jdunnihoo Posted May 25, 2012 Posted May 25, 2012 Hello all, Guy down the street is selling a 1988 DT50. It's in good order. Everything works (lights, etc.). Starts on 1-2 kicks when cold but immediately goes to WOT within no time. He says he has had the carb off a couple times to try and "fix" it. If you mess with the "twist grip" portion of the throttle, it never seems to return to it's correct location. I didn't mess with it too much, but noticed the coolant lines go into the carb and then from carb into block, so didn't want to tear into it if I ddin't need to. If you can shift fast enough, it actually runs. Thought I would pick it up for a couple younger first time riders in the household. Thoughts or ideas? Jay
jdunnihoo Posted May 26, 2012 Author Posted May 26, 2012 Update: Ended up picking the bike up anyway. The grip deffinitely won't return to starting position. Easy way to get into it? Have any repair manual pages to send over? Thanks for any help all,
jdunnihoo Posted May 30, 2012 Author Posted May 30, 2012 Update #2. I ended up lubricating the throttle cable and no such luck. I still can't get the throttle to return to "home position". It will move and you can hear the mechanism working inside the carb, but it pretty much runs as if you have the throttle wide open, regardless of grip position. Throttle cable seems ok visually, but I may question the spring. I originally asked for manual pages, but it appears that is prohibited on this forum, which is really odd. In fact, a lot about this forum is not in-line with my BMW and Suzuki forums. Not even close. In any case, I seem to be getting some views on my thread, but if anyone has an idea, that would be greatly appreciated. Symptom: Bike starts and after a couple seconds it revs up to full throttle, regardless of twist grip position. Twist grip also doesn't return to default location. Related? Ideas? Third day messing with it and getting nowhere. I hate to take to a garage as I am sure the fix will not be too hard... if I knew what it would be. Thanks for anything that helps me out. Take care, Jarrod
jdunnihoo Posted June 3, 2012 Author Posted June 3, 2012 Update #3: Still same spot. I feel like a broken record here, but since NO ONE has replied to ANY help posting of mine, I will try one last time before considering this forum useless. Since I have to start buying parts on a whim, please let me know best options: 1. Throttle spring 2. Carb slide 3. Throttle cable I know this forum doesn't share copyrighted works, but if anyone has a carb diagram or instructions on how to change the throttle cable, that would be brilliant. Bike runs at full throttle regardless of twist grip position. You can hear cable moving parts when grip twisted. Twist grip doesn't return on its own. Even if you don't know what is wrong, even if you have an idea, please post something. This has to be the most impersonal, non-helpful forum I have ever joined. No offense, but I can't recall joining any forum and posting an issue where someone didn't offer at least something. Thanks again, Jarrod
wild foamy Posted June 3, 2012 Posted June 3, 2012 more than likely going to be a carb leak or missing gasket if the carb has been off a few times to be "fixed", also unscrew the top of the carb and make sure the slide has been put in the right way round (with the small tapered cutout facing the idle adjustment screw)
Moderator Airhead Posted June 3, 2012 Moderator Posted June 3, 2012 hi jarrod a few things are possible 1 the carb slide isnt returning to the closed position...can you hear the click as it hits the throttle stop screw? 2 the cylinder base gasket isnt sealing properly 3 the cylinder head gasket isnt sealing properly 4 the carb spigot isnt sealed properly the the intake rubber 5 the reed cage gasket isnt sealing properly 6 the magneto side crank seal is leaking badly 7 the carb slide isnt located properly with the peg in it's groove down the side you say the throttle doesnt return by itself? is the cable badly routed...tight or any sharp bends etc...could it be routed better?
jimmy Posted June 3, 2012 Posted June 3, 2012 Disconnect the cable from the throttle housing and make sure it moves freely inside the cable housing (also ensure the throttle body is not sticking at the bars), if its free return it back to the throttle body, but dont tighten it all the way up. Try it and if its still sticking open the carb top and remove the cable and slide. Give the slide a light rub with 0000 grade wire wool and a light oil. With the slide removed from the carb, hold the carb top and twist the throttle, the spring on the carb slide should compress and return easily, if not thats your problem. If it does return quickly and smoothly refit the carb body and slide ensuring the needle is seated correctly and also the needle is not bent. As stated above, make sure the slide is fitted the correct way round. Sorry for the "sucking eggs lesson" but sometimes it better to begin right at the start.
