DavidSS Posted June 3, 2011 Author Posted June 3, 2011 Sounds like fuel " , if it ran with solvent cleaner, is feul running [ petcock filtre,] is float valve sticking or faulty, leave float bowl off, and let petrol run through. ,, then replace bowl, Blackhat, the bike never really "ran" with the solvent. It just fired up for about 2 seconds. It must be getting fuel to the cylinder chamber because the plug gets wet. I am still suspicious that it could be electrical related.
DavidSS Posted June 4, 2011 Author Posted June 4, 2011 Dont despair David, you'll get there in the end, you need to check the compression, maybe the piston rings are 'frozen' or the crank seals passing oldgitonabke! good news to report.... we have compression! this evening I spoke with me neighbor and he came over and helped me troubleshoot it. We took the plug out. He put his finger over the plug hole and I cranked it over about a dozen times. (checking the compression) He said that his finger should have been real wet after, but it was not. Sooooo, we figured it must be a fuel issue still. put the plug back in. I opened up the air screw a couple more turns. then We took the airfilter out and sprayed starter fluid down in the intake side. put the choke on, and cranked it over a bunch of times (throttle open about 1/4 to half) and it started to fire up! So then I sprayed some more fluid in. And we cranked it some more.... it started again! this time I was able to keep it running for about 30 sec before it died. Sooooo, we are back to a carb issue. As a test. I screwed the air screw back in to factory setting of 1 1/2 turns. Then we repeated the process, and could NOT get the bike to fire up. I then backed the air screw out again, and low and behold we got it to start again momentarily. So tomorrow I take the carb apart AGAIN! should i see if I can get a carb rebuild kit for this and replace that air screw and the jets? I am also going to take the reeds out again and inspect more closely to see if they could be sticky. blackhat250 may have had a good idea.... maybe the float valve is stuck, and that is why it only ran for about 30 sec, until the bowl emptied out. Any other suggestions? I think I am getting close!
Moderator Airhead Posted June 4, 2011 Moderator Posted June 4, 2011 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.
blackhat250 Posted June 4, 2011 Posted June 4, 2011 Good news your near there dave " leave the reed valve, its only for mid range performance & blowback,
DavidSS Posted June 5, 2011 Author Posted June 5, 2011 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 GOT IT!!! it runs now! Thanks all of you for all the help and encouragement! not sure what I did, but it was carb related. I took the choke assembly apart and noticed that it had a strange yellow goopy thing on the end. I thought it might be a damaged O-ring or something, but I took it off. I cleaned it good and re-installed it. I also cleaned out the air screw. So once I got it running I was able to adjust the air screw and idle. It idles smooth at low RPM....very little smoke. however, now I have a new problem! It has no high end power! I took it out for a ride, and when it gets to about 5000RPM under load it starts to run like it has no power, like it has a governed on it! or its running too rich or something. I expected this bike to be much more zippy. What is causing that??? I seem to recall you mentioned something like this happened on your bike in one of the threads I was reading. What did you do to fix that?
DavidSS Posted June 5, 2011 Author Posted June 5, 2011 Good news your near there dave " leave the reed valve, its only for mid range performance & blowback, got it going blackhat! see my reply above for more detail...
NE0 Posted June 5, 2011 Posted June 5, 2011 Well done dave, seems like having cleaned the choke you solved it..... but looking at the thread, pauls first question was.... David, is the choke working, signs of wetness on the plug? see he knows his stuff
DavidSS Posted June 5, 2011 Author Posted June 5, 2011 Well done dave, seems like having cleaned the choke you solved it..... but looking at the thread, pauls first question was.... see he knows his stuff Yes, he certainly does know his stuff! From little knowledge I have of the Mikuni carbs, I assumed the choke was working. I didn't even realize you could take it apart until he mentioned the "choke circuit" to me in the last thread. But I think it was a combination of carb related issues, not just choke. I still have to figure out how to solve this next mystery of no high end power. So not out of the woods yet...
