Topic: SL350 Engine vs CB/CL350 Engine Questions

[bill440cars]

 My situation concerns the fact that I have a SL350K2 rolling frame and a CL350 engine. Now, I am aware that the SL head has different porting along with a different cam for more torque (also has non-CV carbs). My questions are : #1 Would getting an SL cam and putting it in the CL head be worth the effort? #2 Or would the SL head be needed to make it worth the effort? I can get the cam for $20. This bike will be built for messing around in the woods (up and down hills too) and never see any "road time", while I have it.

Opinions? Comments?

[mlinder]

Doesn't the SL also have a lower ratio top gear?

I doubt there is really a noticable difference in most applications between the SL and CB/CL power delivery. I probably wouldn't bother.

[754]

I am not so sure heads are different or even the cams.. sure you can mix and match it all.

What I do know, first SL had CV,s I think, then changed..
 differnt cases on SL,s, maybe not 1st year..

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

some 350 twin rockers are different,  early ones allow more lift I think..

 I have CB350 partsbook, maybe SL too, if so I can provide proof with numbers..

[mlinder]

Only thing I heard was different was the top gear.
And the frame is different..
But I never heard of head and cam being different.
I've been wrong about plenty of stuff though.

[bill440cars]

Doesn't the SL also have a lower ratio top gear?

I doubt there is really a noticable difference in most applications between the SL and CB/CL power delivery. I probably wouldn't bother.

       Wasn't sure about the gear ratio between the 2. The only difference between the CB350 and the SL350K1 was 3rd gear (1.269 vs 1.280) which jumped the Final Gear Reduction from 2.250 (with a 16T countershaft Sprocket & 36T Drive Sprocket vs 2.500 (no input about SL  sprockets). Then the SL350K2 is TOTALLY different:

             CB350          SL350K2              SL350K2
    1st     2.353           2.353                 2.866  
    2nd    1.636           1.636                 1.800
    3rd     1.269           1.280                 1.333
    4th     1.036           1.036                 1.035  
    5th     0.900           0.900                 0.870
  
   Final    2.250           2.500                 2.625

    I used to have the differences around here somewhere and can't seem to find them right now. I have to check out the fit of the Cl engine into the SL350K2 frame also. You see, the SL350K0 was the only SL350 with the electric starter and the frame was completely changed for the K1. I Have /u] noticed an upper half of an SL350 case along with the alternator housing on ebay also and the price doesn't seem too bad. You see, I'm probably going to have to get into this engine anyway. That SL head might even have smaller valves, I don't remember right off. Appreciate your input Mark.  

[bill440cars]

      Yeah, the frame was changed for the K1 model and a 21" front & 18" rear wheels (K0 & K1 had a 19" front & 18" rear) along with aluminum fenders were added on the K2 model. I had read somewhere about the differences and can't seem to find it now! When and If I find it, I'll post it. There were a number of changes in the short time the SL350 was produced, just to try to keep it on the market and be competitive, but the XL250 and then the XL350 were replacements.

   By the way, I just went to Crotchrocket.com and found the P/N for the SL350K2 Cam, which I then cross referenced to see where all it was used and the only 350s that used that particular cam was the SL350K1 & K2.
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SL350K1 A MOTORCYCLE, JPN, VIN# SL350-2000001
Assembly: CAMSHAFT + VALVE
   CAMSHAFT (Honda Code 0229971) (SKU: 14101-312-030) (Superseed: 14101-312-040)    1    $249.57    Add to Cart        [Click to view details]
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SL350K2 A MOTORCYCLE, JPN, VIN# SL350-3000001
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   I then went back and checked the head P/N and found out the same thing. I haven't gone any further. I'm just trying to find out what differences there are and what parts are the same.
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SL350K1 A MOTORCYCLE, JPN, VIN# SL350-2000001
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SL350K2 A MOTORCYCLE, JPN, VIN# SL350-3000001
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     I hope you all understand that I'm looking to learn all I can about the differences between them and use that info to my advantage and that's all. 

