collapse

www.dimecitycycles.com


www.restocycle.com

www.CITYLIMITMOTO.com

www.jadusmotorcycleparts.com

www.bisonmotorsports.com

www.speedmotoco.com

www.lostapostlejewelry.com

www.cognitomoto.com

www.townmoto.com

www.sparckmoto.com

www.Moto-Madness.com

www.pistonsociety.com

www.steeltowngarage.com


Author Topic: Jetting for rebuilt filters CB360  (Read 518 times)

Offline Tonnotyetdone

  • Posts: 22
Jetting for rebuilt filters CB360
« on: May 22, 2017, 16:34:00 »
Working on getting a 1976 CB360 road ready.  The filters were shot, so I cut out the paper element and replaced it with UNI filter foam (60 PPI).  Otherwise, the stock air boxes are unmodified.  I first heard about doing this on one of the forums, but I'm not sure if the carb jetting was addressed.  As far as I can tell, I am running a little rich with the 110 jets (starts without choke, but will start each time - as I understand it, too rich of a condition and it's a PITA to start when hot).  Haven't had a chance to sync the carbs and get a better feel for how she is running.  If anyone else has done this, have you found that you need to address the jetting as you would for a pod filter, or left as is with the stock airboxes?  Should I have used a different PPI foam?  Any feedback would be greatly appreciated!

Offline frogman

  • DTT SUPPORTER
  • *
  • Posts: 1964
  • '74 CB360, '71 CB450, '75 CB550SS
Re: Jetting for rebuilt filters CB360
« Reply #1 on: May 23, 2017, 10:12:24 »
Don't oil the hell out of the foam, more oil causes more restriction, just want very little bit. Get the carbs all tuned up correctly and then do some plug chops to see where you are.

Jets should be 95-100 from factory, later rebuild kits had the wrong stuff in them. Would suggest getting some so you can getting things sorted.

Idle mixture/pilot screws being set incorrectly can also cause hard starting as they control how much fuel it gets when its trying to start up. Good place to start is around 2 turns OUT then screw them IN or OUT for HIGHEST idle. Takes a little fiddling as you have to reset the idle screw once you finish a side.

Offline Tonnotyetdone

  • Posts: 22
Re: Jetting for rebuilt filters CB360
« Reply #2 on: May 30, 2017, 21:06:13 »
Thanks for the extra info!  The rebuild kit came with 100 and 110 jets, seemed to be running a little lean with the 100s, so the 110s were put in.  I don't think I super saturated the filters, but maybe enough so that the 100s weren't cutting it.  Might try some 105s to split the difference (after syncing the carbs, of course).  As far as the idle mixture screws go - I started at 1.5 turns out and played with it from there, but never heard any significant change in idle (the stock tach is little use for this task - creeps really slow, even with new and lubed throttle cable).  Any reason the idle mixture screws would have little to no effect at idle?  Carbs have been cleaned twice, hopefully ruling out blocked passages. 

Offline frogman

  • DTT SUPPORTER
  • *
  • Posts: 1964
  • '74 CB360, '71 CB450, '75 CB550SS
Re: Jetting for rebuilt filters CB360
« Reply #3 on: Jun 02, 2017, 09:18:41 »
If you can't hear or notice any change with the idle screws then you are either idling to fast or they are plugged. If the carbs are not synced you are wasting your time messing with the idle mixture as you are probably running more on one cylinder and the side is past that circuit in the carb and the other side is barely working.

Should be able borrow a spark pick up tach from Autozone or some place the "rents" tools.

Offline Tonnotyetdone

  • Posts: 22
Re: Jetting for rebuilt filters CB360
« Reply #4 on: Jul 07, 2018, 23:49:50 »
So I had the bike going for a few months, well enough to get it inspected with a clean bill of health.  All of a sudden, I am having trouble getting it to remain running (would be hard to start, then stall after a few seconds, seems like a fuel issue to me).  I am in the process of going through the tank, petcock, lines, and carbs (again, I'm afraid).  While doing a little research to see if it is a jetting issue with the increased temp and humidity, I stumbled upon the note in my carb  rebuild kit that states that #100 secondary main jets were used for 745B carbs #110 for 754A carbs.  My carb setup is a mixture of both (I cobbled together the carb using one original carb body and one I picked up on eBay - the 754A is the original carb, and this was before I knew there were different variations of the Keihin carbs used). 

My question is this - should I be using the correct jets per each carb body, or should they be the same on both sides.  I know I had it running with #100 jets on both carb bodies, but could the temp and humidity be affecting the 754A carb body with the undersized jet and causing my current running issues? 

As a side note, these issues did occur after I replaced the stock regulator and rectifier with a combo unit...I don't think this is the issue, but figured this couldn't hurt to add.

Offline Tonnotyetdone

  • Posts: 22
Re: Jetting for rebuilt filters CB360
« Reply #5 on: Jul 09, 2018, 13:57:24 »
Got the bike back up and running this weekend.  I'm thinking it was an air leak from one of the boots on the airbox side of the carbs...mine seem to require a bit of strategy to really get a good seal, and it would make sense since those were removed and reinstalled while swapping out the regulator and rectifier. 

My original question still stands though...I don't think it makes sense to have different secondary main jets, but given my setup and the recommendation from the carb rebuild kit, is it possible that this may be necessary, especially when the temp and humidity soars?  Why would the jetting on the 759A carb require a higher secondary main jet?  Something to do with the air jets on the top of the carb body? I imagine my best bet would be to eventually source a 745B carb body to make it consistent, but I would hate to do anything like that right now since it is operational.

I don't know.  Thoughts, please.

Offline advCo

  • DTT BOTM WINNER
  • *
  • Posts: 2460
  • Nick Ol' Eye
    • adventur Studios
Re: Jetting for rebuilt filters CB360
« Reply #6 on: Jul 09, 2018, 14:37:04 »
I wouldn't think you would really need to re-jet it if you're still running the stock airbox..

Sounds like you may have another issue at hand.
"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0
82 GS550L - Tracker-ish - http://www.dotheton.com/forum/index.php?topic=67229.0 - Sold
74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
73 Suzuki RV125 -http://www.dotheton.com/forum/index.php?topic=73875.0

Offline Tonnotyetdone

  • Posts: 22
Re: Jetting for rebuilt filters CB360
« Reply #7 on: Jul 11, 2018, 03:34:55 »
I'm mostly just wondering what the general consensus is regarding using the "stock" secondary main jets for the respective carb bodies - I think I will source a matching carb body at some point to make it consistent.  Again, it's running.  Not perfectly, but it starts and goes places.  At some point I will try to get it dialed in, but I don't think I can with the current setup of similar secondary mains and different air jets (again, not sure if this is the difference between the two carb variations, but it's the only thing I can think of that would make sense since everything else is able to be swapped out). 

Basically, if I don't have to purchase, dismantle, and rebuild the carbs again, and swapping out the secondary jet on the 754A carb body to stock #110 would provide consistency between the two carbs...I guess I am just looking to know why that would or would not work.

Offline frogman

  • DTT SUPPORTER
  • *
  • Posts: 1964
  • '74 CB360, '71 CB450, '75 CB550SS
Re: Jetting for rebuilt filters CB360
« Reply #8 on: Jul 13, 2018, 00:22:53 »
That jet is the main jet for when you are running at speed with the slide rising. You need them both to be the same unless you notice a major difference in mixtures between sides.  Plug chops and just overall running will tell you what you should need but I would personally run the same sized jet in each carb regardless of the model. I believe I run 115's in mine however I have CJ air filters and shorter pipes.

Getting matching bodies for the year you have is a good idea so that they are at least in theory the same.