots were already set a bit rich. So, I didn't bother going down to 102 mains, figuring there was no way one more clip position was enough to get the midrange back with smaller mains.

This is with a K&N pod filter and stock exhaust.

When I first put on the filter and had the stock #98 jets, even with 4 shims on the stock needles, I could not go past 1/4 throttle and was basically speed limited to about 50mph due to it being unable to rev past about 6k. Am I missing something? How is it making the same power but requiring so much more fuel to run than before?

Thanks.

*edit*


Err, wait, can I put washers below a clip at the 5th setting? Or would needing to do that be a sign of needing to go back up in main size?
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Old December 4th, 2010, 06:33 PM   #113
kkim
 
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The basic rule of thumb is when you get to the 4th or 5th clip position, and the bike still runs lean in the midrange, go up one step in the main and start over trying to select the best clip position.

sounds to me like your mains are too lean if you need so rich a clip position.
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Old December 4th, 2010, 06:46 PM   #114
JMcDonald
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Hmm ok. Tried 102 mains with 2 washers under a clip in the 5th position, and there was still no change in the top end. Midrange was a hair rich, but nothing major.

So, does this not seem weird? How does it run just as well up top with 112s as it does with 102s? Especially if the 102s are, by this general rule, too lean and 112s are surely too rich?
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Old December 4th, 2010, 07:03 PM   #115
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dunno what to tell you. have you pulled the plugs to check what they look like after each main jet change?
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Old December 4th, 2010, 07:18 PM   #116
JMcDonald
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No, I didn't get around to that yet, since I haven't really seen any change in performance.

I am wondering if my diaphragm doesn't have a tear in it that I didn't notice. But, I am kindof grasping for air at this point. It's a little disappointing to spend all this money on mods and such to have the exact same performance I could have had with the snorkel removed, the stock needles shimmed, and the mixture screws adjusted. I hope I can figure this out.

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Old December 4th, 2010, 07:21 PM   #117
kkim
 
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from past posts, if you had a tear in a diaphragm, the bike would run like crap in the midrange and wouldn't get into the top end for max speed.

never hurts to check them, though.
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Old December 4th, 2010, 07:25 PM   #118
JMcDonald
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Yeah I have been reading through some posts and it seems like things would be way worse. I was just thinking if, for whatever reason, it couldn't develop enough pressure to lift the slides up all the way (say like, only 90%), limiting the maximum amount of fuel that could flow despite jet size.

Aarg...


BTW I have definitely noticed differences in the midrange with changes in jet size. I think I will go back to the 108 and play with the needles.


One last question: There really aren't that many things connected to the carbs, but is there anything that, left disconnected, would *slightly* limit power?


And thanks for the responses, Kelly.
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Old December 4th, 2010, 07:37 PM   #119
kkim
 
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loose or cracked vacuum hoses could do it, but the bike would idle like crap if they were your problem.

is the choke cable adjusted so there is some free play when the choke lever is closed?

throttle cables free play correct?
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Old December 4th, 2010, 08:43 PM   #120
JMcDonald
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Hmm, the throttle cable free play was pretty large (a good half an inch of motion was required at the grip to even get tension in the cables) and I adjusted it tighter, but the throttle does open and close all the way. The choke doesn't begin engage until about half way, watching the actual linkage.

I guess, more accurately, I am hoping it is some problem that will be simple to correct.



And damnit, Kelly, you're supposed to know everything :P .
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