                   Thank you Mark & Frank for your input, Bill
     

[mlinder]

The downtubes were different on the SL, that was what wa smost noticably different to me.
Supposedly a litte stiffer, so some of the cb350 racers like to get ahold of the SL frame, and they like the gearbox from the SL more, too.

[754]

Different downtubes?? whole new frame I think, the CB is a single downtube splitting near the bottom and SL is twin downtube.

[mlinder]

Different downtubes?? whole new frame I think, the CB is a single downtube splitting near the bottom and SL is twin downtube.

I wasn't saying they werent different frames, I was saying that was the difference I noticed.

[bill440cars]

       Okay, I just did some more P/N checks and comparisons and I'm getting the idea that the SL350K0 engine was just a basic 350 twin. The head P/N for the SL350K0, also relates to the CB & CL350 heads.
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SL350 A MOTORCYCLE, JPN, VIN# SL350-1000001
Assembly: CAM CASE + CYLINDER ...
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CB350 A MOTORCYCLE, JPN, VIN# CB350-1000001
Assembly: CYLINDER HEAD
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CB350 A MOTORCYCLE, JPN, VIN# CB350-1000001
Assembly: CYLINDER HEAD
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CB350 A MOTORCYCLE, JPN, VIN# CB350-1000001
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CB350 A MOTORCYCLE, JPN, VIN# CB350-1000001
Assembly: CYLINDER HEAD
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CL350 A MOTORCYCLE, JPN, VIN# CL350-1000001
Assembly: CYLINDER HEAD
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CL350 A MOTORCYCLE, JPN, VIN# CL350-1000001
Assembly: CYLINDER HEAD
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CL350 A MOTORCYCLE, JPN, VIN# CL350-1000001
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CL350 A MOTORCYCLE, JPN, VIN# CL350-1000001
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      Be interesting to know how much Honda spent trying to keep the SL350 in production.  Frame, Carbs, 21" front wheel, gastank, fenders switched to aluminum, head, the top of the triple tree, is the same as the early XL250 & XL350, best I can find out (by P/Ns), yhe K0's rear rim was only made for the K0! Also, I think I remember that the top part of the triple tree of the K0, was made only for the K0 (by P/N).

          You know, I have all of the respect for the first model of nearly anything but, if I had the choice of an SL350K0 and an SL350K1 or K2, I wouldn't even have to think about it, the K2 would be sitting in my driveway ASAP! I'm not sure about the K2, but I read that there was the Sl350K1 weighed 60lbs less that the K0! (frame, no electric starter and smaller battery for sure. Not sure what (if anything else) else.

                         More coming as I get it.
   
      
   

[darkbane]

I just purchased a '71SL350K1 a few months back to make a small bobber project.  I also have a '72 CL350K2. 

The SL350 is MUCH Lighter than the CL.  Granted mine is pretty stripped down...can be seen here:
http://www.halffastchicago.com/forum/index.php?topic=173.0

Not having the ugly front starter, aluminum wheels, smaller headlight, super light weight Exhaust (CL pipes are heavy), all seem to make a weight difference.  Unfortunately I don't have my project running to be able to tell you the difference in power/torque.

[bill440cars]

darkbane,

               I just got through checking out what you have gone through with your SL and you are making Quite a statement with that one. Thanks for posting that link so we could check it out!        
       I figure on leaving off anything that's not needed, but, mine will not be on the street, so I'll be looking into a low cost way to eliminate the battery, all lights and might see about making a wiring harness that will only include the necessary wires. Mine will be running trails, going through the woods and such as that. So, with that being said, I will definitely be keeping the rear suspension.     

                            Take care, Bill

[754]

Bill, do you have pics of a yellow rig??

I got the part #s for K5 CB/CL 350 and Ki SL 350 , the heads and the cams are different.. I am starting to think maybe SMALLER ports on ths SL...?

