DavidSS Posted July 1, 2011 Posted July 1, 2011 This is a continuation of an earlier blog I had going when I was trying to get the old 79 DT running. Now that I have it running I find that it is still very hard to start when the engine is cold. Carb has been rebuilt and cleaned 3 times! The air screw is set at factory 1.5 turns. here is a link to a video of how it sounds when first starting. Eventually.... about 50 kicks or so, I can get it to start up. http://s913.photobucket.com/albums/ac333/davidscott59/yamaha%20carb/?action=view¤t=P1010154.mp4 Anybody have any ideas of where to go from here?
Mr Machinist Posted July 1, 2011 Posted July 1, 2011 that's weird. sounds like its only just getting a little bit of fuel through...... dont want to flog a ded'orse but....it does sound like everything else is working.... spark and compression, ( might be worth checking to triply make sure!!) is that on choke for a cold start?
FZR AL Posted July 1, 2011 Posted July 1, 2011 I would agree on the not enough fuel getting through,as soon as you twist the throttle its dying, can you manually fill the carb bowl and see if it runs , or rigg something up without the tank?, pull your petrol tap and inspect
KirriePete Posted July 1, 2011 Posted July 1, 2011 Is the choke working properly? Dunno the specifics of the DT, but every stroker single I've had my hands on had a knack to starting from cold - the best method I found (worked 90+% of the time) was: 1. Ignition OFF, choke ON b. Couple of priming kicks, no throttle. iii. Ignition ON, choke ON, no throttle - kick. x. Leave throttle alone for a good 30 seconds and you should be good to go. This method has worked for me on machines from a Puch Maxi moped, through Suzuki TS50X, Yam RS100/125, Suzuki GP125, MZ250 and on ..... HTH - lovely looking bike, by the way.
rebore Posted July 3, 2011 Posted July 3, 2011 Hello All of the above and have you checked for air leaks around the carb manifold rubbers etc. All the best Mike
DTGordo Posted July 3, 2011 Posted July 3, 2011 Sorry, I've only got the obvious, thinking out loud sort of stuff.... Is that with the choke on or off? It does sound like lack of fuel which points to the carb. If the choke is on it might be a problem with the starter jet. If you can then start and run it without the choke on for sure that's where it is. Maybe there's some moisture in there somewhere which can be quite pesky. What's different when it's hot? Starting with and without the choke? Has it been tuned recently and that's ok? Sounds like the spark is ok but if really cold (like not t-shirt weather) I was thinking it might be the lead/plug/coil and the connections.
DavidSS Posted July 6, 2011 Author Posted July 6, 2011 Well I GOT IT FIXED everyone!!! Here is what I found. I took the carb apart again,,, for the 4th time, and checked the float height. Adjusted it to factory spec (again) using calipers. While in there, I noticed a small orifice in the float bowl that i had not before. Reason for this is when I rebuilt the carb and cleaned it, I had my son help me so I gave him the chore of cleaning the bowl, (figured that would be easy and not too delicate for him to work on) so I did not pay much attention to it, as I figured it was just a float bowl!?? However,,, today I noticed this orifice hole. I noticed that it appeared be plugged! So I soaked it in carb cleaner, and then took my air compressor and flew it out good. Then filled the bowl up with rubbing alochol, and put a drinking straw in this hole, and blew threw it. Yep... bubbles came out now. I Put it all back together again.... tried starting the bike, and pow it started right up on the second kick! so.... I am guessing that small orifice was plugged. The bike then after warmed up, was running too rich on the low end, and was loading up. so I had to adjust the air flow screw in about 1 turn. It now idles smooth, and has a ton of mid and top end power now! Whooo hooo! thanks all for the insight and suggestions.
YPVS TONE Posted July 6, 2011 Posted July 6, 2011 I did suggest this in your previous topic !! "Sounds to me like a fueling issue if you say you sprayed carb cleaner in plug hole and it run. Check to make sure jet in floatbowl for choke is clear . Try blowing down hole "B" in oldgitonabike's picture you should be able to feel air coming out of "A". If not the choke jet is blocked. Try soaking in carb cleaner or if it is stale fuel which has gummed up boil a kettle and pour hot water in the float bowl and let it stand for a while and see if this melts the gum, making sure you rinse out floatbowl with carb cleaner afterwards. DON'T start poking bits of wire down the jet or you will enlarge the jet" And Your Reply "I did clean the entire carb with carb cleaner, and sprayed in every hole I could find. so item "A" is clear. I did poke a fine wire through the jet to unplug it, but I doubt I enlarged it. Tony
DavidSS Posted July 6, 2011 Author Posted July 6, 2011 I did suggest this in your previous topic !! thanks for rubbing my nose in the dirt.... I misunderstood which hole you suggested i look in (lots of them in this carb...). I was focusing all my efforts on the carb side, not the bowl. I did not know what a "jet in floatbowl for choke is clear " was, (sentence made no sense to me) I thought it was the hole where the choke seated at. O-well, live and learn.
Moderator Airhead Posted July 7, 2011 Moderator Posted July 7, 2011 Great new you fixed it David, it's a great feeling to have it running well again eh?...Now to rub your nose in it a little further thanks for rubbing my nose in the dirt.... I misunderstood which hole you suggested i look in (lots of them in this carb...). I was focusing all my efforts on the carb side, not the bowl. I did not know what a "jet in floatbowl for choke is clear " was, (sentence made no sense to me) I thought it was the hole where the choke seated at. O-well, live and learn. Ahh c'mon David, are you saying my photos and description of operation needs clarifyinng?? I did clean the entire carb with carb cleaner, and sprayed in every hole I could find. so item "A" is clear. I did poke a fine wire through the jet to unplug it, but I doubt I enlarged it. Good one David, to clean a carb properly the very least you should have is an aerosol carb cleaner. Better still a compressed air line and an ultrasonic cleaning bath. Pay particular attention to the pilot jet and the choke circuit, really it should have started up fine on the choke and ran on that alone! Empty the bowl and drizzle gas into the choke tube and see if the fuel runs out of the little hole into the bowl. Also check the gasket is intact around the choke tube, if its broken the choke wont work. Hoping for good news soon. I also asked you to specifically test this jet wasnt blocked, even after you stated it was clear, thats why the issue took so long and you became frustrated. Anyway good you now have it beat and it would be good to see another video or your bike at the end of your 'other post' Cheers...Paul
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