| Author | Message | ||
     Jjjoutside |
So... before I get too experimental with it, thought I would take a survey and see what slow jet folks might be running at altitude. I live in the Durango area at 8k feet and ride between 6k and 10k on a fairly regular basis. M2 had a 48 slow and a 200 main when I bought it... I've gone down to 45 slow and 180 main. Pretty happy with the 180 (although I might try a 175) but the 45 still seems a little rich... thinking about a 42. What perplexes me a bit is that if I maximize idle speed by adjusting mixture, I'm about two turns out. If I turn it in another 3/4 (idle drops 200rpm or so), then the bike really comes to life just off idle and in the mid range. Plugs look great on WOT runs, but are pretty blackened (dry) after running around on smaller throttle openings... especially after idling for a while. Thoughts? Comments? Beer? JJJ | ||
| Bob_thompson |
Jeff, Bob here in Utah at 4500 ft. Your jetting seems about right for that altitude. I'm running a 48 slow jet and a 195 main. My 2002 M2 is stock except for a straight thru 2 1/2 muffler and large oval K&N air cleaner. It pulls strong from just above idle to the rev. limiter using the stock vacumn carb which I assume you are using. I also hit 9500 ft. regularly and do not notice any change in its running. My plugs do not blacken like yours and with my 48 slow jet I am about the standard 2 1/2 turns out and do not need the choke to start. I just hit the twist the throttle to trigger the accelerator pump a couple of times. I think if you have any kind of hot cams they might load the idle/low end some which is somewhat usual. Maybe a little hotter plug would help burn off some low speed richness. I have also raised the jet needle about .0060 to help my midrange pull. If you bought your bike used it might have some carb work done which you are not aware of. Check our Knowledge Vault with a search and you will find much about carb work. I believe what you did with turning in the idle mixture 3/4 turn was good but I would then raise the idle to about 1000 rpm using the throttle adjuster. You are already pretty close. Just some final touches. good luck, stay safe and I'll have any kind of dark amber. Bob | ||
| Jjjoutside |
Thanks, Bob. I've been all over the KV and it has been a HUGE help getting all of the mods and safety issues up to date on my bike. I just didn't see much about folks running at altitude, other than the CV carb is apparently not too bad at self-adjusting by design. Which plugs are you running? Based on what I read here and a Buell TSB, I went to 10R12s which are apparently a bit cooler than the original 6R12s that came in the bike. Wondering now if I should go back to the hotter plugs... I will check the needle as well... I haven't played with that yet. The previous owner had someone "go through" this carb right before I bought it and I can tell from the rounded off screw heads and such that this person was probably not someone I would have preferred to have working on it. Thanks for the info though... that's exactly what I wanted... a reference from someone who was running under similar conditions. I have you down for a dark amber...  JJJ | ||
| Cyclonecharlie |
Jeff, You could try the 6R12's maybe in cooler weather. But at the first sign of pinging or hot weather I'd switch back...Charlie | ||
| Bluem2 |
Jeff, Thanks for starting this thread. I live in Denver (5280' - a mile high as we always yarp about), and am curious about others' jetting at altitude. My 2000 M2 is stock with a Wileyco muffler and gutted airbox. The previous owner dyno tuned the carb for the new muffler, and it has a 45 slow, a 195 main, and came with 2 turns out on idle when I bought it. It runs generally well but is a bit vague on low-speed response in town and had a pretty annoying cough sometimes rolling the throttle on out of turns. Especially when I go higher into the mountains for twisties. I changed the intake seals - the cough was the same. I then opened the idle to the Badweb-spec 2.5 turns and it seems better but I'm not totally sure yet. If the idle mix adjustment doesn't fix the cough, I may adjust the jet needle. I haven't worked with the plugs yet. Can you just yank the plugs right out of a hot engine to check the WOT mix? -Jack | ||
| Bob_thompson |
Jeff, I particularly like the NGK DCPR8E and do a modification as seen in the picture below. It is a middle of the road heat range and works good for me from cold weather (40) to hot weather (100+) with no problems with my jetting which you see is close to Jacks (Bluem2) in Denver. They are readily available at almost any store and are only about $2.50-3.00. I do a modification as you see to get the spark directly into the intake mixture. Its an old school trick for racing and really works. Jack, when I do a plug check, unlike in racing where you chop the throttle and coast into the pits I usually just try and stay away from idling too long when getting back to the house and pull the plugs when the motor is cooled down. I keep the engine at 2000 rpm's or above when getting back home. A little black on the plug housing is OK but I look specifically at the porcelain for a light brown color. You guys are 95 % there and doing great, keep up the good work, Bob  | ||
| Jjjoutside |
