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Getting my CB360T going right

This is a discussion on Getting my CB360T going right within the Technical forums, part of the Caferacer.net Forums category; If you are still dealing with vacuum operated carbs directly connected to pod filters and your exhaust system has been raped, then your motor would ...

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Thread: Getting my CB360T going right

  1. #11
    Senior Member TrialsRider's Avatar
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    If you are still dealing with vacuum operated carbs directly connected to pod filters and your exhaust system has been raped, then your motor would be operating way too lean for how it was originally designed. To combat the lean situation people create by opening up the breathing, they flog the fuel through the carburetor by changing jets and settings in an effort to make it run less lean. Yours has been made to run so rich it is producing huge volumes of unburnt carbon which is going to soot up your pistons and valves and exhaust something awful.
    Safety is all fine and good but the thing has to run under it's own power or it is useless as a motorcycle. If you ask a shop to check for safety issues, they are not going to be looking for motor issues they are going to be checking steering, wheels and brakes. Previous owner messed up your motor.


    add: where does your crank-case breathe from? If it can't breath when the pistons go up and down then it will be sucking or blowing oil into places it should not be.
    Last edited by TrialsRider; 05-11-2019 at 05:31 AM.

  2. #12
    Member alwaysavocado's Avatar
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    Thanks... The shop that looked at it said these carbs have original jetting, they installed new needle and seats and fixed the stuck floats. So re-jetting could help resolve the issue here? I found a pretty extensive print out in a parts box from the previous owners order from 6sigmajetkit.com I have a bag with 115-k main jets, and the parts list says 110-k main jets as well, so it's safe to say there are 110 mains in there now, this print out says if its lean to use the 115. Which direction do the numbers go to get it more lean, or better yet, what would be a good jet size to try from here.
    Last edited by alwaysavocado; 05-11-2019 at 12:11 PM.

  3. #13
    Senior Member TrialsRider's Avatar
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    That's the whole problem, the carburetor jetting was designed to work with an air box that you no longer have and an exhaust that has been altered :| you have no base line to set things to, you are carburetor tuning in uncharted territory and your carburetor is not a simple venturi slide type carburetor. If it was I would say lower the main jet needle by one or even 2 notches on the cir-clip. You have a CV carburetor, they don't adjust anywhere near the same.

    ... if a shop guy can tell original jets just by looking that would be truly impressive and if the carb was unchanged it would be running lean not rich, that I can pretty much guarantee you.
    Last edited by TrialsRider; 05-11-2019 at 03:44 PM.

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  5. #14
    Senior Member 8ball's Avatar
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    Quote Originally Posted by alwaysavocado View Post
    Thanks... The shop that looked at it said these carbs have original jetting, they installed new needle and seats and fixed the stuck floats. So re-jetting could help resolve the issue here? I found a pretty extensive print out in a parts box from the previous owners order from 6sigmajetkit.com I have a bag with 115-k main jets, and the parts list says 110-k main jets as well, so it's safe to say there are 110 mains in there now, this print out says if its lean to use the 115. Which direction do the numbers go to get it more lean, or better yet, what would be a good jet size to try from here.
    Pod filters on CV carbs (vacuum slide) are problematic. The issue is that it isn’t as simple as they just run lean. They will also run rich in certain rpm and throttle positions. You won’t just luck into the correct jet configuration. Tuning CV carbs with pods is usually a game of compromise. You might get good WOT performance at the expense of throttle response, or you might be able to get good steady state performance and decent throttle response but WOT performance stumbles. Very rarely will it work across the board as well as it ran with the OEM air box. CV carbs use the pressure differential before and after the carb to operate the slides. When you remove the still air volume that the air box provides, you’ve mucked up the balance, and it is very hard to get around that.

    All that being said, your plugs look extremely rich, but it depends what range that was in when they fouled out. Pilot jets and air fuel mixture screws determine the air/fuel mixture at idle and in lower rpm and throttle positions. The main jet determines a/f mixture at WOT. The needle taper and height is responsible for mid rpm and transitions between ranges and throttle changes. Your carbs may even have an accelerator pump to add to the complexity.

