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  1. #21
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    Quote Originally Posted by JBinNC View Post
    That's reversion and it is mostly influenced by the exhaust system. The air cleaner helps retain some of it. You can see it on drag bikes with velocity stacks quite often. And yes, it is one reason why exhaust pipe selection can make carb tuning difficult.

    Jim
    Thanks.

    This is even an issue with shorty drag pipes?

    Because I know the last time I saw that happen? My new mufflers were completely plugged and I had a hell of a time figuring out what the problem was.

    I posted a thread on it at the time because I was totally stumped on it.

    But this is the opposite? The pipes are wide open and quite large.

  2. #22
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    Quote Originally Posted by confab View Post
    Thanks.

    This is even an issue with shorty drag pipes?

    Because I know the last time I saw that happen? My new mufflers were completely plugged and I had a hell of a time figuring out what the problem was.

    I posted a thread on it at the time because I was totally stumped on it.

    But this is the opposite? The pipes are wide open and quite large.
    There are pressure waves and sound waves going back and forth in the pipe. The two waves behave a little differently, and travel at different speeds. But both are "reflected " from the end of an open pipe and travel all the way to the mouth of the carb (or velocity stack if so equipped). The math is so f***ing complex that most work on motors in the field (by racers and hot-rodders) is done by the empirical cut-and-try methods. I wish I understood it better.

    Jim

  3. #23

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    Confab,

    you must have a flathead since you posted the thread about using a CV carb on one, to which I replied somewhere in there that I am one of the people running one! Post a pic of your bike in here I wanna see it!


    Jim and others,

    Did you watch the video of mine running after I did all the things you said? What do you think, is it sounding ok to you?

    -Chase

  4. #24
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    Yeah... I have a 45. But that's all I have, an engine. I'm going to build a bike around it.

    Following your thread with interest! Hope you get it sorted.
    Last edited by confab; 02-22-2021 at 7:12 PM.

  5. #25
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    I checked out your video. Nice bike! Sounded OK to me, but I'm on a cheap phone and I'm half deaf.

    Jim

  6. #26
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    This bike does NOT have matched heads. The rear is slightly higher compression than the front.
    This wouldn't be enough to require a heat range change on the front plug, would it?

  7. #27

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    Confab,

    Keep us posted man, I love these flatheads ever since I learned basic mechanics on them 24 years ago. (If you guys hadn't guessed I'm a punkass millennial!!)



    Jim, THANKYOU for the help! And, thanks for the compliment! This flathead was my dad's bike and it means a lot to me to be able to put it back on the road. PM me your email so I can send ya some beermoney as a token of my appreciation?




    Confab, That is a valid question you raise. I don't know if my line of thought is correct here, but if this thing was running good for so long with mismatched heads, and the plugs the same, I think it might be OK. Having said this, I'm sure there's some more efficiency and power to be had from dialing in the specific AFR requirements from one chamber to the next.

    Like I think I said, I'm mainly wanting to get it going again as is, after having invested so much time, money and energy; before I splurge on a nice set of new aluminum heads. I don't know what the compression ratio is of these flatheads but I think the difference between the high and low compression heads would be like 5:1 and 5.75:1 ROUGHLY?


    -------------------------

    Thanks guys.

  8. #28

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    Quote Originally Posted by confab View Post
    Stupid Noobie Question I can't help but ask because I don't know any better:

    Is it supposed to blow a mist of fuel (I assume it is fuel?) out of the carb when the throttle is opened?

    Is this a characteristic of flat heads or?
    As JBinNC mentioned that can occur due to harmonic reversion and the sound pulses travel from the exhaust side to the intake manifold during valve overlap and out to the carb mouth and then reverse back through the carb... this is known as 'double pumping' because fuel gets pulled into the airstream twice and throws off the air/fuel mix. Not sure how much valve overlap there is on a flathead but that's something worth keeping in mind.

