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Re: [CT90] SPEEEEED !

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  • Oowonbs
    As the original Trail 90 did its 54-56 decently enough, and looking at the 160-175-175-200 & general trends around then, I saw cc s go up and carbs get
    Message 1 of 6 , May 27, 2017
      As the original Trail 90 did its 54-56 decently enough, and looking at the 160-175-175-200 & general trends around then, I saw cc 's  go up and carbs get smaller as cross-compensation in the new US anti-smog attempt & new laws. Everyone was hit. I was not in the US enough then to really stay abreast... but I'd almost bet that all you need is to research a Traol 90 original, esp around 65... and pick a carb that is an equivalent. Your opening air ducts and adding gas via jetting is beginning to sound like this. 

      The thread is old enough now that suma us geezers have forgotten how your bike ended up so slow. Is a CT 110 that in cc's ? I forget. Carnival tomorrow in San 'Frisky. Used to be really cool. Now? Meh. Happy Day, y'alls.

      BillSF9c

    • Richard Hughson
      Ok, back story time. I bought the bike from Turtle with a smashed back end and no rear wheel. It had 2178 miles on it. I fitted an S90 swing arm so that
      Message 2 of 6 , May 28, 2017
        Ok, back story time. I bought the bike from Turtle with a smashed back end and no rear wheel. It had 2178 miles on it. I fitted an S90 swing arm so that sometime in the future I can fit an 18" rear wheel. I'm using a stock 17" CT110 rear wheel at this time. The engine is essentially untouched other than a clutch replacement that Turtle did and made a video of. It's still at the stock 105cc size. 

        The only modification I made was to open up the air intake from the factory 3/4" to the easily available 1 1/2" by grinding away the stock luggage rack restrictor. The bike no longer ran well.

        It would only rev by closing the choke almost all the way. In the process of checking for air leaks I replaced the carb with a $20, 22mm model off Ebay, which is the standard carb size for this model. It would still only rev by closing the choke. I started ordering larger jets and it finally ran well with a #105 main jet and the needle raised one notch from the middle position, stock main jet is about #72 if I recall correctly.

        It now runs extremely well, starting with one kick and pulling cleanly and strongly through the entire rev range. However, the maximum speed didn't change hardly at all. It tops out at 47mph right now, only hitting 50mph on long down hills. I did not test the top speed before opening up the air intake.

        I have not experimented with changing the timing nor with degreeing the cam. But in my research I found that Honda changed the cam profile to provide more low and mid range power in the early 1980s models. 

        My thinking is that the stock cam simply doesn't have the valve overlap required to let it breathe any faster. 

        Are there any well informed thoughts out there?

        Rick H

        On Sat, May 27, 2017 at 11:08 PM, Oowonbs OOWONBS@... [ct90] <ct90@yahoogroups.com> wrote:
         

        As the original Trail 90 did its 54-56 decently enough, and looking at the 160-175-175-200 & general trends around then, I saw cc 's  go up and carbs get smaller as cross-compensation in the new US anti-smog attempt & new laws. Everyone was hit. I was not in the US enough then to really stay abreast... but I'd almost bet that all you need is to research a Traol 90 original, esp around 65... and pick a carb that is an equivalent. Your opening air ducts and adding gas via jetting is beginning to sound like this. 


        The thread is old enough now that suma us geezers have forgotten how your bike ended up so slow. Is a CT 110 that in cc's ? I forget. Carnival tomorrow in San 'Frisky. Used to be really cool. Now? Meh. Happy Day, y'alls.

        BillSF9c


      • billsf9c
        Your back story was excellant. You may be right aboht the cam... bacause the same cam that can ~ provide more low end also yields less smog ( smog - creati
        Message 3 of 6 , May 28, 2017
          Your back story was excellant.
          You may be right aboht the cam... bacause the same cam that can ~"provide more low end" also yields less "smog" ( smog - creati g blah blah.)

          What yields more low end often yields less high end.

          Thx Richard,
          BillSF9c
        • billsf9c
          ... 3/4 to the easily available 1 1/2 by grinding away the stock luggage rack restrictor. The bike no longer ran well. I m trying to imagine this...
          Message 4 of 6 , May 29, 2017
            > The only modification I made was to open up the air intake from the factory
            3/4" to the easily available 1 1/2" by grinding away the stock luggage rack
            restrictor. The bike no longer ran well. <Rich>

            I'm trying to imagine this... and a general carburator.

            You reduced overall vacuum, and it went to crap.

            Carb venturis suck gas by virtue of the venturi effect... blah blah, creating a vacuum which sucks up the gas and it atomizes in the speedy airflow.

