Beef Supreme Posted July 16, 2008 Posted July 16, 2008 hey , i'm new here and i'm trying to get my 81 dt175 going 100% , but i'm having some issues . you can give it as much gas as you want and it does fine untill you hit 6k , then it just flutters there , does it in neutral or under load . i checked the float height and it was off so i set it to factory spec . the slide needle isn't adjustable , the autolube pump seems to be adjusted right (peg lines up with the dot) , all jets clean . once i'd done all that i could get it to go to 6.5k rpm and sometimes a little higher but it would start gurgling . then i thought hey , maybe the air cleaner isn't as clean as it looked , so i took it out and found the back side of it sopping with oil and pretty much falling apart . i removed it and i took it for a spin up the street and now i could get it up to 7k maybe a little higher but not up to the 8k red line so i'm guessing the clogged up old air filter had something to do with it (i have a new one on order) . but shouldn't i be able to get her up into the red (not that i plan on riding in the red , but theroetically shouldn't it be able to get there ? atleast to the 8 ? ) and if so what could be holding it up ? there's nothing else adjustable on here . compression is good and she starts first kick , idles great , the plug looks a little wet but the tip is somewhat tan . i just noticed that in the diagram for my air box there's a small snorkel that you set into the box before screwing the cover down and mine doesn't seem to have that ...that couldn't cause this could it ? i wouldn't think that an inch long plastic snorkel would make that much of a difference tho . anyone else have any ideas ? tomorrow i guess i'll check the reeds and make sure they're good . and i'll try running it with the fuel off to see if once the fuel level gets lower if it'll rev all the way up . if neither of those pan out i'll run it wide open up a hill and hit the kill switch and then check the plug . i know it's something dumb but i'm running out of ideas .
Beef Supreme Posted July 16, 2008 Author Posted July 16, 2008 ok , well i just tried running it with the fuel off to see if it was still float height , it ran as usual untill it didn't have enough gas to keep going , so i don't think it's float height . then i came down the street as fast as i could , hit the kill switch and pulled the clutch and rolled back to my house , pulled the plug . it was a little wet but the tip was slightly tan . i haven't checked the reeds yet , i'm going to let the engine cool down some first . i think i'll also pull the exhaust off and make sure it isn't all blocked up near the head .
Beef Supreme Posted July 16, 2008 Author Posted July 16, 2008 i just pulled the muffler off and besides being loud as hell i can now get it up to 7.5k rpm . i think i'm going to pull the whole exhaust and make sure it's clean ....i really hope this is it.
Moderator Airhead Posted July 16, 2008 Moderator Posted July 16, 2008 i just pulled the muffler off and besides being loud as hell i can now get it up to 7.5k rpm . i think i'm going to pull the whole exhaust and make sure it's clean ....i really hope this is it. pour some coarse grit in the pipe, block the ends and give it a good old shake up, try to clean the muffler up internally too
Beef Supreme Posted July 16, 2008 Author Posted July 16, 2008 just for the hell of it i fired it up with the entire exhaust off , same deal , it would get to 7.5 and that was that , the exhaust port is fairly clean and the pipe doesn't seem to be blocked up ...i don't think the exhaust is the problem . ehhh , i'm really starting to get tired of this , every single bike i've ever had has always worked 90% because of some undiagnosable mystery problem that bugs the hell out of me untill i give up and sell it .
Moderator Airhead Posted July 16, 2008 Moderator Posted July 16, 2008 just for the hell of it i fired it up with the entire exhaust off , same deal , it would get to 7.5 and that was that , the exhaust port is fairly clean and the pipe doesn't seem to be blocked up ...i don't think the exhaust is the problem . ehhh , i'm really starting to get tired of this , every single bike i've ever had has always worked 90% because of some undiagnosable mystery problem that bugs the hell out of me untill i give up and sell it . But being a two stroke it should work better with the expansion pipe on, thats why they were developed in the first place so your last move was futile, you seem to know your way round that bike well enough, i'm sure youll get it better. I think you should be looking in the carb area, in the uk the main jet size originally is a 130 so yours should be at least that, maybe try a 135 or 140 Also take out the needle jet and check it for wear with a good magnifying glass, check its perfectly round at the top where the needle goes in and not going oval, and while its out make sure that the tiny holes in the side of it are all clear
Beef Supreme Posted July 16, 2008 Author Posted July 16, 2008 i just put everything back on and took it for a spin , it still only wants to pull 7k , tho when i pulled up back at the house for the hell of it i turned the gas off but left it running again . i kept revving it wide open , the first 2 or 3 times it got to 7 , the third and fourth time it got to 7.5 , and on the last rev before it ran out of gas i got it to 8 , maybe i should try lowering the float a little more and see if that does it . when i have the carb off i'll check the reeds , but i dunno why it would run prefectly up to 7k if there was a problem with the reeds but i've seen weirder stuff before . if anyone else has any other ideas feel free to chime in .
Beef Supreme Posted July 16, 2008 Author Posted July 16, 2008 i pulled the carb and pulled the reed block out , they look brand new and they're the metal kind , no missing hunks and they all flap back just fine so i rebuilt the carb again ,i'm running the stock 22.5 pilot and the stock 150 main , i reset the float height again just to see . went out and fired it up again .....still tops out at 7 . i don't think there's anything else i can check . the bike is 100% yet it's not 100% and thus is my off road bike curse , a problem that can't exist because everything is correct , yet it still exists . not one out of the 50 or more dirt bikes i've owned has ever worked right , it's always something . i'm starting to think i should swear off anything that's not meant for the road and just be done with it .