[bill440cars]

   Frank, I'll have a PM to you later this evening. I do have some pictures.

   
    Now, I have another question about the SL350. The Sl350K2 weighs about 306lbs. If I can successfully eliminate the battery, lights, lights and mufflers (and anything else that I or you all can think of), leaving it with either the aluminum fenders or plastic ones, it makes me wonder just how much weight I can shave off of it? Honda took about 60lbs off of the SL350 when they removed the electric starter, Changed the frame, reduced the size of the battery and I don't know what all. I'll probably use the aluminum stock fenders, since I have them. Thinking about making a wiring harness that would include only the necessary wires and putting the original harness up (that would save some weight. If I put an aluminum, plastic or fiberglass tank on it. that would help too. Thinking about pods instead of air cleaners and a smaller (lighter) seat also.

         Here's a shot of an SL350 K2

     


        And here is one with plastic fenders


     
         

[mlinder]

Pretty sure the SL came with aluminum rims, too.
Theres some weight loss, too.

[bill440cars]

      I AM getting kinda interested in getting to the point to where I can see just how much more weight I can shave off of this bike.

[bill440cars]

Pretty sure the SL came with aluminum rims, too.
Theres some weight loss, too.

       Not sure about that Mark, mine doesn't, but I don't know how much of mine is stock. Since my last post here, I've learned that I can't just swap out the upper case half, to get rid of the electric starter mount. I'm going to have to swap out both case halves and the left side cover (that mounts the alternator stator coils) also or carefully trim off the part of the upper case half that the starter mounts on and reshape it, where I would have cut it off. Oh well, I've got time.    

[scunny]

Bill, does it require the battery to run or does it just need that for the starter and lighting ?
my 79 XL250s had a battery but I just junked that since mine is purely off road.

[bill440cars]

Bill, does it require the battery to run or does it just need that for the starter and lighting ?
my 79 XL250s had a battery but I just junked that since mine is purely off road.

        I believe that it is setup to include the battery, like the CB & the CL. Best I know of, it has basically the same electrical system. That capacitor setup, I was talking about, would take a charge as the engine was running and hold it, making it capable of using some lights while the engine was running. Not sure what kind of electrical system the XL has, since I haven't had any experience with those. I HAVE had some time with 2 stroke enduro type bikes of the early 70's and I could just unplug the ignition switch, if I couldn't find the key (it had a magneto though). The  SL350 has an alternator and that's why I don't think I can make it work without some sort of "Battery Eliminator". Appreciate the input though. I'm ALWAYS open to suggestion. How's that XL doing BTW?

[scunny]

haven't ridden in 4 months due to a bung shoulder so my brother has borrowed the XL. he says it's running great

[bill440cars]

haven't ridden in 4 months due to a bung shoulder so my brother has borrowed the XL. he says it's running great

        That's good that the XL is running great, not so good that you've got that shoulder problem. How much longer you going to be down with that? Hope things are healing up quite well.

[scunny]

off work for probably another 3-4 months.
on the bright side I should be able to finish the 650 soon

[TomC]

Hi Bill
     Do the CB, CL, & SL 350s have a permanent magnet rotor in the alternator? If so they can be made to run with out a battery.
          TomC in Ohio

[bill440cars]

Hi Bill
     Do the CB, CL, & SL 350s have a permanent magnet rotor in the alternator? If so they can be made to run with out a battery.
          TomC in Ohio

       Tom, I owe you an apology. When I saw your post here just now, I thought I remembered seeing that question before, so I checked and found that you'd posted over on the Battery Eliminator and I never responded to it. Completely slipped my mind. Sorry bout that. Now, to answer this question. Yes, the SL350 (I assume the CB & CL are the same also) has a permanent magnet type rotor. S, I am all ears, as to what I need to do to make this engine run without a battery.

