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Discussion Starter · #1 ·
I've been reading alot here since getting a 72 cl175. The engine is locked up and I've put mystery oil in cylinders and in intake/exhaust ports.

A few questions;
- can't I just put a stronger bolt on the stator side to try and break it free? I've read to be careful not to sheer off bolt head. And also it would be breaking the engine free in the wrong direction.

- if I pull the engine now, how would I get the cylinders free from the corroded pistons and rings without prying on the fins or other parts? I don't know how to disassemble if these parts are rusted together.

-If I free the engine up won't it immediately score the cylinders? Should I put new rings and possibly pistons in as a minimum, assuming both are rusted?

-anyone have complete exhaust system for a 72 cl175?

Oil has been penitrating since Friday. So far she is rock solid seized.

Thank you all in advance!!
Looking forward to getting her running again.
 

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At this point, I'd just pull the motor from the frame, remove the cylinder head and use a hammer and a wooden drift to try to breaking them free.

I've read that a 50/50 mix of ATF (automatic transmission fluid) and acetone is the best penetrant oil for this job.

Also, where are you located? I've got a motor from a 1971 CB175 that I'd like to sell. I parted the rest of the bike several years back, as the bodywork and chrome were rough, and a friend of mine needed a titled frame. It was running, and is still free (stored with a little oil in the cylinders, and gets turned over by hand every now and then).
 
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Discussion Starter · #4 ·
I'd pull the clutch cover and try to turn the crank from that side instead of the stator. But that's just my opinion, I could be wrong.
What would I grab hold of on that side to turn the crank? I've pulled that cover an dont see anything I could grab hold of.
At this point, I'd just pull the motor from the frame, remove the cylinder head and use a hammer and a wooden drift to try to breaking them free.

I've read that a 50/50 mix of ATF (automatic transmission fluid) and acetone is the best penetrant oil for this job.

Also, where are you located? I've got a motor from a 1971 CB175 that I'd like to sell. I parted the rest of the bike several years back, as the bodywork and chrome were rough, and a friend of mine needed a titled frame. It was running, and is still free (stored with a little oil in the cylinders, and gets turned over by hand every now and then).
Im in st louis, where are you located?
 

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There are a number of products you can use to loosen frozen cylinders. The main thing here is not to get in a hurry. I like Deep Creep. Put it in the cylinders and let it set for a week or two. Dont remove the motor yet. After letting the motor set for awhile Put it in second gear and rock the bike back and forth and let the weight of the bike work for you. Again dont get into a hurry . Do this several times. If you do end up removing the motor go to your local Auto Zone or other auto parts store and rent a steering wheel puller. This will let you use down force on the pistons. Then its just a matter of soak, pressure on the puller and add heat. Dont worry about damaging the cylinders or pistons if its stuck that tight your going to have to repair or replace most of it any way.

Keep us posted.
Bill H
 

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Discussion Starter · #7 ·
I have not worked on a CL 175. Is that a 360 or a 180 degree motor? That will mater on removing the pistons from the cylinder .

Bill H.
That I dont know, I do now that both pistons appear to be at the top of the head, I can only put a small amount of marvel mystery oil in the cylinders.
 

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The pistons will need an inspection at least so you may as well remove the engine. Then take off the head. There are a few methods of safely freeing the pistons from the cylinder but rather than go through them may I refer you to a recent topic on Facebook where a John Stenerg had the self same problem and solved it. It is facebook group' Honda CB/CL160 & CB/CL175 Owners Group 'and the date was Oct 24 2021. Don't hit it with a hammer!...it will only make it worse.
 

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Discussion Starter · #10 ·
The pistons will need an inspection at least so you may as well remove the engine. Then take off the head. There are a few methods of safely freeing the pistons from the cylinder but rather than go through them may I refer you to a recent topic on Facebook where a John Stenerg had the self same problem and solved it. It is facebook group' Honda CB/CL160 & CB/CL175 Owners Group 'and the date was Oct 24 2021. Don't hit it with a hammer!...it will only make it worse.
Yes I am against the hammer method. I dont have Facebook but I would likely make an account for my dog so I could view this process. I will rock the bike again this evening. I just figured it would be easiest to free the engine before disassembly if it were still in the frame. I'm going to also try threading a grade 8 bolt on the crank and see if that does anything. I'm guessing I will have to hone and replace rings, possible pistons as well.

Honing is intimidating to me, never done it.
 

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Even if you (or your dog) joins FB, it might be a closed group you'd have to join the group itself to see anything. as for the cylinders, even if the pistons come free fairly easily you'll likely be looking at getting the cylinders bored and buying 2nd or 3rd over pistons because of rust rings and/or pits in the cylinders. Honing rarely takes care of advanced rust that causes stuck pistons, and it can also enlarge the bore as well as make it out of round if you hone it excessively
 

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Discussion Starter · #12 ·
Even if you (or your dog) joins FB, it might be a closed group you'd have to join the group itself to see anything. as for the cylinders, even if the pistons come free fairly easily you'll likely be looking at getting the cylinders bored and buying 2nd or 3rd over pistons because of rust rings and/or pits in the cylinders. Honing rarely takes care of advanced rust that causes stuck pistons, and it can also enlarge the bore as well as make it out of round if you hone it excessively
How or who would I take it to for an oversized bore and then how would I know what size piston and rings to get. Totally foreign territory for me.
 

