Moderator Cynic Posted March 24, 2012 Moderator Posted March 24, 2012 Could try dropping the needle a clip, see if that improves it by leaning out the midrange.
flyday58 Posted March 25, 2012 Author Posted March 25, 2012 Could try dropping the needle a clip, see if that improves it by leaning out the midrange. I tried it already, and it REALLY didn't like it. So I tried it up a notch, also to no avail. I know it should not affect idle doing that, but I could not keep the bike running in either postion without revving constantly. This is a very temperamental carburettor.
Morpheuz Posted March 26, 2012 Posted March 26, 2012 Cant be bothered to read all previous, as its a sunny day and work is calling... But, may have been mentioned, idle mixture maybe lean, it explains it all, mine is lean and it does the same, going from lean, to a nice mix or rich mix will result is a slight fart or hesitation, as it picks up the fuel flow, air screw might even the mix out, but the fuel is the power and you'll need a bit more, and a bit more air after. from idle, to midrange to WOT, the flow in any carb likes to be constant and steady, and steep rise, or lean/rich mix will confuse the smooth operation. I'd love to know where my idle mix screw is on my xvs.....
flyday58 Posted March 26, 2012 Author Posted March 26, 2012 Cant be bothered to read all previous, as its a sunny day and work is calling... But, may have been mentioned, idle mixture maybe lean, it explains it all, mine is lean and it does the same, going from lean, to a nice mix or rich mix will result is a slight fart or hesitation, as it picks up the fuel flow, air screw might even the mix out, but the fuel is the power and you'll need a bit more, and a bit more air after. from idle, to midrange to WOT, the flow in any carb likes to be constant and steady, and steep rise, or lean/rich mix will confuse the smooth operation. I'd love to know where my idle mix screw is on my xvs..... Indeed. There's a pic somewhere in the post of my air screw, and the o-ring is cut on it. I reassembled it gingerly with a dab of grease to ease insertion (??). It ran a little better until I rode it, then it was back to the same. Awaiting an OEM carb for installation the end of the week.
nayruf Posted March 27, 2012 Posted March 27, 2012 Hi FD 58 I used this manual to set up my Mikuni carb, it may be of some help, (http://www.mikuni.com/pdf/vmmanual.pdf)
flyday58 Posted March 27, 2012 Author Posted March 27, 2012 Hi FD 58 I used this manual to set up my Mikuni carb, it may be of some help, (http://www.mikuni.com/pdf/vmmanual.pdf) This is why I come to this site, cos you people have all these little jewels. Thanks for the linky, great stuff. Always been a sucker for sexy cutaways! On the way to Tokyo now, oem carb should arrive while I am away.
flyday58 Posted April 1, 2012 Author Posted April 1, 2012 Last one is cos Locomotive Breath is screamin' on the stereo... Gents, it was the carb. Sputter no more. The carb I bought on ebay cured my problems, except can't get it to idle like I want. The OEM unit had some water in it and had begun the corrsion process, but it was all superficial and cleaned up nicely. The slide was correct, but the needle was almost a full cm longer than the 4J13; I put my old slide/needle combo in. I will remove the drain plug sporadically over the next few weeks to drain out any accumulation of crud and see if all is well. For now I'm happy with the results, just wish I hadn't wasted money on the aftermarket carb. That thing didn't even fit in the filter box correctly, wouldn't go all the way in. Wait, did I mention ?
Moderator Airhead Posted April 1, 2012 Moderator Posted April 1, 2012 Great news Richard, c'mon lets see her then! maybe today i'll put mine back together :spin2:
flyday58 Posted April 6, 2012 Author Posted April 6, 2012 (Heavy sigh) Not as sputter-free as it started out. After a few rides the sputter has started again. AND I cnnot get it to idle properly. If I set it to 1800-2000 it idles mostly fine, some hunting, but once I set it to 1500 or below, it slowly bogs then dies. REALLY irritating, this. Removed the side cover, there was a little oil film in the bottom. Removed the magneto, the crank seal is dry, no dampness of any kind, so I don't see that the seal could be leaking causing my probs. I think the film is WD40 I was using to try to find any leaks on the carb. I know some of it ran down into the case. So removed the carb again. Well, first time for THIS carb. There was fuel puddled around the air screw inlet hole. I thought, hmm, that probably should not be. Disassembled the carb for a really good look. I can see that the air screw hole has a port straight thru to the needle jet, so I tried to blow air thru it with a plastic WD40 pipe. Nada. Tried to spray WD40 thru it. Nada. Got my junk Mikuni and tried spraying WD40 thru it, success! So I know the new one is clogged. Will work on getting it open today. Found the main jet says 120. Saw it before but ignored it in the interest of seeing how well it performed, It won't rev much over 6500 under load, New proper 140 on order. On setting the float height: I measured 24mm with the float just touching the needle plunger. Do I need to measure with the plunger depressed, or just touching the tip of the plunger? I did the latter, which is how I've always done it, and set it to 21mm. But the fuel in the intake made me wonder if it's too high. But the air screw hole is clogged, so that is where I think that fuel came from. Ordered a new needle and seat anyway. Hopefully sometime next week I will get the parts in and can continue my saga. Will still consider the crank seals and reeds if I still have the probs. The spark plug looked good btw, clean and a dull brownish.
