tanaka tc-47 not staying tuned

Discussion in '2-Stroke Engines' started by locksmith, Apr 16, 2014.

  1. locksmith

    locksmith Member

    Hey y'all i got a question about tuning my carb... My old carb was bad (used motor) and i replaced it with a brand new one! it started right up and ran great! i did very minimal adjusting (low screw 1/8 turns) to the right cause it was dying from too much fuel

    It went from about 70 to 50 degrees (texas lol) and the engine is starting, then getting bogged down when I pull the throttle. like it goes for a second then bogs... sometimes it dies

    when it's been off for 10 minutes, i have to put it in choke again when it should start in run.. if it bogs when i first pull the throttle do i tighten the low screw? or do i need to adjust the high? once it's running it's great, but off the line at low RPM's it dies

    please tell me how to tune it

    thank you

  2. HeadSmess

    HeadSmess Well-Known Member

    unless youre completely lost and have to start over again...

    back off counter-clockwise, to richen the bottom end slightly.

    basically, when warm, set idle a bit high, then adjust lo speed until engine peaks, back off 1/8th. reset idle. blip throttle, if it bogs, back off another 1/8 or so..
  3. locksmith

    locksmith Member

    thank you, yesterday i tightened the lo screw and it runs better!

    i feel it was too open and was being flooded with fuel. it seems better with the idle faster
  4. locksmith

    locksmith Member

    i still can't get the lo screw in the right place! When i start it up, the low screw is too tight and the motor stalls. Then I open it up a bit and it's fine.

    But after 30 min of riding, it starts to stall at low RPM's when i pull the throttle. So it has to be tightened again.. it's so strange

    what am i doing wrong?
  5. HeadSmess

    HeadSmess Well-Known Member

    doing the exact reverse to what i said, and ignoring the fact that the LO speed only controls the low throttle settings, and really, you should be tweaking the HI needle at the same time as thats the needle that does the most work...

    tightening LEANS IT OUT.

    leaning it out causes it to die.

    loosening the screws richen the mix.

    this makes it burble, smoke, drip wet goop from the exhaust and never quite rev out fully, but it will run, and always run...

    wheres my wall?

  6. locksmith

    locksmith Member

    Actually, you're wrong. Loosening it makes the engine stall and die... I air on the side of loose for the engine sake, but it does have to be tightened after riding. It runs better when tighter after riding for a while

    I am really tired of this engine. I have a 40cc on my bike that I may put here instead. I live in TX where the weather changes all the time, so I carry a screw driver with me, but the constant adjustments are super annoying

    The engine is fast as hell, but it is also very temperamental to tune and it's getting on my nerves. I will never buy another hi/lo tunable carb
  7. RollingStones

    RollingStones Member

    What kind of carb is it exactly?
  8. HeadSmess

    HeadSmess Well-Known Member

    and how did you replace the carb? dry or with plenty of sealant? if you used sealant...oops. bad idea.

    my experience with any walbro/tama (or other diaphgram manufacturers) carb is to simply strip them completely, and get the compressed air on to them, in every hole, port and orifice. check rubbers for holes, then retune, set both needles at 2.5 turns out, get the hi end right, then fiddle til the lo is right. all of half an hour, not catering for removing shrouds, cables, covers, and other grrr bits that belong in the bin :jester: resorted to a rebuild kit once and never used it.

    one speck of dirt, or sealant in the wrong places...

    but everything points to either you not being familiar with the operation and tuning of these carbs, or something is wrong with the carb itself, despite being new. unfortunately, im inclined to suspect some degree of operator error...

    what do tree loppers and lawn maintenance people do around there? same type of carbs on their engines, doubt most have ever touched them with a tool other than to change blades...
  9. BigBlue

    BigBlue Active Member

    You stated the engine was used. Did you check the muffler? If they are clogged, the engine will bog or die.

    AKA: BigBlue
  10. locksmith

    locksmith Member

    -It is a walbro hda 97 carb. It's big

    -I didn't use sealant, I just bolted it on. The carb was brand new and sealed, so I'm confident it's intact and functional. I am sure I'm doing something wrong... At first I wasn't giving it enough time to start up... Each 2 stroke motor I've had (I've had lots) is a little different for starting. This one, I've found it's better to let it idle at half choke for 20 sec before putting it in run. But today, it died after idling for 20 sec in run...

    Then I loosened the Lo screw 1/8 and it was worse, so I tightened it back 2/8 (1/8 ahead of where it was). Then when I got to school, It was bogging from being too tight, so I loosened it up and it ran well, where the scooter is strong off the line. I am no genius at these, but I can tell that the motor is inconsistent in where the screws should be.

    There is about a 1/2 turn 'zone' where the motor runs well for the lo screw. It seems to want a different position in this 'zone' every day. my 40 NEVER has these problems and runs a lot better. I will talk to some lawn guys. thanks.

    -thank you, I will check out the muffler
  11. keatonx

    keatonx Member

    If it starts to sound a lot smoother and you need to ease on the gas really carefully to rev it up, it's too lean. It also might "gallop" slightly (best way i can describe it).

