Black and Gold Cafe - 71 CB350

[Korsch_RS]

Re: Black and Gold Cafe - 71 CB350 - Exhaust work

Thanks all!

I'm not really a fan of lots of chrome, so I'll be keeping it to functional chrome only (like on the forks). Final product (ever changing in my head) will probably have shiny stainless spokes, but the rest will be mostly brushed or satin finishes. These pipes will start life painted black, and will possibly get either ceramic coated or wrapped in the future.

There's enough flexibility to get then on and off when they were tacked (not 100% sure about fully welded). If I have problems installing the plan is a single slip-fit joint with spring retention in this section:

So after I got it all tacked together I promptly cut it apart to do the full welding. The right primary was cut off at the collector inlet tacks. I finished up the welding and smoothing on both primaries last night, I'll rejoin them and finish the aft section tonight, paint and final install should be tomorrow!

Also, got new tires!! Old ones were weather cracked

More soon!

 

[Korsch_RS]

Re: Black and Gold Cafe - 71 CB350 - Exhaust work

Well, exhaust is finished, installed, and painted.

I spent a lot of time this weekend just trying to get the VM30's I had jetted in, and after many trials and tribulations, I came to the conclusion that I need jets that I currently don't have.

My current selection:
2.5 slide
6F5 needle (middle clip position)
unknown needle jet
2.0 Air Jet
150 Main (have a selection from 130 to 220)
30 pilot (have a selection from 10 to 30)

I ordered the "Scott Turner" kit from DCC (3.0 slide, 6F4 needle, P0 needle, 2.0 Air, 150 Main, 50 pilot) along with 45 and 47.5 pilot jets, hopefully with those it will run nice, or at least idle. I could get it to idle on the 30 pilot, but if I touched the throttle it would immediately die.

So, because I really wanted to ride at least a little, I put the stockers back on and ripped around the block. Runs like crap with these (stock except for 115 Mains). Idles around 3000, pig rich off idle so it hardly revs and then shoots out little flames, then runs ok 5-7000, and kinda dies beyond that, but it was enough to get around the block, which was awesome! except that it stalled a couple times as it dipped below 3000 pulling away from a stop

Anyway, while waiting for the new jets I can get the tires installed.

More soon!

 

[axeugene27]

Re: Black and Gold Cafe - 71 CB350 - Trying to tune VM30's

interested to see what you come up with I have found 30 pilots to be pretty spot on but it sounds like you are a little lean. exhaust turned out nice man. nice job

 

[overdraft]

Re: Black and Gold Cafe - 71 CB350 - Trying to tune VM30's

your exhaust is VERY similar to mine (well yours is smoother under the bike, but they're both 2:1 with a shorty muffler) and i've got 140 mains and 40 pilots and i'm leaving a carpet of soot on the plugs, so rich somewhere, but the top half of the throttle is excellent, so i'm guessing my main jet is good and the soot is coming from the pilot/needle jet/needle end of the system. i've got some smaller pilots coming and i'll keep you posted.

 

[Korsch_RS]

Re: Black and Gold Cafe - 71 CB350 - Trying to tune VM30's

interested to see what you come up with I have found 30 pilots to be pretty spot on but it sounds like you are a little lean. exhaust turned out nice man. nice job

your exhaust is VERY similar to mine (well yours is smoother under the bike, but they're both 2:1 with a shorty muffler) and i've got 140 mains and 40 pilots and i'm leaving a carpet of soot on the plugs, so rich somewhere, but the top half of the throttle is excellent, so i'm guessing my main jet is good and the soot is coming from the pilot/needle jet/needle end of the system. i've got some smaller pilots coming and i'll keep you posted.

Thanks! We'll see how these work, I only ordered 45 and 47.5's in addition to the 50 pilots, so hopefully those will work. Unfortunately the expected delivery isn't until Monday

One thing I'm confused about on the low-speed VM30 tuning is the function of the air screw. From what I've read, it seems likes it basically helps make fine adjustments to the air/fuel through the pilot circuit, but I've seen some places saying that turning it in on the VM series makes the idle richer, and some places turning it out makes it richer. Does anybody know for sure which way is correct?

