just got it running, tunning help
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just got it running, tunning help

This is a discussion on just got it running, tunning help within the Technical forums, part of the Caferacer.net Forums category; I have a cb 450 that was purchased in buckets and is now partially assembled and running-sort of. It wont idle correctly, and the left ...

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  1. #1
    Member clutchkith's Avatar
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    just got it running, tunning help

    I have a cb 450 that was purchased in buckets and is now partially assembled and running-sort of. It wont idle correctly, and the left cylinder runs at about 280deg. while the right hovers between 50 and 80 deg. It is mainly stock, right now has the mufflers removed and open carbs. I have the air bleed adjusters turned out about 3-half turns or 1.5 full turn from all the way in. Also the right cylinder backfires loudly at about 3k.
    I like yer style Dude...

  2. #2
    Senior Member Geeto67's Avatar
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    are you sure you have the timing setup correctly? with the 450s the honda manual procedure for timing is to set the left cylinder and the right one you just have to hope is in the right place. It sounds like your right cylinder point is out of whack and not firing the cylinder completely or at all.

    if you have a dwell meter you can set the right side point but it is not as easy as setting the left.
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
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    A tool is just an opportunity with a handle
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  3. #3
    Member clutchkith's Avatar
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    well i set the left one up first, i used a continuity meter and just had the points open exactly at the LF mark, then wondered over to the right side and set it up the same only with it at the F mark. I did notice the dwell doesnt start directly at the 180^ almost a few degrees off, but it is the same on both cyl. I' m going to check it out later today, but I remeber having to set the right side timing by adjusting the points directly to get it set right on the F mark. Also the right cylinder was not getting fuel because the bowl was sticking. I may not have adjusted the float correctly. What about the air bleed adjustment? Where should I start with that? I started with it out 1.5 turns, then I went to 3 turns out and it "seemed to improve".
    I like yer style Dude...

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  5. #4
    Senior Member Geeto67's Avatar
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    have you checked for air leaks in the manifolds? 1.25-1.5 turns out from fully closed is about right, 3 turns and it might as well not be there.

    To check for air leaks spray carb cleaner on the manifolds themselves with the bike running at a constant rpm. If the rpms jump up then the manifolds are sucking air in from somewhere outside the carb and need to be adjusted. Make sure the carbs a re pushed all the way into the manifolds, it is common for people to push them in only half way since it is such a pain in the ass job.
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
    - Samuel Beckett
    A tool is just an opportunity with a handle
    - Kevin Kelly

  6. #5
    Member clutchkith's Avatar
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    maybe the fact that left cylinder has about 130 psi compression and the right only has about 90!!! eeewwwwhhhhh that blows!!! maybe time for some 500 pistons, but I found that a cylinder leak test shows only about 10 percent and its seeping past the rings, what are the characteristics of glazed cylinder walls?
    I like yer style Dude...

  7. #6
    Senior Member Geeto67's Avatar
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    unless you are going turbo 500T pistons won't help you (the 500T uses the same size piston with longer stroke to make 500ccs, not a bigger piston.)

    I have recently found that kz1000 overbore pistons are the same size as cb450/500 pistons and use the same wristpin size and everything. Plus you can get kz pistons forged and in high compression (you loose about 2 comp points with a kz piston in a cb450 bore).
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
    - Samuel Beckett
    A tool is just an opportunity with a handle
    - Kevin Kelly

  8. #7
    Member clutchkith's Avatar
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    makes since, thank for the info! looks like im gonna have a long search ahead of me.
    there are so many combo's that i've come across, its hard to decide which is going to be best for me.
    I like yer style Dude...

  9. #8
    Senior Member Geeto67's Avatar
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    First thing I would do is pull the engine down to the pistons and see what is causing your low compression. It could be all the rings are wasted or it could be the expansion gaps in all your rings are lined up. If the bore is good and the piston is good, just throw a fresh set of rings in the engine and you are good to go cheaply. If you know you have to bore it out then think about hot rod parts.
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
    - Samuel Beckett
    A tool is just an opportunity with a handle
    - Kevin Kelly

  10. #9
    Member clutchkith's Avatar
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    ther is a good chance that i dont have the rings lined up, since i kinda fought them to get them going when i painted the jugs, i had it all apart, i used a modified hose clamp to get the rings in, and it sucked!! Who makes a good piston ring compressor for motorcycles?? Thanks a bunch for you help.
    I like yer style Dude...

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