How important is it to have the cover on the vacuum ports?
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Thread: How important is it to have the cover on the vacuum ports?

  1. #1
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    How important is it to have the cover on the vacuum ports?

    Seriously, cos i have one missing on the right hand side and my bike is running on 3 cylinders. Trying to narrow it down.

  2. #2
    Ace Aduro's Avatar
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    Really, Super, mega important. The bike is sucking air through that port rather than the fuel air mix from your carby and that cylinder is not firing.

  3. #3
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    So you're saying this is the reason why it isnt running on the 3rd cylinder proper? So i can assemble my carbs again and chuck it back on and just tape up the port?

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    Senior Biker zane's Avatar
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    hahahahaha
    [size=x-small]This is my engine. There are many others like it, but this one is mine. My engine is my best friend. It is my life. I must master it as I must master my life. Without me, my engine is useless. Without my engine, I am useless.[/size]

  6. #5
    Ace Aduro's Avatar
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    Unscrew the port and block it with an m5 bolt, don't dodgy it with tape. Sleep the port for when you need to balance the carbs. And yes, if its not blocked off that cylinder is drawing regular air instead of fuel and so has nothing to ignite.

  7. #6
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    Thats strange. When my bike was running like shit (due to running on 3 im pretty sure) i pulled off the carbs to clean as i assumed this was the culprit. I noticed that the left hand side port had a plug on it the but the other one didnt. I thought nothing of it as it had been like that since i pulled the tank off. Had a look at the carbs and they were pretty schmick. didnt need a clean but since i was there i blasted it with carby cleaner. I put it back on set the screws to 1 3/4 turns (L import) fresh spark plugs, fresh sub air filter, fresh air filter. Connected the hose to a funnel and poured fuel down it and started it. It runs very similar if not slightly better than before i had pulled the carbs off.

    I noticed that it sounded like shit and couldnt figure out why. I sprayed water on the manifold and the 3rd one wasnt as hot. Checked the spark plug again grounded it against the engine and it was sparking. Slightly black so it must be burning fuel. It was hot but not hot like the others. I'll cover the port and see if this resolves the isssue.

  8. #7
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    Don't "tape" it up or whatever you mean by that. Either have a rubber bung which fits well enough for an air seal or just get a small bolt as aduro said. Although i would personally put an o-ring on the bolt.

    Unless the only open port you have is supposed to connect to the fuel petcock. In which case only block it when you are trying to tune it without the tank on.

  9. #8
    Biker Slipry's Avatar
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    I blocked mine off with some vac hose with a ball bearing in it and then some silastic to best replicate the original caps. don't use a bearing smaller than the port. its obvious why not...
    Quote Originally Posted by schultzy View Post
    I stuck a battery up my arse.
    Yeah, that's a cool story...

  10. #9
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    So i chucked my carbs back on the bike and replaced the vacuum port with a screw and washer. Connected funnel to fuel line and poured in petrol to simulate fuel tank. Fired her up but eventually got it to run warm for a few minutes and boy does she sound better! All she needs now is a balance i'd say. Huge props to Aduro and the rest of you's for the advice! If you're ever in Melbourne i'll buy you a beer!

    Also anyone else that knows how to balance carbs and is located in Melbourne let me know! I'll make it worth your while. No gay shit though.
    Last edited by fairplay; 22nd October 2013 at 07:38 AM.

  11. #10
    Ace Aduro's Avatar
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    Lulz, least it was an easy fix.

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