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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Advice from VM owners needed-tuning-UFO /cgi-bin/YaBB.pl?num=1274118639 Message started by BurnPgh on 05/17/10 at 10:50:39 |
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Title: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/17/10 at 10:50:39 I just got my head and cylinder back from valve work and a rebore and slapped on my VM and Im getting nowhere with tuning. I have the UFO from Lancer with the pilot jet soldered shut. Im having a whole lot of trouble with the idle and mid-range so closely tied together. No matter what setting I have the needle at when I come off idle I get a hesitation. No matter what needle setting Im at idle speed is not affected by the air screw. Raising the slide at all makes for an extremely high idle. I was able to minimize the hesitation but not eliminate it with the needle at the middle setting and the air screw 1 turn out. I took it out for a couple mile ride which wouldve been longer but it died on me suddenly and I had to push it home. Im about to just take it somewhere and pay to have it tuned. I waited a month to get my head and cylinder back and I just want F&^%king ride. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by MMRanch on 05/17/10 at 19:28:56 Been there ! The first thing that came to mind is the float level ? I've found more fuel in the bowl makes for rich running and vice versa. There is more that just "Right or Wrong" in adjusting the fuel level in the carb. Its like a high fuel level with a small jet do the same thing as incressing a jet size. Good luck with it |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/17/10 at 19:40:48 with the main jet too or just in the midrange(or in this case idle/midrange)? Do you have a UFO installed? Was your float height the underlying issue? If so did what did you end up setting it at? edit - My first question was dumb after thinking it over. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/18/10 at 10:29:15 Update - Raised float level. Still idles well. Still, if I increase throttle very slowly it will rev up. Still hesitates/stutters right off of idle if im anything but very slow and steady with the throttle. Does not hesitate/stutter with the choke on. Im upping the main jet to see what happens. Any advice or ideas welcome. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by klx650sm2002 on 05/18/10 at 10:39:43 The way I saw it the pilot jet with the UFO should be in the area of 15 to 20. That will richen idle and off idle,without choke. Clive W |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/18/10 at 19:03:23 Lancer told me it was unnecessary and that the UFO increased air velocity to the point that fuel would be drawn up through the needle valve even at idle. To that end he soldered the pilot jet shut. After some more screwing around - At 0 turns out on the air screw with the slide raised slightly, the needle on the lowest clip, and a 195 main jet I was able to reduce the hesitation/stutter to almost nothing...almost. Any messing from that point with the air screw, slide height or needle height bring the hesitation back with a vengence. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by onelunger on 05/19/10 at 04:39:15 0 turns and a big main are definately not the "correct" settings. You should never have to change the main to fix a low speed setting. Here's the best tuning advice I've been able to find: http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm_engines.html Good luck. 8-) |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/19/10 at 10:44:15 you shouldnt except that the pilot jet has been soldered shut and idle fuel is drawn up from the bowl through the needle jet and the fuel has to go through the main jet which is right under the needle jet before it goes anywhere else. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/19/10 at 11:32:22 took a ride. Died on me. Now I have no spark. I get the feeling Im not going to get this to work before the end of summer. Where is Lancer? He's usually all over this kind of thing. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by onelunger on 05/19/10 at 12:25:05 7D4A4D516F58573F0 wrote:
The pilot fuel jet is soldered shut not the pilot air jet??? If that is indeed the case I can't see how you're ever going to get it running good. There is no way the main fuel circuit is going to be able to accurately provide a low speed mix. That's the whole point of the pilot circuit. If it's just the air jet that closed that's a different story and there's just some tweeking that needs done. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/19/10 at 13:00:50 It ran "well" except for the stumble right off idle. If I yanked back on the throttle hard it would stumble for second and then continue revving as normal. At this point its irrelevent because my ignition coil seems to have died on me mid ride. Im getting power in the two line up to the coil but no spark. Which might have been the cause of the stumble in the first place. