Author Topic: CB350F full engine rebuild  (Read 9707 times)

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Offline PeWe

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Re: CB350F full engine rebuild
« Reply #50 on: June 07, 2018, 09:52:15 PM »
Dissolves nitrile gloves and probably o-rings too. Is all carb cleaner this aggressive?


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The Yamaha cleaner does not hurt rubber or plastic
Motorex chain cleaner work fine too. It cleaned better than the CRC carb cleaner I also used. I used it for the oil pump clean too.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline camshaft1991

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Re: CB350F full engine rebuild
« Reply #51 on: June 08, 2018, 11:45:14 AM »
I think I'm going to go with the yammi dip and then use tooth picks, chopsticks, and cue tips for cleaning build up on carbs. I'm going to have to just buy a bunch of o-rings from 4into1 because the quotes I got from manufactures said they would be special orders for each which is a lot of money.
What do y'all use to replace carburetor linkage tubes? The CB350F tubing between the carbs is 2.5x16mm. I've traditionally used windshield wiper tubing and zip ties, but I feel like it doesn't make the vacuum seal I need. Any suggestions? Also how important are the felt washers for the butterfly valves? I know it has nothing to do with vacuum sealing. Can they be omitted on reassembly?

Offline camshaft1991

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Re: CB350F full engine rebuild
« Reply #52 on: June 08, 2018, 01:00:56 PM »
I came across this old post on CB350F carb o-rings. His dimensions differ from what 4into1 has for o-rings
thanks for the reply Bryan.

I did some more digging around and I think I found the sizes although I'm not too sure how credible the sources are. I figure I'd post my findings in case someone with a 350F or 400F is looking....

Main jet O-ring:
1.2mm cross section x 3mm I.D. Quantity 4

Float Valve Seat Seal
1.5mm cross section x 5mm I.D Quantity 4

Fuel Connect
1.9mm cross section x 5.8mm I.D Quantity 12

I think I remember Hondaman stating that most metric O-rings range by 0.5mm so I may need to do some rounding. Also I think he mentioned Buna fits a bit bigger than Viton or Visa Versa...??

I still need one top gasket. Maybe I'll search the salvage yard this weekend.

http://4into1.com/replica-keihin-press-fit-secondary-main-jet-o-ring/
4into1 has 4.2mm x 1.1mm for the primary jet o-ring
danf  has 3mmx1.2mm for the primary jet o-ring.
I bought fuel connector o-rings based on his post. They hold up good but they are a tight fit. However I chose to go with Viton o-rings and the seller on ebay didn't have the Durometer listed. Buna-N is usually 70 and Viton is usually 75 by default, but those values can be changed upon order from a manufacturer.
Anyways, whose dimensions should I go with? I can find danf's o-ring dimensions on manufacture sites but not 4into1's dimensions, unless I place a special order.
I was able to find the o-ring dimensions according to danf on ebay and the drain plug o-rings according to 4int1 on ebay as well.
« Last Edit: June 08, 2018, 01:47:43 PM by camshaft1991 »

Offline camshaft1991

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Re: CB350F full engine rebuild
« Reply #53 on: June 11, 2018, 10:48:52 PM »
What is the the default jetting for the CB350F with the 4into4 exhaust configuration? And can any 350F owners in the south or Gulf coast states shed light on what jetings they chose? Where I live it's hot, humid, and at or below sea level.

Offline camshaft1991

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Re: CB350F full engine rebuild
« Reply #54 on: June 21, 2018, 11:48:50 PM »
I got all the the stuff I needed for my carb rebuild including the new o-rings that i'm going to see if they can fit with my jets. my carbs are soaking in Yamalube  (Yamaha chem dip) for the night.

It looks like Chem-Dip initially, but it turns into milk after you add warm water. Letting them sit overnight. instructions say for 8 hours but I'm going to check after 6.

On sad note I found my boy Clint Eastwood dead in his case. I had it in the the bottom of a cabinet in my dad's shop. We don't know when this happened exactly, but it happened when no one was around. There was a 10" water line indicated on a few things like on a mini fridge we have but there were other containers and stuff that had no water line. Next to it is my compression kit. It doesn't have a computer built into it but there does not look like there is water in the compression gauge.

