Topic: '73 cb350f siezed barn find!

[574hondarider]

Found this original owner bike in a barn over the weekend.  17000 miles.  Original owner (widowed), has been sitting since the early 80s.  100 percent there and never been molested (doesn't even look like carbs have ever been opened.  Engine is siezed.  This is my first attempt at bringing a bike back to life (the other 350f I got early this year was already running decently).

I removed the plugs and shot a squirt of wd40 and let is sit a few hours, then tried to gently rock the bike in gear.  Then, shot a little pb blaster down there and let it sit overnight, still not budging.  Next step....top cover removal??

Electrical seams to work besides bad battery and bad turn signal relay.  Some surface rust inside tank, clutch goes through gears.  Triple top clamp has 2 cracks.  Looks like it may have had a leaky head gasket.  Front brake not working.

My thoughts to bring this back to life.....
1.  pull carbs and soda blast and get new o rings/kit and reassemble
2.  use some product to get rust out of tank and go through petcock.
3.  take top cover off and attempt to get pistons free.  While doing so, maybe remove the top end assembly and soda blast, then replace gaskets.
4.  buy new triple top off ebay.
5.  master cylinder brake kit?
6.  new tires

Does this sound like a proper course of action?  I am openn to any suggestions as I am new to all this but thought this would be a good winter project.  Also debating about taking it down to the frame for a proper restore.  BTW, paid $700 for this...don't think it's a steal, but thought price was reasonable.

[bek1966]

Nice 350f, I love these bikes!  Just this Spring I picked up a 1974 350f... out of a barn... from the original owner... unmolested... with about 10000 miles on it ...also seized - sound familiar? .

I haven't gotten very far with it yet other than to remove the plugs and pour some Mystery Oil into it.  It also didn't budge, but I haven't tried more than a couple of times.

Thanks for sharing the pictures, I'm following along with interest.

Regards,
Brad

[574hondarider]

Brad,

That is really similar!  We can go through the rebuild together then hahaha.  Thanks for the reply!

[Mark1976]

For what its worth,
   Making a list is a great starting point, you have a great find there. Try to avoid dismantling anything at first. Keep soaking the cylinders with PB blaster or WD40, let time do its job first. Put a battery in it and find out what does and doesn't work. Then start making a list of what needs to be addressed on the electrics. Pull the carbs, clean rebuild and reinstall. All the while keep trying to carefully break the pistons free, it'll make pulling the topend that much easier if that's what has to be done eventually.  This is a great find and taking the time to carefully restore it to its original running state without any unnecessary tear down is a great place to start.

[calj737]

Drain the oil. Pull the plugs. Fill the cylinders with a 50/50 mix of Acetone and ATF. Keep filling them as the mixture drains out. It may take days to release the rust between the rings and bores. You can even pull the exhaust temporarily to aid in accessing the piston tops.

Dismantling is a last resort. With a seized engine you’d have to cut the cam chain anyway and that requires much deeper disassembly. Patience and repeated soaking. It will come free.

If you can ascertain which pistons are down, they’ll be the stuck ones.

[574hondarider]

Will give this a try, thanks!  Would the wife's finger nail polish remover work (says it is acetone)?  I have fork oil but no atf, guess a trip to wal-mart is called for!

I will go ahead and remove the exhaust, be a good time to try to tackle some of the rust on it.

Keep the advice coming!!

[WhyNot2]

Nice bike........it may take a week or so to get it unstuck, but well worth the wait if it works.

I've got a 74, and can't get it to run at all, hoping you have better luck.

[calj737]

Will give this a try, thanks!  Would the wife's finger nail polish remover work (says it is acetone)?  I have fork oil but no atf, guess a trip to wal-mart is called for!

I will go ahead and remove the exhaust, be a good time to try to tackle some of the rust on it.

Keep the advice coming!!

Buy a gallon of Acetone at Walmart.

[574hondarider]

Will give this a try, thanks!  Would the wife's finger nail polish remover work (says it is acetone)?  I have fork oil but no atf, guess a trip to wal-mart is called for!

I will go ahead and remove the exhaust, be a good time to try to tackle some of the rust on it.

Keep the advice coming!!

Buy a gallon of Acetone at Walmart.

will do!

[574hondarider]

Should I go ahead and order replacement insulator boots going from carb to engine?  I don't want to have to pull the carbs more than once, but the original ones looks decent currently (probably very hard though).

[calj737]

That is a prudent purchase as long as you buy genuine Honda units. Many of the aftermarket types are of lesser quality and either tear easily, or don't quite fit the profile.

[574hondarider]

OEM carb rebuild kit and OEM boots ordered!  Now, if I want to get a 4 into 1 exhust, are the standard jets going to work?  I don't feel like making this decision now, but I am about to go through the carbs in a few weeks so I guess I need to order the correct jets if the oem ones can't handle it.

Acetone and ATF purchased, hopefully will have time to give them a dose tonight. I know it's 50/50, but how much fluid goes in each piston?

Thanks,

Bob

[574hondarider]

Nice bike........it may take a week or so to get it unstuck, but well worth the wait if it works.

I've got a 74, and can't get it to run at all, hoping you have better luck.