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by Charon on 05/19/10 at 14:23:25 That "stumble" right off idle when the throttle is yanked suddenly open is precisely the reason accelerator pumps were invented. The sudden throttle opening reduces air velocity because of the suddenly larger air opening. The reduced velocity reduces the suction that pulls fuel up through the jet, so the mix goes very lean until air velocity increases. CV carbs pretty much eliminate the difficulty, because they control the air velocity. Accelerator pumps squirt an extra shot of fuel into the air stream to overcome the momentary leanness. Lacking either of those, you will have to learn not to yank open the throttle at low engine speeds. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/19/10 at 18:29:52 I understand now why its happening. Theres just no way to tune it out totally? I was able to minimize it to almost nothing but theres no way to be totally rid of it? Just a feature of the type of carb then? |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by Charon on 05/20/10 at 12:19:21 I'm not sure I'd call it a "feature." More of a "characteristic." To add to the sport, the problem is more pronounced when a larger bore carburetor is used. So, when one installs a big-bore carburetor to get that wonderful top-end power, and a mechanically operated slide for that wonderful responsiveness, one also installs an off-idle stumble. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by bill67 on 05/20/10 at 12:30:41 I had a 1973 Suzuki 550 with the VM carbs and a 1975 750 Suzuki with the CV carbs,To me the CV carb was a big improvement to throttle response at all speeds. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by LANCER on 05/20/10 at 17:00:03 I am out of state visiting my youngest daughter and family and my computer time is pretty limited. Sorry but this is the way it is for now. We will be home in 2 wks. You mentioned that you were moving the needle clip all the way "down" ? that would give you the most rich mix in the midrange, and then with a #195 you would have a very rich high range. The UFO should take care of the low range by itself. with hesitation coming off idle-lowrange there is a fuel gap between there and the midrange go back to the float and reset the floaat at the lowest end of the recommended range, to keep the fuel supply from being too rich. try the pilot screw at 3/4 turn out and the needle clip on the very first (top) slot. also drop back to a #185 main jet. I know it is a lot of change at one fell swoop but give it a try. If you do not like it than will will try another attack. IF you prefer to make one change at a time then do that, but start with the float setting at the lowest of the range. then pilot screw then needle clip then main jet. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/21/10 at 01:09:28 Thanks for the help as always. I was actually starting to get a bit worried about you. Like I said, you're usually all over this kind of thing. Glad you're well. I'll do as you suggest as soon as my new CDI comes in >:( |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/25/10 at 11:38:39 well...i set it back as lancer suggested and started over again. Same results. The richer I make it the better it runs, but I've gone as rich as possible with the jet kit. Im 1/4 turn out on the air screw, bottom clip (richest, right?) on the needle and the 220 main. I've checked for air leaks at the intake and exhaust leaks at the head. No dice on either. The plug is still white as a ghost and acceleration is still pretty crappy. Its running now, about as well as it did before the cam,overbore, high comp piston, and carb. I'm at a loss. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by LANCER on 05/25/10 at 15:21:01 SORRY MAN, MY BRAIN IS SLIPPING AS USUAL THESE DAYS; I WAS NOT THINKING OF ALL THE MOD'S DONE SO FAR. WE HAVE PLENTY OF CONFIRMATION THAT IT IS RUNNING LEAN AND WANTS MORE JUICE, SO THAT IS WHERE IT NEEDS TO GO. YOU HAVE NO LARGER JETS AVAILABLE RIGHT NOW ? PILOT OR MAIN ? IF YOU WANT TO LIVE ON THE EDGE OF REALLY FUN JET TUNING YOU CAN TAKE ONE OF YOUR SMALLER PILOT AND OR MAIN JETS AND USING ONE OF THE TINY ROUND FILES EVER SO GENTLY MAKE THE HOLE IN THE JET LARGER. USE A DRILL BIT THAT YOU FIND TO BE THE SAME SIZE AS THE LARGEST MAIN JET YOU NOW HAVE, THEN GENTLY TWIST THE FILE IN THE OTHER JET UNTIL IT IS JUST BARELY LARGER AND GIVE THAT A TRY. THE BRASS JETS WILL FILE V E R Y EASILY SO BE GENTLE. IF YOU FILE UNTIL YOU CAN "FEEL" THE DIFFERENCE THEN YOU HAVE GONE TOO FAR VERY LIKELY. IT ONLY TAKES THE SLIGHTEST TURN OF YOUR THUMB AND FOREFINGER AND ONE TWIST FORE AND AFT...THEN CHECK YOU ONLY WANT TO APPLY ENOUGH PRESSURE ON THE FILE SO THAT YOU CAN BARELY FEEL IT BITTING THE BRASS; ALMOST AS IF IT WERE NOT FILING AT ALL. GENTLE. SINCE YOU NEED LARGER JETS, THE SMALLER ONES ARE OF NO USE TO YOU RIGHT NOW SO SACRAFICING ONE OF EACH FOR TESTING IS NO LOSS. IF I WERE HOME I WOULD SEND YOU A NEW SET OF LARGER JETS JUST USE THE DRILL BITS AS YOUR GUAGE OF WHEN YOU HAVE GONE UP A SIZE. IF THE FILE IS TOO LARGE FOR THE PILOT JET, THEN A GUITAR STRING MAY WORK FOR YOU |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by Boule’tard on 05/25/10 at 17:16:37 Here's how I got my VM going good. I never soldered the pilot jet shut, I just used the smallest recommended jet, a 15. I think there was also a 12.5 in Lancer's kit, but the guy from Thunderproducts didn't recommend it because "it would clog." What he did recommend was to enlarge the hole in the UFO (the hole that the needle goes through) with a 5/16" bit. I did that, and also drilled an air bleed as outlined in the UFO instructions. It is a small, perhaps 1/16" hole in the brass shroud just upstream of the needle. Drill it just above the "floor" of the throat. Those two little mods allow you to go back to an unblocked pilot jet. And if you select a small one like 15 or 12.5, the low speed mixture should be within range so you can fine tune it with the air screw. