Topic: 1973 CB350F "Modest Original" build

[calj737]

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...

[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?

[calj737]

expensive.

[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.

[calj737]

That is the same advice given earlier.

[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.

[calj737]

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. 

[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!

[grcamna2]

You did a nice job cleaning the valves off,I would certainly do a good,complete lapping on a couple of those.

[iiAtlas]

You did a nice job cleaning the valves off,I would certainly do a good,complete lapping on a couple of those.

Will be lapping all of them tonight!   

[iiAtlas]

Exhaust valves: lapped!  Will get to the intakes tomorrow.  These cleaned up pretty nicely I'd say.  I used a standard wooden lapping handling, some lapping compound, lots of patience, and a bit of time.  Here is the valve after lapping.



And the seat


I was carful not to get any of the lapping compound on the valve stems or anywhere else it shouldn't be, though I will of course be flushing the whole head once again.  I noticed something strange when I went to insert the valves into the guides.  There appeared to be a rust like coating on them.  Surface rust, or maybe a film.  I fed a paper towel through and it came right off, like it hadn't adhered but rather just sitting on the surface.  I decided to spray the inside of the guides down with WD-40, this washed away the rust-like deposit.  Then I coated the valve stem in motor oil before inserting it in the guide to ensure any contaminants were carried away.  I'm curious as to what this stuff was.  Maybe it was from one of the solutions I used?  Pine-sol?  Evapo-rust?  Nonetheless after WD-40 and some motor oil on the stem the valves inserted smoothly.  I have yet to check if the guides and valves are in spec.  I wanted to do something with my hands so I went with the lapping instead.  Will get to the measuring soon.  Is "valve guide replacement" a home job on these little Honda 4's?

[calj737]

Its not unusual for flash rusting to occur on the guides. I'd suggest assembly lube on the stems or Marvel Mystery oil if the head will sit a while (dripped into the guides). The guides should be done by a shop as most times, new seats should be cut afterwards  Let's hope all the work you just did isn't out the window...

[iiAtlas]

Its not unusual for flash rusting to occur on the guides. I'd suggest assembly lube on the stems or Marvel Mystery oil if the head will sit a while (dripped into the guides). The guides should be done by a shop as most times, new seats should be cut afterwards  Let's hope all the work you just did isn't out the window...

I had fun lapping them so no worries never heard of that marvel mystery oil but will take a look.  What's it's main use?  Thanks for chiming in.

[calj737]

Rust prevention. Penetrating oil. Gun cleaning. Defouling. Brushing your teeth. Fogging fuel tanks. Gargling after a weekend in the drunk tank (ask RevDoc). And about 1,001 other uses.

[iiAtlas]

Rust prevention. Penetrating oil. Gun cleaning. Defouling. Brushing your teeth. Fogging fuel tanks. Gargling after a weekend in the drunk tank (ask RevDoc). And about 1,001 other uses.

Hah!  Sounds like it really is mystery oil...will pick some up, thanks.

[grcamna2]

Rust prevention. Penetrating oil. Gun cleaning. Defouling. Brushing your teeth. Fogging fuel tanks. Gargling after a weekend in the drunk tank (ask RevDoc). And about 1,001 other uses.

Hah!  Sounds like it really is mystery oil...will pick some up, thanks.

lol 

[iiAtlas]

An update from a few days ago...intake valves lapped!





I'm happy with how they came out.  I can see and feel a nice even cut where the valve met the seat.  It seems like both sides "lapped" well.  Next up I'd like to redo my engine measurements.  Cylinder ID, pistons, valves, and valve guide play.  Then I want to tear open the bottom end and see how the crankshaft and everything is looking down there.  I'll most likely spend the rest of today soda blasting some frame components.  Maybe I'll soda blast the head while I'm at it.  Probably should have done that before I lapped the seats, but I doubt the soda has enough power to do any meaningful damage.  ^^ feel free to tell me not to do the above

That's all for now!

[grcamna2]

Good work.

[iiAtlas]

An update -

Thanks to grcamna, MoMo, and Sbeckman I've managed to get a set of CB350F STD Bore cylinder sleeves.  MoMo had a spare cylinder head with good sleeves lying around and was able to remove them and ship them to me.  Thank you Calj for the tips on removal.  He said 15 mins at 350F in the oven and they popped right out.  I'll be taking two for myself and replacing those sleeves sometime this week.  The other two are for Sbeckman should he choose to use them.  If anyone else needs the sleeves and Sbeckman goes another route I'd be happy to pass them along.

I spent most of this weekend working on the airheads.  We've got three in the garage now and they we're all well past due for a full oil change.  All three bikes are plagued by the infamous $2000 O-ring.  If you'd like to see how that went check here: http://advrider.com/index.php?threads/recently-acquired-1977-r100-7-questions.1055409/page-54#post-29148335.  More soon!

[calj737]

I spent most of this weekend working on the airheads.  We've got three in the garage now and they we're all well past due for a full oil change.  All three bikes are plagued by the infamous $2000 O-ring.  If you'd like to see how that went check here: More soon!

Sometimes it doesn't pay to service a bike 

[grcamna2]

Nice to hear that Larry was able to help you with a pr. of good STD. size cylinder sleeves !

[iiAtlas]

I spent most of this weekend working on the airheads.  We've got three in the garage now and they we're all well past due for a full oil change.  All three bikes are plagued by the infamous $2000 O-ring.  If you'd like to see how that went check here: More soon!

Sometimes it doesn't pay to service a bike 

Hah! Maybe I should clarify... potentially plagued I.E. they are the models potentially effected.  Nothing catastrophic just yet...

Nice to hear that Larry was able to help you with a pr. of good STD. size cylinder sleeves !

Yes!  Thanks again for your help in tracking them down.

[iiAtlas]

The sleeves are here!  Thank you Larry (MoMo) for the quick work removing them from the cylinder and shipping.





I've only opened one thus far but I'm assuming they're all there .  I know the only shot which really matters for this is the inner walls.  I'll get you a good one of that as soon as I can.  What's next?  Can I hone these while they're out of the cylinder block?  Maybe stick them in a vice?  I need to hone and mic them, then choose the best two to swap in.  Any advice would be greatly appreciated!