This is also my first ever vehicle with a carb, so this is all black magic to me, but I'm (very slowly) learning....

 

[Kanticoy]

Re: Black and Gold Cafe - 71 CB350 - Trying to tune VM30's

Turning in makes it richer on a VM. The air fuel screw is directly connected to the air jet hole in the mouth of the carburetor. You turn it in and it closes off that air passage, screw it out and it lets more air in. It's not connected at all to the choke circuit.

 

[teazer]

Re: Black and Gold Cafe - 71 CB350 - Trying to tune VM30's

That confusion is not uncommon. VM mikunis and almost all other regular slide carbs have an AIR screw on the filter side. Out = more air = leaner.

Mikuni BS CV type carbs and many Keihin CV carbs have a mixture screw on the engine side of the carb. On those, out means more (air and fuel) mixture through that drilling = richer mixture.

So slide carbs, out = leaner
CV carbs out = richer

 

[Kanticoy]

Re: Black and Gold Cafe - 71 CB350 - Trying to tune VM30's

There ya go.

 

[Korsch_RS]

Re: Black and Gold Cafe - 71 CB350 - Trying to tune VM30's

That confusion is not uncommon. VM mikunis and almost all other regular slide carbs have an AIR screw on the filter side. Out = more air = leaner.

Mikuni BS CV type carbs and many Keihin CV carbs have a mixture screw on the engine side of the carb. On those, out means more (air and fuel) mixture through that drilling = richer mixture.

So slide carbs, out = leaner
CV carbs out = richer

Turning in makes it richer on a VM. The air fuel screw is directly connected to the air jet hole in the mouth of the carburetor. You turn it in and it closes off that air passage, screw it out and it lets more air in. It's not connected at all to the choke circuit.

Great, thank you! I didn't know there was a screw on the Stock CV carbs (I really haven't looked at them too closely), I'll have to fiddle with them and see if I can lean them out a bit at idle to make it run better!

 

[Korsch_RS]

Re: Black and Gold Cafe - 71 CB350 - Tires!

Well I fiddled with the stock carb mixture screws and its running much much better now! The screws were about 3.5 turns out, and I set them to 2 turns out and it idles about 1000-1500 now, revs cleanly with just the slightest hesitation off idle (but I'm used to fairly responsive FI engines, so I'm guessing this is the slight lack of throttle response I've heard of with CV carbs). On the road it doesn't stall pulling away from a stop when the revs dip anymore, and pulls pretty good in the midrange basically no matter what. Only downside is it only revs to about 9000, so there's is still something funny at the top end, but I'm not going to worry about it right now as I got the new jets for the VM30's, but haven't tried them out yet.

Also, I did a compression test and I got 155psi on the right cylinder and 145 left. My service manual says 140-170 is the recommended range, so I'm on the low end but acceptable.

At the moment I'm working on the tires. I got the front off last night, and thankfully there is very little rust on the inside of the rim. I wasn't really that worried because there is almost none on the visible surfaces, but it is an old bike, so there's always that unknown factor. Thankfully the front is good. I'm trying to mount and balance the new tires myself, we'll see how it goes.

Here's a pic of the wheel, this is the worst rust on the front, and the only place with any rust near the spoke nipples. Most of it is just surface rust near the bead surface.

More soon!

 

[Korsch_RS]

Re: Black and Gold Cafe - 71 CB350 - Tires!

Got the front tire mounted last night. I used the gigantic zip-tie method and it went on pretty easy easy. This tire is definitely a little too big for the wheel, but the next step of the project is to rebuild my CB550 forks with RT springs emulators, 18x2.15" Aluminum wheel and refresh the disc brake, so I wanted to go a little larger on the front for when that fork goes on.

And yes I know my garage is a mess

Rear tire goes on tonight (hopefully)!

 

[Korsch_RS]

Re: Black and Gold Cafe - 71 CB350 - Tires!

Got the rear tire on, tried to go out for a test ride, and the damn thing is running like crap again. I'm not sure why the carbs go to shit after sitting for any more than a day, but it's really starting to bug me. Plan for tonight is drain the tank, get the petcock spotless to make 100% sure I'm not getting crap in the bowls, check all my valves, re-check the ign timing, and then put the VM30's back on and try to get it running well enough to ride.

