| Author | Message | ||
     Nocompromise |
Ok, here is my jetting update - I installed the 175 main jet, 27.5 pilot jet, and have the needle raised to the #4 position (with #1 being leanest and #5 being richest). I also adjusted the Pilot Air Screw, which helped a lot with the rough idle and backfiring on deceleration. The new main jet has cured the pinging, but I seem to have another problem now. When I open the throttle quickly at 3000 rpms or below in 4th or 5th gear, the engine bogs and stutters really badly. If I open the throttle at a slow or moderate speed from 3000 rpms or below, the engine will behave normally and gradually pick up revs. Everything seems fine above 3500. This was not the case before I rejetted everything. I adjusted the needle 2 positions richer (from the stock #2 position to #4 position) first while I was waiting for the new jets. I didn't specifically notice the stuttering/bogging problem while running the stock (default might be a better term) jets and the richer needle position. So, I read through the HSR tuning manual and it sounds like it might be the main jet. I was guessing perhaps the needle might be in too rich a position so it allows too quick of a transition to the main jet. Could a 175 main jet be too rich for my engine? When I had the default 162.5 main jet it didn't exhibit this behavior. My setup is 1250 kit, Mikuni HSR42, 536 cams, Stage 2 XB heads, SE Ignition, Force exhaust, CF Ham Can filter. Any advice would be greatly appreciated! | ||
| Jayvee |
Here's that same sympton on the 4strokes.com site: BIKE COUGHS & STALLS WHEN YOU WICK OPEN THROTTLE Needle too lean Slide cutaway too lean did you try this test, one from the Nightrider sight: http://www.nightrider.com/biketech/hd_cv_mods.htm To test the main jetting, you must be in fourth or fifth gear and running fairly high RPM (4000+) then open the throttle all the way to the throttle stop, noting the feel of the bike. Immediately let off the throttle about 1/8 turn and note the feel of the bike. If it seems to accelerate some when you let off the 1/8, your main jet is too lean. If it hesitates or the top speed is poor (i.e. less than 80 MPH) you are too rich. There's a ton of sites with tuning hints, I would hope they about all say the same thing. All I can add is, I wish I had your problem! (Message edited by jayvee on November 03, 2007) | ||
| Nocompromise |
Thanks for the link! I haven't done that test. It is given in the Mikuni manual as well, but I didn't think of it when I was out riding today. I talked to Jim on the phone and he thinks that either the needle or the main jet is too rich. That's interesting that 4strokes.com says that the needle could be too LEAN. I definitely don't think that is the case. It didn't exhibit these symptoms when the carb was too lean overall (162 main, 23 pilot, pilot screw only one turn out, needle at 2nd leanest position), so I think when I richened everything up (175 main, 27.5 pilot, pilot screw 2.25 turns out, needle at 2nd richest position) something got too rich. It does seem strange to me that a too rich condition could cause bogging like that, but I am totally ignorant about troubleshooting this type of thing. | ||
| Nocompromise |
So, I did a bunch of reading in the archives and still haven't found the answer to my problem. I have tried adjusting the needle positions, the accel pump timing, and changed out the main (175 to 167.5), but it still stumbles (and pings a little just prior to stumbling). Here is an e-mail reply from Gary Poland, who used to post on Badweb: Kevin, From what I see of your set up, your timming is way to agressive. The SE modules are designed for a lot lower compression than you are running. It is putting to much timming in at mid range. This causes your stutter. By adding more fuel you are cooling the chamber reducing the heat, but this approach is only a band aid. From my experience, you probably want no more than 30 deg total. It needs to come in a lot slower than the SE module does it. You will find that when you get the timming right you are going to have to lean out the carb big time. The HSRs come from the factory, very, very rich in the mid range. The motor and heads you are running don't like a lot of timming. Pull your plugs and check for silver flecks on the insulator and electrode. Probably with your set up you would be better off with one of the many aftermarket adjustable ignitions. Let me know if you have any questions. -Gary I am currently running a 27.5 idle jet (1 turn out), 96 needle (clip in the middle position), and a 167.5 main (although I think I need a 170-175, I don't think it affects the mid-range stumbling problem), and the standard 70 accel pump adjusted as late as possible. The stumbling is preceded by a little pinging and it starts before the throttle even gets half open if I open it quickly, so I don't think the main jet is an issue. Should I spring for the adjustable ignition module? Is the Buell Race module/SE 6800 rpm module really too aggressive? Should I continue to richen the midrange - adjust the clip on the 96 needle and/or adjust the accel pump to come on earlier? Any advice would be great since I've been pulling my hair out trying to get it set up correctly!  (Message edited by nocompromise on November 06, 2007) | ||
| Jayvee |
Spring. You likely have more changes in your engine than the SE Ignition was designed for already. Seems like at the least, an adjustable one would give you another thing to vary, although it would be a small step back as far as now you have a whole new variable to start tuning, at least you will be able to tune it, not just stuck with whatever one curve the SE unit has. | ||
| Nocompromise |
JV - Thanks for the reply. I talked to Jim Higgins and he recommended the Dyna 2000 set on the least aggressive curve. I agree that it is worth a try, especially considering that the SE is getting me nowhere fast. | ||
| Cyclonecharlie |
You might want to make sure your running a cold enough plug before you go spending a bunch of money on a new ignition. Although if you do go with a new ign. I also can recommend the Dyna 2000. I use the 2000i(nose cone) ign.,single fire, fourth curve. But I switched because I was going to have to replace mine anyway.Have about ten K on that ign. now with no problems...........Charlie | ||
| Nocompromise |
Charlie - I have NGK DPR9EA-9's, so they should be fine. Thanks for the Dyna 2000 info. Now I just have to figure out the cheapest place to get one. (Message edited by nocompromise on November 06, 2007) | ||
| Blake |
Dyna 2000 works great for my hot-rod Cyclone. I can confirm that using the 4th curve, least aggressive works best too. | ||
| Nocompromise |
Thanks Blake! It sounds like it's a consensus. I'm assuming that people are using the stock ignition timing combined with the least aggressive Dyna 2000 curve? (Message edited by nocompromise on November 07, 2007) |
