CalNub 0 Posted December 2, 2012 I've got a '98 620 Adventure with low pipes and a dellorto phm 40 carb and it's having some difficulty starting. I took it for a ride the other day and noticed the throttle was very hard to pull open and then the revs hung after releasing the grip. I pulled the carb yesterday and noticed some orange tacky substance on the inside of the carb and on top of the valves, which I'm told is likely varnish or a residue from gasoline or bad gas. I'm told this varnish will burn off once i get everything running properly again. Is this correct or is there a better solution? I poured some seafoam in the tank as a precaution to treat the remaining gas, but I'm now starting to wonder if that could be part of the problem. I cleaned the carb, pulled it apart as per the rebuild thread on advrider, cleared the jets, and when i put it all back together again it fired up just fine. Today I took it for another short ride (20 min) just to make sure everything was working properly. I stopped at the hardware store to have a spare key made and when I came back out to the bike it wouldn't start for me. I sat there for 20 min playing with the choke, throttle, hot start button, etc, trying to get it to turn over. It definitely wanted to start, but never fully engaged on its own. I dropped the float and tried to clear the jets hoping something was just clogging the starter jet. Still wouldn't go. When i got the bike back to my house I pulled the plug and saw it was wet, so I'm starting to wonder if my starter jet or emulsion tube need to be adjusted - according to dellorto's tuning manual if you have a hard time starting and the plug is wet, you need an emulsion tube with holes drilled higher up to to lean out the mixture. Which brings me to my first question, where can I buy different emulsion tubes? I'm having some difficulty locating them online. When the bike was running I adjusted the idle speed to about 1500-1700 as per the manual's instructions. When i came back out is when it wouldn't start up again. Is it possible this would have something to do with it? Even if it was running smoothly at that rpm range? When i pulled the starter jet I noticed the o-ring on the top of it was disintegrating so I went back into the hardware store and picked up the closest match i could find. When i put the jet back in with the new oring I found the float bowl was difficult to get seated all the way up by hand, it wasn't until I got the drain nut back on and tightened it down with a wrench that the bowl seated properly against the carb body. Could this have some impact on the hard starting issue? My impression is that the new oring is slightly larger than the original and it's just getting a very tight seal to the starter well in the float bowl. I've also replaced all the fuel lines to the left hand petcock with a new paper fuel filter. I have yet to hook up the rh petcock because I'm not exactly sure how it ties into the fuel lines and I haven't been running my fuel that low anyway. I did notice, however that the new paper filter has some blue marks or stains that have developed. What are these from? Could they be indicative of another problem? I know i have a lot of questions here, I'm just trying to get this thing back up and running. I've been told to ditch the dellorto carb for an FCR. I actually have an FCR off a ktm four-wheeler, it's a 3900s. Would that work? It has some electronic cables coming out of one side, but I'm confused as to what purpose they would serve. Thanks for your help! -Aaron Share this post Link to post Share on other sites
tntmo 887 Posted December 2, 2012 I am going to cut straight to the chase....ditch the DelOrto carb and get a Kiehin FCR installed. It's a much better carb with a lot more/easier aftermarket support. The electrical connections are for the TPS (throttle position sensor) and are not needed. You will not be disappointed once you get the FCR installed and dialed in. The only item of concern I have is that you may need a FCR41 for that engine, the FCR39 is usually used on 400-450cc engines. Share this post Link to post Share on other sites
CalNub 0 Posted December 2, 2012 I am going to cut straight to the chase....ditch the DelOrto carb and get a Kiehin FCR installed. It's a much better carb with a lot more/easier aftermarket support. The electrical connections are for the TPS (throttle position sensor) and are not needed. You will not be disappointed once you get the FCR installed and dialed in. The only item of concern I have is that you may need a FCR41 for that engine, the FCR39 is usually used on 400-450cc engines. My plan is to get an FCR eventually, but I was hoping to postpone this at least a few months noting the entrance price is at least $350 including throttle assembly, jetting and boots. What can i do to get the dellorto functioning properly in the mean time? Also, where do you measure to find the 39mm or 41mm? Is it the internal diameter to the motor intake? external diameter? slide? I have a phm 38sd on my 400 lc4, it's nearly identical so i'm going toi pull the starter and idle jets from it to get me some variety in tuning the 620. Share this post Link to post Share on other sites
CalNub 0 Posted December 2, 2012 Ok, i just tried switching the starter jets from both dellorto carbs. Conveniently they were both 45s, but the 400's had an emulsion tube with the holes much higher up. Still would not start. So i decided to to go back to the basics. I know i have fuel (the plug is wet), i know i have compression (can feel it when I remove the plug and cover the socket). But when I took the removed plug with the coil still connected, laid it against something grounded, and cycled through with the kick starter - no spark. Am i doing this wrong? Is it possible the spark would go out that quickly? I tried it with a new spark plug too and still no dice. Share this post Link to post Share on other sites
tntmo 887 Posted December 2, 2012 Start troubleshooting your ignition system. Make sure you have continuity through your kill switch, check or disable any safety switches (clutch/kickstand/etc) and ensure you have a good ground on the coil. Share this post Link to post Share on other sites
KTMrad 508 Posted December 3, 2012 You should get the correct size o-rings and gaskets, etc., anytime you work on a carb. Using a close fit does not work well. Share this post Link to post Share on other sites
Strega 0 Posted December 4, 2012 Bike is junk, carb will never work, sell to me =P All kidding aside, that carb you have isn't so good. I may have a line on one for ya though, lemme make a call tomorrow. Share this post Link to post Share on other sites