Moderator Airhead Posted April 6, 2012 Moderator Posted April 6, 2012 (Heavy sigh) Not as sputter-free as it started out. After a few rides the sputter has started again. AND I cnnot get it to idle properly. If I set it to 1800-2000 it idles mostly fine, some hunting, but once I set it to 1500 or below, it slowly bogs then dies. REALLY irritating, this. Removed the side cover, there was a little oil film in the bottom. Removed the magneto, the crank seal is dry, no dampness of any kind, so I don't see that the seal could be leaking causing my probs. I think the film is WD40 I was using to try to find any leaks on the carb. I know some of it ran down into the case. So removed the carb again. Well, first time for THIS carb. There was fuel puddled around the air screw inlet hole. I thought, hmm, that probably should not be. Disassembled the carb for a really good look. I can see that the air screw hole has a port straight thru to the needle jet, so I tried to blow air thru it with a plastic WD40 pipe. Nada. Tried to spray WD40 thru it. Nada. Got my junk Mikuni and tried spraying WD40 thru it, success! So I know the new one is clogged. Will work on getting it open today. Found the main jet says 120. Saw it before but ignored it in the interest of seeing how well it performed, It won't rev much over 6500 under load, New proper 140 on order. On setting the float height: I measured 24mm with the float just touching the needle plunger. Do I need to measure with the plunger depressed, or just touching the tip of the plunger? I did the latter, which is how I've always done it, and set it to 21mm. But the fuel in the intake made me wonder if it's too high. But the air screw hole is clogged, so that is where I think that fuel came from. Ordered a new needle and seat anyway. Hopefully sometime next week I will get the parts in and can continue my saga. Will still consider the crank seals and reeds if I still have the probs. The spark plug looked good btw, clean and a dull brownish. how well did you strip and clean the carb Richard, did you have the needle jet (emulsion tube) out? typically you would find this when it needs to be this and of course the chamber this sits in needs cleaning out too I use a ultrasonic bath it does the job well but an aerosol carb cleaner would be a good second best...even better if compressed air (or an air duster) is to hand, Take care with 'O' rings such as the one on the air screw...best removed and not subjected to the carb cleaner. I think you are on the right track with further cleaning, it seems to me that you are getting round the problem of a blocked air mixture passage simply by raising the throttle slide enough to suck fuel up the needle jet and thus the idle is too fast another thing to check is the carb vent from the bowl and out the side of the carb...and the tube connected to it are clear If your main jet is too smalll dont take chances, get the right one fitted before you overheat or burn a hole through your piston crown
flyday58 Posted April 6, 2012 Author Posted April 6, 2012 Emulsion tube is in good shape as is the passage. I have a diff tube than in the pic but I get the idea. As for o-rings, I have none, nor does the parts list show any. I thought that odd, what's to keep gas and air from leaking? I got the air screw to emulsion tube hole cleared. Now I'm just Waitng for parts next week. What about float height, pin depressed or just touching?
Moderator Airhead Posted April 6, 2012 Moderator Posted April 6, 2012 just touching, i find it best to hold the carb...not completely upside down but angle it until the float arm is not compressing the spring plunger into the valve...with the float pivot uppermost does your needle jet screw into the carb body then...rather that pressing in like the one in the pic? This is the type of our early ones too, they dont have an o ring fitted to the mixture screw so that's correct, they also have a small brass orifice (air jet) pressed into the carb mouth as in the pic, wheras the later ones dont also there is a really tiny passage from the mixing chamber of the needle jet that exits into bottom of the venturi behind the throttle valve...engine side (part of the pilot cct)
flyday58 Posted April 7, 2012 Author Posted April 7, 2012 just touching, i find it best to hold the carb...not completely upside down but angle it until the float arm is not compressing the spring plunger into the valve...with the float pivot uppermost does your needle jet screw into the carb body then...rather that pressing in like the one in the pic? This is the type of our early ones too, they dont have an o ring fitted to the mixture screw so that's correct, they also have a small brass orifice (air jet) pressed into the carb mouth as in the pic, wheras the later ones dont also there is a really tiny passage from the mixing chamber of the needle jet that exits into bottom of the venturi behind the throttle valve...engine side (part of the pilot cct) Thanks Paul, good idea on holding the carb at an angle. My needle jet does screw in, and the air jet was clogged. I managed to sand down a sewing needle to get it to poke thru enough to dislodge the schmutz that was in there, and the WD40 cleaned it out. Now I have a nice stream flowing thru the air jet. Nope, I didn't jam the needle thru, just gently poked - didn't want to screw up the jet size. All ports now seem to be open. So next week, and the new parts. Hopefully they will arrive before I leave town.
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