73' CB350 rebuild

[Dr.Roe]

Hello from Quebec,

Skip to First part of the project if you rather not read the intro.

Story is standard, never owned a bike but would like to improve my mechanical skills. I worked on my Defender 110 for the last 2 years (actually still working on, because it seems to be a never ending project haha) with a friend of mine who knows the in's and out's of rebuilds. The defender is great fun, but also a heavy financial and work load which ment some week-ends were spent watching Netflix while funds for the next part of the project we're stacking up.

Enter a CB350: seemed like a good idea, small, nimble, plenty of parts and a relatively straight forward engineering. Great project I could piece together little by little. Spotted a 73' that was part-way through a rebuild so enter CB number 1.

(oh yes, Iris Purple)

The seller also proposed to throw in another CB with a little tougher life (72 ?) if I could help him pull it out of his barn. So, enter unexpected CB number 2.

Number 1 will be project bike and number 2 donner for whatever she has left. Neither bikes are running, Number 1's engine is spread in boxes.

First part of the project
Engine rebuild,

Right now I have 2 engines and will be looking at both to find the best candidate for rebuild. My intended upgrades while I'm rebuilding are:

KA tensioner + new chain
New piston rings
kerosene test the valves + thinking of lapping them (chance to learn how to do it)
new full set of seals
new bolt kit
looking into PAMCO ignition upgrade too (any comments on this?)

Clean (maybe soda blast) + rebuild then test compression

First question, any other things you guys would change while I'm at it?

Part two will be new set of plugs, Mikuni carbs and K&N filter kit.

Many thanks and I'll keep updating as best I can!

Andrew

 

[xb33bsa]

cant think of a lot of but just a cupl things to =check
the eccentric oil pump drive can get badly worn be sure and check it and the pump/piston itself as per the fsm specs
be sure and check the cam journal clearance,and set the camshaft endplay as per the fsm go for the very low end of the spec ,you can set this up on the bench well befiore final assembly all you need is the empty rocker box ,cam, 2 new gaskets and the 2 end housing/journals do a dry assmbly and figure out what shims, if any are needed
check the valve guides for wear, lapping seats is ok but only as a minor touch up,you dont want great wide seat contact keep it in the spec
check both ends of the rocker arms, i have seen a couple that are sweet at cam pad end but badly pitted at the valve stem end
check out the cranks as per all the fsm specs and tests and pay close attention to the rod small ends
have fun !!

 

[Barnburner]

Welcome to DTT. You'll be happy with the 350 as a first bike project. The 73 you found is a great start too because of the front disc brake (not to mention the overall good condition). I'd take a look at the serial number on the motor for the second bike. From the points cover, it appears to be earlier than a 72, possibly a K0 (first year) model. IIRC, those had a "fatter" cam that made a few more hp with a higher redline. If the internals are in decent condition, it may make a better powerplant than whatever pieces came with the 73. Also, what carbs are on that second bike? They don't look like the stock Keihins.

 

[xb33bsa]

thats a good eye burner 8) looks like 450 carbies from here and looks like the "type one" points cover
yeah that one should have the 286 code cam and rockers the "fat cam"
if it is then the cam, rocker arms and cam sprocket can only be used as the sets they are, unfortunately no mixing of those bits, if good spares are needed

 

[Dr.Roe]

Thank you both for the replies!

Interesting comments on Number Two, took a look at the carb (only have one of the two) and it dose look like the ones from a 450, brand is Keihin.

Engine serial is:

CB350E-1047338
Point cover says TYPE-1

 

[xb33bsa]

Thank you both for the replies!

Interesting comments on Number Two, took a look at the carb (only have one of the two) and it dose look like the ones from a 450, brand is Keihin.

Engine serial is:

CB350E-1047338
Point cover says TYPE-1

yep thats an early one with the fat cam spec a bit more top end hp and higher redline .(unless it has been changed out for later bits not likely) the cam parts that move,as mentioned will not mix n match with the later model everything else in the engine is interchangeable and the early one may even have the smaller output cast iron oil pump ,better to use the later pump if swapping parts

 

[Dr.Roe]

Hello,

Good and bad news, Number ones cam assembly is not so good, rusted and pitted, sprocket is useless and would need to changed. Valves aren't great and have accumulated some rust. Cylinders have been bore to + 0.25" at some point during her life, both are clean and smooth.Have yet to crack open the bottom end.