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How or who would I take it to for an oversized bore and then how would I know what size piston and rings to get. Totally foreign territory for me.
Once you get the engine apart and the cylinders off the engine (without beating on the pistons and potentially damaging rod bearings), you would take the pistons and cylinders to a machine shop to be measured and inspected. The machine shop would tell you how much would need to be cut from the bore to clean it up and you would then buy the proper size pistons and rings to fit, then take them to the machine shop with the cylinders for them to do the boring. Many aftermarket stores like Scrambler Cycle and CruzinImage sell oversized pistons and rings for vintage Hondas
 

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Discussion Starter · #14 ·
Once you get the engine apart and the cylinders off the engine (without beating on the pistons and potentially damaging rod bearings), you would take the pistons and cylinders to a machine shop to be measured and inspected. The machine shop would tell you how much would need to be cut from the bore to clean it up and you would then buy the proper size pistons and rings to fit, then take them to the machine shop with the cylinders for them to do the boring. Many aftermarket stores like Scrambler Cycle and CruzinImage sell oversized pistons and rings for vintage Hondas
Thank you very much! I'm no pro but really looking forward to getting it road worthy. I think I'm going to get the frame power coated and crome redone and see if I can get it looking like new. Any suggestions on getting the gas tank painted and pinstriped? I have the blue tank and side covers, right one is broke and left one isn't in great shape.
 

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If both pistons are at the top of the cylinder its probably a 360 motor which means both pistons go up and down at the same time .This will make it easier to take the cylinder off when you get to that point .As I said dont get in a hurry let the motor soak another week then try rocking it again. Once you get it out of the bike it will be harder to hold it in place so you can work on it .You may have to but do all you can before then. I have drilled some flat steel bars. using head bolts to bolt them to the cylinder, then drilled and tapped a bolt over the center of the piston and used them to put pressure on the piston but its a lot of work. Again I suggest you pick up a steering wheel puller. As I said take your time . I spent 3 weeks getting the cylinder off a 305. Dont worry about what to do after you get it apart. First get the cylinder off then there will be some pretty smart members that can help you.

Bill H
 

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I've read that a 50/50 mix of ATF (automatic transmission fluid) and acetone is the best penetrant oil for this job.
I've been using this concoction as my general penetrant of choice for many years now. It will indeed unlock an engine, as I've done many times working on small equipment engines like Briggs and Stratton and Honda GX's. My son and I also used it to get his beater F-150 4x4 back on the road. It was his first vehicle, and when we got it, the front end was just worn slap out. We bathed all of the fasteners from wheel to wheel, and using nothing but hand tools, pulled his entire front suspension apart (remember, this is a 4x4!), and replaced all of the bushings, joints, etc.

Ever since I've started using this stuff, I've not bought one single can of WD-40, PB Blaster, Aero Kroil, nor anything else for that matter. The stuff really is amazing. Plus, it smells good! Bonus!
 

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Whatever you use, top it off every couple of days and above all don't be in a big hurry. It took years for this engine to get stuck, it'll take weeks to unstuck it with the least damage.

With the engine still in the frame and a drive chain still in place put it in 3rd gear and just rock the bike back and forth for a few minutes at least once a day.

Add heat, use a heat gun on the cylinder barrels and rock the bike some more. Lean the bike left to right to swirl the oil in the cylinders too. You'll break it free eventually.

If you're in a hurry, another engine will be your best bet while you take your time with this one.

You CAN do this, we're here with collectively several decades of experience to explain and advise.
 

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I've freed up a few in my time, and I don't think the recipe is that important. PB Blaster Penetrating Catalyst in the spark plug holes works as well as anything else. What I've found to be important is HEAT. Let it soak overnight then heat up the cylinders gently and evenly with a propane torch. I'd grab both sides of the crank. An oil filter wrench on the rotor, and a spanner on the oil filter nut on the other side works well. Heat, try to turn, Heat more, add more Blaster, repeat. It's a lot easier with the engine in the frame. Once it's loose, put some oil in the cylinders, turn it over and listen. If no weird sounds, and the valve train is working, adjust the cam chain and valves, put everything else back together and go ride!!! The rings will often break free and work OK once it's running. THIS ADVICE IS NOT FOR A CONCOURSE RESTORATION, but for a cut-rate get-it-back on the road/trail project.
-48
 

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Discussion Starter · #20 ·
I've been using this concoction as my general penetrant of choice for many years now. It will indeed unlock an engine, as I've done many times working on small equipment engines like Briggs and Stratton and Honda GX's. My son and I also used it to get his beater F-150 4x4 back on the road. It was his first vehicle, and when we got it, the front end was just worn slap out. We bathed all of the fasteners from wheel to wheel, and using nothing but hand tools, pulled his entire front suspension apart (remember, this is a 4x4!), and replaced all of the bushings, joints, etc.

Ever since I've started using this stuff, I've not bought one single can of WD-40, PB Blaster, Aero Kroil, nor anything else for that matter. The stuff really is amazing. Plus, it smells good! Bonus!
Isn't marvel mystery oil half atf halve kerosene, basically the same thing? I'm open to anything better.
 
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