Topic: 1973 CB350F "Modest Original" build

[grcamna2]

Depending on how deep the scratch is.. you could possibly replace/source just the one cast iron liner in your cylinder block w/ one that's STD size and good shape as long as it measures good clearance for that piston.

[iiAtlas]

Depending on how deep the scratch is.. you could possibly replace/source just the one cast iron liner in your cylinder block w/ one that's STD size and good shape as long as it measures good clearance for that piston.

The vertical scratch is from a piston ring snagging the wall, or some piece of metal trapped during rotation of the crank. You must eliminate it before considering engine assembly. I doubt it will hone out, so I'd replace that one sleeve.

If you attempt to hone it out, you will undoubtedly "oversize" that bore and have compression issues and leaking oil in that sleeve. I say this because it is still readily apparent after a thorough hone.  A few 0.00s matter greatly on piston/bore clearance.

I would also suggest you clean the head completely before honing in the future. Once honed, you want to wipe with oil the cylinders to prevent any flash rust or damage occurring to them from cleaning products used elsewhere.

So if you do opt to replace the sleeve, turn the jugs upside down in the oven, about 1/2" spaced from a sheet pan. Only provide room for the damaged sleeve to "slide out" when hot. Bake them until that sleeve slips out (use great care because the other sleeves will be loose too). To install the new sleeve, jugs upright, and place the new sleeve in the freezer. It should drop in due to thermal contraction.

Good ideas guys!  This morning I was thinking, if I oversize the cylinders with the flex hone I'd probably just be doing more harm than good.  More chance for an ill fit.  I wiped the cylinders down before honing to make sure there wasn't any debris, and I had the head soaking a few days back.  EvapoRust and the pine-sol mixture.  Should I clean them even more in the future?  I've coated the cylinders with a thin film of oil to prevent flash rust as mentioned.  Thanks for the tips on sleeve removal/install.  I'd be happy to replace that one if I could track down a CB350F STD sleeve.  Any thoughts on where to find one?

[grcamna2]

I hope someone here on this forum has a good spare for you otherwise get the part# online and do a search..

[iiAtlas]

I hope someone here on this forum has a good spare for you otherwise get the part# online and do a search..

I can't find the part number anywhere on this fiche...I'll keep looking!

[grcamna2]

I looked also and it seems they won't sell the cylinder sleeve separately,you may have to get a good,used one that hasn't ever been bored/honed-out or get a new one from a sleeve company like 'LA Sleeve'. I hope someone will offer a good used one to you.

[iiAtlas]

I looked also and it seems they won't sell the cylinder sleeve separately,you may have to get a good,used one that hasn't ever been bored/honed-out or get a new one from a sleeve company like 'LA Sleeve'. I hope someone will offer a good used one to you.

Okay good so I'm not crazy!  Looks like LA Sleeve doesn't carry anything that small.  Fingers crossed for a donor!

[iiAtlas]

Might be cheaper/easier to overbore all four cylinders and get new pistons/rings?

You could send a PM to Bill Benton and see if he's a set of jugs lying about and buy those. Also, on another thread, there was mention of a Parts Salvage guy in South Carolina who likely has a set of jugs in his heap. Get a set, clean them all, hone them, and mic them. Take the best one and swap it back into your jugs.

Here's the link to that Salvage guy:
http://www.motorcycle-recycle-center.com

Wow great link!  I've sent that guy a message, and will see about contacting Bill.  I'd prefer to keep this at the standard bore, especially after I spent so much on this STD piston rings.  I could relist, but would rather not have to.

[iiAtlas]

Found this set.  Thoughts?

http://www.ebay.com/itm/72-73-74-HONDA-CB350F-CYLINDER-JUGS-/280830712540?_trksid=p2141725.m3641.l6368

[grcamna2]

I'd be careful on ebay as sometimes you can buy something that has a high claim but unless you can get the seller to precisely measure the bores they may be worse than what you have.. That seller only has a 99.3% feedback score & for what you're looking for(a cylinder liner in excellent cond. w/ a clean STD bore measuring similar i.d. dimensions as you already have)I would want 100% feedback score.I wonder who makes new liners for the CB350F ?
Have any other sohc4 members been in touch w/ you about a good liner? Someone may have already needed to 'borrow' one cyl. liner from a nice set of four and now they're stuck with just three.. just hoping for you. 

