TRC is primarily funded by ad revenue. If you like the content you find here, please do not block our ads. Thank you.
Page 3 of 4 FirstFirst 1234 LastLast
Results 31 to 45 of 52

Thread: Pit bike wont start

  1. #31
    Should Get Out More Trogladyte's Avatar
    Join Date
    Dec 2007
    Location
    Felpersham
    Posts
    12,454
    Like
    337
    Liked 575 in 318 posts
    Blog Entries
    11

    Default Re: Pit bike wont start

    Quote Originally Posted by a_morti View Post
    And this turns two into one. Now you've barely got more problems than hands
    http://m.ebay.co.uk/itm/Pitbike-monk...257Ciid%253A12
    Awesome. Got to be worth 15 nicker.


  2. TRC is primarily funded by ad revenue. If you like the content you find here, please do not block our ads. Thank you.
  3. #32
    Should Get Out More Trogladyte's Avatar
    Join Date
    Dec 2007
    Location
    Felpersham
    Posts
    12,454
    Like
    337
    Liked 575 in 318 posts
    Blog Entries
    11

    Default Re: Pit bike wont start

    OK. It starts. It won't run without the choke on, but we are making progress.

    Astonishingly it appeared to have diesel in it. I am amazed by this. I have never had diesel in a can, and that bike has been fuelled from cans only. So either there was some diesel or contaminated fuel in it when it came home after being lent out, or I filled a can with diesel without noticing, which seems unlikely. Another possibility is that someone put two stroke in it. Anyway, with new fuel in it, at least it will start.

    Watch this space for the next exciting update.

  4. #33
    Should Get Out More Trogladyte's Avatar
    Join Date
    Dec 2007
    Location
    Felpersham
    Posts
    12,454
    Like
    337
    Liked 575 in 318 posts
    Blog Entries
    11

    Default Re: Pit bike wont start

    So having done the valve clearances (what a pain that is!) and cleaned out the carb 500,000,000 times, the bike now starts! Yay!

    That is the end of the good news.

    It doesn't want to run without choke. It will idle without choke once warm, but as soon as you open the throttle it dies. It runs with no air filter - but that can't be the issue as it always did. The mixture screw makes little difference to this behaviour. I have it two turns out right now, but it is much the same from half a turn out to three turns out. The main and pilot jets are clear. The needle is on the middle position where its always been, and looks fine - it is moving in and out of the jet OK.

    Putting my hand over the air inlet and limiting the air helps - which is just choking it in effect - so I am thinking there's just not enough fuel. I removed the fuel filter, and the needle jet and float all seem to be functioning.

    What's next?

  5. #34
    Should Get Out More maccecht's Avatar
    Join Date
    Jan 2008
    Location
    South East England Kent.
    Posts
    6,505
    Like
    153
    Liked 708 in 403 posts

    Default Re: Pit bike wont start

    Have you checked the float height? Bit of plastic tubing on the drain screw outlet held up against the side of the carb and open the drain screw and check the fuel level in relation to float height. Assume you changed the plug as it will have been fouled.

  6. #35
    Should Get Out More Trogladyte's Avatar
    Join Date
    Dec 2007
    Location
    Felpersham
    Posts
    12,454
    Like
    337
    Liked 575 in 318 posts
    Blog Entries
    11

    Default Re: Pit bike wont start

    Quote Originally Posted by maccecht View Post
    Have you checked the float height? Bit of plastic tubing on the drain screw outlet held up against the side of the carb and open the drain screw and check the fuel level in relation to float height. Assume you changed the plug as it will have been fouled.
    Yeah its a new plug.

    float height it tricky - there's no drain screw. But if you take the float bowl off, there's good flow if you let the float drop down a bit.

  7. #36
    Should Get Out More maccecht's Avatar
    Join Date
    Jan 2008
    Location
    South East England Kent.
    Posts
    6,505
    Like
    153
    Liked 708 in 403 posts

    Default Re: Pit bike wont start

    Quote Originally Posted by Trogladyte View Post
    Yeah its a new plug.

    float height it tricky - there's no drain screw. But if you take the float bowl off, there's good flow if you let the float drop down a bit.
    Lift the float slowly and look where it is when the fuel cuts off. Ideally it should be perfectly level with the carb body. Too high it will flood too low not enough fuel. Also on some carbs there is a small jet in the corner of the float bowl which can get clogged up. May no have one on yours.

  8. #37
    Should Get Out More Julian_Boolean's Avatar
    Join Date
    Jan 2008
    Location
    Nearly at the dawn of Britain
    Posts
    12,578
    Like
    636
    Liked 1,864 in 1,115 posts

    Default Re: Pit bike wont start

    Sounds like weak mixture, apart from blocked jets and float height, the only other causes I can think of are an inlet air leak, or it had air corrector jets that heave fallen out.

