New carb, new piston, bored cylinder, what could be wrong?? - Page 2
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  1. #16
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    Quote Originally Posted by diericx View Post
    Also got an air filter and put that on, but that'll make it a lot harder to spray starter fluid into the intake so I really hope it starts haha
    Maybe not.

    You really should NOT spray starting fluid directly into the carb throat but into the air intake housing so it has a better chance of mixing with the intake air.
    Don't believe everything that you think.

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  3. #17
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    2012 Yamaha FJR1300, 2009 Yamaha V Star 1300 Tour; 1989 Yamaha Virago 750
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    I've been reading this thread and first of all - THANKS. I love these kind of threads. One thought kept coming into my head as I read this, "Since its a bigger piston, the displacement has changed" This suggests to me that re-jetting is in order because you are now displacing more air with each stroke. Another thought is since its 2 stroke, you may be fouling the plug?? That's my 2 cents.

  4. #18
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    hey D, its been a few days since you posted last. Just FYI... the 'non-adjustable' screw is actually a slide guide. it protrudes into the slide bore and keeps it from lift the needle out of emulsion tube. another issue you may be having are reed valves or the whatever device your machine uses to keep pressure from backing out through the carb. also check that your exhaust pipe is clear of oily deposits and excess carbon.
    ​after eliminating the probable only the improbable remains

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  6. #19
    Where Am I ?
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    1975 Suzuki TS185
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    Denver, CO
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    Hey everyone! Sorry I took so long to reply, I got super busy with classes.
    @easyRider I have an air filter now, thanks for the tip!
    @BossGeek I'm glad the struggle is interesting! �� I've been thinking about that too. I've tried adjusting the mixture screw and it's as perfect as I can get it. It idles well and the throttle feels as nice as it's felt but still no cold start I'll have to look into re-jetting I just reeeeally don't wanna pull the carb apart haha. Is there any way I can rule out every other option other than the jets? How can I be positive it's not some sort of carb adjustment that's still holding me back? How would I know if I need bigger or smaller jets?
    @VFR321 This bike doesn't have any reed valves, and thanks for answering that question! I was really confused about that for a while hahaha and do you mean check the part of the exhaust that connects to the engine?
    Last edited by diericx; 03-17-2019 at 12:12 AM.

  7. #20
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    Technique can be important.

    Make sure that the choke is closing.
    Make sure that you are NOT twisting the throttle at all; it needs to be fully closed.
    Crank it for a few seconds and then crack the choke open a tiny bit and crank again.
    DO NOT OPEN THE THROTTLE until you hear it fire.

    P.S. Having the idle speed set too low can hamper cold starting too.
    Don't believe everything that you think.

  8. #21
    M-J Lifetime Achievement Award
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    Check the baffle isnt carboned up there will be a small screw right at the end of the outer skin of the muffler. Undo it and pull the baffle out....you may need to persuade it to come out if its rusted. Check the baffle for carbon build up.....you can run the bike without the muffler on to see if this helps. Use a blowtorch on any carbon bulid up.

    Two strokes need compression for fuel transfer so if its low, (crankshaft seals) starting may be difficult. If the bike is hard to start once warm then it may be due to some loss of compression in this area...oil smears around the bottom outer cases might also be an indication of this. Carburetion can be a problem...check the oil pump isnt oversupplying...an oiled plug, (fouling) will be evident.

    The initial setting for most carb jets is around one and a half turns out from light bottoming of the jet tips. I wouldnt think the rebore would make any difference to the fuel ratio so changing to a larger jet will not be an issue. Your throttle needle may be adjustable...a small circlip fits into one of several grooves in the top of the needle...raising it enrichens the fuel...lowing it leans the fuel.

    Be very careful if you lean the fuel ratio out...two strokes are very susceptable to burning a hole on the piston top if run too lean. A spark plug chop test may be needed.

    To do this you take the bike out to a straight bit of road and ride it at hight throttle settings....you dont need to speed just stay in second or third and get the rpms up. Stay riding for about two to five minutes then cut the ignition while pulling the clutch in so the motor stops dead. Then pull the plug and check the colour...watch out it will be hot! Light coffee brown is what you want...white is too lean and black/sooty is too rich.

    Any oil on there is indicative of either worn bore....in your case not likely.... or broken ring/s....possibel. One other thing is did you rotate the rings around so the gaps were not aligned?

    Finally What is the air filter/spark plug condition. The spark...needs to be fat and blue...anything less is suspect...it may be the cable/either boot/cap or the coil...even the current supply may be a bit iffy so all connectors need to be tight and clean. Check the connections to the CDI unit are clean and tight.

