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Discussion Starter · #1 ·
]I picked up at 72 CB175 in New Mexico a few weeks ago for $50(title included!). I've been wanting to get one for a while and saw this chance to grab one cheap to play on. I knew it would require work, and I'm not afraid to dive into it myself. The bike had been sitting outside for 25 years. The odometer says 6300 miles. There is very little surface rust, gas tank has a little rust inside but nothing major. My dad picked it up, and thought he could kick it over, but it turns out it is seized.
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I drained the oil (picture below), and am just glad it was stored with oil in it. No shiny metal came out or major parts, but letting it sit it looks like there is rust or something in the oil. The bowl was dirty before putting oil in, so that dirt was there before. Pulling out the spark plugs, it looks like there is a bunch of ash in the cylinders. The picture below shows a little bit, sorry for the blur. There is already sea foam oil in it when I took the picture. Also one of the sparks plugs may have been stripped coming out, so that will be something I get to deal with.
image1.JPG image2.JPG
I'm going to let the engine soak for two weeks. I will then just start to take it apart. I tried loosening a few of the screws on the cover and they are all really stuck. I've got a impact tool so that may be helpful. Can I replace these with hex heads when they go back in? If you guys see anything obvious in the pictures, let me know. Otherwise I'll just update the thread as I go along in case somebody in the future needs some ideas. Or if I give up and someone sees parts they need.
 

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I've been working away on a '71 CB175 for the last few months on and off. It was dry stored as yours looks to have been and the other week I took the engine out the frame and onto an ad hoc engine stand for further dismantling. I've been amazingly lucky with getting screws and bolts out so far, the only one that was really difficult was the big drain plug in the sump - I couldn't shift it when the engine was in the frame and ended up with the engine on its side and me sitting on it to hold it down while I heaved away with a really long socket extension which did the trick. But do as much as you can with the engine in the frame as it's much easier! With the crosshead screws - and similarly with bolts - I followed the same routine. After cleaning I'd give the screws a good squirt of ACF-50 and give it a minute or so to penetrate, then put a suitable drive through screwdriver in place and give it a few good whacks to break the stiction in the threads. A final couple of whacks to get the screwdriver well settled in the crosshead then twist. About 90% of the screws freed up first time around using this technique - shown to me by an old bike mechanic in the local shop who rarely bothers with an impact driver. It's a method that replicates the kind of thing an impact driver does but it's a lot easier to calibrate the force used so less chance of chewing up the crosshead. Anything that didn't free up first time around got some more lubrication then left for 24 hours and the next time around they'd free up too. So far it's been a really nice machine to work on and from the first peek into the innards it looks like the engine internals are in good condition.
 

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Discussion Starter · #4 ·
I'm glad to see someone is in the same boat as me. I'll take that advice as I don't see my wife coming out to the garage to help me much. I had to use a big cheater bar to get the drain plug off, luckily it came off nicely. I used WD-40 and overnight soaks on all the cover screws, with no avail. Looks like I'm using the wrong screwdriver though so I'll get the right one and try it out. I plan on replacing everything with hex head anyways. Philips heads are a waste IMO. I'll try his method when I get the right ones and see how it works. Thanks for the advice. I'll also post some pictures of the inners in the next couple weeks to compare.
 

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Discussion Starter · #5 · (Edited)
The cover screws are JIS (japanese industrial standard) not Philips, use a JIS bit on a manual impact driver. They wont put up any resistance and you wont mash the heads
Use a philips and youll just turn them to cheese
I've seen the advise on the JIS before... and I honestly thought it was a different hardness of philips head (meant to be used with the impact driver) so there I am being a Newb. Thanks, I'll get some on order if I can't find them locally. I've only torn up 3 so far, and they were all on the chain cover.

In case someone finds this in the future. Here is a link explaining the difference. http://www.webbikeworld.com/motorcycle-tools/jis-screwdrivers/
 

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I've seen the advise on the JIS before... and I honestly thought it was a different hardness of philips head (meant to be used with the impact driver) so there I am being a Newb. Thanks, I'll get some on order if I can't find them locally. I've only torn up 3 so far, and they were all on the chain cover.

