1974 CB360 Fallin' Ditch Hell Ride

[irk miller]

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.

 

[cxman]

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

 

[crazypj]

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?

 

[irk miller]

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?

 

[crazypj]

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

 

[irk miller]

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...

 

[teazer]

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.

 

[teazer]

Here's one of the pages

 

[cxman]

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

 

[crazypj]

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

 

[irk miller]

Here’s the situation:

Slides are 2.5 cutout
5F21 needle
O-8 Primary needle jet
130 main jet
30 slow jet

I bought a P-0 bleed style needle jet to replace the primary style.

Sent from my iPhone using DO THE TON

 

[Sonreir]

What size bleed style did you end up with? In my (limited) experience, you usually have to go a lot bigger on the needle jet when you swap from primary to bleed. Often a full letter up, or more.

 

[irk miller]

What size bleed style did you end up with? In my (limited) experience, you usually have to go a lot bigger on the needle jet when you swap from primary to bleed. Often a full letter up, or more.

Went from O-8 to P-0.

 

[Sonreir]

Cool. I'm interested to see how it turns out. Been meaning to go to VMs on my 378 for a while.

 

[MiniatureNinja]

this is a great build I have been following from the start, regarding the oil injection into the rocker box, does that just dump into the galley or does it intersect with the end of the camshaft where oil can move around the cam and into the galley

 

[irk miller]

this is a great build I have been following from the start, regarding the oil injection into the rocker box, does that just dump into the galley or does it intersect with the end of the camshaft where oil can move around the cam and into the galley

Thanks. Hopefully, a little a both. The hole lines up directly with the end of the cam shaft, but it's above the seam between the head and the cover.

 

[MiniatureNinja]

Great, I've seen a lot of oil mods but yours is the most clearly photographed and seams simple enough! yours is the version I will attempt

 

[irk miller]

Great, I've seen a lot of oil mods but yours is the most clearly photographed and seams simple enough! yours is the version I will attempt

It took me a minute to dig it up, as I couldn't remember if it was the 3RM CB360 or Kanticoy's Gretta. On Gretta, Kanticoy did it similarly, but he drilled the valve cover at all the journals and used a rail to feed the oil. He may be using a pump and reservoir, but I can't remember. I do know he's using an external oil cooler.

http://www.dotheton.com/forum/index.php?topic=10530.1270

 

[crazypj]

Yep, I have full breakdown somewhere, found an electric pump that wouldn't 'kill' 360 generator but I don't remember if external reservoir was added as it would need drain back to sump.
Over-engineered in my opinion but I believe zero chance of cam/rocker damage plus all the extra lines, distribution points, etc. looks damn cool 8)

 

[MiniatureNinja]

I know that there are micro oil pumps out there for industrial or specialized applications, I would love to find one that wasn't much larger than the starter solenoid and do it that way