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Discussion Starter #1
Ok, got my "new" CL350 engine up and running....oil leak fixed at cam chain tentioner....there was only 1/4 a gasket!!! some idiot's..... Anywho, I have a problem, Im using Kinihn slide carbs and It sinply wont idle unless I hold the throttle back a bit. Ive tried all the normal adjustments, am using 117.5 main jets and im at about 4500 feet or so. Ive had to adjust the top cable screws on the carbs till there almost all the way out, so now the idel screw is pointless! The cable adjustment on the throttle is all the way out....what am I doing wrong? It was perfect on my olf SL350 engine, I didnt change a thing, till I learend it would not idle... Ideas? should I go down to 110 main jets? Thanks!
 

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Sensei
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As counter-intuitive as it seems, bolting up SL 350 slide type carbs to a CB or CL350 engine doesn't work very well......... The SL head has much smaller intake port and carb venturi (to increase intake velocity) the CB and CL have larger ports and a larger throated (BUT CV) carb.....
The "step" in the intake tract caused by this size difference (from 24 to 28mm) alone is enough to cause problems..... You can either swap heads, or put the right size/type carbs back on.... (different cable for the CV carbs as well...)If you MUST have slide-type carbs, you'll need ones with a 28mm throat, (or 30'mms, but you'll have to "flow" the intake passage ...Not a job for beginners).... Then you'll have to "play" until the jetting is correct.....
 

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Discussion Starter #3
ok i have the CV carbs still, but I just got new jets for the slide carbs....I wanna try that first and rerout the cable...maybe that is causing problems too. I'll start on that in the morning...
 

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Discussion Starter #4
I forgot to mention my CV carbs are off an electric start SL...the 1969 year...will that matter any?
 

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Sensei
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As long as the port sizes are matched (same size as carb throat) it will work..... Changing the jetting in the PW 24's ...WILL NOT SOLVE the problem...ALL the 350 CV carb heads have (nominally) 28mm intake ports
Technical explaination:... As the fuel/air charge travels down the intake tract, it SUDDENLY has room to expand from a 24mm circle to a 28mm circle....This expansion slows down the charge enough that NOT enough enters the cylinder before the valve closes (a part of the explaination why you need the slide "overlifted" to get an idle)
Actually, it's a LOT more involved....But you should get the idea
 

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Discussion Starter #6
Is this why, when I am able to get an idle (With all the adjustments maxed out) it'll sometimes rev up to 5 grand on start or when I release the throttle it is so SLOW to come back down?
 

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Discussion Starter #7
Ok, after a LOT of work...(Timing, adjustments, ect) I got the slide pulls to work GREAT on my CL350 engine....did not need to "Flow" the head or anything...am using 117.5 main jets and ?? on the idle jets (Didn't bother to check) also using K&N Filter pods, I got rid of the stock air boxes. I had re cleaned my CV carbs, and put those on and not only did I have zero power (Could only get up to 30 Mph!!! :( ), but they mae the bike sound like crap....I mean seriously, the CV carbs affect the bikes sound ALOT! (I'm only running straight pipes with a end baffle). No more horrible idel issues (Least not now) with the exception of a slight 200-400 RPM ups and downs. It's holding well at about 1400 RPM, with amazing amount of power, MUCH more than the '71 SL350 engine I was borrowing...he can have his SL's, the gearing is different too, least in 1st....anyways thats my update.
 

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Sensei
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Glad you finagled it to work, but it would work better with a tapered "ramp" to adjust the size difference.....Regardless, the 1400 idle IS a bit high, and you probably can do better if you get the carbs accurately syncronized......It will/could also lessen the up and down 200 revs problem.....
 

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Discussion Starter #9
how would I go about making a "ramp"? I can visulize what your speaking of, but how to make one....got me on that!
 

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It should really be "flowed" or ported by a professional or at least someone that's done it enough to have experience in that area. It takes an old "hand" to do it right. Unless you're very good at using a die grinder yourself.

GB :mrgreen:
 

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Discussion Starter #11
Ifits all that, it can wait till I rebuild the engine, anyways next engine for it is a CB350 with a 69 electric start SL350 head, so I should be fine when it comes time to swap engines...I thought I could just make something and stick it in the intake to make a ramp....
 

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No, the manifold and the head have to be "flowed" together by removing, and in some cases adding material where the two meet. Then polished.

GB :mrgreen:
 

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Discussion Starter #13
but I will be able to use my sl350 head on my cb350 im rebuilding right and thatll fix any of these problems, correct?
 

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I honestly have no idea on that one? I just know what's involved in porting work and have mildly ported some two strokes and altered their timing by doing so (RC's). It's easy to smooth out port imperfections and polish them but port matching requires major skill and a VERY steady hand. Steve will likely know as he used to work for the CIA, KGB, FBI, and still takes a spacewalk for NASA once in a while.. :lol: Seriously though, he knows what will interchange on these old bikes better than anyone I've ever came across.

GB :mrgreen:
 

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CPC... Once you are back using the SL head, you are fine..... A plate of 3/8 aluminum (cut like a manifold gasket ) could be internally "ramped" with a taper to smooth the flow for now....Don't forget to add a "real" gasket(s) so it seals.... Plus, as a bonus, it will give you some added "low-end grunt" ....We used to call these "torque-plates".....
Steve
 

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Discussion Starter #16
Ok that sounds better than having the entire head machined....only machinging I want done to my head is to shave about 0.03" off the bottom for more compression....So I thke it a SL head will fit, no problemo on a CB or an CL? It seems to line up and fit correctly on my CB, with the exception of different holes...they line up and all, only one is circles the other is different, but I for get the shape. Im sving the $$ for new rings and for gaskets....this place sells our gaskets individually! http://www.northcityvintagehonda.com/se ... L350+Twins :)
 
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