    Sent from my SM-T560 using Tapatalk

  9. #38
    Should Get Out More Trogladyte's Avatar
    Join Date
    Dec 2007
    Location
    Felpersham
    Posts
    12,454
    Like
    337
    Liked 575 in 318 posts
    Blog Entries
    11

    Default Re: Pit bike wont start

    OK. Thanks.

    Elsewhere folk are talking about valve timing and stuff. I don't buy it. This has to be a carburetion issue.

    I've cleaned out the juets so many times, but I am going to strip that carb completely and soak it in carb cleaner and blast it all out with an air line. Then I'm checking the float height, and checking for air leaks downstream from the carb. Something must be causing this issue. I'm also going to clean out the tank and maybe put a new hose on from the tap.

    Anything else?

  10. #39
    Should Get Out More Weeksy's Avatar
    Join Date
    Jan 2008
    Location
    Reading, Berks
    Posts
    51,664
    Like
    1,793
    Liked 6,779 in 3,923 posts

    Default Re: Pit bike wont start

    Quote Originally Posted by Trogladyte View Post
    OK. Thanks.

    Elsewhere folk are talking about valve timing and stuff. I don't buy it. This has to be a carburetion issue.

    I've cleaned out the juets so many times, but I am going to strip that carb completely and soak it in carb cleaner and blast it all out with an air line. Then I'm checking the float height, and checking for air leaks downstream from the carb. Something must be causing this issue. I'm also going to clean out the tank and maybe put a new hose on from the tap.

    Anything else?
    If you're suspecting tank issues, why not remove the tank from the equation for testing ? Use another container and gravity feed it ?

  11. #40
    A Bit Bored
    Join Date
    Dec 2016
    Posts
    226
    Like
    26
    Liked 152 in 60 posts

    Default Re: Pit bike wont start

    Quote Originally Posted by Julian_Boolean View Post
    Sounds like weak mixture, apart from blocked jets and float height, the only other causes I can think of are an inlet air leak, or it had air corrector jets that heave fallen out.

    Sent from my SM-T560 using Tapatalk
    Got to be this or related. Carb rubber split. Inlet manifold gasket. Is there a vacuum pipe missing.

  12. #41
    Should Get Out More a_morti's Avatar
    Join Date
    Jan 2008
    Location
    Gibraltar
    Posts
    11,294
    Like
    1,072
    Liked 806 in 521 posts

    Default Re: Pit bike wont start

    Replacement carbs are so cheap I just wouldn't bother. Buy a new one and stop the headaches.

  13. #42
    Should Get Out More Trogladyte's Avatar
    Join Date
    Dec 2007
    Location
    Felpersham
    Posts
    12,454
    Like
    337
    Liked 575 in 318 posts
    Blog Entries
    11

    Default Re: Pit bike wont start

    Quote Originally Posted by a_morti View Post
    Replacement carbs are so cheap I just wouldn't bother. Buy a new one and stop the headaches.
    I might do that just to rule out other issues.

    However...

    Today, I took the tank off and swilled it out, dismantled and rebuilt the petrol tap, and stripped the carb (again) and filled up with new fuel.

    The good news is that it's better. But not better enough. Currently it will start fine, and will run at idle without choke. Once armed up it will run at idle and will rev up with a small throttle opening. It will also rev well with a large throttle opening. It doesn't like it in between.

    that suggests needle and slide issues, doesn't it? But it all looks fine.

  14. #43
    Should Get Out More a_morti's Avatar
    Join Date
    Jan 2008
    Location
    Gibraltar
    Posts
    11,294
    Like
    1,072
    Liked 806 in 521 posts

    Default Re: Pit bike wont start

    Could be a split in the diaphragm so small vacuums don't hold it open steady?

  15. #44
    Should Get Out More Julian_Boolean's Avatar
    Join Date
    Jan 2008
    Location
    Nearly at the dawn of Britain
    Posts
    12,578
    Like
    636
    Liked 1,864 in 1,115 posts

    Default Re: Pit bike wont start

    Have you cleaned the emulsion tube?
    Has the clip fallen off the needle?

    Sent from my SM-T560 using Tapatalk

  16. #45
    Should Get Out More Trogladyte's Avatar
    Join Date
    Dec 2007
    Location
    Felpersham
    Posts
    12,454
    Like
    337
    Liked 575 in 318 posts
    Blog Entries
    11

    Default Re: Pit bike wont start

    It doesn't have a diaphragm - it's just a simple slide carb.

    No - I haven't specifically cleaned out the emulsion tube - although I have blasted compressed air through it with the jet in place. Just in case I am being really stupid, the emulsion tube is the larger brass piece into which the main jet screws - right?

    And no - I haven't actually taken the needle off the slide, but it is securely in place - it has some side to side wobble, but is firmly in place. Maybe I should dismantle and reassemble for completeness. I'm off to visit my unfeasibly ancient owners who I have parked in a care home in Somerset tomorrow, so Monday is the next chance I will have to play.

Page 3 of 4 FirstFirst 1234 LastLast
Go Back to Forum My Forum