And now good news. Number two's cam assembly has no pitting and only minor surface rust (a rub with fingers got it off). Stopped there after swearing for a while at two of the four 6mm screws securing the cam case.

 

[Dr.Roe]

With that in mind, I'll go with your recommendations and use the cam assembly from number 2, how ever, I'm not seeing a 286 mark? It should be on the sprocket right?

 

[barnett468]

.
if you are at around 4000 feet or higher elevation , i would consider increasing the compression with high compression pistons.

 

[xb33bsa]

With that in mind, I'll go with your recommendations and use the cam assembly from number 2, how ever, I'm not seeing a 286 mark? It should be on the sprocket right?

lucky you that is very cool it looks like a usable lashup !!
yeah it should have a 286 onnit.not easy to see when assembled

no matter you can see what they mean by calling it the fat cam the center casting section is fat compared to later ones. they actually quit using that cam blank on the last 286 grinds because of a few rare cam breaks in half i wouldn't worry about that though ..i have a sweet nos set of cam and rockers for my 350 in 286 grind on the skinny blank woo hoo
you can physically verify it as well by comparing the measure at the cam base circle, 286 is something like 30.25mm the later ones are 33 hence the need for difference in rockers and also the 286 sprocket has a i think 2mm smaller bore at the cam fit

 

[Dr.Roe]

Thank you all for the info!

Thankfully I wont be taking pass the 2000 feet mark!

I'll keep you posted on progress

 

[Dr.Roe]

Springs are just barely in specs, I think I'm going to change them.

Where could I find a set of springs that won't cost a fortune? Leaning toward these from KPMI:

http://valvetrain.kpmivalvetrain.com/item/in-components-honda-cb-cl-350-twin-br-1968-to-1973/purchase-individual-components/chrome-silicon-28?

Any feedback?

Thanks

 

[xb33bsa]

i dont know about those but i wouldn't hesitate to use rust-free stockers that still spec good .rust is a sure spring killer
are you using some digital calipers ? just be sure and close them often enough and make sure zero is set at zero.then a tricky method is slide them open to the minimum length of spring in the service limit ,press the zero button exactly on that number and then when you measure each spring it will read how much + or minus to the number you enterd as zero.. caliper does math for you !
and of course you can switch back and forth mm to imperial i am stuck in the steam age and still relate everthing in inches
the main thing about replacing them is with the stock cam you dont need or want a stiffer spring rate .that will just invite extra heat and wear on a used set of lobes and followers

 

[Dr.Roe]

Hello!

Springs right now are ranging from 47.83-47.94 mm (using a digital calliper), serviceable is 47.8mm I believe? I wouldn't mind keeping them, but then again I can easily fit the springs in my budget. Either\or kind of situation, I guess it boils down to which is best?

I'm not banking on any performance gain by just changing springs, but it would be one less thing to change down the road right? My only worry is it might mess a little with compression (if using performance springs, without the matching cam)? (ugh, this is past my paygrade, but hey! Live and learn!)

Thank you for your time!

 

[xb33bsa]

yeah you got the right spec i figger i just looked in the old factory service manual
well i kinda subscribe to the if aint broke dont fix it, according to your measurements mr honda says they are still viable ,the inners have a diff spec minimum of replace if under 39.3
just so happens i gotta whole bucket full of 350 valve springs and i am going to look at them soon, for i got 350 parts scatterd everwhere , ill measure a bunch of em get back to ya, maybe well see a trend

 

[Dr.Roe]

Awesome, thanks!

 

[barnett468]

.
ok, you can do this . . measure how deep the spring pocket in the head is then go to an industrial hardware supply store and buy hardened machine shims that just fit in the pocket and around the guide . . get ones that will be at least .050" below the top of the pocket so it will still hold the spring . . the shim thickness that will work will probably be between around .025 and .050 thick.

if you can fit .050 then do that . . if they are .025 thick then use two of them etc.

you can also just order valve spring shims in the ize you need.

 

[Dr.Roe]

Hello guys,

still working on the engine, had to wait over 30 days for the oil filter spanner tool (got stuck at customs).

I'd need some help, my crankshaft bearing number 91001-312-014 is busted.


I'd need to find a replacement but it's discontinued. The only one I found was 110Usd, or the price of a full crankshaft assembly in used.

Any one know an aftermarket source for that item, or, anyone have a full crankshaft assembly in good condition they'd want to sell?!