Ahhhh... the ole side gap trick! Used to do that to an old 289 Derby Ford motor in a '68 Cougar! Hadn't even thought about that in years. Worth a shot. I have some DCPR8Es that I can play with. Sounds like my extra turns in on my slow jet may be in keeping with me tuning at just over 8k feet. I have noticed that the bike seems to be smoother off idle in town (6.5k feet). I think I'll keep playing with idle mixture/plugs for now and stick with the 45 slow jet. Once the bike is really warm, most of the non-linear throttle response disappears. I use the enrichner to start when cold and then immediately push it in. Warm the bike up a bit by holding the throttle open (no acc. pump action) and it really doesn't seem too bad, there's just this sort of "feel" that it doesn't pull smoothly through the throttle... there's a "breakover" point on the throttle where the bike suddenly starts to pull like I would expect. After dropping down a couple thousand feet, the throttle response smooths out. Once it's good and warm (10 minutes of road speed), the "breakover" point almost disappears, but I still have a little more plug blackening than I would like. I have pulled the plugs hot several times after WOT runs and they are clean/tan. After tooling around at 2500-3000 rpm in fifth gear, they start to load up. They never get to the point of misfiring, but I can feel the difference... if that makes any sense. Been messin' around with cars and bikes all my life and the "feel" comes pretty easy for me. It's pretty clear to me that something is not quite right... very close, but not quite there. Perhaps I'm expecting too much from the poor girl. As always, thanks to everyone for the input. What a fantastic resource this board and the KV are. JJJ | ||
| Bluem2 |
Thanks Bob and JJJ. Now I can think about plugs as both a variable to tweak and a fuel mixture indicator. -Jack | ||
| Yo_barry |
Hi Bluem2, You need to shim your needle up. Get some SS washers at your local hardware store and add one under the needle. This will make it just a little richer as you come off the idle circuit into the midrange circuit. Should fix that hesitation. Barry | ||
| Bob_thompson |
Jeff, if you decide to do what Yo_barry has suggested and I agree as I also did this about .060 under the jet needle you might find it hard to find small enough washers to shim at a hardware store. In that case look at a hobby shop and get model car axle spacer washers. Mine were .015 thick each. Experiment with the amount of spacing and test ride for the best response. Thanks Yo_barry. See you a little higher up, Bob | ||
| Jjjoutside |
Sounds like a little shimming might be in my future, although the hotter NGKs helped as well this morning. It was 39 degrees when I left the house and about a mile down the road it was noticeably better. Not perfect, but better... whether it was the hotter plug or the side-gapping, who knows. Anyway... if I can find suitable washers around here (Durango resources can be a touch thin), I will play with needle height next week when my schedule slows down. Thanks again for the info. JJJ | ||
| Bluem2 |
I put in some DCPR8E plugs last night and it seems like it's running a bit better. I won't really know on the cough/hesitation until I get it into the twisties where it does that. If the idle mix and plugs seem about right in town and I still have the roll-on cough, I will try shimming. That model car tip is a good one. I'll keep tweaking until the cough is gone and report back into this thread in case anyone else can learn from it. Thanks again Jack | ||
| Cyclonecharlie |
If all of this doesn't get rid of the cough, you might want to take a good look at the slide/ diaphragm. Somebody may have attempted to modify it and over did it....Charlie | ||
| Jjjoutside |
Curiously, with the DCPR8Es (side-gapped), the bike seems to take longer to warm up... however, once warm I really like the way it's running now. I fattened it back up a little on the idle mixture and it seems pretty smooth now and I can start it cold without the enrichner. It's been raining the last two rides, so I've been a little hesitant to play with it too hard. May play with needle height just to see what kind of difference it makes, but all in all I like it. JJJ | ||
| Cyclonecharlie |
Better watch your gas mileage, it may be fixing to go in the  | ||
| Jjjoutside |
Ah well... I paid cash for the bike. I can take out a loan for the gas if I have to...  ... appears to be getting right at 50mpg. Better than my FXRT ever got... Of course, it weighs half of what that bike weighed. JJJ | ||
| Cyclonecharlie |
As long as you are getting that, your in good shape. You have a good base line, check it again when you get through with all the carb. enrichment.Anywhere in the mid forties would be good. Another thing to look at is the slide spring,a lot of them have been cut off short.This can add to your cough problem....Charlie | ||
| Bluem2 |
I still have a cough. This sometimes occurs (and sometimes does not) at around 3,000-4,000 RPM, rolling the throttle on from 10%-20% to 30-50% or so, usually as I'm coming up from a healthy lean into a turn. The cough is less annoying now since I've done: new intake seals, open idle from 2 to 2.5 turns, and put in new NGK DCPR8Es. But it's still there and it's enough to disturb the whole bike briefly - I would not describe it as a mere "hesitation." Now I have the carb off again, and I'm planning to try some needle shimming. Charlie, while the carb is off and apart, is there a way I can tell if the slide spring has been modified? It doesn't look cut - the ends are crimped back toward the last coil on both ends like springs look like from the spring factory. The diaphragm looks fine too. The little offset slide hole does not look drilled either, as some recommend. JJJ, sorry to hijack your thread. | ||
| Jjjoutside |
Hmmm.. if it's lean (as in bike angle) related, have you checked your float bowl level? I wonder whether the level could be a little low and as you straighten up the sloshing/movement of the fuel sometimes causes a starved condition?? Just a thought... JJJ | ||
| Bluem2 |
JJJ, Good idea. I checked the float very carefully and adjusted it to get it right. It seemed pretty close anyway. Also, I shimmed the needle about .030". Result: I'm pretty sure the bike coughs WORSE now. It doesn't seem to matter if I'm leaning into a turn or not. I'm not quite sure what to try next. I'll probably take the shim out from under the needle, and I'm actually considering trying a 42 slow jet, which I've never run. I'll monitor the plugs more closely though. -Jack |