Anyways I don't plan on doing any torquing or compression test this weekend coming up. I will post more later   

Offline camshaft1991

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Re: CB350F full engine rebuild
« Reply #55 on: June 23, 2018, 02:59:02 PM »
Almost done cleaning my carbs. The milk spa treatment with the yamidip worked great but rinsing with water and scrubbing with a toothbrush didn’t quite get it all off. They began to oxidize so I took some cue tips and xylene to it. The xylene not only stops the oxidation but it really brings out that chem-dip rainbow
Going to get more cue tips. Still haven’t heard word on the felt washers. Are they related to the vacuum? Let me know


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Offline camshaft1991

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Re: CB350F full engine rebuild (Carburetors, Clutch and Kickstand)
« Reply #56 on: June 27, 2018, 03:19:02 PM »
Alright So I finally rebuilt my carbs. A lot of cleaning and trial error with assembly. On top of a stuck float, two of the four pilot jets were completely clogged. Only one was not clogged. I used the light on my iphone to shine through it. So the light didn't pass through two of them, one had a green faded glow to it and the light twinkled through the last one. I poured xylene in a cup to let them soak for an hour while I worked on other things.

I didn't use most of the o-rings I bought in bulk but they do fit. I replaced all of my float valves with OEM valves that have more sensitive valve springs. The new float valves already had o-rings. I replaced one of my main jets with a new replica. It's a little different but the jetting number is the same. In the picture, the older main jet has one of the O-rings I bought in bulk. Three of the main jets have new o-rings based on the dimensions I mentioned earlier. The o-rings I bought in bulk for the main jets fit, but are tight. I used a drop of oil on each of the three. I twisted the main jets a little and sure enough they slid in.
I'm going to try get my bike to run on a little on the rich side, but not too rich. The bike was previously set to run really rich, but that eventually led to the engine washing out. I checked my spark plugs. They were all rich with the last one covered in gas (1-4 left to right). I put my floats back on and found the floats were at 24mm, the manual calls for 21mm. I teetered with them and decided to go with 22mm for float height.

After I assembled my carbs I replaced my kickstand. I replaced it with a new one. I took off the pipes on the left side and installed it. I'm not sure if the old kick stand was actually bent or if the bolt and nut holding it in was loose, but it does seem more secure than previously. After I reinstalled the pipes, I noticed the kickstand spring was catching on the bottom of pipe 1. Something is off but I can't do anything if it has to do with the frame. My question is how can I protect my pipe from the spring? Can I put shrink wrap on the kickstand spring? How can I can prevent contact between the spring and pipe?

I can't remember when my clutch was ok. I rebuild it a couple of years back. I replaced the friction plates and clutch plates along with the springs. Barnet springs, they are bit stiffer than the original springs. Anyways at one point the clutch was just stiff. During one adjustment, I tried to give my self more play because of the the stiff clutch and the clutch stopped engaging. I tried to set as it was before and even removed all the play. The clutch lever feels like it's at 40 or 50lbs. My hand was hurting in the morning and still feels weak. I had someone rebuild my bike from his garage, he did more harm then good. He took some things apart, claimed they were broken, charged me for a whole replacement assembly and handed me the "broken" assemblies with parts missing. I'm referring to my first set of carbs. They were deemed unfixable, but I never got back all of the pieces. The second set of carbs I have now came as a complete assembly with nothing missing. Anyways I believe when he inspected my clutch housing he must have put something in backwards or omitted something. The rebuilt clutch has less than 1,000 miles on it and it's unresponsive along with being insanely stiff. I'm probably going to have to open it up to see. The oil hasn't been changed in over a year so that needs to be done anyways.
« Last Edit: June 27, 2018, 03:27:16 PM by camshaft1991 »

Offline camshaft1991

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Re: CB350F full engine rebuild
« Reply #57 on: June 27, 2018, 04:30:11 PM »
I also need to replace my carb slides in the future but I put oil on them in mean time. I found a little scoring in each carb cylinder and the slides are all little bit nasty around the bottom ends. I already had to swap out one slide that had a long gash from top to bottom. 
And I just realized that a 22mm float height makes it leaner but it is just 1 mm so I can compensate in other ways


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