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Author Topic: 1974 CB360 Fallin' Ditch Hell Ride  (Read 33392 times)

Offline irk miller

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Re: 1974 CB360 Fallin' Ditch Hell Ride
« Reply #440 on: Nov 13, 2017, 09:10:59 »
goes up in 2.5 increments

125 127.5 130 132.5 ect till you hit 200

in the video it still sounds a bit boggy or timing late

and if your needle is that high you may want to go a bigger jet needle or needle ?

what do you have and are they both the same

how is your idle to 1/4 mixture

what slide do you have both the same ?
Thanks Murray.  I think I lost sync on the carbs (or I never had it).  It feels too much like a buzz box.  The idle seems good, nice and smooth and with good rpm.  No starts without choke.  When I set them up originally, I did it in Augusta when it was still in the upper 80s.  The day of the video it was low 50s and wet, plus I'm in the foothills near the NC/SC border.  Not sure how much any of that factors in.  I haven't looked at the numbers on the needle or the slide, but I can pull the carbs this afternoon and check everything I have.  I was hopeful I could get by with just a needle position change and the main jet.  The plugs look good for whatever that's worth.

Offline cxman

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Re: 1974 CB360 Fallin' Ditch Hell Ride
« Reply #441 on: Nov 13, 2017, 11:55:20 »
meh good plugs on mikunis mean your not close enough to the edge lol

but i would quickly strip them to make sure they have the same parts and you are not chasing a mismatch

then go from there

to small a slide it will run ok but not produce the power it can till 7/8 to wide open when the slide is above the venturi
1978 CX650 Super Deluxe
1979 XS1100 Special
1974 xl350
1983 cx650 Custom
1973 cb750
1980 cb750
1981 cb650
1982 cb900 c
1974 kawasaki 350 bighorn
1983 GL1100 aspy full dress
1983 GL1100 Nekid
and a bunch of others

Offline crazypj

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Re: 1974 CB360 Fallin' Ditch Hell Ride
« Reply #442 on: Dec 12, 2017, 19:10:56 »
cxman, what do you mean by too small a slide? The cutaway?
The 2.5 or 3 in almost every Mikuni VM is too big a cutaway for 360/378 and gives a bad pick up/acceleration. Smaller cutaway gives higher airspeed over rimary choke and can cause too rich a mixture when accelerating, that's when you need a bleed type emulsion tube. You can get something very close from Yamaha RD350/400 aircooled or some of the earlier two stroke 350 'Banshee' ATV's, late models had some weird carb mods and I can't remember if emulsion tubes are the same?
'you can take my word for it or argue until you find out I'm right'
I gave my girlfriend an orgasm the other night, but, she spat it back at me
 Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying 'End-of-the-World Switch. PLEASE DO NOT TOUCH', the paint wouldn't even have time to dry
 Itís not worth doing something unless someone, somewhere, would much rather you werenít doing it  (Terry Pratchett)
CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline irk miller

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Re: 1974 CB360 Fallin' Ditch Hell Ride
« Reply #443 on: Dec 12, 2017, 19:37:18 »
cxman, what do you mean by too small a slide? The cutaway?
The 2.5 or 3 in almost every Mikuni VM is too big a cutaway for 360/378 and gives a bad pick up/acceleration. Smaller cutaway gives higher airspeed over rimary choke and can cause too rich a mixture when accelerating, that's when you need a bleed type emulsion tube. You can get something very close from Yamaha RD350/400 aircooled or some of the earlier two stroke 350 'Banshee' ATV's, late models had some weird carb mods and I can't remember if emulsion tubes are the same?
Are you saying it needs to be a 2.0 or smaller slide with a bleed type needle jet? 

Offline crazypj

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Re: 1974 CB360 Fallin' Ditch Hell Ride
« Reply #444 on: Dec 12, 2017, 20:49:33 »
Yep, can't remember specifics, probably have it written down somewhere?
There is a lot of misinformation on VM modifications, much of it written by peole who don't understand how a carb works. You can make almost anything run and seem OK until you try something that is actually running properly.
I have several sets of VM's in various sizes (mostly for XS650's) the ones that 'work' all have emulsion tubes not 'primary choke'. I think I posted about it in 2009 or 2010? Photbucket has screwed everyone though so I'll re-do post when I get time and inclination.
Just spent some time getting software and did section of VM manual showing both types of needle jet.
Not quite the picture I wanted but OK
« Last Edit: Dec 12, 2017, 20:58:37 by crazypj »
'you can take my word for it or argue until you find out I'm right'
I gave my girlfriend an orgasm the other night, but, she spat it back at me
 Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying 'End-of-the-World Switch. PLEASE DO NOT TOUCH', the paint wouldn't even have time to dry
 Itís not worth doing something unless someone, somewhere, would much rather you werenít doing it  (Terry Pratchett)
CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline irk miller