[TomC]

Hi Bill
     With a permanent magnet rotor alternator electrical power is being generated any time the crankshaft is being turned. If the crankshaft is spinning fast enough the alternator will produce enough power to run the ignition system.
     The first question is can you kick it over fast enough to start. My guess is the answer is yes.
     My guess is that the 350s use a bigger & better version of the charging system on my Super 90. Which has six generating coils. One pair of coils is connected when the engine is running and the other two pairs of coils are switched in when the lights are turned on. There is a rectifier but no voltage regulator. Voltage regulation is by matching the load with the output of the alternator and using the battery to take or give back the difference.
     If the 350 is of this general type you can test to see if you can start with out a battery by. Get a capacitor. I have a 10,000uF that I payed $2.50 for should be more that enough. With the key of the 350 turned off, and it stays OFF for all of this, connect the capacitor in place of the battery. The capacitor should be polarity sensitive. The one I have has a black dot on the negative terminal. At this point put a voltmeter across the capacitor and give the kick starter a few kicks and see how much voltage is produced. I would expect to see at least 15V. If there is good voltage then connect the positive terminal of the capacitor to the wire going to the coils, black with a white stripe maybe?, and try to start the 350. If the 350 starts great. If not adding the lighting coils will help.
     If the 350 started the next problem is that the alternator may be making more power that the ignition system needs. An automotive ballast resistor in series with each coil may be enough. Test for this problem by checking the voltage across the coils.
     Do you have a link for a 350 wiring diagram, just the diagram please, that I could down load. It would help me to keep from sending you down the wrong road.
          TomC in Ohio

[ohiocaferacer]

Bill,

Yes....you can make these bikes run without the battery by changing the stator/alternator in to an engery transfer magneto. There are a couple articles at my website about this.

I have done this on my CB175 race bike and it works......the problem is getting the spark advance set to fire at proper timing for higher rpms. If you get the bike to run at idle....it tends to bog down at higher rpms......if you get it to fire at higher rpms....it wont idle.

I was able to get my bike to run with the ETM, but above 5 or 6K the bike bogs down(using stock coils). Think I have to use low resistance coils...have some yamaha RD coils......but havent got them to work yet.

So.....overall it works.....but still havent got it to run perfect yet.

[bill440cars]

      Hey Greg, Thanks for that. I'm looking for any input on the subject because I want to put together a "play in the fields (or woods) bike that will be as bare as possible (with mostly what I have on hand) Now, I have a 72' SL350 rolling frame and another 72' (that I want to put together as a decent looking example of the SL350) So, after I remove anything that I could use to resurrect 1 72' the other one will be the "Bare Bones Play Bike". I need to try to come up with a low priced (it that's possible) set of SL cases to put the CL engine(that I already have) into. The CL engine might bolt into the SL frame without removing the "Protrusion" that the electric starter bolts to, but it would not look right ans so, I can either swap out the cases or attempt to remove that portion of the upper case half (and try to make it look as if it never existed) or swap the cases. I thought about swapping out the upper case half (there is one on ebay, but kinda "up there" pricewise, for my budget) but I didn't know it that was feasible. I'm concerned that the SL upper case half won't mate properly with the CL lower half. Any input on this , would be appreciated.


        BTW, good to hear from you Greg,  Bill      

[kirkn]

Hey, Bill,

A fellow by the name of Wayne Huff over on the Thumpertalk Forum, vintage sub-forum has done a no-battery conversion of the early Honda SL100.  This would be virtually identical to what you'd want to do to your 350.  Other than the 6-volt / 12-volt differences and 1-cyl vs. 2-cyl, I think it would work perfectly.

Here's his website where you can find a very good write-up on how to do it.  http://waynescyclegarage.mysite.com/

A couple guys over there have done it per his instructions, and all rave about it.

Good luck.

*edit* - here's Wayne's write-up from a thread he posted on the subject on The XL Forums on oldrice.com:

SL 100 battery free!!