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/25/10 at 19:20:19 Well....the pilot circuit is actually alright now. I still cant tell a discernable difference tuning with the air screw but if I idle for a few minutes then check the plug its a nice toasted brown. Its from about 1/8th throttle and up were Im obviously lean. Havent got any tiny files unfortunately and to go and buy some I might aswell buy some more jets and be sure Im not going to screw anything up. Besides im getting tired of tinkering. I've got a 330 main from a VM junker i picked up to play with. I'll throw that in just for the hell of it. Im betting its too rich but who knows? |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by LANCER on 05/26/10 at 05:56:14 I'm just bummed that I am not home to send you the larger jets. I've got a bunch just sitting there and never being used. Have you thought about this ? Thunder PowerJet More Power Improved Fuel Efficiency Easy Precision Jet Changes Adjusts For Altitude and Temperature Works on Snowmobiles, Motorcycles, ATV's & other vehicles The Thunder PowerJet fits any size or brand carburetor. It is exactly what you need to achieve maximum performance with your engine. The TPJ improves performance by precise fuel metering with needle valve adjustment. Fuel distribution is improved by adding fuel through two sources instead of just one. This means more horsepower at any temperature or altitude. The TPJ gives you a range of over 10 to 12 jet sizes with precision external adjustment. Thunder PowerJet works great on stock or modified motors, two cycle or four cycle engines. TPJ can be used on Turbo, Blower or Nitrous equipped engines. A one way check valve is included which holds fuel close to the TPJ for extra quick throttle response. The one way valve also protects against blow back from the engine to the carburetor. The TPJ can be used with fuel injection by adding a remote float bowl. The TPJ body is nickel plated to resist corrosion and keep it looking sharp. The viton seals are compatible with all fuels including race gas and alcohol. A large knurled knob with an index pointer makes adjustment easy. Each kit comes with complete instructions and necessary mounting hardware. Installation is easy and tech support is available. TPJ-Single - $64.95 http://www.thunderproducts.com/thunder_powerjet.htm This would solve your problem with just one simple installation, and if you changed exhaust systems later or made some other mod then a quick and simple adjustment is all you would need. NEVER HAVE TO CHANGE A MAIN JET AGAIN. Call Lonn at Thunder Products and talk to him about it, tell him what you are dealing with. He is a good dude and very helpful. HE KNOWS HIS STUFF ! ! Be sure to tell him I suggested you call. 320-597-2700 He will treat you right. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by Boule’tard on 05/26/10 at 09:55:52 182F28340A3D325A0 wrote:
I still think a functioning pilot jet will help with the transition between 1/8th throttle and 1/2 (or so) where the main jet becomes the overwhelming factor. I haven't exactly run a finite-element analysis on it (and could well be talking outta my a$$ -- really, I would not contradict Lancer's advice without trying it both ways) but I imagine this is happening: When the slide is all the way down, the UFO funnels the stream of air right on the needle jet, just above the main. So if you just install a UFO and don't touch anything else, that concentrated stream causes too much fuel to be sucked through the main circuit, thus the idle to 1/8 mixture is crazy rich. This part I experienced directly and joked about it on here while I was still trying to sort it out. Then when the throttle is cracked above 1/8, that concentration of air is no longer on the needle/jet. There is a more uniform distribution of air within the open cross section, and it goes back to a good mixture. One can fix the low speed richness by blocking off the pilot, and then fix the 1/8 throttle mixture with a bigger main jet, but by sizing the main to fix a 1/8 throttle lean condition, it will turn out too rich at large throttle openings. That's why I think it's better to leave the pilot circuit working, and do other things to lessen the UFO's effect at idle to 1/8. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/26/10 at 10:04:04 Im going to hold off on that for the moment. I can tell Im going to need to at least shim my clutch springs and maybe end up with a barnett kit so I'm trying to hold onto the cash for the time being. Once I get this figured out I still need to send you my stock cam. I threw the 330 in. Needle on the richest clip is too rich with sluggish boggy acceleration. The leanest clip is too lean with surging but boy on the upswing of the surge...sure was surprising. The middle clip is so-so. Im taking a break from it for an hour or two. Strange thing though, my plug is still pretty much white. A wee bit grayish after a 6 mile ride. I find it hard to beleive I jumped from 220 to 330 and am still lean. Even if I am I cant do much about it. The only dealership nearby only has (from 220 upward) 240, 260, 270, and 280. Nothing richer than what I've already got. