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Thread: DT175 Yamaha Enduro issues

  1. #1
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    10th February 2007 - 21:02
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    DT175 Yamaha Enduro issues

    Hey everyone

    Recently purchased a 1980 road legal enduro yamaha DT 175.

    Problem: runs like a bag of crap in the lower revs (less than say 5500) kinda makes a 2-stroky uneven sound, its a real pain in the butt when you are trying to drive around town at 50kmph, its sort of jerky and not smooth.

    Although... once you hit the power band she goes like a cut cat! It also starts really easily, spark plug is looking good etc. Its just ugly in the lower revs, seems to use a fair bit of gas too.

    I pulled the carb and checked the jetting, main is 135 and pilot is 25, everything was clean and clear. Air filter is clean and in good condition (looks like someone has drilled some holes in the airbox thats all).

    After looking in the manual a main of 135 seems quite small, but then again it runs great in power band... or with the throttle wide open.

    Any ideas?

  2. #2
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    27th September 2008 - 18:14
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    My first bike was exactly that model and year. Good reliable bike but i still managed to wreck it.

    Your problem could possibly be that the reed valves are munted.
    I mentioned vegetables once, but I think I got away with it...........

  3. #3
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    26th January 2008 - 07:37
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    My first bike was a 79 dark blue one. Unbelievably slow compared to an IT175.
    I recall mine used to "miss" sometimes when not on the pipe. Took it back to the shop a few times & had the mechanic ride it - he swore there was nothing wrong with it- there was but I was a young kid with not enough confidence to call his BS.
    Anyway the pipes on those get really really clogged up. The only way back then was to burn the shit out of it with a gas torch.

    How many kick starts have you been thru? I went thru 3 before I left the last one off & just crash started it.

    Oh & did you know when they first came out they cost $1500 & when they brought them out again 10 years later with better this & that the price was exactly the same. Crazy huh.
    In life as in dance Grace glides on blistered feet

  4. #4
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    Hi thanks for the replies!

    Woodman I have pulled out the reed valves and look OK, they seem to be sealing fine and opening OK, is there anything specific I should be looking for in stuffed reed valves?

    Padmei, I'll have a look at the state of the exhaust and see if that is an issue. I haven't had any broken starters yet haha! Although the bike only has 9,000kms on it (imported from South Africa) so not overly surprising!

  5. #5
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    With reeds check for frayed edges and chips, exhausts do clog up with oil/carbon residue on 2 smokes if the muffler packing is clogged this will effect the bottom end power .
    Get it replaced and de carbon the muffler core .

  6. #6
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    20th September 2008 - 12:50
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    Here a link to a old DT thread, and a quote i put on it,

    Do you know if your timing side crank seal is still good and not dried out and hard from doing bugger all kms in 30 years?

    http://www.kiwibiker.co.nz/forums/sh...aha-DT175-help

    Quote Originally Posted by RDjase View Post
    Took the carb off my DT today, 1979 model

    160 main jet

    20 Pilot jet

    1.5 Slide cutaway

    4J6 Needle

    267 0-8 Needle jet/holder/Emulision tube?

    VM28 round slide, 3U5 00 code on it

    The needle clip was on the top position, leanest, will put back to the centre position as its a mongrol cold, never had the carb off the old girl, was chocka full off crap in the Needle jet
    Dale Kerrigan: If there's anything Dad loved more than serenity, it was a big two stroke engine on full throttle!

  7. #7
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    10th February 2007 - 21:02
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    Thanks Jase that is very helpful!

    But how do I check the crank seal exactly?

  8. #8
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    25th March 2004 - 17:22
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    well 'exactly' you do a leakdown test but you need a tester + a bung for the inlet manifold & the exhaust. In a pinch you can see if it smokes heaps even when warm which would indicate GBox oil entering crank, or if it is oily under flywheel cover (excepting chain oil that has gotten in).

    It does sound lean at low throttle (rich is burbly, but feels similar if less bitchy), try taping up the airbox holes and/or adjusting the idle mix screw (in is richer, out leaner).
    Don't you look at my accountant.
    He's the only one I've got.

  9. #9
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    Thanks Dave

    I have played with the mix screw.

    Basically (following what someone on the interwebs said) I adjusted the air/fuel-mix screw till the idle rpm was at it's highest.

    Ended up with the mix screw out by about 3 turns (lean) before it ran at its best.

    My guess is my pilot jet is a bit too rich.

    Thoughts?

  10. #10
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    Could well be esp if Jase's is a 20, it is hard to figure rich or lean some times. I probably have a 20 in the toolbox if yer coming out to the racing in the weekend (you'll have to clue me into who you are).
    Don't you look at my accountant.
    He's the only one I've got.

  11. #11
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    Quote Originally Posted by Yakman12 View Post
    Hi thanks for the replies!

    Woodman I have pulled out the reed valves and look OK, they seem to be sealing fine and opening OK, is there anything specific I should be looking for in stuffed reed valves?

    Padmei, I'll have a look at the state of the exhaust and see if that is an issue. I haven't had any broken starters yet haha! Although the bike only has 9,000kms on it (imported from South Africa) so not overly surprising!

    I think the reed valves can get floppy e.g. lose tension and don,t work properly but I am no expert. What padmei says about the kicksarters is exactly my experience too.
    I mentioned vegetables once, but I think I got away with it...........

  12. #12
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    will be steel reeds & they last forever.
    Don't you look at my accountant.
    He's the only one I've got.

  13. #13
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    10th February 2007 - 21:02
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    Just going to drag this thread back to life...

    Over the last couple of weeks I have tried multiple different pilot jets in the hope it will fix the problem (from .20 - .30, was .25 standard) but to little avail.

    No matter what, I still have a rough running bike when I'm driving around town, with the throttle only slightly open.

    Any other ideas?

  14. #14
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    It could be the way your riding it a 2smoke hates being idled around at partial throttle as the plug gets oil fouled, ride it like you stole it and it will love it.Take it for a 10k up the motorway once a fortnight to burn the excess oil outta the barrel.

  15. #15
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    Nah thats largely a myth perpetuated by conservative rich jetting on MX bikes meaning they sputter to heck. Want proof? Ride a decent trials bike.

    I'm suspecting you have an airleak if you've got to a point where changes are not doing anything. Or a faulty choke, blocked passage in carb.
    Don't you look at my accountant.
    He's the only one I've got.

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