Heres how I did it which is easily reversable if you don't like it which I can't imagine.
This is for racers or bikes that need no lights and is not a cure for tuning problems etc.

You will need an AC coil (where the plug wire comes from). I used one from an old Honda Express which had the condensor (capacitor) built on. Just about any coil from most of the two stroke magneto powered bikes will do if you can mount it.You will need a Honda rotor puller. Do not try to remove the rotor without it, It is basically just a short bolt but would be a good investment(cheap) and will remove just about every Honda rotor out there.

STEP ONE: Start with a well tuned SL , the point gap and timing should be in specs.If not your reference points will be wrong.

STEP TWO: Lock the advance to full. I simply removed the bolt/washer that secures the point cam and advance mechanism,I found the perfect washer that just fit over the camshaft end and was just thick enough to bind the point cam in a fixed position.(full advance).when I replaced the bolt & washer.There may be many ways to lock the advance but this was so easy.

STEP THREE: Remove the rotor and woodruff key. Set the key aside as you will not need it. Clean the rotor and crank taper with contact cleaner etc to remove all oil and residue so the rotor will not slip.Turn the engine over to the point the contacts just start to open (fire).Install the rotor with the magnets aligned with the windings on the stator. If the holes instead of magnets are lined up with the coils you will have no spark when you need it.Replace the rotor bolt and tighten to normal torque. It should not slip as the taper is the main thing keeping it in place and not the key.Scribe your new fire and TDC mark on your rotor for future tune ups.

STEP FOUR: Unplug the harness coming from the stator.It should have 4 wires, one is for the neutral light switch. Remove that one to get it out of the way.That leaves three, you will use two.The pink wire goes to your newly installed AC coil.The yellow wire goes to ground to complete the circuit. The other one is not used at this time.

STEP FIVE: Wire you up a simple kill button or switch, remove the rectifier, uneeded fuse and excess crap and enjoy the simplicity.

I have had time to test this and it works great, the bike should start easy as ever and maybe even run better.Mine hits a little harder from the bottom(the advanced timing). Play with your timing some if you want just remember the magnets have to line up with the windings when it fires.I like things as simple as possible and I don't have to worry about keeping a battery charged as well as the weight and corrosive propertys of a box of lead and acid!

Your bike will crank and run with the original DC coil but do not be tempted to ride it! It can cause major engine damage like holes in pistons.The AC coil is key to this mod.Now what do I do with all that extra room where the batt and rectifier went? I'll think of something.

Thanks for all the help, This works really well and should give you no problems.

DirtHippie, wayne huff

I will remove the extra windings in the stator soon and will update that procedure.

[bill440cars]

       Tom C, I am so sorry that I completely passed through without acknowledging your post. I read what you had to say, then I read what Greg posted and completely forgot to thank you for the info and all. I'm trying to soak up all I can and apply what I can to this "Mixed Up SL350". Sorry about that. I DO try to recognize each and every one that puts in on any post that I am involved with.

                                 Thank You, Bill

[bill440cars]

       Hey thanks Kirk for your input on this too! Man, with all that I'm learning about this, I should be in business! Here is a photo of a 71' SL350 (unless someone could give me an assist here) just try to picture this bike without the light, gauges, mirrors, a smaller (but adequate) seat, open air behind the carbs (with pods) where the side covers, battery and other electrical items (that won't be needed) were  and stock exhaust system (replaced with something higher up & lighter). Have I given enough info that someone might be able to modify this photo and make it resemble, at least somewhat of a resemblance of my vision for that SL350?  would certainly appreciate it.

         

[bill440cars]

       Bumping this forward, so I can more easily find it to access the info on setting it up to run without Battery Voltage. Got some pretty good info, thanks to Tom C, Greg (ohiocaferacer) and Kirk (kirkn). Just might be able to work this out to where even an "Old Man" can kick start this thing!