Mikuni carbs on Honda CL350
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Mikuni carbs on Honda CL350

This is a discussion on Mikuni carbs on Honda CL350 within the Technical forums, part of the Caferacer.net Forums category; I know this subject has been beat to death but I need help with 30mm Mikuni carbs on my cl350. I know basically how the ...

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Thread: Mikuni carbs on Honda CL350

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    Junior Member Geezergen's Avatar
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    Mikuni carbs on Honda CL350

    I know this subject has been beat to death but I need help with 30mm Mikuni carbs on my cl350. I know basically how the jetting should be done. Short history: got the carbs jetted like this: needle jet 159P5, jet needle 6F5 clip in center slot, slide 2.5, main jet 135, secondary jet 27.5, air jet 2.0. Bike is stock bore, electronic ign, cl pipes with shorty open mufflers, pod filters. When I put the carbs on, the bike would not run on main jet. Jetted up in steps to 180 mains and now is a little rich on top end but running pretty well, however it is missing and running lousy right off idle to about 1/3 throttle. I have raised the needle and changed the secondary jets in steps all the way up to 40's and still runs lousy (cutting out and spitting). I don't know what else to do except changing the needle jet and needle, but I don't have cubic dollars to throw at this project and would appreciate any advice.

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    Senior Member TrialsRider's Avatar
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    did you do a compression test? You can't make the carbs work if the pistons and valves don't want to play, compression test is the quickest easiest way to see if things are behaving as they should inside the motor.

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    Junior Member Geezergen's Avatar
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    Yea, I put new rings in to start with along with a new timing chain set up. The compression is about 180 on right side and 175 on left side but I am about ready to believe the trouble is somewhere else but don 't know where it could be.

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    Senior Member TrialsRider's Avatar
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    does it still have points ignition? "cutting out and spitting" sounds spark related. Points and condenser are highly suspect if the firing is hit and miss.
    ... trust you already realize CV carbs and pod filters is a poor combination with vacuum operated carbs. No mention of year model so I assume you have CV carbs as most do.

    Good battery is also very important on a battery/coil ignition, others here might chime in on that.
    Spark plugs, ignition wires and plug cap, all good? I've bought brand new plugs in packs of 2 where 1 was DOA, crack in a plug insulator can sometimes result in the spark intermittently happening up inside instead of at the gap, that will also make the bike sputter and fart like crazy. Water in fuel also produces similar symptoms.
    Last edited by TrialsRider; 10-03-2018 at 08:35 AM.

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    Senior Member TrialsRider's Avatar
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    Rule out all those things and you might simply be experiencing CV carb combined withshorty open muffler & pod filter syndrome.
    Did it run well with the stock air box and an exhaust system that has some reasonable back pressure in place, or was that ever an option?

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    Junior Member Geezergen's Avatar
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    Mikuni carbs on CL350

    The carbs are Mikuni 30mm and ignition is electronic. What baffles me is the trouble is only in the lower throttle position. Most mechanical troubles would not occur only in this range. Bike runs very well at high RPM's.

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    Senior Member 8ball's Avatar
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    Quote Originally Posted by Geezergen View Post
    The carbs are Mikuni 30mm and ignition is electronic. What baffles me is the trouble is only in the lower throttle position. Most mechanical troubles would not occur only in this range. Bike runs very well at high RPM's.

    You say Mikuni carbs like that is supposed to mean a type. Mikuni is a brand, not a type of carb. They made several types of carbs. BS (CV), or VM (mechanical slide), etc.. What type do you have.
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    Senior Member XB33BSA's Avatar
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    put some cb750ko carbs on it and it will run perfect straight away
    that said you do need to make sure all is well with the ignition
    what brand e ign do you have
    process of elimination dictates testing with points ignition back on the system because they work perfect without issue this is a known
    the mikuni vm carb while it can be set up to run quite well at wot and higher rrevs
    well it was never designed as a four stroke carb and it is simply impossible to get them to work anywhere near as well as an oval venturi keihin as far as ridability and throttle response
    what kind of exhaust have you got on that turd
    you need loooong pipes baby shorties will only work on a nitro motor running wot all the way up the hill
    short pipes rob every bit of exhaust scavanging untill up near redline and then it doesn't loose as much but short pipes create the same effect as having too much back pressure

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    Junior Member Geezergen's Avatar
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    Okay. VM carbs, and I have used this muffler set up on CL pipes before with stock CV carbs and they work great. No reason they shouldn't work with the MIKUNI CARBS.

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    Senior Member TrialsRider's Avatar
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    Quote Originally Posted by Geezergen View Post
    Okay. VM carbs, and I have used this muffler set up on CL pipes before with stock CV carbs and they work great. No reason they shouldn't work with the MIKUNI CARBS.
    In very general terms, VM is good, CV can get evil without an air box ymmv.

    ? maybe a problem in one of the float bowls ? if fuel level is off the venturi effect don't work so great.
    ... that would do the same symptoms you described.
    ? fuel level too high maybe, on Some carbs you can accidentally install floats upside down and it's a bitch to spot that.
    Last edited by TrialsRider; 10-03-2018 at 11:47 AM.

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