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Author Topic: cb350f valves  (Read 2914 times)

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Offline hondamatteo

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cb350f valves
« on: June 06, 2011, 03:20:04 PM »
hey guys, so Im in the process of doing a head rebuild for my 74 cb350f and I just took it to the machine shop to have the head cleaned up and resurfaced. Well I got a call back saying that my valves are in pretty ruff shape and I should look into getting new ones. They were quite carboned up when I pulled them out but I did manage to clean them up. The technician said that they are pitted fairly bad and that these valves are coated on the surface and the metal underneath is quite soft. I have done a quick search online and it seems alot of places only have the exhaust valves only or dont carry them at all. Can anyone recommend a place were I can find new ones, or perhaps someone has a used set they wouldnt mind parting with? Thanks so much.
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'74 CB350F

Offline hondamatteo

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Re: cb350f valves
« Reply #1 on: June 06, 2011, 10:41:10 PM »
So here is a pic I snapped when I first pulled them out


Also there were no valve stem seals on the exhaust valves but the seal kit I bought came with 8 valve seals? I didnt notice any oil burning when I had the bike running but I am thinking I will install all 8 seals. Any thoughts?
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'74 CB350F

Offline bryanj

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Re: cb350f valves
« Reply #2 on: June 06, 2011, 11:11:49 PM »
Those valves will lap in OK for anything except racing work and i dont think the 350 had exhaust stem seal and they won't fit on the original guides, you would have to fit 400 guides and have them reamed and the seats in the head cut.

Try Dave Silver for the valves if you want to change them
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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Offline hondamatteo

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Re: cb350f valves
« Reply #3 on: June 06, 2011, 11:31:36 PM »
Ya you think so? The guy at the machine shop seemed to feel pretty strongly that they would need to be replaced. Although the bike did run fine when I had it up and running....I checked out david silver and a whole new set of valves would run me about $300, yikes....
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'74 CB350F

Offline MRieck

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Re: cb350f valves
« Reply #4 on: June 07, 2011, 04:19:17 AM »
Quote from: hondamatteo on June 06, 2011, 11:31:36 PM
Ya you think so? The guy at the machine shop seemed to feel pretty strongly that they would need to be replaced. Although the bike did run fine when I had it up and running....I checked out david silver and a whole new set of valves would run me about $300, yikes....
That is actually pretty reasonable. I can understand where the fella at the machine shop is coming from....it is difficult to guarantee work when using old parts like valves (unless the parts are relatively new). Same with guides etc.
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Offline bryanj

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Re: cb350f valves
« Reply #5 on: June 08, 2011, 10:05:05 AM »
Believe me, i have seen way worse carry on for a long time.

Look closely at the mating surface part, if it's flat it's O.K. if its indented where it sits on the head you need new, wish i knew how to do a sketch and insert it, perhaps Mike can explain it better in US english?
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline camelman

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Re: cb350f valves
« Reply #6 on: June 08, 2011, 10:33:09 AM »
If you get a continuous seal all around the mating surface(even if it is thin) then it will likely be fine to use. I've put 4000 miles on valves in much worse shape than yours on my 350f and I routinely bounce off 11k rpm. I also just finished a 700 mile road trip loaded to about 800 pounds, and the engine ran fine the entire time.

However, don't expect a mechanic or machine shop to accept those valves, and don't expect old parts like that to perform like new ones.

Camelman
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Offline hondamatteo

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Re: cb350f valves
« Reply #7 on: June 09, 2011, 11:34:25 PM »
Ok so I ended up sticking with my old valves. The machine shop did a great job, they specialize in smaller motors like motorcycles, atvs and outboards so they knew what they were doing. I didnt have any compression issues before the tear down and now that everything is freshened up I'm thinking everything should be fine. The shop glass beaded the ports, cut the seats, adjusted the valve stem height, refaced the valves and resurfaced the head. And now a few pics:




I gave the intake ports a little bit of a polish so hopefully that should help a little bit with flow

Before

After


Thanks for the help guys, I appreciate it. I think I will have to start a build thread soon;)
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'74 CB350F

Offline jaguar

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Re: cb350f valves
« Reply #8 on: June 09, 2011, 11:38:36 PM »
what did you use to clean up those ports?
did you port match them to the intake?
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Offline crazypj

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Re: cb350f valves
« Reply #9 on: June 09, 2011, 11:44:32 PM »
Quote from: jaguar on June 09, 2011, 11:38:36 PM
what did you use to clean up those ports?
did you port match them to the intake?


 He said he cleaned them up and machine shop bead blasted them.
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Offline hondamatteo

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Re: cb350f valves
« Reply #10 on: June 10, 2011, 08:15:26 PM »
To clean it up I just used a dremel with multiple sanding bits then it was bead blasted. If by port match you mean sand down the intake boots to match the intakes I didnt do that but perhaps come winter time. For now just trying to get it back on the road for the summer
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'74 CB350F
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