Topic: '73 cb350f siezed barn find!

[rusty2078]

Hi Bob, my first guess would be damage to the rings, not a whole lot of material there, and being seized there's a very good chance that when the engine broke free, a corroded/rusted ring broke apart. That said I'm no mechanic, just an enthusiastic amateur. A bent/damaged valve may resist turning the engine over (??), and if there's a dropped valve, a good chance of piston damage (and nasty stuff in the oil). All that said, I'd defer to the many skilled/experienced minds here, who know these engines a lot better than myself.

Cheers!

Rusty

[knowsnothing]

Nice progress so far Bob.  These little 4s are a blast to work on.

Another thing to check is the cam tensioner bolt (12).   2 of 3 cb350f/cb400f engines i have came with them broken.  For some reason people like the tighten them till they break.  I can't tell how your is from the photos posted, but if yours is broken, you basically have to split the cases to get it out.  Both of mine were stuck and wouldn't back out, so i had to drill it out and then split the cases to get the tiny tip that remained.

[574hondarider]

Nice progress so far Bob.  These little 4s are a blast to work on.

Another thing to check is the cam tensioner bolt (12).   2 of 3 cb350f/cb400f engines i have came with them broken.  For some reason people like the tighten them till they break.  I can't tell how your is from the photos posted, but if yours is broken, you basically have to split the cases to get it out.  Both of mine were stuck and wouldn't back out, so i had to drill it out and then split the cases to get the tiny tip that remained.

Thanks!!  I will check and see, so try to back it out all the way and if it's stuck, then I know I will be splitting cases.  I'm really not wanting to split cases, so let's hope that isn't an issue too!!  Will squirt some pb on that bolt and let it sit overnight just to help things along!

[Mark1976]

Congrats!!!
   How you want to proceed is up to you, check the valve lash on #4. If you have really excessive lash on one of the valves, it may be stuck. (It really doesn't take much) if so then you'll need to free it up before going any further.
   More than likely the rings are stuck to the piston. Keep soaking that piston, the rings may free up some more (or not). Maybe reinstall the carbs check the points and condensers (you'll need to do it anyways) and see if it'll fire up, its up to you.
   Or this can be your starting point for a topend rebuild, at least you'll be able to get the cylinders off without any real issues now.

[rusty2078]

+1 on Mark's "rebuild the top end" idea...if #4 was seized up, there could be pitting/damage to the cylinder wall. The top end isn't really all that hard to do...just keep doing what you're doing, buy at least 2 manuals (if you haven't already....good to have different wording and pictures of process for explanation) and keep asking questions...also a good time to replace base and head gaskets.

[574hondarider]

Im thinking that since I plan to paint or pc the frame, I might as well go ahead and pull the engine at this point, then do a complete top end off frame.  This was meant to be my winter project anyways.  Any thoughts as to why the kickstart doesn't wanna budge?

[rusty2078]

It's been a little while since I've taken down an engine with a kicker...IIRC basic design for the shaft has a helical gear pattern cut into it that allows another gear to rotate and ultimately engage with the crank in some manner (help me out here, masters of SOHC design...) to turn over the engine. Did the PO (original owner??) state why the bike was parked?

If the engine is turning over now, via engaged gearbox and turning the rear wheel, my initial guess would be something specifically within the mechanism itself. Not sure as I've never had a 350, but one should be able to pull the clutch cover off and have everything there to inspect...?

[Stev-o]

My guess is it's the valve.  Time to tear it down...

[HondaMan]

Those carbs don't look bad at all. Go to NAPA if you can, get their gallon container of carb cleaner with the little basket inside to soak the carb bodies clean. About $16.

[574hondarider]

Those carbs don't look bad at all. Go to NAPA if you can, get their gallon container of carb cleaner with the little basket inside to soak the carb bodies clean. About $16.

