Topic: CB350F Engine Differences?

[jimbojangles]

Hi All,

Are there any noted variances between years of the CB350F?  I have two 350F motors and have noticed some differences. The biggest being the valve springs.

When replacing the top end gaskets on my running motor I noticed some moisture had made its way in through the tach seal and caused rust on the #3 exhaust valve. I decided to replace this spring with a good spring from my non-running motor. When I compared the two I noticed that one spring was taller and appeared to be made of a slightly thinner gauge wire. I don't own any calipers to measure the differences, but they looked enough different that I am not comfortable making the swap. My wife also agreed that these were not the same springs.

The other difference I have noticed is the front sprocket cover on one of the motors has the shift pattern engraved (R-N-1-2-3-4-5) while the other motor does not. Is there anything else I should be aware of when stealing parts between these motors? 

I would also like to mention that neither of these motors seemed to use the sticky asbestos Honda gaskets, The head gaskets peeled right off of both of these bikes.

[carnivorous chicken]

Do you have photos?

AFAIK there wasn't any differences between the engines in the CB350F over years, but perhaps someone here knows differently. Valve springs were also the same for 400Fs if the parts fiches are correct. An R? for reverse? I've never seen that either. The 400F shift pattern is different because there is a 6th gear, and the shapes of 350F and 400F covers are different. Photos would help.

[jimbojangles]

My bad on the shift pattern. I was trying to do too many things at once. Just 1-N-2-3-4-5. This pattern is only engraved on one of the cases and definitely looks factory.

I'll try to get a picture comparing the valve springs tonight. It may just be my eyes deceiving me, but they do look different enough that my wife agreed they aren't the same. Is it possible that a spring left uncompressed longer will appear taller than a spring just recently removed? 

[markreimer]

There is a difference of valve guides. I can’t recall the years though. When I owned a 350F (1974) I believe it did not have exhaust guide seals. The guide design was such that they weren’t possible  to fit. My engine was never opened until I did it a few years back. I replaced the guides with ones from yamiya, with seals on all eight guides.

Otherwise I didn’t think there were any differences.

NOTE. If you ever go down this road, do NOT use the cruizin image 350F big bore kit. There are many users here, me included, who used these pistons and suffered permanent large oil consumption problems. If I still had it, I’d bore it out to accept stock 400F pistons and rings. Or just transplant a 400F engine entirely and gain a sixth gear.


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[jimbojangles]

Thanks, I've seen the issues on the forums with the big bore kits. I'll stick with what I have now since I've got good compression and it runs fine. (just leaked oil) I didn't think the 400f pistons would fit in the 350f sleeves.

I was concerned when my NOS gasket kit came with 8 valve guide seals. My original engine (1974) only had them on the exhaust, but this engine (no idea what year) has them on all 8.

[markreimer]

Ah so we had the same engine. I couldn't' remember which side had the seals, but yes, you're correct of course.

I've read the 400cc pistons can be put in, but it's at the absolute limit. Running an oil cooler is strongly recommended. I wouldn't use it for a daily rider or something you expect to get many years of trouble-free use from... If your pistons and bore are still looking good, and the clearance in spec, I'd absolutely do the same as you and keep it stock.