In case someone finds this in the future. Here is a link explaining the difference. JIS Screwdrivers - webBikeWorld

Interestingly there's been a bit of a debate on this topic in CMM sparked by an article on a CB125 fixup. The guy who wrote that article mentioned JIS vs. Philips but actually used a Philips No. 3 for the job he was doing. He got told off for this in the letters column in the next issue but his reply was that he's never owned an actual JIS screwdriver or ever felt the need for one in a few decades worth of bike mechanics. As he said screws on Japanese bikes get chewed up by people using either the wrong size of bit or the wrong technique, then they blame either the tool or more usually flimsy Japanese metal. You can chew one up just as easily with a JIS screwdriver as a Philips. Just to confound the issue - and annoy any purists - as the screws on my 175 had already seen a bit of action from the look of them I wasn't concerned about re-use and, as I only had Pozidrive drive through screwdrivers to hand, used those for the job. Worked perfectly well and I didn't mangle anything in the process.
 

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Interestingly there's been a bit of a debate on this topic in CMM sparked by an article on a CB125 fixup. The guy who wrote that article mentioned JIS vs. Philips but actually used a Philips No. 3 for the job he was doing. He got told off for this in the letters column in the next issue but his reply was that he's never owned an actual JIS screwdriver or ever felt the need for one in a few decades worth of bike mechanics. As he said screws on Japanese bikes get chewed up by people using either the wrong size of bit or the wrong technique, then they blame either the tool or more usually flimsy Japanese metal. You can chew one up just as easily with a JIS screwdriver as a Philips. Just to confound the issue - and annoy any purists - as the screws on my 175 had already seen a bit of action from the look of them I wasn't concerned about re-use and, as I only had Pozidrive drive through screwdrivers to hand, used those for the job. Worked perfectly well and I didn't mangle anything in the process.
LOL, just because I can use a 1/2 inch chisel to open a can of paint doesnt mean its the right tool for the job regardless of technique.
The reason for mashed cheese heads is using a philips on them, people winge and moan about the heads being soft then smack a Pozidrive into them with a hammer.... Sure they come off but then I could just drill all the heads off and get the same result
View attachment 80220
And heres my impact driver ( notice the first bit is JIS)
View attachment 80221
And heres my CL175 engine when I got it
View attachment 80222
Despite the salt water corrosion I got all the machine screws out without issue
 

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Nice project. Bit off topic but I found the only place on old Hondas I have ever found where slotted head screws are used as standard from the factory is on CB250/350K ND coils to mount the coil to the alloy frame.
 

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I've been following that thread in CMM about the CB125 rebuild, and to be honest, got quite irritated with the blokes attitude in general.

Comes across as a patronising dick. I almost wrote in to the mag about this, didn't bother in the end.

That said, I recently bought a special offer of Makita bits from Screwfix, and the No3 Phillips bits are a good fit in Mr Megapacks JIS alike crosshead screws.
 

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Discussion Starter · #10 ·
LOL, just because I can use a 1/2 inch chisel to open a can of paint doesnt mean its the right tool for the job regardless of technique.
The reason for mashed cheese heads is using a philips on them, people winge and moan about the heads being soft then smack a Pozidrive into them with a hammer.... Sure they come off but then I could just drill all the heads off and get the same result
View attachment 80220
And heres my impact driver ( notice the first bit is JIS)
View attachment 80221
And heres my CL175 engine when I got it
View attachment 80222
Despite the salt water corrosion I got all the machine screws out without issue
I actually bought a very similar impact driver based on one of the other threads you posted that picture on. All because of the information you provided in that post haha. It came with a JIS bit so that has been helpful so far. I had to order some JIS screw drivers on Amazon last night and they won't be in until this weekend, so hopefully I can remove them without tearing everything up. Even the ones that worked with a phillips head, I wouldn't put them back in. I've got new cables on their way as well. 4 day weekend should provide time to get some work done.