Thanks Hondaman.  I went and got the Berryman Chem Dip, as well as ultrasonic cleaned them.  It appears there has been some damage from the 40 year old varnish.  Are these going to work ok still?

[knowsnothing]

Those carbs don't look bad at all. Go to NAPA if you can, get their gallon container of carb cleaner with the little basket inside to soak the carb bodies clean. About $16.

Thanks Hondaman.  I went and got the Berryman Chem Dip, as well as ultrasonic cleaned them.  It appears there has been some damage from the 40 year old varnish.  Are these going to work ok still?

A little corrosion, but those should be fine. 

[574hondarider]

Update:  Carbs are fully cleaned, just need to re-assemble (waiting for time that I can devote a good chunk of a day to do them all in one setting).  I sonic cleaned in simple green aircraft aluminum cleaner, so much so that I removed the finish on the gas intake connector, it looks brass now instead of silver in color.  Some of the jets are slightly discolored, but I think they will be fine.

The bad news:  I put evaporust in my gas tank, and discovered a small leak in the tank on the lower left in front of the petcock.  My guess is a little liquid was in there and from sitting on the side stand for 40 years that area got rusted through.  What would be the best option at this point...weld the holes, or use caswell tank liner (didn't really want a liner), or source another tank?  This bike is starting to wear at my resolve, good thing I am pretty bull headed and don't know when to quit!

[Mark1976]

+1 on the repair.

[574hondarider]

Weld it or braze it.

Thanks, will try my hand at brazing.  I have a benzomatic so I guess it's time to start using it!  Should I be concerned if I braze this one spot that others will pop up later?  I am planning on having this tank professionally painted and just want to make sure I'm not painting something that's just gonna give me issues down the road.  Is there a good way to tell if there are other weak spots in a tank?

Thanks for all the suggestions!

[rusty2078]

Mild media blast (soda) or dustless blaster that uses glass/water...someone that's experienced working with light metal...traditional sandblasting is too aggressive and will warp your tank (lots of variables here). I haven't personally tried a cheap KMS "dustless blaster" (or Harbour Freight, or any other discount tool vendor), but there are small kits that one can pick up that aspirate water and media, the idea being that the water keeps the surface cool and less prone to warping.

A good paint stripper as well (if you're re-painting the whole tank, or just do the underside (?) will allow you to be able to visualize the surface, however may not really give you a good idea of "thickness" or structural integrity of your tank wall.

[574hondarider]

Mild media blast (soda) or dustless blaster that uses glass/water...someone that's experienced working with light metal...traditional sandblasting is too aggressive and will warp your tank (lots of variables here). I haven't personally tried a cheap KMS "dustless blaster" (or Harbour Freight, or any other discount tool vendor), but there are small kits that one can pick up that aspirate water and media, the idea being that the water keeps the surface cool and less prone to warping.

A good paint stripper as well (if you're re-painting the whole tank, or just do the underside (?) will allow you to be able to visualize the surface, however may not really give you a good idea of "thickness" or structural integrity of your tank wall.

I recently purchased a cabinet and have been blasting with soda.  I will strip the tank with it to see what lies beneath, thanks for the advice!

[rusty2078]

Mild media blast (soda) or dustless blaster that uses glass/water...someone that's experienced working with light metal...traditional sandblasting is too aggressive and will warp your tank (lots of variables here). I haven't personally tried a cheap KMS "dustless blaster" (or Harbour Freight, or any other discount tool vendor), but there are small kits that one can pick up that aspirate water and media, the idea being that the water keeps the surface cool and less prone to warping.

A good paint stripper as well (if you're re-painting the whole tank, or just do the underside (?) will allow you to be able to visualize the surface, however may not really give you a good idea of "thickness" or structural integrity of your tank wall.

I recently purchased a cabinet and have been blasting with soda.  I will strip the tank with it to see what lies beneath, thanks for the advice!

