custom Posted March 14, 2013 Report Share Posted March 14, 2013 Hello everyone and thanks in advance for sharing your knowledge. I have a 2003 SY that I recently bought. Everything was working fine. Last ride I put the bike in the garage. Didn't wash it. 10 days later I loaded it in the truck to try out my first trials event. Once at the event it was hard to start and would not idle with the choke off. I assumed a plugged pilot jet. Unfortunately I didn't grab my tools. Back home I go. I pulled the carb off and disassembled it on my workbench on top of a fresh paper towel. No dirt or debris anywhere. Pilot jet was completely clear. Mmmm. So I proceeded to tear the entire thing down and blew every orifice out with carb cleaner. Vent tubes, main jet, pilot jet, choke, all passages, etc.. Then I set the float height at 22mm. Verified that all the seals on the top of the carb and throttle cable are sealing properly. Needle and slide look perfect. Proceeded to install some brand new fuel tubing. Made sure the tank was venting properly and plenty of flow out the petcock. Installed brand new spark plug. Set air screw at 1.5 turns out. Reassembled bike. Same exact issue! Bike will not idle with the choke off. Interesting. Now what? With the bike idling and choke on I proceeded to spray WD40 all over the reed cage, carb, base gaskets, cases, etc.. in an attempt to find an air leak. Nothing. No rise in idle. If I close the choke by pushing the knob down you can almost instantly hear the RPM's rise and then die. Its obviously running lean and starving the motor the second the choke is closed. Anything else I am missing? I am out of options and feel like I have checked everything possible. Thanks! Keith Quote Link to comment Share on other sites More sharing options...
breagh Posted March 14, 2013 Report Share Posted March 14, 2013 Just a guess.sticky float? Tip the bike over should flood. If not could be your problem. Cleaning the tank out wouldn't be a bad idea. Had an Sy for years and any problems tended to be water in carb issues and you seem to know what you're doing. Had a coil go and it would short and stop when ticking over,but doesn't sound like your problem. Cheers. Quote Link to comment Share on other sites More sharing options...
scraggydog64 Posted March 14, 2013 Report Share Posted March 14, 2013 I had similar issues with a Mont 315. Turned out to be carb icing. Often this is visible on the outside of the carb, in my case it was not. I made a shield to keep the wind off the carb and direct heat from the barrel onto it. As soon as the temparature got a little bit above freezing it ran fine. Quote Link to comment Share on other sites More sharing options...
custom Posted March 15, 2013 Author Report Share Posted March 15, 2013 Thanks. It's pretty warm here and the issue is present immediately after startup Quote Link to comment Share on other sites More sharing options...
custom Posted March 15, 2013 Author Report Share Posted March 15, 2013 Float is working very smoothly and floats just fine in gas Quote Link to comment Share on other sites More sharing options...
copemech Posted March 15, 2013 Report Share Posted March 15, 2013 Hello everyone and thanks in advance for sharing your knowledge. I have a 2003 SY that I recently bought. Everything was working fine. Last ride I put the bike in the garage. Didn't wash it. 10 days later I loaded it in the truck to try out my first trials event. Once at the event it was hard to start and would not idle with the choke off. I assumed a plugged pilot jet. Unfortunately I didn't grab my tools. Back home I go. I pulled the carb off and disassembled it on my workbench on top of a fresh paper towel. No dirt or debris anywhere. Pilot jet was completely clear. Mmmm. So I proceeded to tear the entire thing down and blew every orifice out with carb cleaner. Vent tubes, main jet, pilot jet, choke, all passages, etc.. Then I set the float height at 22mm. Verified that all the seals on the top of the carb and throttle cable are sealing properly. Needle and slide look perfect. Proceeded to install some brand new fuel tubing. Made sure the tank was venting properly and plenty of flow out the petcock. Installed brand new spark plug. Set air screw at 1.5 turns out. Reassembled bike. Same exact issue! Bike will not idle with the choke off. Interesting. Now what? With the bike idling and choke on I proceeded to spray WD40 all over the reed cage, carb, base gaskets, cases, etc.. in an attempt to find an air leak. Nothing. No rise in idle. If I close the choke by pushing the knob down you can almost instantly hear the RPM's rise and then die. Its obviously running lean and starving the motor the second the choke is closed. Anything else I am missing? I am out of options and feel like I have checked everything possible. Thanks! Keith No expert here, although just offering general advise as I cannot even recall which carb is on the SY. Sounds as though you know your way round the carbs, yet in my experience many have been fooled by the smallest particle missed in the idle jet or passeges. This is why I usually use a fine wire to pass through it, same for the small passage in the bore of the carb. A blast through with carby spray also helps insure proper flow of the low speed fuel circuit which is basically bypassed using the choke circuit. Hope that helps, Quote Link to comment Share on other sites More sharing options...
ridgrunr Posted March 15, 2013 Report Share Posted March 15, 2013 I know you said you checked the vent tubes, but it might be worth a second look. Sounds like the same thing that happened to a Fantic I had. Quote Link to comment Share on other sites More sharing options...