Moderator Airhead Posted July 16, 2008 Moderator Posted July 16, 2008 i pulled the carb and pulled the reed block out , they look brand new and they're the metal kind , no missing hunks and they all flap back just fine so i rebuilt the carb again ,i'm running the stock 22.5 pilot and the stock 150 main , That would make it a VM24SS 3J100 on a DT175H or DT175G, mine uses a 130 main jet as standard, wonder why they are so different! Still think you should clean out the exhaust and check that needle jet as I said earlier, if only because you have done everything else and i know for a fact that mine has become worn in the past and ive had to clean out those little holes in it
Beef Supreme Posted July 16, 2008 Author Posted July 16, 2008 dt175 video there's a video of it . when i rebuilt the carb last time i noticed i didn't have the float at 21mm i had it at 22 , so thats where it should be now . but still , 7k in neutral , and 6k tops if i'm on the street . when you say the needle jet are you talking about the needle for the float , or the needle for the throttle slide . because i couldn't see any way to get the one for the throttle slide out , i took out the main jet , the part the main jet screws into , and then there was still a brass tube in the carb under all that . but i shined a light up in it and couldn't see any holes , it looked very clean but i ran a pipe cleaner thru it anyway , the hole isn't ovaled out .
Moderator Airhead Posted July 16, 2008 Moderator Posted July 16, 2008 Ive checkut, its different from the european model, the part i means is number 3 Here But I know this as the needle jet and it just screws in, like i said yours is different and i am not sure if it has the same holes in the side, we need to investigate this further
Beef Supreme Posted July 16, 2008 Author Posted July 16, 2008 well i couldn't see any way to get that out unless i put something up against it in the throat of the carb and hit it with something , it doesn't unscrew . the part that butts up to it and the main jet unscrew , but it looks like that part is just pushed into the carb and the rest of that stuff hold it in .
Moderator Airhead Posted July 16, 2008 Moderator Posted July 16, 2008 well i couldn't see any way to get that out unless i put something up against it in the throat of the carb and hit it with something , it doesn't unscrew . the part that butts up to it and the main jet unscrew , but it looks like that part is just pushed into the carb and the rest of that stuff hold it in . Think you might be right there, and we dont know if its got those little holes in the side now its a different carb, might be worth checking up somehow. What about ignition timing can you strobe that, I know its a 6v system, but you can still do it if you connect up to a 12v battery, cant remember but have you tried removing the air filter in case its restricting air flow?
Beef Supreme Posted July 16, 2008 Author Posted July 16, 2008 the air filter has been out today for just that reason . and it's falling apart , i don't want parts of it to get sucked in . a new one is on it's way ....as well as about $300 in other parts that hopefully wern't bought for nothing . i haven't tried timing it , but it's supposed to be cdi , normally you can't adjust timing on those .
Beef Supreme Posted July 17, 2008 Author Posted July 17, 2008 i got that needle jet out that you were talking about , it did have holes in it and they were all clogged up , sadly that still didn't fix the problem . maybe when my air filter and air box intake horn shows up it'll work better . i'm going to clean out the whole exhaust tomorrow and remove the stupid restrictor thats in it .
Moderator Airhead Posted July 17, 2008 Moderator Posted July 17, 2008 i got that needle jet out that you were talking about , it did have holes in it and they were all clogged up , sadly that still didn't fix the problem . maybe when my air filter and air box intake horn shows up it'll work better . i'm going to clean out the whole exhaust tomorrow and remove the stupid restrictor thats in it . If memory serves me correct the ignition timing is indeed adjustable, its just an assembly thing though, ie if its been assembled right it will stay right as there is no points heel to wear, you still wont know if its right unless you check it, but i'm afraid you would need a DTI and an adapter to fit it in the plug hole. What is the restrictor in the exhaust you mention?
Beef Supreme Posted July 17, 2008 Author Posted July 17, 2008 in the last few years of the dt the epa was busting down on 2 strokes , they made yamaha put a restrictor in the exhaust to limit power and emissions , here's a pic of the dt exhaust with and without the restrictor . some of the people that have the same bike as me on the dt forum said that theirs would only rev to 7.5k before they removed it , i figure at this point it can't hurt to try it , worst case i need to buy some new jets .
Moderator Airhead Posted July 17, 2008 Moderator Posted July 17, 2008 Yes, removing that would help the breathing without doubt
Beef Supreme Posted July 17, 2008 Author Posted July 17, 2008 ok , well today i got that restricter out of the exhaust , without a rotary tool . there was alot of chiseling and the plasma cutter took care of the bulk of the cutting . even tho it's badly out of tune i can already feel more oomph . i also checked the timing and it was dead on . it still doesn't rev up tho .
The Golden Shot Posted July 24, 2008 Posted July 24, 2008 I have had the same problem of my bike not reving past 7thou, i have discovered that if i take the rubber connection from the back of the carb that connects onto the airbox it will run a lot better, this leads me to believe that its the main jet that is to big and i havent got the correct fuel to air ratio, it sounds like its being choked and not getting enough air, i've been at this problm for ages, if you think of anything else let me know
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