Pistons are still soaking in ATF and penetrating oil, no luck moving them with kickstarter yet. Plan to remove left cover and rotate from stator soon. I've got the lower filled with oil just soaking so I haven't done this yet.

For track record (USD):
Throttle Cable (ebay): $11.32
Handle Bar Grips with Tube Sleeve (ebay, just really needed the tube sleeve as it was cracked): $13.51
Clutch Cable (ebay): $15.75
New clutch and break levers, old ones were snapped off (ebay): $14.95

I probably could have shopped around, but I wanted to hurry and get them ordered with a long weekend coming up.
 

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Discussion Starter · #11 ·
Nice project. Bit off topic but I found the only place on old Hondas I have ever found where slotted head screws are used as standard from the factory is on CB250/350K ND coils to mount the coil to the alloy frame.
This is interesting. I would have thought they would be more prevalent because they seem easier to manufacture. Who knows.

I've been following that thread in CMM about the CB125 rebuild, and to be honest, got quite irritated with the blokes attitude in general.

Comes across as a patronising dick. I almost wrote in to the mag about this, didn't bother in the end.

That said, I recently bought a special offer of Makita bits from Screwfix, and the No3 Phillips bits are a good fit in Mr Megapacks JIS alike crosshead screws.
I looked at some of these. In the US there seems to be bits called "demolition bits" and they appear closer to JIS than phillips. This is just from looking while walking around the hardware store. I didn't buy them to try, but will compare when I get the JIS in.
 

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Discussion Starter · #12 ·
I made a little progress over the last few days. The pistons are officially unseized! After about two weeks of soaking in a mix of penetrating oil and ATF, I put a wrench on the stator and it turned really easy. It moves smoothly now from both the kickstarter and the stator. I tested the compression just for giggles, and it was about 70 psi on both pistons. This was with the carbs off (I rebuilt the carbs too). I see a lot of carbon build up in the intakes of both cylinders. There is also some stuck on the top of the pistons when I look through the spark plug hole.

Could the compression issue be just carbon build up on the valves? I guess I should take it apart as planned and clean up the valves and check the pistons while putting in new rings. I've discovered the bike is actually a 1971 CB175. It had about 3000 miles on it originally. What should I do as a minimum as it has sat around for 35 years? If I replace the rings, I'll hone the cylinders too, any recommendations on tools for honing?

Thanks for the help!
 

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So a teaspoon of oil in each cylinder should up the compression if its valves, id guess its thd rings are stuck in the pistons and not sealing but 70 is about 100psi short of where it should be
Your bikes a K5 which is a far better way of describing it for parts than a 1971 since 71 would be the year it was registered where as K5 is the series
It takes less than 30 seconds to dissengage the speedo and then the odometer stops counting miles....you could clock thousands of miles too and from work, keeping your speed in check with the traffic and simply screw the cable back in when you wanted to sell the bike as a low milage machine..... Im not saying you should do this simply i wouldnt trust a 40year old odometer to be correct
http://www.hondatwins.net/forums/67...n/16105-basic-checklist-new-you-old-bike.html
 

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My CB450 K5 is assembled 100% with stainless steel Allen (Hex) head screws. The base kit was purchased on ebay and I was lucky to have an Ace Hardware store near by and I used an online supplier too. Every steel screw stainless or not should be installed with anti seize compound (copper grease). This includes the oil drain plug and the spark plugs. Be careful of the torque values. 5-7 ft/lbs is about right for a 6mm screw lubricated with anti sieze. You and the next owner will appciate it.
 

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Could the compression issue be just carbon build up on the valves? I guess I should take it apart as planned and clean up the valves and check the pistons while putting in new rings. I've discovered the bike is actually a 1971 CB175. It had about 3000 miles on it originally. What should I do as a minimum as it has sat around for 35 years? If I replace the rings, I'll hone the cylinders too, any recommendations on tools for honing?

