Black plugs Black exhaust on my CB750 pt.2
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Black plugs Black exhaust on my CB750 pt.2

This is a discussion on Black plugs Black exhaust on my CB750 pt.2 within the Technical forums, part of the Caferacer.net Forums category; Hey Geeto, thx for that tire info, those venoms look BADASS! About the choke, I only need it for a couple secs, I turn it ...

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  1. #1
    wildcatmahone's Avatar
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    Black plugs Black exhaust on my CB750 pt.2

    Hey Geeto, thx for that tire info, those venoms look BADASS! About the choke, I only need it for a couple secs, I turn it off and she revvvvvs like hell then just dies...Is it possible that the points coulda come out of sync by kickstarting the hell outta the bike. I'm tryin to think what has changed since I got it, not much, but it was running perfect when I got her. There was one or two days that I was tryin to kickstart her like crazy cause the battery when kinda dead....Let me know dude-and I owe ya a drink...

    Banned From The Pubs...
    '73 CB350(RIP)
    '74 CB750K3 Cafe Thriller

    Edited by - wildcatmahone on Jul 18 2007 01:44:54 AM

    Edited by - wildcatmahone on Jul 18 2007 01:46:50 AM

  2. #2
    Senior Member Geeto67's Avatar
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    points should not "come loose" from kickstarting the crap out of it. They can come loose if the bike gets knocked on it's left or right side. However points are a natural wear item and should be filed square, otherwise they are nod delivering optimal spark.

    How are your carb boots? are they cracked at all. The only thing I can think of is that maybe you have a vaccum leak causing it to rev. Sure it would cause a lean condition but there is a chance something else is causing your plugs to foul.

    Have you checked all plugs or just one? If you park your cb750 on its side stand for any length of time without running it the bike tends to foul the #1 plug. therefore it could be that 2,3,& 4 are lean and one looks fouled.




  3. #3
    Senior Member kenessex's Avatar
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    Are you sure that the choke linkage is working properly? Just because you are pushing the cable in, are the chokes on the carbs turning off?

    Ken

    AHRMA 412
    Vintage racing - old guys on old bikes

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  5. #4
    wildcatmahone's Avatar
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    Ok I'll definetly check my points..gotta find where to get a timing light. My carb boots are tight as hell, and my choke valve seems pretty tight. Yess it is all 4 plugs that were fouling up until I turned all my idle air screws 1/2 turn above factory spec, cleaned all plugs, and ran it again to discover the second one to the right of the shift lever side
    (no.2?) was okay though the other 3 were fouled again...I am pretty convinced I am running too rich...

    Banned From The Pubs..
    '73 CB350(RIP)
    '74 CB750K3 Cafe Thriller

  6. #5
    Senior Member Geeto67's Avatar
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    the stock airbleed settings should be 1 and 1/4 turn out. Bottom out the screw and then back it out 1 and 1/4 turn. that should get you close but you will need to synch the carbs to get them just right (and if you don't have the tool you need to go to a shop).

    I was thinking about something else yesterday, check to make sure none of your slides is sticking, that could be why the engine is racing when you shut the choke off.


  7. #6
    Senior Member xander450's Avatar
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    It revs like hell and then dies, and then you're looking at the plugs and wondering why they're fouled? Which problem are we trying to fix here? Because if that's what you mean to say, a perfectly tuned bike will have ugly plugs if you put the choke in, start it up cold, rev the shit out of it and then turn it off. SO, is the problem that it revs like hell after you take the choke off? Let's solve that one, because generally speaking, running rich doesn't make your bike rev like a bastard - the engine only burns as much fuel as it has air to mix with.

    Check for air leaks around the manifolds at carbs and intakes. Check for a kinked throttle cable. Check to see that all slide pistons are returning to their happy homes on the low side of the venturi. Have you checked your choke linkage yet?

    A



  8. #7
    Senior Member snorkelfork's Avatar
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    i say F tuning four carbs, you should sell a kidney and get a set up like this

    [
    ...connoisseur of slack...
    the shot came from cyclexchange, from a occ type chopper built from a cb750. they built a tight bike (except maybe the exhaust) but the style still makes me want to barf

    Edited by - snorkelfork on Jul 24 2007 02:04:31 AM

  9. #8
    wildcatmahone's Avatar
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    So I was working on her all last weekend and looks like I've had a total breakthrough. From not even starting to running pretty smooth<img src=icon_smile_tongue.gif border=0 align=middle> Man that Clymer is my new best friend lol. You know I was just standing there scratching my head, wondering what the hell is wrong cause everything on it looks sweet. It would start right up with the choke then just die and foul all my plugs (and I felt like breaking shit). I eventually found out that I had to tune my idle circuit which after many hours and plug filing I did...Just messed around with the throttle stop screw and the idle air screws and that was it. There was just one problem...I couldn't get her to idle below 3000rpm without dying. After riding around for about a half an hour she started calming down a bit now she's idling at about 1200rpm.....Just wanna say thx to everyone for their advice. So what exactly is the correct procedure for tuning these carbs, reckon I should know the right way for next time(and I know their will be one)!

    Banned From The Pubs..
    '73 CB350(RIP)
    '74 CB750K3 Cafe Thriller

  10. #9
    wildcatmahone's Avatar
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    Hey Snorkel whatsup yeh I actually discovered these revamped carbs the other day while surfing around....http://www.cyclexchange.net/Carb%20S...omp%20Page.htm
    Any of you guys got anything good or bad to say about these carbs...? Looks like a sweet upgrade to have.

    Banned From The Pubs..
    '73 CB350(RIP)
    '74 CB750K3 Cafe Thriller

  11. #10
    Senior Member Geeto67's Avatar
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    they are ok for a stock bike, a little better than the stock carbs but that may be because mukuni VM carbs are just better overall. they don't really fit inside a stock frame without some mods and custom air cleaners. they do look sick however.

    If you really want to get the most out of your CB you can buy the CR carbs cycle exchange also sells, which are only $100 more than the dual mukuni setup they sell and are way, way, way better. The fastest cb750s I have ever rode all had CRs or FCR carbs.

    www.cyclexchange.net


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