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by LANCER on 05/26/10 at 11:26:56 THE #330 IS A BIG JET FOR THE SAVAGE, EVEN MODIFIED. (I was running a #240 or #250 before on the 36mm VM I had; UFO and DAJ...ah ... the DAJ was also on that carb and that would make a difference. It was running a bit rich on the very top at the time. I had the 36VM as noted, 94.5mm piston with silicone carbide cyl, stage 1 cam, stock CR, just slightly opend exhaust port at the head/header mount, and the header/muffler I made, plus the Barnett clutch/spring pack. A bigger piston w/ higher CR, full exhaust porting and stage 2 cam would make a significant difference though) WITH THE #330 MAIN JET INSTALLED, HOW DID IT PERFORM AT WIDE OPEN THROTTLE ? THAT EFFECTIVELY ISOLATES THE MAIN JET FUNCTION FROM THE OTHER CIRCUITS FOR TESTING, IT IS MAX FUEL FLOW AT THAT POINT. GET IT IN 3RD OR 4TH GEAR AND AT ABOUT 3K RPM GO WIDE OPEN AND HOLD IT UNTIL AT REDLINE THEN CHOP AND HIT THE KILL BUTTON. THEN CHECK THE PLUG. -WHAT PLUG COLOR FOR WIDE OPEN THROTTLE ? -DID IT RUN HARD ? -BOG DOWN ? ... IF SO, DID IT PICK UP IF YOU BACKED OFF SLIGHTLY ON THE THROTTLE ? -RUN BUT NOT HARD ? any other symptoms ? |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/26/10 at 12:37:59 I really havent got anywhere nearby where I can do that. Nothing straight or long enough. Even the roads where it MIGHT have been possible have all been oiled and chipped in the last week. Its all fresh and Im almost locked into my neighborhood. Theres no way to work even going all the way around that doesnt have a short stretch of the crap. The 330 is very big, but why then is my plug still white no matter what needle setting I have? Since I got a nice tan/brown on the idle circuit I've been focusing my rides in the midrange and cheking the plug after each change. It isnt bright white like new. A very very light gray/white. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by LANCER on 05/26/10 at 17:55:44 1F282F330D3A355D0 wrote:
Your plug is still showing the white color of the lean low and/or midrange throttle setting, since that is all you have been able to do on your restricted street. You will not see the true color of the 330 main jet fuel mix on the plug until you can get to a place where you can run it with a WIDE OPEN throttle setting...ideally in 4th gear. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/27/10 at 10:51:04 Was able to hit the highway after work. Slowly accelerated to avoid slipping and hit the main circuit. How do I know? Its stopped accelerating altogether and just started crackling sharply and missing. Let off and it stopped all that nonsense and "jumped" forward. Beleive it or not I think Im still lean all around except the pilot circuit. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/28/10 at 10:44:28 Drove way out to the nearest dealership (no indy shops nearby) and picked up a few larger main jets to play with. Their choices go from 280 to 370 with nothing between so I got a 370. Too rich. 330 is close. Im geussing 340/350 will be the ticket. I also think having the pilot jet blocked up has created more difficulty than necessary in doing this but the smallest I have is 17.5 and it is way too rich and the dealership didnt have anything smaller than 22.5. It will barely idle and puffs black smoke. So Lancer, when you get home and get a chance I can send some of the smaller mains I wont be using and the 3 non-blocked pilots to trade along with my stock cam if thats alright with you. 340,350,360 main and 15,12.5, 10 pilots ought to do. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by LANCER on 05/28/10 at 19:11:33 6651564A74434C240 wrote:
Typical "too rich" response. -wide open it runs like crap -when you back off slightly you reduce fuel flow which leans the mix and it jumps forward and runs better -conclusion: the 330 is too big for the time being keep the jets you have and just send the cam core. I will send jets extra jets for you next week unless you tell me otherwise before then. Do you have a new carb or was yours one of the used ones ? If used, what needle jet and jet needle, slide, air jet and needle valve do you have in it ? And if used, are you positive you have all the internal parts that are supposed to be there ? |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by BurnPgh on 05/28/10 at 22:08:05 new carb. Thanks as usual. I'll send the cam tomorrow or monday so it should be at your door when you get home. |
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Title: Re: Advice from VM owners needed-tuning-UFO Post by LANCER on 05/29/10 at 08:12:03 1126213D03343B530 wrote:
ok, now I am hitting my forehead and going "daaaaa", since you did say earlier that the pilot jet was soldered closed and that is what I do when intalling the UFO on a new carb. I may very well need adult supervision on the Dragon Ride this year ! Man, am I getting S L O W E R of what ? ? ? ? ::) |
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