Losing power on my TA200 Phantom

Discussion in 'Technical' started by lmacka, Aug 3, 2009.

  1. lmacka

    lmacka Active Member

    I'm having a bit of an issue which is proving to be very dangerous. I nearly got collected twice today because I didn't have enough omph to perform an overtake.

    What happens is that I lose roughly 40% of the engine's power from time to time. I can hear an audible difference in the performance; it doesn't have the loud hollow sound I normally get when I hit the gas. My top speed is capped at about 80 in 5th. Can't go to 6th - engine doesn't have enough torque to handle it.

    It seems to happen after I come out of a 'slow period'. I generally cruise along at about 90-100k/h but slow to 40-60k/h for villages, gravel and other hazards. When I exit the hazard, I've lost power.
    Sometimes it comes back after a few Ks by itself, other times I'm able to fix it by getting speed up, dropping down to 2nd or 3rd and coasting for a few hundred meters.

    Now, I have a theory. Straight up - I'm still learning about engines so please help me with the names to the bits I'm talking about...
    It seems the problem is with my carb. The engine is either being starved of fuel or air. I initially thought it was fuel but not any more.
    There's a component of the carb which is like a cylindrical piston. On the top there's what appears to be a sealed air reserve which compresses and then forces the 'piston' back down if it's pushed up.

    I'm guessing here but that 'piston' has something to do with the amount of fuel being let into the engine. When you open the throttle, the pressure pushes the 'piston' up and thus allows more fuel into the engine.
    I think it's getting stuck and when I coast, the pressure generated in the carb loosens it up. Maybe.

    Having a guess here but I'm tempted to spray some lubricant on it (WD40 or the likes). Should I do this? Gonna check this again tomorrow arvo for hints and tips, otherwise I'll just go ahead and spray it.

    Thanks in advance!
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  3. lmacka

    lmacka Active Member

    Ok, I found a pic of a carb that looks a bit like mine.

    http://www.johnsmotorcycleparts.com/kei ... images.htm

    So I was right about the vacuum/pressure chambers. Didn't realise there was a spring there. The 'piston' I'm talking about it kinda what "C"points to, but I'm not talking about the hole.

    Oh and the reason I think I should lube the piston (I'm not being rude, I swear) is because if I manually push it up or down now the movement isn't very smooth. It 'grabs' quite a bit.

    By the way, my carb has a float tank underneath it. This seems to be clean and snagless.
  4. Pikey

    Pikey www.tbbtours.com

    Sounds like you are on the right track. I'd check that the carb diaphragm (J in the pic on your link) doesn't have any small holes in it. It's made of a thin rubber and seals against the top of the carb body thus forming the vacuum. If there is a hole, less vacuum and less pressure to lift the slide. Be careful when pulling it out and even moreso when putting it back to ensure you get a good seal.

    There is some speculation about that these diaphragms are the main carb part to suffer if gasohol is used in the engine.

    You also say that the slide feels a bit rough against the spring pressure then run your finger down the edge of the slide and also in the chamber and if any rough burrs e.t.c are felt, gently take them out with a bit of scotchbrite.

    Hope this helps.


  5. lmacka

    lmacka Active Member

    Thanks for the tips. It wouldn't surprise me if this bike has had a fair dose of gasohol. It's an ex-rental after all. In fact, it's number 3 out of the fleet you were looking after when I met you.
    I'm the Aussie guy who came in when Tony was overseas and asked you about buying bikes. You may remember me.

    I'll pull apart the carb tonight. Not sure if I've got the confidence to take out that diaphragm though. I'll assess it when I see it.
    Don't have any scotchbrite and I have no idea where I'll get any here in Phnom Penh. Going to keep on the conservative time until I get back to Thailand. Don't want to get stuck here...

    I shall take pictures and post them here later on.
  6. Pikey

    Pikey www.tbbtours.com

    Oops, didn't realize it was one of ours as it was sold by my partner Tony. Don't mess about with it, just bring it back into the shop and we'll do our best to fix it for free.

    We tell all our customers to use only 91 "Benzine" but some cheap charlies like to save a few baht and put gasohol in. Pretty hard for us to detect and control if they mix the blends.

    Edit: sorry, just re-read your post and see you are in PP. If you get it repaired locally and it is something you feel we should have addressed, bring the receipt into the shop and I'll re-imburse you (within reason). This is Jeff and it was me who was overseas when you bought the bike.



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