Topic: '73 cb350f siezed barn find!

[574hondarider]

Ultrasonic Cleaner with varnish remover in it will allow you to dislodge the jets. PB Blaster is worthless on cleaning varnished fuel- stop using it.

Soda blasting your carbs needs to be done carefully and hefty cleaning afterwards is required to unplug all tiny orifices of the media.

Will Jasco® Premium Paint & Epoxy Remover be safe to dislodge the jets and floats if put in the sonic cleaner?  Should I dilute with water?  Are the floats plastic or metal?  Will try this tonight if I can. 

[calj737]

Yikes! I would not use that near my carb internals. Floats are likely plastic.

When I said varnish remover I was referring to varnished fuel, not varnish as a surface finish. The Lacquer Thinner might work well enough too. Berrymans carb cleaner dip is another great option.

[Stev-o]

Vapor blasting is without doubt, the absolute best way to get to get old carbs to look better than new!

These old, nasty Mikuni's were sent to RestoCycle...



...and came back immaculate!

[574hondarider]

Yikes! I would not use that near my carb internals. Floats are likely plastic.

When I said varnish remover I was referring to varnished fuel, not varnish as a surface finish. The Lacquer Thinner might work well enough too. Berrymans carb cleaner dip is another great option.

Gotcha!!  Good thing I asked lol.  I might give Berrymans a try, I've heard good reports from others using it.  Thanks

[574hondarider]

Vapor blasting is without doubt, the absolute best way to get to get old carbs to look better than new!

These old, nasty Mikuni's were sent to RestoCycle...



...and came back immaculate!




Wow, thos look really nice!!  I want to clean them on my own though just for the learning experience, but those really do look good!!

[574hondarider]

Another question:  what hose is acceptable to use as the breather hose going from carb to carb?  I know there won't be alot of gas going through these, but I don't want them breaking down in a year or two if I can avoid it.

[574hondarider]

Progress!!!

After soaking the cylinder heads in 50/50 acetone and atf for about 2 weeks, last night I rocked the bike and heard a snap sound from around cylinder 4 and the fluid shot out (that's the good news).

The bad:  It seams I have no compression on cylinder 4.  With carbs and plug off, and no gas, I verified some compression just by plugging the spark plug holes with my finger.  Cylinder 4 has no sign of compression.  I inserted a wd40 straw and hit the starter and verified cylinder 4 movement, and looked in access areas to verify tappet movement both exhaust and intake, and I can feel it sucking from the carb insulator.  So I am thinking maybe stuck valve or snapped piston ring??  Any ideas??  Also, my kickstart still seams to be locked up, so there is something wrong there too.

I also was able to get all the carbs apart fully and working on cleaning them.

Thank you all for your suggestions!!!  I am new to this and wanted a learning experience, and I sure am getting an experience!!

Thanks!
-Bob

[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!

[calj737]

Weld it or braze it.

[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!

[calj737]

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!

Brazing one spot won’t open any others unless you warp the metal sufficiently that extremely weakened metal will crack or open up.

If you successfully de-rusted the interior and only 1 spot surfaced, I’d say you’re safe to go. You could use silver solder or gas bronze if you have the rod. If there’s any rust on the inside, brazing will not be successful.