Moderator Airhead Posted June 5, 2011 Moderator Posted June 5, 2011 Yes, he certainly does know his stuff! From little knowledge I have of the Mikuni carbs, I assumed the choke was working. I didn't even realize you could take it apart until he mentioned the "choke circuit" to me in the last thread. But I think it was a combination of carb related issues, not just choke. I still have to figure out how to solve this next mystery of no high end power. So not out of the woods yet... Aghh youre embarrassing me now so this may be harder to find than the last issue, I would stick with the carb, David you said you cleaned it and obviousy from the outcome not near well enough. The carb would be my first port of call again, a total strip including removal of the needle jet (emulsion tube) here is a dirty one from a DT175. If yours is this type take care when tapping it out of its seat. I use a pin punch of the correct size and re fitting it if I remember right it only goes in one way (locating peg?..cant remember for sure but watch out for one. The chamber that fits into has a small hole into the bottom of the carb bore (engine side) seen on this picture All jets and also the float valve need to be removed and I recommend at the very least inspecting them closely...I use a magnifying glass... Buy an aerosol carb cleaner and spray it everywhere and compressed air supply is also useful if you have the means. Only when your carb is cleaned 'as new' can you eliminate it from your power issue and move on from there. Can you not redline the bike in 2nd 3rd 4th? or close to it? Oh and about that compression test you did earlier using your neighbours finger...Not Really
DavidSS Posted June 6, 2011 Author Posted June 6, 2011 Aghh youre embarrassing me now so this may be harder to find than the last issue, I would stick with the carb, David you said you cleaned it and obviousy from the outcome not near well enough. The carb would be my first port of call again, a total strip including removal of the needle jet (emulsion tube) here is a dirty one from a DT175. If yours is this type take care when tapping it out of its seat. I use a pin punch of the correct size and re fitting it if I remember right it only goes in one way (locating peg?..cant remember for sure but watch out for one. Buy an aerosol carb cleaner and spray it everywhere and compressed air supply is also useful if you have the means. Only when your carb is cleaned 'as new' can you eliminate it from your power issue and move on from there. Can you not redline the bike in 2nd 3rd 4th? or close to it? Oh and about that compression test you did earlier using your neighbors finger...Not Really paul, Let me clarify..... the only part I could find that looks like your photo is labeled in the book as a "main nozzle" I assume this is what you are calling the needle jet. It is the ONLY piece I was not able to get out to clean on the 1st and 2nd attempts. I only cleaned it with a pipe cleaner down it. I did not realize it has little holes in it! When I tried to push it out, it appears it is flanged on the end that is near the throttle throat side. I was not sure it was supposed to come out so I did not force it. But now I will try a bit harder to get it out. I think this time I will boil the entire carb parts in hot water and then flush them out again with carb cleaner and spray with my air compressor. Geeze! these things are picky! Oh, and yes, the finger compression tester is not calibrated very well. I'll see about getting a real gauge. For the RPMs. I am able to rev it close to redline 7K while in neutral. All beit, it seems to lag some on the rev up, but I am used to motocross bikes that are snappy fast on the throttle. I assume that behavior is a reed issue. It is when I put the bike into motion under load that it seems to not have much power. No matter what gear I am in. I bet that needle jet is gunked up like the one you showed in the photo. I think it is still running rich on high rev.
DavidSS Posted June 9, 2011 Author Posted June 9, 2011 Well I removed the carb again and was able to get the needle jet out to clean it. It actually was not real bad! looked like oxidized but not clogged. I cleaned and polished and made sure the holes were clear. Then also went through and cleaned again the carb and all the holes everywhere! Reassembled and installed. Started the bike up, and NO DIFFERENCE! It is still running rich on the top end after it gets past about 5000RPM. I should clarify,,, that I mentioned earlier that it seemed to run fine in neutral, but this is not true, it is running rich even in neutral. However when it is idling it runs just fine. Very nice actually. At this point I am about to give up on the carb and look into buying a new replacement. Any suggestions on what model I can use on this old bike? And where a good source is to buy them? Could I take a newer Mikuni from a say YZ125 or 250 and use it? Just disconnecting the oil pump and go to manual mixing of the fuel??
DavidSS Posted June 9, 2011 Author Posted June 9, 2011 Buy an aerosol carb cleaner and spray it everywhere and compressed air supply is also useful if you have the means. Only when your carb is cleaned 'as new' can you eliminate it from your power issue and move on from there. Can you not redline the bike in 2nd 3rd 4th? or close to it? Oh and about that compression test you did earlier using your neighbours finger...Not Really Paul, got the needle jet out and cleaned it. It was not realy dirty, just oxidized. Carb is cleaned AGAIN... but the bike still runs just the same. Engine is running rich on the top end after about 5000RPM. I have not done the compression test yet. But I think the issue lies with a rich fuel mixture. I am ready to just try a new carb. Any suggestions of carbs I could use for this model of bike? I was thinking about taking the oil pump out of it and doing the traditional oil/fuel mix.