    If the engine sounds like it's stalling from simply running too slow to stay going, and the sound of the individual power strokes is really distinct, you're probably running rich or you're idle is too slow. If I were you I'd turn in the idle speed screw a full turn or something (so it idles really fast) until you get it running right.

    You tuned it when it was fully warmed up, right? Because that's what matters, the whole purpose of the choke is to temporarily change the a/f ratio for when the engine's cold.

    If you need to leave the choke on all the time tho, then obviously you're too lean.

    I have a feeling you're idle speed is set too slow, and you're naturally trying to make it idle faster by making it run excessively lean. Which causes it to bog out and die every once and a while because it's right on the edge of being too lean to run (very fine line, it'll be like falling off a cliff).
  12. keatonx

    keatonx Member

    But man, 1/2 turn is a pretty big range, assuming the engine was always fully warmed up when it seemed to want a different position.
  13. HeadSmess

    HeadSmess Well-Known Member


    now, firstly, is the carb the same as original, or another breed? they do have internal jets, sized to certain engines temperaments, besides having different chokes and throttles and all these other configurations. while you may have two seemingly identical carbs, they can tune differently. anyway.

    no sealant is good. have you checked the pump hole is clear? that the gasket/holes in the manifold line up correctly and will transfer crankcase pressure through that tiny little hole in the face of the carb next to the main bore? if it cant pump, it can run sometimes but will be really erratic.

    some versions have external pump lines...

    if the bores bigger than stock, give up.

    back to the first post. get the original carb and strip it. clean it. reinstall it. petrol and compressed air.

    you asked how to tune them. here is how.

    screw both needles in. all three actually. idle as well.

    back them all off 2.5 turns.

    helps to hang the thing from a rope if its attached to a bike for this...

    start it, let it warm up. it should be buzzing its brains off. let it.

    hold full throttle, adjust the hi until it peaks. usually by screwing in.

    then back off 1/8 turn.

    next, let it idle now. it should be idling fairly fast. clutch will be engaged, etc.

    adjust the lo until it peaks. back off a 1/4 turn.

    adjust the idle screw so its a bit lower and clutch has disengaged.

    blip the throttle. if it coughs, screw lo out a touch. otherwise, screw in until it coughs then back off...

    when riding, the hi will determine if it revs out to the top end, so you may have to tweak that a little bit.

    the lo determines how it accelerates.

    idle screw sets how slow it goes.

    but generally, when working, these are meant to be one shot, self adjusting and basically foolproof.

    just take some understanding.

    oh. and try the odd plug chop ;)
  14. locksmith

    locksmith Member

    You guys won't believe this!!

    First, thanks again to everyone who replied. you guys won't believe this..

    I took this to a mechanic before I put the new carb on it, who redid the fuel system to try to fix it.. he took out the return fuel line and gromet and left a hole in the tank...

    i could only fill the tank a 1/3 full before gas would leak, so a couple weeks ago, i ordered a return grommet and a tube for the return line. he put an aftermarket primer on, which was ugly so I ordered a new primer assembly to put on it as well.

    this morning i put everything on and noticed when the motor started, it sounded much deeper, fuller and healthier. it didn't stall and didn't sound like it wanted to...

    it turns out, the primer the guy put through the fuel line was starving it from fuel, which is like drinking from a coffee straw.

    look at the diagram, and you'll see that the primer line and return line are on separate "chains" or "systems" and that the main fuel should go DIRECTLY from the gas tank to the fuel intake. so the primer in between was an impediment to the fuel supply.


    so no wonder i was having problems... i'd stop along side the road to tune it like a ****, and the whole time, it was the fuel system. on a side note, i am glad i'm going to mechanic school this summer, bcos if you want it done right, do it yourself

    here is the parts site! i recommend them, they're cheap and oem parts

    Last edited: May 14, 2014
  15. HeadSmess

    HeadSmess Well-Known Member

    this is one of those examples of why...i service my own equipment, and service other peoples. there is nothing funnier than fixing something in five minutes a "really good" mechanic couldnt fix in two days...

    but yes, it takes some patience. a little bit of thinking. some common sense.

    the number of times ive cleaned out carbs because some monkey has gotten the hoses around the wrong way. great when theres only one, but people just dont seem to think, (or care?) when theres two or three. just have to experiment. squeeze the bulb, which way does the fuel or air squirt out? which hose has the filter on the end? how does air get in to replace the fuel thats being used?

    yarda yarda.

    glad you fixed it yourself.

    what do they say? if you want it done properly...

    and now...you didnt say what carb you have now, but without that primer...oh yeah :) now you should see what i was on about...either somethings wrong or somethings wrong when a walbro plays up :jester:
  16. locksmith

    locksmith Member

    Oh sorry, it's a walbro hda 97

    http://wem.walbro.com/walbro/produc...97-1&GroupName=Brush Cutter&FamilyName=TANAKA

    Here are pics of the first one that didn't work, cause of a bent piece that was attached to the choke lever. It was getting too much air cause the plate was bent. Didn't figure that out till I compared it to the new one lol


    This has been a huge learning experience for me, so thanks to everyone