            So this vacuum may (???) be seen as adding to the venturi vacuum, perhaps, in their smog reducing design.

            In removing that, you carb is now all wrong. Less vacuum means you have to open the jets WAY up... whereas before, a smaller carb maybe (?) did the job.

            Dare I ask...
            can we get a rundown list of years, model numbers, and carb sizes? If each (1st 5???) who can, can give us these details, and some kindheart makes a file of these? (My ph is my 'net in the midst of this remodel and Fil-making seems not a function.)

            I saw the 160-175 sloper-175 upright-200 upright get increasingly smaller carbs (!!!) and barely maintain performance.

            I think that's a share of what's going on here... + if you tried to outwitt it, THIS was their ninja-answer - they-will-fail, honorable uncle-sam-san... If so, velly inscrutable....

            22mm? The 200 went down to a 20.
            You, ideally, might be overcarbed. Get it running well & atomization may be so poor that mph is silly low.

            BillSF9c
            Remember the fallen... and that guy panhandling w and bag held open by two handles for donations!!! And hooks for hands... . . . . . . .
          • jeffscycle
            Bill, and the rest. just getting back from the weekend, I spent it painting, YEA!! Anyways to recap, I did machine my head to drop sink it down into the
            Message 5 of 6 , May 30, 2017
                 Bill, and the rest. just getting back from the weekend, I spent it painting, YEA!!  Anyways to recap, I did machine my head to "drop sink" it down into the cylinder to make a .025" squash chamber, along with the 12:1 compression, along with a virtually bullet proof gasket seal. In that process I also built a "big wheel" cam chain adjuster to take up the slack on the cam chain. At this time I am using the stock 110 cam at an advanced timing, more due  the chain being off time slightly, and a 50t sprocket, and it'll do 50mph consistently with a#76 main jet & stock rack. Up here at 4000ft. use of just a cone K&N filter made very little difference. 
              . Webb Cam http://www.webcamshafts.com/index_blank.html?pages/vehicle_search.html  will regrind your cam to one of their specs for like $180, but the #298 has to early of a intake closing for my use, but does bring out more low end grunt in a stock engine, and may pull the 45t gearing better. I also have a #303 for big engines & high compression, but its in my 131cc  & I'm happy with that bike. I may pull it out and try in the 12:1 engine at some time. before having another one made. The last time I looked, Webb may have a 298 in their clearance page, so you may get a better buy.
            • Richard Hughson
              Thanks Jeff, I m heading out of town for a couple weeks but I ll look into this more when I m back home. Bill, instead of thinking of vacuum think of the air
              Message 6 of 6 , May 30, 2017
                Thanks Jeff, I'm heading out of town for a couple weeks but I'll look into
                this more when I'm back home.

                Bill, instead of thinking of vacuum think of the air pressure within the
                air box which is available to fill the cylinder. We only have 14.7psi to
                work with at best. When you limit the atmosphere's ability to fill the
                airbox then you limit the airbox's ability to then fill the cylinder and
                you end up with less air being pushed through the carb.

                Jeff, according to the attached graph you have about half the air pressure
                at 4000 ft. that I have.

                And now back to packing,

                Rick H



                On Tue, May 30, 2017 at 2:16 PM, jeffscycle@... [ct90] <
                ct90@yahoogroups.com> wrote:

                >
                >
                > Bill, and the rest. just getting back from the weekend, I spent it
                > painting, YEA!! Anyways to recap, I did machine my head to "drop sink" it
                > down into the cylinder to make a .025" squash chamber, along with the 12:1
                > compression, along with a virtually bullet proof gasket seal. In that
                > process I also built a "big wheel" cam chain adjuster to take up the slack
                > on the cam chain. At this time I am using the stock 110 cam at an advanced
                > timing, more due the chain being off time slightly, and a 50t sprocket,
                > and it'll do 50mph consistently with a#76 main jet & stock rack. Up here at
                > 4000ft. use of just a cone K&N filter made very little difference.
                > . Webb Cam http://www.webcamshafts.com/index_blank.html?pages/
                > vehicle_search.html will regrind your cam to one of their specs for like
                > $180, but the #298 has to early of a intake closing for my use, but does
                > bring out more low end grunt in a stock engine, and may pull the 45t
                > gearing better. I also have a #303 for big engines & high compression, but
                > its in my 131cc & I'm happy with that bike. I may pull it out and try in
                > the 12:1 engine at some time. before having another one made. The last time
                > I looked, Webb may have a 298 in their clearance page, so you may get a
                > better buy.
                >
                >
                >


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