    You will need to do plug chop runs to get the different regions dialed in as best as possible. You have to find an isolated straight road that you can do some rather high speed runs. You need to run the bike in the range you are testing for about a quarter mile and hit the kill switch and pull the clutch. Pull to the side of the road and pull the plugs and give them a read. Make adjustment and repeat. Every adjustment will require removing carbs. You can see this will get tedious, right?

    My personal methodology is to get the idle running right first. In order to do this, I start with a valve adjustment and a carb sync. Then start with the pilot jet. With the right pilot jet in, the mixture screw should be between 2 to 4 turns out. If you mixture screws are on the engine side, they are fuel screws. Screwing them in leans the mixture. If the screws are on the filter side of the carb, they are air mixture screws, and screwing them in richens the mix. If the adjustment screw is required to be too far out, or too far in, you need to go up or down on the pilot jet size.

    Once the idle is good, I go do my full throttle plug chops, and get the main jet right.

    Then I do the needle height to get mid rpm and throttle response as good as possible. I do the needle after WOT because any change to the main jet will require adjustment to the needle height.

    After all that I go back and sync the carbs.
    Last edited by 8ball; 05-11-2019 at 04:08 PM.
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  6. #15
    Member alwaysavocado's Avatar
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    Quote Originally Posted by 8ball View Post
    Pod filters on CV carbs (vacuum slide) are problematic. The issue is that it isn’t as simple as they just run lean. They will also run rich in certain rpm and throttle positions. You won’t just luck into the correct jet configuration. Tuning CV carbs with pods is usually a game of compromise. You might get good WOT performance at the expense of throttle response, or you might be able to get good steady state performance and decent throttle response but WOT performance stumbles. Very rarely will it work across the board as well as it ran with the OEM air box. CV carbs use the pressure differential before and after the carb to operate the slides. When you remove the still air volume that the air box provides, you’ve mucked up the balance, and it is very hard to get around that.
    Are there other pod filters that might work better with these bars? Or is pretty much either stock air box or pod filters. My test ride was less than 2 miles, but I am not sure how fouled they were prior to the test ride. But I didn’t get passed 3rd gear. I cleaned the plugs and also buying some new ones today, going to take another test ride and check the plugs after the same ride. Maybe everything is ok and they were just filthy before huh? Doubtful

    So, a plug chop is new to me. I’ll try this today, sounds easy enough for testing. After pulling over and checking the plugs you say make an adjustment, you mean back at home with jetting or some kind of adjustment on the fly after pulling over? It actually idles really nicely.

    Thanks for all the tips Im glad boards like this are around. My uncle owned a Harley shop for years but he lives 6 hours from me, too bad for me!

    Even buying Mikuni carbs would require some tuning but are they a good investment and better style carb? Debating on where to invest my time and money to get things right.

  7. #16
    Senior Member TrialsRider's Avatar
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    you didn't ride it enough to get a fair assessment reading the plugs, ride more and observe for other symptoms.
    If you buy used ones from a place like I was at today, carburetor swap would be a great investment. Have you ever been to a motorcycle wreckers yard :I is awe inspiring.

  8. #17
    Member alwaysavocado's Avatar
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    Quote Originally Posted by TrialsRider View Post
    you didn't ride it enough to get a fair assessment reading the plugs, ride more and observe for other symptoms.
    If you buy used ones from a place like I was at today, carburetor swap would be a great investment. Have you ever been to a motorcycle wreckers yard :I is awe inspiring.
    For sure. I only got a 1.5 mile ride before it died on me. The plugs may have been pre-fouled already. I put new plugs in and the left side threads were less than perfect so I am waiting for a thread tap to clean up the threads. Will report back with test ride results! Hope to be dialed in... somewhat soon Appreciate all the help so far.

  9. #18
    Junior Member Racegun's Avatar
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    If it was running and then it wasn't, that would lead me to think it could be a fuel delivery problem.

    Check for clogs, dirty filters, kinked hoses, stuck floats, bad petcock...etc.

  10. #19
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    Have you checked the electrical system? Run diagnostics on that? Usually when I have a died and won't restart problem when warm it's because the coils or the ignition trigger is failing. I am assuming your bike runs points so it's unlikely that they are the problem, but might want to check a few things in the electrical system, esp those janky ass honda fail prone coils.
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  11. #20
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