jdunnihoo Posted June 3, 2012 Author Posted June 3, 2012 Thanks for help everyone. Took the top of the carb off, where throttle enters carb. Looks like the slide is stuck and I can't force it... not trying to anyway so I don't ruin it. Would remove carb, but since these are rare in the USA, I am unfamiliar with a carb that looks like the coolant flows through it. If I am interpreting it correctly, the coolant actually gets pumped through the carb before entering the block. Is that correct? If so, why? Can I remove the carb without dumping all my coolant?
jdunnihoo Posted June 3, 2012 Author Posted June 3, 2012 Also should note that I tried to spray WD40 into as many "leaky spots" as I could find and no change. Will post more as I can Jarrod
Moderator Airhead Posted June 3, 2012 Moderator Posted June 3, 2012 yes some carbs have the coolant passing through a duct in them, the heat from the coolant helps prevent 'carb icing'. If it were me i would be happy to remove the coolant pipes without draining the system, just be ready to work quickly and shove something like a pencil in the tubes to stemn the leak so your bike is a water cooled version then
jdunnihoo Posted June 3, 2012 Author Posted June 3, 2012 Thanks. Yes, water cooled version. This bike only existed for 2 years in the USA in a water cooled version. At least from what I can tell here and there. I will see if I can't find something to plug the hoses and remove the carb. I'm not new to two strokes, mostly lawn and garden equipment and outboard motors. Can't recall something so picky about an air leak, but this seems solid and as mentioned spraying WD40 on seals has not helped any. Will post when done.
jimmy Posted June 3, 2012 Posted June 3, 2012 Took the top of the carb off, where throttle enters carb. Looks like the slide is stuck and I can't force it... not trying to anyway so I don't ruin it. I would say you've found your problem then. If you have got the carb top unscrewed, try to get some wd40 sprayed into the carb body and then with a bit of patience, work the slide loose. Clean as suggested above, ensure cable runs free and refit. Cany help with the coolant through the carb question tho
Moderator Airhead Posted June 3, 2012 Moderator Posted June 3, 2012 cant see it being stuck too badly jarrod, you'll soon have her sorted, dont forget you cant rotate the slide inside the carb bore because its pegged, you should be able to gently tap it down and pry it back up through the bellmouth, a bit at a time...you will soon free it Take care not to tap the needle though, work away from the centre
jdunnihoo Posted June 3, 2012 Author Posted June 3, 2012 I have a pic if it will help. Thanks for some advice, as it looks so stuck that I was going to cut it out and replace everything from scratch. Not wanting to be so drastic, but with the spring and cable still attached it's a bit of a pecker, for sure. Will start the saturation and gentle tapping now
jdunnihoo Posted June 4, 2012 Author Posted June 4, 2012 Update: Could not get at it. Stuck and is seriously wrenched in there. Would say that the previous owner had forced it, realized it and sold it. No worries. Cut throttle cable. Spring and needle fine. Slide is jammed in the old carb and I can't find an effective way to remove it. Does anyone know the part number or where to order a new carb? Will order a new cable and carb. If slide is seperate from the carb, does anyone know a part number? This will be the easiest way to do it. Looks like the previous owner really wrenched on that carb some. Jarrod
Moderator Airhead Posted June 4, 2012 Moderator Posted June 4, 2012 is the cable still attached to the slide jarrod? if so perhaps you can grip it in a vise and pull / tap against it? cant help much with getting parts in usa...ebay or bikebandit?
jdunnihoo Posted June 4, 2012 Author Posted June 4, 2012 Thanks for all the help. Will still see hwat I can do about trying to get the slide free, but if anyone has a part number or model number for the Mikuni, I will pick one up. Thanks everyone Jarrod
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