Cookiemonster Posted March 15, 2013 Report Share Posted March 15, 2013 can't believe something similar just happened to me rode the bike (2007 model) a couple of weeks ago all day without a problem, came home, cleaned it, put fresh petrol in (same petrol I'd used for the ride) started the bike & it was fine week later dropped the oil, cleaned the air filter & left it until today took the bike out of the garage & the bike will run on choke but dies when push choke off looked at air filter which was new about 4 rides ago & it's frayed around the edges & easly tears (am I the only one that finds it difficult to get the air filter back in on a Scorpa or is there a trick?) so I'm fearing the worst that some foam has been sucked into the carb no expert on carbs having never dismanteled one, had the bike since August last year & so far this is the only problem before I look at the carb I'll check all other venting as mentioned so any other tips would be appreciated thanks Quote Link to comment Share on other sites More sharing options...
breagh Posted March 16, 2013 Report Share Posted March 16, 2013 Almost certain it will be dirt in the carb,get somone who knows what they're doing to give it the once over. When fitting the filter put the filter on the plastic rectangle that fits in the top of the airbox first. Then fit as one part.easy. Quote Link to comment Share on other sites More sharing options...
custom Posted March 17, 2013 Author Report Share Posted March 17, 2013 I tore the carb down and removed any seals and other rubber or plastic items like floats, choke, seals,etc... I then cooked it in the ultrasonic with fresh simple green for an hour. It is impressively clean. I verified the passages were all clear with fishing line and I can see the light through it. I will post up some pictures later. I also used some simple green and cleaned the inside of the airbox. Cleaned and oiled the air filter too. Now I am off to get some fresh ethanol free gas and see if she runs. Will report back later.... Quote Link to comment Share on other sites More sharing options...
custom Posted March 18, 2013 Author Report Share Posted March 18, 2013 She runs! Really well at that. There must have been something in there that I just couldn't see. Amazing as it was thoroughly cleaned with carb cleaner and compressed air a few times. The simple green and ultrasonic did the trick. Click the links below if you want to see pics. https://picasaweb.google.com/106702910610956071173/VariousDirtBike?locked=true#5856509278623635090 https://picasaweb.google.com/106702910610956071173/VariousDirtBike?locked=true#5856509448597198706 https://picasaweb.google.com/106702910610956071173/VariousDirtBike?locked=true#5856509494741884178 https://picasaweb.google.com/106702910610956071173/VariousDirtBike?locked=true#5856509524997729426 https://picasaweb.google.com/106702910610956071173/VariousDirtBike?locked=true#5856509582593161058 Quote Link to comment Share on other sites More sharing options...
copemech Posted March 18, 2013 Report Share Posted March 18, 2013 Good job then lad. Now you know why I know what I think I know! Quote Link to comment Share on other sites More sharing options...
bigmike1961 Posted March 18, 2013 Report Share Posted March 18, 2013 Click the links below if you want to see pics. https://picasaweb.go...509278623635090 https://picasaweb.go...509448597198706 https://picasaweb.go...509494741884178 https://picasaweb.go...509524997729426 https://picasaweb.go...509582593161058 All I see is page no found Quote Link to comment Share on other sites More sharing options...
Cookiemonster Posted March 19, 2013 Report Share Posted March 19, 2013 Almost certain it will be dirt in the carb,get somone who knows what they're doing to give it the once over. When fitting the filter put the filter on the plastic rectangle that fits in the top of the airbox first. Then fit as one part.easy. thanks breagh wouldn't mind having a go myself, I've an engineering background so I feel like a fraud for not trying confident I could get the carb off the bike but do you know how far you have to strip the carb in order to get at the jets? regarding the airfilter I've tried putting it into the plastic rectangle first but the rim of the filter doesn't hold, I bought it from Birketts so thought it would be OK, are there better options? thanks Quote Link to comment Share on other sites More sharing options...
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