[iiAtlas]

I'd be careful on ebay as sometimes you can buy something that has a high claim but unless you can get the seller to precisely measure the bores they may be worse than what you have.. That seller only has a 99.3% feedback score & for what you're looking for(a cylinder liner in excellent cond. w/ a clean STD bore measuring similar i.d. dimensions as you already have)I would want 100% feedback score.I wonder who makes new liners for the CB350F ?
Have any other sohc4 members been in touch w/ you about a good liner? Someone may have already needed to 'borrow' one cyl. liner from a nice set of four and now they're stuck with just three.. just hoping for you. 

Thanks grcamna, appreciate the hopes!  I agree with you on the eBay concerns. At a glance the four cylinders I have would look great, and it's only upon further inspection that their true conditions reveal themselves. There's a chance one or two out of those listed four are salvageable, but I think I'll leave that as a last resort. I've reached out to two sleeve manufacturers, Advanced Sleeve and LA Sleeve. Patiently awaiting their response! Would love to know roughly the cost of a custom order like this. You know...I do have a lathe and mill....maybe I'll look into making my own....we'll see

[iiAtlas]

All,

Thoughts on this strategy for cleaning my valves?  Chucked in a drill (with something to protect the stem), then gently rub down with lubricated scotchbrite red while she spins.  I'm thinking of doing a 30 min chem-dip soak to loosen up the major bulk then finishing them off with this drill + scotchbrite method - unless of course one of you talks me out of it...thanks

[grcamna2]

I hope you score a cylinder liner sleeve soon 

[iiAtlas]

I hope you score a cylinder liner sleeve soon 

Maybe this will help...

[grcamna2]

I hope you score a cylinder liner sleeve soon 

Maybe this will help...

That should help;I think you should add 'STD size bore i.d.' to the thread.

[iiAtlas]

I hope you score a cylinder liner sleeve soon 

Maybe this will help...

That should help;I think you should add 'STD size bore i.d.' to the thread.

Fixed

Thoughts on the valve cleaning procedure I posted above?

[grcamna2]

I like that youtube video,learned something new 

[iiAtlas]

I like that youtube video,learned something new 

That's todays project!  Will report back results shortly.

[iiAtlas]

Ugh...not the best day in the shop.

It all started off well.  I separated the valves, labeled them, and soaked for 30 minutes in the chem-dip.



After removing the valves from the chem-dip I placed them in cups labeled 1, 2, 3, and 4.  From here I went on to chuck them in the drill (with cardboard to protect the stems).  I lubricated both the scotchbrite red and valve itself with WD-40 then let the drill fly.  Easy peasy.  I slowly applied pressure to where the carbon had built up.  With enough persistence and re-soaking I think you could achieve some pretty good results.  Here were the intakes after...



The exhaust before soak


After soak


After clean in drill




Some more time in the chem-dip, fresh scotchbrite, and another round in the drill and I think these would clean up nicely. 

Now for the bad news.  I am absolutely petrified that I've switched intake valve 4 and 2.  The cups were labeled 1, 2, 3, 4 and placed in order, but when I went to clean up they were sitting 1, 4, 3, 2.  Instinct tells me I must've placed the right valve in the right cup after removing from the soak, and that the mixup occurred while I was chucking the valves in the drill - but it's impossible to say either way for certain.  I'm so frustrated and disappointed at this point  the chem-dip must've got to my head and caused a momentary lack of concentration    Discouraged, I packed the valves back up and went upstairs.  I really don't know at this point if I've switched 2 and 4.  I'm hoping I didn't and that I matched the tape label up with the cup label, but who knows for sure.  Ugh!!

On top of that I've noticed some decent pitting on the intake valves.  Bleh.  Bad day, would like to write this one off and move on   Baking a cake to take my mind elsewhere.... 

[grcamna2]

The valve faces look better,you may have to do a bit more careful scraping on the stubborn carbon.
You may want to consider getting the valves ground or at least spend lots of time w/ using a suction handle(it's better not to use a drill) and lapping them in by hand to get past the corrosion;any pics of the heavy corrosion on the valve seats ?

[iiAtlas]

The valve faces look better,you may have to do a bit more careful scraping on the stubborn carbon.
You may want to consider getting the valves ground or at least spend lots of time w/ using a suction handle(it's better not to use a drill) and lapping them in by hand to get past the corrosion;any pics of the heavy corrosion on the valve seats ?

No good photos but will try to take some better ones tomorrow.  I'll see how close I can clean these up before lapping.

Swapping intake valves isn't the worst of things. As long as they and the guides are within spec, you're fine. You'll need to lap the valves into the seats gently anyway to insure a good seal. Breathe easier...