Thanks for the help!
I'd suggest caution when it comes to taking the valve gear apart. I'm passing on info from a fellow member of the VJMC who's worked on a few of these bikes rather than my own experience as I'm at a roughly similar point. He told me - and I can see the bits he was talking about in the parts diagram - that the valve gear for these bikes have some features that didn't appear on other models. There are some seals in the valve guide that - because they were only used for a few years - are now very tricky to get hold of and may not be re-usable if you take it apart. Basically if it doesn't need a strip down leave well alone was his advice and if you do need to take it apart check parts availability before you commit.
 

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djc, Im not trying to be dissagreeable but there are plenty of work arounds
2 piece valve stem seals are NLA, but you can just use more modern 1 piece ones heres a link
http://www.wemoto.com/bikes/honda/cb_175_k4_k5/70-71/picture/valve_stem_seal_exhaust/ Less than £1 so about $1.25 USD + postage
A number of 175's only use seals on the exhaust valve only
Stock Cb160 didnt have any valve stem seals at all but TOOLS fit some off of a subaru 2.5L engine that worked fine for him and should fit the 175 guides, or fit cb200 guides that take 1 peice seals

If the valve seals are so shot they cant be reused they probably arent working anyway so i wouldnt worry about pulling the valves if theyre needing it
 

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Discussion Starter · #18 ·
So a teaspoon of oil in each cylinder should up the compression if its valves, id guess its thd rings are stuck in the pistons and not sealing but 70 is about 100psi short of where it should be
Your bikes a K5 which is a far better way of describing it for parts than a 1971 since 71 would be the year it was registered where as K5 is the series
It takes less than 30 seconds to dissengage the speedo and then the odometer stops counting miles....you could clock thousands of miles too and from work, keeping your speed in check with the traffic and simply screw the cable back in when you wanted to sell the bike as a low milage machine..... Im not saying you should do this simply i wouldnt trust a 40year old odometer to be correct
http://www.hondatwins.net/forums/67...n/16105-basic-checklist-new-you-old-bike.html
You are right, you never know what the PO did with the bike. I've made some discoveries today that make me feel like it may have had that low of miles. I took the engine out, took the top end off and measured everything. The cylinders and pistons are both well within original spec. No boring needed. The top piston ring is stuck in the groove of one piston and pretty tight in the other. This explains the low compression. The second rings are both pretty tight as well, the third is loose. I'll order some new rings for reassembly.

Does anyone have a recommendation for pulling seized rings out? Also I've read that I need to hone the cylinder walls for the new rings. This isn't a problem, the cylinder walls don't have any edges but you can see vertical marks vs 'x' style marks.

While I wait on the new rings and reassembly, is there a proper way to preserve everything so I don't have any flash rust? I've sprayed it all in oil, should I reapply daily?
 

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Discussion Starter · #19 ·
djc, Im not trying to be dissagreeable but there are plenty of work arounds
2 piece valve stem seals are NLA, but you can just use more modern 1 piece ones heres a link
Honda CB 175 K4/K5 70-71 Valve Stem Seal Exhaust Parts at Wemoto - The UK's No.1 On-Line Motorcycle Parts Retailer Less than £1 so about $1.25 USD + postage
A number of 175's only use seals on the exhaust valve only
Stock Cb160 didnt have any valve stem seals at all but TOOLS fit some off of a subaru 2.5L engine that worked fine for him and should fit the 175 guides, or fit cb200 guides that take 1 peice seals

If the valve seals are so shot they cant be reused they probably arent working anyway so i wouldnt worry about pulling the valves if theyre needing it
20160704_131514154_iOS.jpg 20160704_132240265_iOS.jpg 20160704_132304281_iOS.jpg 20160704_135122461_iOS.jpg

Here's a few pictures of the insides. I don't even know what to look for on the valves but they look pretty good to me? I think I'll leave them and hope replacing the piston rings fixes my issue.
 

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Having got that far, it seems a shame not to sort out the valves whilst the head is off. Head looks badly coked up to me.
 
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