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Re: 1974 CB360 Fallin' Ditch Hell Ride
« Reply #445 on: Dec 12, 2017, 20:55:39 »
Yep, can't remember specifics, probably have it written down somewhere?
There is a lot of misinformation on VM modifications, much of it written by peole who don't understand how a carb works. You can make almost anything run and seem OK until you try something that is actually running properly.
I have several sets of VM's in various sizes (mostly for XS650's) the ones that 'work' all have emulsion tubes not 'primary choke'. I think I posted about it in 2009 or 2010? Photbucket has screwed everyone though so I'll re-do post when I get time and inclination.
Just spent some time getting software and did section of VM manual showing both types of needle jet.
Not quite the picture I wanted but OK
These carbs are much closer than I've been so far, but there's certainly a lot of work to do to get them right.  It has some spots where I think it goes lean. 
There's a a thread in Hondatwins you posted with this pic...



Offline teazer

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Re: 1974 CB360 Fallin' Ditch Hell Ride
« Reply #446 on: Dec 12, 2017, 21:29:59 »
With our tiny Hondas we tried all manner of needle jets and even when we thought they were running right with Pilot types, the amount of unburned fuel was way too high.  So we went to bleed types and that improved fuel atomization and made slightly more power while using less fuel. There's another page from an old manual somewhere that shows how fueling changes in a Bleed versus Primary needle jet.  Basically at the same throttle openings, a primary type will get progressively richer than a bleed type as revs increase.  That makes them great for 2 strokes that need more unburned fuel to keep them cool when run hard.

That same books showed the effect of air jets on fueling with bleed types and height of fuel shroud on primary types.  I should probably dig out those scans and post them somewhere.
 

Offline teazer

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Re: 1974 CB360 Fallin' Ditch Hell Ride
« Reply #447 on: Dec 13, 2017, 01:42:04 »
Here's one of the pages


Offline cxman

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Re: 1974 CB360 Fallin' Ditch Hell Ride
« Reply #448 on: Dec 13, 2017, 08:05:01 »
a 2.5 should be about right but with the 28 a 3.0 would not scare me and might be better at cruising

they only make bleed type jet needles in very small sizes so i dont bother with them a lot as i am above in size most of the time

tell me what you have in it or better give me a quick call and we can figure it out and i can tell you how to do the sync
1978 CX650 Super Deluxe
1979 XS1100 Special
1974 xl350
1983 cx650 Custom
1973 cb750
1980 cb750
1981 cb650
1982 cb900 c
1974 kawasaki 350 bighorn
1983 GL1100 aspy full dress
1983 GL1100 Nekid
and a bunch of others

Offline crazypj

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  • Split personality, I fake being smart
Re: 1974 CB360 Fallin' Ditch Hell Ride
« Reply #449 on: Dec 13, 2017, 22:54:55 »
Coo, that's the pictures I was looking for last night. They are from a 1974 Suzuki carb manual.
There's one on eBay but way overpriced
https://www.ebay.com/itm/Suzuki-Carb-Carburetor-Shop-Service-Repair-Manual-9-74/140663475336?hash=item20c0324c88:g:K~UAAOSwkNZUar9C&vxp=mtr
(I think I paid around $12~$15.00 for mine15~20 yrs ago)
The main reason to have a smaller cutaway is to help prevent major 'flat spot' if throttle is opened too fast at slow speed. The best emulsion tubes I've ever had in XS650 (or 800) were a pair I made with a higher discharge height (only by 1~2mm, I forget, it was a while ago) Doing the cross drilling in brass was a 'challenge' to say the least which is why I aven't made any more
« Last Edit: Dec 13, 2017, 23:01:29 by crazypj »
'you can take my word for it or argue until you find out I'm right'
I gave my girlfriend an orgasm the other night, but, she spat it back at me
 Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying 'End-of-the-World Switch. PLEASE DO NOT TOUCH', the paint wouldn't even have time to dry
 Itís not worth doing something unless someone, somewhere, would much rather you werenít doing it  (Terry Pratchett)
CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0