I'm fairly confident that I (with lots of help from all you great technical advisors!) can get the main/needle jetting pretty good as long as I can get it to idle and rev. That was my biggest issue before with the VM30's, it was a pain just getting it started and then if I touched it it would die right away.

Fingers crossed!!

 

[foundation982]

Re: Black and Gold Cafe - 71 CB350 - Tires!

Got the front tire mounted last night. I used the gigantic zip-tie method and it went on pretty easy easy. This tire is definitely a little too big for the wheel, but the next step of the project is to rebuild my CB550 forks with RT springs emulators, 18x2.15" Aluminum wheel and refresh the disc brake, so I wanted to go a little larger on the front for when that fork goes on.

And yes I know my garage is a mess

Rear tire goes on tonight (hopefully)!

Curious to what the giant ziptie method is

 

[Korsch_RS]

Re: Black and Gold Cafe - 71 CB350 - Tires!

Here's the zip tie method:
http://www.youtube.com/watch?v=S6WPzRRJLpA

I had to use a pry bar to get it the last little bit of the beads over the wheel. Also make sure you zip-tie your tube inside the tire before mounting. I don't know if I would widely recommend it, but I'm replacing these wheels within a year or so, so I wasn't too worried about marring the finish with a pry bar and willing to try it to see how it worked.

In other news, all is not going well on the carburetor front. The Scott Turner internals kit I ordered from DCC came with a missing air jet, a damaged slide that jammed in the carb barrel, and also incorrectly manufactured slides, one has the cutaway machined on the wrong side. I've sent them an email and expect them to quickly respond and resolve the error, but unfortunately, even with their good customer service it's one step forward and one step backwards.

I adjusted the valves last night, and the left side intake and right side exhaust were both about 0.001" too far gapped, but I fixed that. I don't think that would be enough error to be causing any significant running problems. Tried running with the stock carbs some more and it runs great initially, and falls on it's face when it warms up. When i left my house it felt pretty good up to ~8000rpm, and within 10minutes I couldn't get it above 3000. Guessing it's too rich.

Anyway, going to try to following with the VM30's tonight, and maybe tune from here:
2.5 slides
150 Main jets
6F4 needle, clip position 4 (almost full rich)
159 P-0 needle jet
2.0 air jets
20 pilot jet
1.25 turns out on the air screw

Pics:

 

[overdraft]

Re: Black and Gold Cafe - 71 CB350 - Tires!

fwiw, i'm running decently at the moment with 140 mains, 25 pilots, screws out 1½ turns and needle clip 2nd from the top. i haven't done ANYTHING to try and fine tune it like syncrhonize them or do the thing where you wind the screws out to get max rpm etc... it needs choke on a cold start... idle changes over the life of a ride... starts low, have to blip it go keep it running... then idles at 2200, then settles at 1400... no idea how that can happen but whatever... revs nicely off idle and spins up to 9 grand without much trouble... i'll get into it more when i have time but with those settings it's rideable... let me know how you get on!

 

[Korsch_RS]

Re: Black and Gold Cafe - 71 CB350 - Tires!

Well, I made some progress and then broke some stuff.

I spent Saturday morning tinkering, and finally got it idling correctly. My problem up until now was it would idle fine for a minute or two, then just take off to 5-6000rpm. I did some searching in the Mikuni book I have and also my shop manual and couldn't find anything about that in the carb troubleshooting section, so I was thinking that if it's racing, it must mean there's too much fuel, but no matter how many turns I added on the air screw to lean it out it would still do it. So i did some searching through google to try and find an answer, and I found someone saying that a racing idle actually means too lean, so I backed the air screw way off and walah! finally a stable idle! Some fiddling with the idle speed screw and it was burbling along at 1100rpm like clockwork. Finally it was idleing well enough to actually do the pilot jet tuning. A few rounds of that and I ended up at this jetting:

2.5 slides
150 Main jets
6F4 needle, clip position 4 (almost full rich)
159 P-0 needle jet
2.0 air jets
25 pilot jet
1.00 turns out on the air screw

Now, only the pilot circuit has any tuning on it, but the rest of the jetting was conservative enough that I wasn't worried about blowing it up. I put the bike together and went for a short ride with a friend of mine. While we were riding, I was noticing that the twist grip was super stiff, and getting harder. We decided to turn around. About halfway back, the cable broke

We were only a few miles from my house, so he went back to my garage, grabbed my car and all the parts/tools needed to swap back to the stock carbs, and came back to where I was waiting. We did a roadside carb swap to the stockers and I rode it home without issue. It certainly doesn't run very well on the stockers, but running like shit is better than not running.