I'd probably try to use a stripper first, then a light blast with soda to see if there's any Swiss cheese...I'm also assuming that it would be sufficient to concentrate on your primary area, then the base of the tank where H2O is most likely to accumulate and cause problems. I like Cal's description of brazing as well!

[574hondarider]

Not the best pic in the world, but at least gives a reference.  Looking from the pics perspective, the hole is to the left of the petcock and up a half inch.  Maybe also in the seam at the bottom...it was difficult to tell trying to move this around with a full tank of evaporust.  Will drain it tonight then start the paint removal by this weekend. 

Evaporust says flush with water then fill immediately.  Is flushing with water necessary/advisable?  Seams counter productive to rust prevention.  I was wondering if some rubbing alcohol would be better??  Then maybe in my case spray some wd40 or 2 cycle oil in there since the tank will be dry until next year??

[574hondarider]

Denatured alcohol is better. Then a bit of acetone but keep that away from your paint. The acetone will dehydrate the moisture. Avoid any oils if you plan to braze or weld it.

I will buy some tonight.  How much should I put in the tank, just enought to swish around qt/gal?  I have a bunch of heet at home, but that is methanol and not ethanol if that would work it would be free?  But a gallon of alcohol is only $11 anyways.  The paint is coming off this weekend hopefully so shouldn't be an issue.

[MauiK3]

Powder coating the frame is certainly good but difficult to repair if you ding it.
Consider POR15, hard as nails, repairable, DIY.
Check Jay Leno's Garage, he has a session on it.

[574hondarider]

Powder coating the frame is certainly good but difficult to repair if you ding it.
Consider POR15, hard as nails, repairable, DIY.
Check Jay Leno's Garage, he has a session on it.

Thanks, will check that out!!

[574hondarider]

I went home and removed some paint on the area in question.  I see 2 pinhole leaks around a darker section.  Do I need to braze over this whole dark section too?

I also removed the evaporust and rinsed the tank and dried with a heat gun.  Let it sit overnight and took these pics in the morning.  I need to get a scope in there but way to the back (you can't see in the pics) on the sides there is a lot of white scale.  Is this still rust or is it varnish or ??

My plan here is to remove all the paint, braze all the holes, check for leaks, then do more rust/varnish remediation if any flash rust comes up.  The possibility of caswell liner is still on the table too. 

Thoughts?

[574hondarider]

Some Progress

Stripped the tank with Jasco paint stripper.  Found 3 pinhole leaks.  Tried my hand at brazing (looks awful but doesn't leak, and is under the tank anyways.  Found another leak I need to braze after sloshing with a chain for awhile.  I regret removing all the paint as I am afraid of rusting the tank.  My painter is bringing over some self etching primer to put on to limit flash rust until he can paint it first part of November.  Until then, I only handle with gloves on and store in humidity/temp controlled room.  I also cleaned the petcock, which doesn't look too bad for the original (needs new consumables though).

[574hondarider]

Progress update:

I lined the tank with Casewell liner.  I followed directions to the T, but almost no leftover stuff drained out.  Oh well, at least it looks like it's gonna work out ok.  I didn't wanna line it but kept finding more pinhole leaks and I would braze them and then find more so I figured the metal was pretty weak in the bottom.

I sprayed self etching primer just to give it a coat until my painter can get to in in November.

I removed the engine from the bike!!  I also took off the top cover.  Can someone take a look and see what they think about the wear, I'm not really sure what to look for as this is my first engine that I've had the cover off.  Also, I assume I need to take these acorn nuts off to get the head off....I may have to consult the manual.

I only had one difficult bolt, the tach bolt.  It sheered two of my JIS bits and didn't blink, so besides soaking in PB blaster, not sure what's next with that one.

Any suggestions on this engine would be appreciated, I need to get to the cylinder to see why #4 has no compression, also to inspect the side walls for rust/pitting.  Not really sure what to look for but will post pics and use the manual.   Thanks!!

[574hondarider]

more pics