Moderator Airhead Posted June 9, 2011 Moderator Posted June 9, 2011 If the carb is clean and all the airways are clear I dont see the point of trying to source a new (old) carb, it may be worse than the one you have already? I would do the cheap things first like borrow a compression tester. Your bike is easy to check as theres room to fit it without taking stuff off first. Cant you ask at a local car garage if they will do it for you for a nominal cost...I mean a repair shop of course not a dealer franchise. To me we have finally eliminated the carb as long as 1:your needle is in the right notch with the clip 2: The float height is correct at 21mm? 3: The choke is not passing fuel because of an imprinted rubber seat Do the test of compression next. Like I said before these things can be much more difficult to find than 'bike wont start issues' in my experience.
blackhat250 Posted June 9, 2011 Posted June 9, 2011 Yip as he says " am thinkin Choke, unscrew an look at rubber, its like a ballcock washer, . if its badly dented, it could be passing excess fuel. one other thing " i take it the air filtre is clean
DavidSS Posted June 10, 2011 Author Posted June 10, 2011 If the carb is clean and all the airways are clear I dont see the point of trying to source a new (old) carb, it may be worse than the one you have already? I would do the cheap things first like borrow a compression tester. Your bike is easy to check as theres room to fit it without taking stuff off first. Cant you ask at a local car garage if they will do it for you for a nominal cost...I mean a repair shop of course not a dealer franchise. To me we have finally eliminated the carb as long as 1:your needle is in the right notch with the clip 2: The float height is correct at 21mm? 3: The choke is not passing fuel because of an imprinted rubber seat Do the test of compression next. Like I said before these things can be much more difficult to find than 'bike wont start issues' in my experience. OK, still working on a compression tester. My neigbor down the way works on cars a lot. He might have one. For the needle. I have tried it at factory default slot 3. And at slot 4. I measured the float height with my calipers, and it was spot on per the # in the book. don't have the book in front of me right now. Now... you got me thinking about that choke again! When I took it out, I did NOT see any rubber seat on it. Where would this be located? At the end? Mine just has this brass plunger with nothing on the end of it. I did not see anything down in the hole where it sits. When I took it out the first time, I found some yellow gunk looking stuff that kind of looked like epoxy glue stuck to the end. I pealed it off. do you have a photo of a good choke plunger you can share? David
DavidSS Posted June 10, 2011 Author Posted June 10, 2011 Yip as he says " am thinkin Choke, unscrew an look at rubber, its like a ballcock washer, . if its badly dented, it could be passing excess fuel. one other thing " i take it the air filtre is clean Yep airfilter is clean. I think we are getting close here! where does this rubber washer sit?? I did not see one. In less you are referring to the rubber cup that goes on the outside of the choke near the nut?
Moderator Airhead Posted June 10, 2011 Moderator Posted June 10, 2011 ........Now... you got me thinking about that choke again! When I took it out, I did NOT see any rubber seat on it. Where would this be located? At the end? Mine just has this brass plunger with nothing on the end of it. I did not see anything down in the hole where it sits. When I took it out the first time, I found some yellow gunk looking stuff that kind of looked like epoxy glue stuck to the end. I pealed it off. do you have a photo of a good choke plunger you can share? David Yes the seal is in the end, I havent got a picture but I will get you one
DavidSS Posted June 11, 2011 Author Posted June 11, 2011 Ok, I took out my choke assembly and here is what it looks like Does this look OK? I see that the black seal on the end has some grooves in it. But looks good to me. Here is a link to other photos of the carb after I cleaned it. And the dirty needle valve before I cleaned it. http://www.flickr.com/photos/davidscottphotos/sets/72157626922308430/
blackhat250 Posted June 11, 2011 Posted June 11, 2011 HI daVid " just took out the choke of my dt, and its in better shape than yours, its got the small indentation ,like your centre one, but not as deep ,, , renew if i was you,,
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