I fiddled around with the stockers some more today, and got it running a little better. I also noticed that I am leaking from the front fork pretty good. I ordered new seals, but in the meantime I'm catching the oil to prevent it from getting any more on my pants or exhaust with this:

I also ordered the parts needed to convert from a single throttle cable with a splitter box to a complete dual cable set up. I'm thinking that the junction box was contributing to my heavy throttle, so hopefully eliminating it will help. My friend was also saying I was blowing some smoke at heavy acceleration so I definitely need to do a little more tuning, maybe a little smaller main jet and/or lean out the needle a bit.

More soon!!

 

[axeugene27]

Re: Black and Gold Cafe - 71 CB350 - Tires!

i have the identical setup as overdraft on my 72' 350 and it seems pretty damn good. I am running 145 mains though and top end is nice. Midrange seems a little spotty like the engine revs but the power doesn't come on like the rest of the rev range. Plugs look good though . Definately not rich anymore. Amazing how much of a difference putting the clip into the 2nd position made in the midrange. If you are bogging down in the midrange try moving that clip korsch. Did you make your own cables? Weird to snap like that those cables are super tough. Did the end pop off in the throttle housing?

 

[Korsch_RS]

Re: Black and Gold Cafe - 71 CB350 - Tires!

I used the 2-1 throttle cable kit from DCC and put my own ends on it. I didn't have the nice solder on ends, so mine were a little sketchy. I used crimped small fittings for the carb side, and a steel hitch pin for the twist grip side with a spot weld to the cable. I pulled on it as hard as I could when I first did it and couldn't break it, but I guess the repetitive loading just fatigued it to failure. For the dual pull cable set up I'm going to go to a local bike shop with my throttle grip and also the carb slides, and see if they can make me some custom cables with the proper end fittings, and hopefully also with some nice inline adjusters as the ones on the carbs don't have much adjusting range.

 

[teazer]

Re: Black and Gold Cafe - 71 CB350 - Tires!

Sometimes the end nipple is too tight in teh throttle barrel and if it isn't free to rotate slightly, it fatigues the cable right there at the end fitting.

 

[Korsch_RS]

Re: Black and Gold Cafe - 71 CB350 - VM30's!

Well...I got the dual pull-cable throttle all put together and working. It works great so far, nice and smooth pull, fast and snappy return, everything seems fine. I used a Norton (I think?) dual pull cable throttle assembly from eBay, along with 2x each of 90* brake noodles, universal MTB 1.5mmbrake cable, 5mm cable housing, and Shimano CB-70 inline adjusters. I used these ones as they were the only ones I could find that were rated for brake cables, instead of just shift cables.

Unfortunately, when I tried to start it with the Mikuni's reinstalled and this new throttle setup, it wouldn't go. After much sweat and cursing, I got it to run a bit but only the left cylinder was firing. I checked the usual fuel and spark, turns out there is no spark on the right cylinder. Looked under the timing cover and found this

I was missing one of the screws holding the ignition plate. There was black/silver dust all over, and it turns out the rotor had been rubbing on the transistors. The top one looks to have more damage then the lower. Here's another shot:

I've ordered a replacement PAMCO ignition, but while I'm waiting a couple weeks for it I decided I would try to fix this one. I managed to figure out the transistor P/N as the current ones were conveniently each worn on different halves. It's an International Rectifier GB14C40L, so I've ordered a few of those and we'll see if I can get this ignition working again. There was a little damage to the hall effect sensor as well, so no guarantees that I'll get it to work, but the transistors were only $4 each, so not an expensive experiment.

More soon!