gaerc Posted June 6, 2014 Share Posted June 6, 2014 Hello All, I have a 1979 DT 175 I need help with..It has1800 origional miles..Heres situation. When I got It it had sat for quite awhile. So I Cleaned gas tank cleaned petcock rebuilt carb It had nice fat blue spark It started right up Idled for a bit when I started increasing rpm,s it started bogging out then finally die. It would start eratticaly a sometimess run for sveral minutes but always die.Sometimes id prime cylender with no avail. I figured it was the oil seals and so I did the following. Honed cylinder new rings new oil seals new gaskets thruout kick start spring tested coils under flywheel ( currently have fat blue spark) assembled engine with torque wrench Did a leak down test (it passed fine) New fuel new fuel line with inline filter After completion of above work..She fired right up Ideled nice increased rpm,s a 1/4 throttle twice.for a total runtime of several minutes..Went to increase rpm,s again..and it started bogging like it did when I got it. Im definetly missing the problem..If anyone has any ideas I would appreciate it.. Thank You Link to comment Share on other sites More sharing options...
Noise Posted June 7, 2014 Share Posted June 7, 2014 Hi mate. Are you running this with the air filters and exhaust on? Will she rev properly with the choke on? When you "re-built" the carbs did you actually clean them or did you just have to put them together? reason i ask is that you may have a blocked main jet in the carbs which isn't letting in enough fuel to make her rev, and IIRC on idle this is only done with the pilot jets (so if they are clean it will idle nice) then when you rev it, it then switches over to the main jets which if they are blocked your have more air than fuel thus it will bog down and die. Hope this helps at all? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted June 7, 2014 Moderator Share Posted June 7, 2014 There are filter screens both in the gas tank and the petcock, what is the fuel flow like? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted June 7, 2014 Moderator Share Posted June 7, 2014 +1 The main jet could be loose, ethanol damage could have increased the bore. Needle jet/emulsion tube issues as well. You mention all gaskets, crank seals? Link to comment Share on other sites More sharing options...
gaerc Posted June 7, 2014 Author Share Posted June 7, 2014 Hi Guys I appreciate the input..Ill answer best I can Im running with exshaust and air filter. When starting I use choke but when it starts to bog down I try it with and without choke,,,no difference. On carb cleaning...I cleaned the carb thourly.I made sure every passage was blown out with carb cleaner as well as every jet. ethanol sucks lol petcock screen is clean ,,I used clear fuel line and new inline filter ( i use clear line so i can glance and see if im getting fuel to carb.) Im not sure about main jet bore size...It is possible I wonder with that in mind why sometimes it wont start at all ... Ill double check all this for sure ... you guys are great thank you Link to comment Share on other sites More sharing options...
blackhat250 Posted June 7, 2014 Share Posted June 7, 2014 What does the plug look like -- wet ? Link to comment Share on other sites More sharing options...
Preload Posted June 8, 2014 Share Posted June 8, 2014 Sounds like the carb to me but the only other thing is fit a new spark plug it could be breaking down! Link to comment Share on other sites More sharing options...
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