Slow acceleration
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Thread: Slow acceleration

  1. #1
    Member jamesA's Avatar
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    Slow acceleration

    I feel like my CL350 isn’t producing nearly enough power during acceleration. In order to keep up with any kind of traffic I have to shift into 3rd or 4th gear quite quickly, and I’m not even at 40mph yet. I’m not revving the engine past 5k rpm since it was just rebuilt and I’m letting it break in, so I haven’t tried going crazy with it or anything. 40-45mph in 5th gear seems to be as fast as I can get it without revving above 5k. I’ve set the timing to be as close as I can get it, set the point gap, cam chain, valve clearance, checked the carbs a million times for clogs, charged my battery, etc. I can’t tell if this is just how it’s supposed to run, but it seems like it’s not performing correctly compared to what other people say they experience. There’s just not a lot of pull/acceleration, ESPECIALLY in first gear after 2500-3k rpm.

    Anyone think this sounds suspicious or is it normal?

  2. #2
    Super Moderator ancientdad's Avatar
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    The 350 engine is designed to turn twice that rpm and only begins making its power where you are shifting for now for break-in purposes, so the description and sheer numbers you've mentioned sounds right. Gearing isn't variable in a manual transmission, so if you're only revving to 5000 in any gear your results in mph will reflect the speeds the gearing relates to at that rpm in each gear. Once you have enough miles on the break-in that you feel ready to rev it higher, you'll discover the true maximum speeds for each gear - properly realized when the full rev range is used, and once broken in do not be afraid to use them all
    Last edited by ancientdad; 10-15-2019 at 11:58 AM.
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    Tom

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  3. #3
    Sensei 66Sprint's Avatar
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    When your rings are fully "seated", you should be able to get 50 mph at 5K revs in 5th.....
    Once there try 6.5K as your new limit until you feel comfortable.....
    I'd be spinning it to 6K now (already) myself.....
    "I have a mind like a steel trap.....Old and rusty, of antiquated design, and hard to get stuff back out of...."
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  5. #4
    Member jamesA's Avatar
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    Thank you both for your replies. I get nervous when it revs above 5k just because it sounds like it’s really working hard. Just not used to that and worried something is going to catastrophically fail and I’ll get hurt. If 6k is acceptable during the break in period then I will definitely give that a shot.

    Once the break in period is over what rpm is recommend to shift at for these bikes? I know some of the earlier CB engines redline around 9k-10k or something like that. I thought I read in the shop manual that the CL was lower though? Like 8k or something like that.

  6. #5
    Super Moderator ancientdad's Avatar
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    The factory redline for your bike should be reflected on the tachometer, and once it's broken in there's no harm whatsoever in using all of it. These engines like to rev and make their power in the upper rev ranges, so air it out and enjoy the sound... it might take you a bit to get used to it but trust me when I tell you, it isn't working hard at 5000 to 6000 rpm, it's just getting into its sweet spot. See my avatar? That picture is a still from a GoPro video, not Photoshopped - if you want reassurance that these engines like to rev, just watch my drag strip run in the link in my signature.
    Tom

    CL450 project reboot, street legal this time
    Budget drag bike project
    CB350K1 full patina project
    Ride along at the drag strip


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  7. #6
    Senior Member JamesPal's Avatar
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    Honda recommends a 600 mile break-in period and then change the oil and check the valves. I did it to my '72 CB450 at around 640 miles. I could really tell a difference in the engine's willingness to rev once it got near 600 miles. The owners manual for the 450 says either 2/3 or 60% throttle, I don't remember an RPM limit. It is OK to reach into the upper RPMs for a short burst, Don't let the engine to get too hot. Yes, you are going to have problems keeping up with modern traffic, especially if you live in hilly territory and like to ride on the freeway.
    Jim Palmer
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  8. #7
    Member jamesA's Avatar
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    Ancientdad, I watched your drag strip video and that was awesome. Ah while I do have an original tachometer, I don't believe it's the one that belonged to this bike originally. I restored the bike from several boxes of parts taking the best ones, so I had no idea which tach was the original one. Tonight I took it for a longer ride to test it out. I tried shifting at higher rpms and it really did make me see the difference! First gear is still kind of slow, but I was able to get up to 40mph in 3rd.

    After my ride though I noticed that there was a lot of cam chain noise again even though I just reset it the other day. Could the tensioner just be too warn to retain it's position? This is the second time it's started to get noisy after a ~30 min ride.

  9. #8
    Supporting Member Yendor's Avatar
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    Did you replace the Cam Chain Tensioner Rollers?

    Have you changed the OIL and Looked for any debris?

    It could be the rubber roller for the Cam Chain is disintergrating and that is making the chain loose.

    I'd change the oil and look for stuff (rubber bits) that shouldn't be in there.
    1970 CB 350 CAFE - Current Project on the bench,
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  10. #9
    Sensei 66Sprint's Avatar
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    When you adjusted the cam chain, did you properly snug the bolt and then its jamb nut?....
    If the bolt wasn't correctly tight, the plunger possibly can get pushed/forced back slightly at higher revs......
    The most likely cause is still degrading rubber wheels... Check your oil for rubber bits, black specs......
    If none, pour it back in or add fresh oil.....
    "I have a mind like a steel trap.....Old and rusty, of antiquated design, and hard to get stuff back out of...."
    Contact info: E-mail; [email protected] Phone; 540-525-5199

  11. #10
    Member jamesA's Avatar
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    I tried adjusting the cam chain again last night and it still made more noise after a ride. When I had the stator cover off I did notice that the oil had silver/metallic bits in there. Couldn’t tell if it was rubber or actual metal though. I did replace the larger tensioner wheel but just can’t remember if I changed the smaller one. I’m pretty sure I did not. And there’s no way that can be changed without ripping the whole engine apart...

    Perhaps the noise I’m hearing could be something other than the cam chain? I’m not entirely sure how much noise it should be making considering that this is the only one of these bikes I’ve heard running.

    Also, I did make sure the bolt and nut that secures it were quite snug when adjusting the cam chain tensioner.

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