    Generally speaking there are two ways to help dissipate or reduce the effects of harmonic reversion without restricting exhaust flow. Firstly if you're really set on having a loud bike and like the sound of straight pipes, you're better off with open cocktail shakers... their megaphone shape helps break up the sound pulses that travel up and down the exhaust system because it's forcing the pulses to change velocity and amplitude as they travel down an ever increasing diameter and further dissipates their energy as they also try to return back up the exhaust. Another thing you can do is increase the length of the pipes which can bring 'drag pipe sag' lower in the rpm range where it's less noticeable or doesn't affect the portion of the power band that's used most often... it's a generalization but I've found during dyno testing that the shorter the straight pipes, the higher up in the mid-range 'drag pipe sag' occurs, usually where most street bikes spend most of their time. Of course the initial diameter of the pipes also comes into play but that's something for another day.
    Last edited by Skjoll; 02-23-2021 at 8:08 AM.

  9. #29

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    I'm running drag pipes. Only temporarily. Building on what JB and SK have already mentioned, I think the short length drag pipes contribute to that poppy exhaust sound. And, I'm sure the short length, individual pipes between each cylinder is a less than ideal exhaust setup which is causing some reversion.

    I sniffed my exhaust tonight with a WB02.


    Here is a good video I fround from S&S regarding reversion and drag pipes and how this is quite possible what I am observing:

    https://www.youtube.com/watch?v=KjKUKhHQLHg

    And here is my video with me testing the AFR of each cylinder individually with a WB02.

    https://www.youtube.com/watch?v=lQzbT2gghLo
    Last edited by CDeeZ; 02-26-2021 at 3:03 AM.

  10. #30

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    CDeeZ, first off props to you for being so thorough, astute and resourceful. I watched your vid (with the WB02) multiple times using a high end Sennheiser studio headset and honestly, the bike sounds good to me at idle. I hear a clicking sound (in both vids) that is similar to a a slight exhaust leak or head gasket leak but then it could just be extraneous shop noise. Usually a stethoscope with an open end (sans bell or probe) can be used to target specific areas of the motor to verify whether or not there is an actual leak around those areas I referred to. I mention this because it seems you've verified that the ignition is in good nick and that you don't have any intake leaks so I'd suspect that the premature fouling of the front cylinder would be due to low compression or the introduction of trace amounts of oil into the front cylinder and combustion chamber somewhere/somehow. In your other video I noticed you don't really get close to the rear exhaust opening with your hand yet you do with the front as though you felt the exhaust pulses were less than on the rear. Is that the case... did you feel a big difference?

  11. #31
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    Late to the party CD, but sounds good. Well done on asking for help and being as thorough with your steps.

    Lots of people here with great info and knowledge, Jim being one of them. It sounds great, carb might need a little jetting to suit your higher rev range. As for running though. Sounds just like mine did!

  12. #32
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    Did you ever get compression readings wet and dry?
    Dusty

  13. #33

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    Skjoll,

    Wow, thanks man. I appreciate the compliments. It sounds good to me as well. But thankfully I have the treasure trove of informed people like all you guys who have chimed in on this thread to help me.

    And yes, there is an exhaust leak on the front exhaust pipe. The front exhaust pipe is something I had to cobble together from a set of drag pipes and the stock front pipe. It doesn't seal great in the exhaust port on the jug. But then, considering the pipes for a flathead just stick inside the port with no gasket or anything, they probably weren't that great to begin with. I'm going to get a proper exhaust on there at some point.

    Last time I did a compression test everything was good, but the numbers were a little off, from the fact that the heads are different compression from front to back. I do keep a stethoscope in the shop though.

    I still have a new condenser and points setup on it's way. Going to slap them in soon when they get here just becuase they probably need to be replaced anyways.

    I think the front plug was fouling out mainly from the fact that I didn't have it timed correctly. But Jim sorted me out on that I probably overoiled the internals on reassembly the last time just to be sure everything was lubed. Probably oiled everything a bit much and that could be contributing to the plug fouling perhaps. Sure seems better overall since I timed it right though.

    The front exhaust pipe definitely sounds a bit different, but that's likely from the fact that I have a known exhaust leak up near the exhuast port causing that. Can't say I feel much difference, not perceptibly at least.


    ----------------------------------------------------------------------------------------------

    Rhysmort,

    Thanks for the king words as to me being thorough. I do try haha.

    Yep, I am sure thankful for all you guys here. And yes! Jim is one of them!

    I'm glad to hear you say in addition to others that it sounds good. And I think you're right, the carb needs some tuning at some point.


    ----------------------------------------------------------------------------------------------


    Dusty,

    I haven't tested the compression since last time, maybe a few months ago.

    The compression numbers were off like I mentioned because of the different compression heads.