    Hope this helps and good luck
    Last edited by Aussie Steve; 03-17-2019 at 10:20 PM.
    Smoke me a kipper I'll be home in time for breakfast

  9. #22
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    1975 Suzuki TS185
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    Quote Originally Posted by Easy Rider View Post
    Technique can be important.

    Make sure that the choke is closing.
    Make sure that you are NOT twisting the throttle at all; it needs to be fully closed.
    Crank it for a few seconds and then crack the choke open a tiny bit and crank again.
    DO NOT OPEN THE THROTTLE until you hear it fire.

    P.S. Having the idle speed set too low can hamper cold starting too.
    I'll keep all of this in mind when I keep trying to adjust it this week, finals are over and it's finally spring break! I'll have a lot of time to mess with things. Can having the idle set too high also mess with cold starting?

  10. #23
    Where Am I ?
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    1975 Suzuki TS185
    Location
    Denver, CO
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    Quote Originally Posted by Aussie Steve View Post
    Check the baffle isnt carboned up there will be a small screw right at the end of the outer skin of the muffler. Undo it and pull the baffle out....you may need to persuade it to come out if its rusted. Check the baffle for carbon build up.....you can run the bike without the muffler on to see if this helps. Use a blowtorch on any carbon bulid up.
    I just bought the muffler a couple months ago so everything looks pretty good there, except it has a small hole near the engine. Could that be affecting it enough to make it this hard to start cold??

    Quote Originally Posted by Aussie Steve View Post
    Check the oil pump isnt oversupplying...an oiled plug, (fouling) will be evident.
    My oil pump is broken so I've been mixing the suggested amount from the service manual.

    Quote Originally Posted by Aussie Steve View Post
    Be very careful if you lean the fuel ratio out...two strokes are very susceptable to burning a hole on the piston top if run too lean. A spark plug chop test may be needed.
    I've been slowly leaning it out (turning the screw out by about 1/4th turn every time I ride) to see if that can help it start. I'm thinking if I can get it starting well then I can do what you said below to make sure I'm not too lean. I've been getting this a lot from the forum and the shop I go to so I'm being super careful not to make it too lean!

    Quote Originally Posted by Aussie Steve View Post
    Finally What is the air filter/spark plug condition. The spark...needs to be fat and blue...anything less is suspect...it may be the cable/either boot/cap or the coil...even the current supply may be a bit iffy so all connectors need to be tight and clean. Check the connections to the CDI unit are clean and tight.

    Hope this helps and good luck
    Air filter and spark plug are both brand new... but I'll pull it when I go to make some more small repairs this week. Maybe that will give us some more clues.

  11. #24
    M-J Lifetime Achievement Award
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    If cold starting is the only problem then I would be checking the choke is actually working...not too sure but most of that era are simply a butterfly plate in the inlet of the carb. One other thing is to check the idle circuit....the tiny jets just after the venturi are used to assist cold starting too. Another point...is the carb a Cv type or the old slide type. Many CV types have a small 'o' ring fitted to the top that is directly associated with the choke mechanism.
    Smoke me a kipper I'll be home in time for breakfast

  12. #25
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    Quote Originally Posted by diericx View Post
    Can having the idle set too high also mess with cold starting?
    Yes. But having it set too low can too.

    P.S. That little hole in the bottom of the muffler is there to drain out condensed water. Perfectly normal.
    Don't believe everything that you think.

  13. #26
    Where Am I ?
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    1975 Suzuki TS185
    Location
    Denver, CO
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    Sorry for the late response, but I got everything working! It cold starts perfectly (in around 8 kicks) and it runs sooo well! There isn't as much power as I think there should be in the higher rpms but I think that might be a jetting issue. I couldn't have done this without all of your guys' advice and help, and I can't thank you all enough!!

    My next mission is to get the electronics working (turn signals, tail lights, etc.), hopefully that doesn't prove as difficult as this was hahaha

  14. #27
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    2012 Yamaha FJR1300, 2009 Yamaha V Star 1300 Tour; 1989 Yamaha Virago 750
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    Quote Originally Posted by diericx View Post
    Sorry for the late response, but I got everything working! It cold starts perfectly (in around 8 kicks) and it runs sooo well! <img src="http://www.motorcycleforums.net/forum/images/smilies/icon_smile.gif" border="0" alt="" title="Smile" class="inlineimg" /> There isn't as much power as I think there should be in the higher rpms but I think that might be a jetting issue. I couldn't have done this without all of your guys' advice and help, and I can't thank you all enough!!
    So what was the final solution?

  15. #28
    Where Am I ?
    My Bike(s)
    1975 Suzuki TS185
    Location
    Denver, CO
    Posts
    35
    Just carb adjustments. A friend of mine helped me out and with the bike warmed up he turned the mixture screw left until it revved up and then right when it started to drop he lowered it half a turn. He then upped the idle and now it runs really well


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