Phew...thanks...will try.  Was a wretched afternoon - and yes...I did make that cake...



Had a female helper so excuse the color scheme 

Will check to ensure valves and guides are in spec before reassembly.

[iiAtlas]

Got a response from LA Sleeve.  They do in face make CB350F sleeves and have one in stock for $150...thoughts?

[iiAtlas]

expensive.

Agreed!!

Here is a reply I got on ADVRider regarding the score.

Time to bore it the block or find another one. Since the score line doesn't reach the top my guess is a ring had broken and the ring edge dug into the cylinder wall. Perhaps the distance from the top of the bore to the top end of the score line matches the distance from the top of the piston edge to centerline of one of the rings. As it is, that score will bleed off cylinder pressure, possibly allow gas/combustion gases to get down into the crankcase, perhaps even pressurize the crankcase. Aside from that score, have you checked the bores for taper wear? Is the bore ID within spec from top to bottom?

If the engine were assembled, a leak down test would confirm how the score may reduce compression, or cause higher crankcase pressure. Either way, that score will impact how the bike runs. To me, I would not reassemble that block as is. Have the block bored out, to an oversize bore, new pistons and rings, which gives you the option to increase power slightly. Maybe even increase the size to a 400cc. That, or find another block and hone it, then use the pistons you have and new rings.

[iiAtlas]

That is the same advice given earlier.

Correct, just thought I'd share!  The more input the better in my mind.  I'm still actively trying to NOT overbore these cylinders.  I spent the money on the STD rings I'd rather keep it that way.  I also don't have a good source for doing that kind of engine work here in NY.  Would love some recommendations if any of you have someone in mind, should I have to go that route.

[iiAtlas]

Easy enough to ship the block and pistons to a known, reliable machine shop. The shipping costs plus the savings on machine work out of your area will more than make up for the difference locally.

I would return the rings and buy new pistons and rings in an overbore and be done with it. I would suggest politely, that you are stuck in "analysis paralysis" and fear something that is rather ordinary. Its not a big deal at all to overbore a cylinder a first time. Sure, if you go crazy with displacement change, you encounter other potential issues. But a tried-and-true size change resolves all doubt and damage in your existing block.

Or, buy a complete used block and hope that a hone cleans up at least 1 cylinder sleeve and swap it. Simple.

you have yet to post whether the bores and stock pistons have been mic'ed and whether they are actually within spec anyway. So your stock ring purchase may be moot already. 

Gah "analysis paralysis" is indeed where I'm stuck.  As you aptly guessed this is my first time overboring a cylinder.  I understand the benefits that a moderate overbore would only be beneficial.  A clean hone, fresh pistons, new rings.  It all sounds great - but my initial budget didn't really allow for this level of engine work and I'm hesitant to open up this can of worms.  I am, however, willing to spec it all out.  Prices for the shop work, new piston, and rings.  The bore ID is posted a few pages back (post #153, they were are all within spec.  I need to now re-mic having honed the cylinders to make sure they stay that way.  And mic the pistons.  Maybe I can get that done tonight.

[iiAtlas]

Had a good night working on the bike yesterday!  Decided to give the valves another shot - they came out looking much better.  Trick is to really just be patient and give each and every part of the bike your full attention.  These restorations take time, and you need to give them that. 

Anyways...here are the exhaust valves before round two



and after...







I think they cleaned up pretty well!  I used the Berkabile 2+2 gum cutter, the scotchbrite + drill trick, and a screwdriver to chip at the deposits.  My thumbs are raw from chipping at it but I think they're looking good.  Or at least much, much better.  All four sets of seats shine and feel to be smooth. 

The intake valves cleaned up decently but I didn't feel the need to go as far as I did with the exhausts.  Less hard carbon build up. 







That black carbon on the top can be cleaned off with judicious runs in the drill+scotchbrite getup, but after I got the seats cleaned up I stopped.  I felt the more I ran it the more chance I would have to mess up the seats.  Do you think it is worth it to continue cleaning the carbon off of these?  The seats are as clean as they will get.  Here is my worst intake.  This is what I believed to be "pitting" a few posts back but it is actually just specs of carbon.  When I run my finger over the seat I cannot feel it, so it must really be baked on there.



I have not mic'd the valves to ensure they are still within spec.  I will do that tonight.  Pistons and cylinders also need to be mic'd as well.  I had a good time last night though and I felt like I made some progress!