Thanks!  I hope you get your bike running, I will have to look for your thread to see what's going on with yours and if I can help.  Good luck!!

[K7-Steppy]

Just throwing this out there the other day I started tearing down my cb350f engine which was also seized luckily for me after trying everything to get it unstuck I took off the alternator cover which apparently revealed there was a small leak where the wires entered and completely rusted out the rotor but once I got the cover off it spins freely now with ease. probably not your case but if you haven't already take off the alternator cover to see if you're in the same situation as me

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[574hondarider]

Just throwing this out there the other day I started tearing down my cb350f engine which was also seized luckily for me after trying everything to get it unstuck I took off the alternator cover which apparently revealed there was a small leak where the wires entered and completely rusted out the rotor but once I got the cover off it spins freely now with ease. probably not your case but if you haven't already take off the alternator cover to see if you're in the same situation as me

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Wow....that looks bad!!  I pulled the alternator cover and it looks mint...in fact, never seen one so clean!!  I wish that was true with the rest of the bike!!  Thanks for the tip and good luck!

[574hondarider]

Will give this a try, thanks!  Would the wife's finger nail polish remover work (says it is acetone)?  I have fork oil but no atf, guess a trip to wal-mart is called for!

I will go ahead and remove the exhaust, be a good time to try to tackle some of the rust on it.

Keep the advice coming!!

Buy a gallon of Acetone at Walmart.

I have been filling the cylinders every other day with acetone and atf, hoping that it will break free soon.  When it does, can I try to turn it over, or would there be potential of rust and junk on top of the pistons that I need to remove before I try that?  I don't want to damage the walls any, but would like to get a compression test before I tear it down.
Thanks,  Bob

will do!

[calj737]

After is releases, you'd best fill it with clean oil and filter, and pour a little down each cylinder to lubricate the bores before rotating the motor.

[574hondarider]

After is releases, you'd best fill it with clean oil and filter, and pour a little down each cylinder to lubricate the bores before rotating the motor.

Will do, thanks!  Going to have to shop for some cheap(er) oil than my honda gn4 stuff that's on hand for this little trial run.

[calj737]

Drizzle some down the tappet inspection covers too so you get some lubrication on the cam journals as well.

[Stev-o]

+1  make a cocktail of ATF & Acetone, pour a "shot" down the spark plug hole every couple days or so, be patient if you want this to work.  Keep the plugs out and then try to rock it back and fourth in 3rd or 4th gear, it should free up.

FYI - it is most likely not seized, that would be a mechanical failure. When these motors set for a long period of time, the piston rings rust to the cylinder wall...we call it "stuck". You need to "unstuck" it!

What brand of carb kits did you buy?  If they are not Honda, send em back!  [gaskets may be ok]
As a general rule, resist buying cheap china crap for your Japanese motorcycle!
The cheap stuff ends up costing you more when you have to replace it prematurely.

Good luck.

[574hondarider]

+1  make a cocktail of ATF & Acetone, pour a "shot" down the spark plug hole every couple days or so, be patient if you want this to work.  Keep the plugs out and then try to rock it back and fourth in 3rd or 4th gear, it should free up.

FYI - it is most likely not seized, that would be a mechanical failure. When these motors set for a long period of time, the piston rings rust to the cylinder wall...we call it "stuck". You need to "unstuck" it!

What brand of carb kits did you buy?  If they are not Honda, send em back!  [gaskets may be ok]
As a general rule, resist buying cheap china crap for your Japanese motorcycle!
The cheap stuff ends up costing you more when you have to replace it prematurely.

Good luck.

Thanks for the reply.  I purhased the genuine honda carb kits, and was hoping to use all the old brass parts.  All the engine seals I am buying are original honda as well.  I will start rocking the bike this weekend as you suggues, I have filled the cylinders with the mixture 4-5 times now in the last week.

I'm going to post a pic of the inside of the carbs as they are awful.  All gas has turned to hard varnish, so much that I can't get the main jet out and I don't want to damage the jet.  I used carb spray, then bp blaster, and this morning hit it with liquid wrench as that is what I had laying around.  I do have a sonic cleaner and a powder blaster, may give the sonic cleaner a shot to help remove the main jet.

[574hondarider]

Here's a pic of 40 year old gas turned to varnish.  Everything is frozen in place.  Bike has 17000 miles on it.  Will any of this be able to be re-used?  I was hoping to re-use everything but the o rings, but may need to look for new parts?  I guess really won't know until I get everything disassembled and cleaned.....

[WhyNot2]

yep, all the rubber is toast...........

every thing else is usable after a thorough cleaning of course.

[calj737]

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.

[BigJimG]

Another option I have used for varnished fuel in the past is Lacquer Thinner.  I just find a suitable container, coffee cans work nice for single carbs or pieces, and fill to cover the part.  Put the lid on the coffee can and leave it alone for a day or two while you work on other things.  Use gloves when working with it because it is NOT good for your hands/skin. 

Some light agitation with an old toothbrush or similar after the soak will clean things up nicely.  Sometimes, if they are really bad or dirty, you may need to soak longer. 

This will pretty much destroy all rubber components, but that's not usually a big deal since you were going to need to replace them anyway.