    What do you mean wet and dry? Throttle open and closed?

  14. #34
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    You need to know how many kicks with the throttle wide open to reach maximum compression reading on a engine at room temp that hasn't been started IE dry. and them with oil sprayed on the cylinder walls IE wet.
    Dusty

  15. #35

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    But just remember, no matter the topic, wetness is the most important concern.
    Last edited by Skjoll; 03-04-2021 at 1:38 PM.

  16. #36

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    I have ridden the bike around a little and it was running good.

    The float was sticking and dumping fuel everywhere from the CV carb. Adjusted the float and fixed that issue.


    The bike got a little rained on last night and now it won't start. Don't know if they're related or coincidental.

    With the plugs laying on the heads and me kicking the bike over there is no spark at either plug.

    I installed the new condenser. Still have the same points on it for now.

    Can ayone tell me the best way to test this coil? Or point me in the right direction as to why I don't have spark all of a sudden?




    Looks to be a yellow coil, (maybe accel brand?) that my dad painted black years ago.



    --------------------------------------

    Once I figure this no spark thing out there is really only one thing left to do and that is to figure out why it is spewing oil out of the crankcase breather while running.

    Brand new CHP oil pumps so I would think the checkball is sealing.

    AFAIK I timed the breather correctly for the scavenger pump.

  17. #37

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    I think something got wet and the dried out, bike started up last night.

    Does anyone have any idea why this thing is spewing oil from the crankcase breather on the bottom of the timing/cam cover? Seems to get worse the more I ride it.

  18. #38

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    No one chiming in on the wetsump problem?

    I'm not talking about it leaking a bit on startup like these tend to do.

    I mean, it leaks little to no oil on startup, and the more the motor is run the more oil is puking from the crankcase breather on the cam cover. Riding it down the road, it is gushing oil from the breather, all over the side of the motor, exhaust, frame etc.

  19. #39
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    It's a dry sump system. If the scavenge (return) side does not have enough volume or flow, it won't be able to keep up with the feed side. You mentioned changing the pump set-up, did you not? If so, it sounds like your new system is not functioning as you had hoped. So, what did you change from stock, and why?

    Jim

  20. #40

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    Yeah, I have both a new gerotor style feed pump, and, a new scavenge pump with 40% larger gears than OEM for more scavenging.

    Got them both from CHP, Calas High performance in Sweeden. Carl is the guy in Sweeden that does CHP. Nice guy with some pretty impressive stuff for older big twins.

    Feed pump below:

    http://www.calas-hp.se/e_prod.php

    Scavenge pump below:

    http://www.calas-hp.se/e_prod2.php

    ( I got an entire new scavenge pump from him also, rather than swap larger gears in the original scavenge pump, figured it would be easier on me with so much other stuff to be screwing around with on this project )



    I changed from stock because as long as this bike has been in the family, it blows up a top end every 10,000 miles or less. Probably less. I think the general consensus is, while the stock oiling system worked, it definitely wasn't very good.

    Air cooled motor = oil cooled motor.

    So I changed it hoping to make it more reliable. Or, maybe that's not the right word. To make it more usable in modern traffic without having to service the top end nearly as often?

    I added jets or squirters to spray oil on the bottom of the piston crowns. Got the idea from Dick Linn :

    https://dicklinn.webs.com/

    So mainly the new pumps were an effort to hopefully:

    a) have enough oomph to lubricate this thing a little better, including powering the piston squirters

    -and-

    b) have enough scavenging ability to return the oil back to the tank, where it belongs.


    I'm going to pull the cam cover again soon and have a look. I installed a new flutter valve a ways back because the old one was stuck. I'm not sure the new one was any good though. I think the new flutter valve may have been bad right out of the box.

    The "test" is to hold the cam cover in your hands and try to "blow and suck" air through the flutter valve. It should pass air one way and not the other. A checkvalve basically........ I never felt like I had much confidence in the NEW flutter valve I installed a few months ago, I seem to remember being able to both blow and suck air....... But I thought, how scientific can a test like this really be? And I slapped it back together that way.

    Really hoping that it's something simple like the flutter valve not working correctly.

    I will recheck the breather tower timing for the scavenger pump while I'm in there too.
    Last edited by CDeeZ; 4 Weeks Ago at 5:37 PM.

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