DT175 help?

[Colorado]

I posted these questions in the general repair forum, but didn't get any help.

Maybe some longer in the tooth riders hang around here and can help me.

I picked up an old DT175 for next to nothing yesterday. I think it's a '79, because the swingarm is still round, black tubing, and pictures I found of '80's all have retangular, silver swingarms. The guy I got it from has had it just sitting around for a few years and said he didn't know if the oil injector pump works, so put premix in the tank (while there's still oil in the injector tank). It's running pretty crappy, maybe because it has twice as much oil in the fuel as it should --- I don't know. I haven't checked the plug, air filter or anything else yet either.

Is there an easy way to check if the pump is working? If I pull the injector hose from the pump to the front of the carb won't it just let air in at the reed valve boot (and rev like mad)? If I simply drain the oil tank, then run premix without it having two oil sources, will that be fine, or will the pump them pump air into the intake? What about if I unhook the pump cable? Will that isolate the injector, or do I really need to plug something to do it right?

Also, all of my other old Yamys have had the frame serial number on the front tube between the triple trees. This one doesn't have a number there. My others have also had the engine serial number on a serated flat spot on the right case half, kind of above the kickstart. This DT has a flat spot there, but it isn't serated, and there's no number. Any ideas where they put the numbers on the 175s aroung that year?

I'm hoping to get it in good order for my daughter. She's really outgrown her XR100, but the newer bikes scare her because of the high saddles. I forgot how small full size enduro bikes used to be! She fits the DT great.

 

[kdx220freak]

well there is an easy way to check, i have an old 1972 yamaha CT175. It has an oil pump. The way i checked it is by draining the lines and taking out all the oil. Then put new lines in(well at least you should). Then fill the oil tank back up. You will notice that the oil wont got into the motor by itself. wait untill the oil slowy makes its way to the pump, when it gets there start the bike. when you start the bike keep the cover off were the oil pump is. when the bike is running see if the oil is going through the lines past the pump. It will take a while for the oil to makes its way all the way to the motor so you will be running you bike without oil for a little while. If you dont understand something ask away, these are not the clearest directions. Also this will not neccasrily make the bike work great becuase you will still need to adjust the pump to put the right amount of oil in the motor.

 

[John Harris]

My DAD rode a DT 175 for years and I wish I had it back. It had Scott forks and a high compression head. Nice trail bike. He ran it forever with premix and not the injector. I believe if you disconnect the actuator cable you will disable the pump. I think he just pluged the line to the carb and of course just used a single wire throtle cable (that was easier to turn). This is all from my 30 year old memory so take it with a grain of grease! Cheers John

 

[Colorado]

Thanks for the help guys! MY buddy has a Clymer's for the Yamaha 2-stroke enduros through '76. Any ideas about the injection later than that? Will his book walk me through adjustment, etc., or do I need to shell out $30 for the book on the later years?

 

[kdx220freak]

i to have that same manual, i would try to get the manual because it will give you exact instructions, but thats up to you.

 

[Colorado]

...wait untill the oil slowy makes its way to the pump, when it gets there start the bike. when you start the bike keep the cover off were the oil pump is. when the bike is running see if the oil is going through the lines past the pump....QUOTE]

I do have a question about that. Is your line from the pump to the carb clear? The DT has a black line, so I really won't be able to see, unless I replace it with clear.

 

[kdx220freak]

i would replace the line if it is dirty and old, with clear new stuff.

 

[sunnyboy]

if you look in the manual it will tell tou how to check the pump-if my memory is correct you remove the bleadder screw and manually operate the pump,oil will be pumped out of the bleadder hole.

 

[Colorado]

I don't have the manual, and don't want to spring for it this week (the wife's angry that I brough another project home). I decided to just forego the injection for now, as I don't plan to pull the bike up at any gas pumps anyway.

I pulled the carb and did a chem-dip cleaning, then blasted the tiny little pilot jet out of my fingers with compressed air and lost it. When I took the slide out I found out someone had crimped a sleeve end to the throttle cable, so the ratio between the throttle and injector were probably wrong anyway, so I'm just going to have a new single cable made. It makes more sense for me to run premix anyway, as everything else I have uses it except my daughter's XR100, which I'm hoping to sell if this DT works for her.

I did about a two hour chem-dip, and the alluminumn came clean, but the brass still looked bad. Is there something else I can use to attack brass corrosion? Laquer thinner or something? Silver polish? I remember a comercial years ago on TV where they dipped a penny in something and it came out bright and shiny.

Nobody stocks the pilot I need, so I'll have to order it. In the meantime I can clean up a few other things. The steel tank is rusty inside, but not really bad. Any ideas on that? I know they sell an epoxy coating, but it's almost $80, and I don't want to spend that. Any thoughts on sloshing some epoxy garage floor paint around in there?

 

[kdx220freak]

ok, well in my metal ct175 i used some stuff that works real well. It is called Creem. you can get it at most motorcycle stores. It is about $30 for the whole kit. Which cotains stuff to clean the rust, prep the surface and then you coat it with the coating they give you thats meant for metal gas tanks. It wokrs very well.

The stuff that you are thinking about on tv is.. i think.. oxyclean :) . I would reccommend trying to find a carb rebuild kit. Normally they are under $20. I got one for my 1972 for under $20 so im sure you can.

 

[Colorado]

Thanks again. I sprung for the Clymer's, and checking the carb numbers informed me that the bike is actually an MX175 ('79-'81). That made the longer forks make sense. I did disable the injector pump, and will pull the nylon gear that runs it after my right side cover gasket gets in.

I think the bike must have been stolen sometime since '81, as the engine and frame numbers were thoroughly removed. I don't have any way to get it back to whatever victim there might have been, so ain't going to sweat it (it's only a $150 bike now anyway). It runs pretty darn good, considering all the slap with only 60lbs of compression after four kicks. Once I do the top end, it is going to be a big move up for my daughter from her XR100. I think it may be more powerful, at least in the midrange, than my kdx175.