'71 cb175 take 3!

Re: '75 cb550 and '71 cb175 double build!


jag767 said:
Well here's an strange update.

So out of curiosity I rechecked the compression. 130. And there's my issue. So last night the engine came out, and I tore into it. Now I was told the motor had never been messed with. HA! What a lump of crap. First thing I notice is all the gaksets, no adhesive on them. They literally were just kind of there, and we're so hardened I thought they were metal for a second. Next thing to jump out was the big Ole .25 on both pistons. So my conclusion is someone in the past rebuilt at least the top end of the motor.

Here's my question, can poorly sealing gaskets, including the head gasket, cause that low of compression and a shitty idle?

I know it can cause issues, but we're talking like -50 psi compression and a motor that's hard to kick over, with an erratic idle, that stalls within a minute. The pistons and rings look like maybe there's 500 miles on them, so the only thing I haven't measured up is the valves, which if I can avoid taking apart I'd like to.

I'm taking it to have helicoils put in for the spark plugs today, and was going to do a 1 mm overbore as well as have it decked. Now I'm thinking just do the helicoils and put it back together properly.

Thoughts?
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What makes you think it was put together improperly? Something out of place other than the hardened gaskets?

No sealant was used on my base or head gasket. Didn't think it should be used. Was the head torqued down when you got it?
 
Re: '75 cb550 and '71 cb175 double build!

1sttimer said:
What makes you think it was put together improperly? Something out of place other than the hardened gaskets?

No sealant was used on my base or head gasket. Didn't think it should be used. Was the head torqued down when you got it?
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Hmmm, says right in the clymer manual to apply on both sides of the gaskets.... head was torqued. The gaskets were hard as shit too which I know makes getting a good seal almost impossible. The gaps in the pistons rings weren't spaced correctly either, but no idea if that happened as I took it apart or not.
 
Re: '75 cb550 and '71 cb175 double build!


jag767 said:
Hmmm, says right in the clymer manual to apply on both sides of the gaskets.... head was torqued. The gaskets were hard as shit too which I know makes getting a good seal almost impossible. The gaps in the pistons rings weren't spaced correctly either, but no idea if that happened as I took it apart or not.
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Ha! Learn something new every day. Even the base gasket with the crush ring?
 
Re: '75 cb550 and '71 cb175 double build!

I will check. I remember seeing in for all I think but I will make sure. Either way a little no. 2 permatex wouldn't hurt anything. While I've have time to twiddle my thumbs I've been looking into adapting this to work

http://www.ecotrons.com/products/kawasaki_ninja_250cc_fuel_injection_kit/

I know 28 mm is too big, but they have 22 mm throttle bodies for uav's that I think could be adapted. I have a fair amount of time put into tuning with efi, and up til now the roadblock was throttle body size, and the ecu needing more juice than the engine returns to the battery. I'm willing to bet the uav kit uses a lot less, may even be what I need to make it work.

http://www.ecotrons.com/products/uav-engine-efi/
 
Re: '75 cb550 and '71 cb175 double build!

Little update.

All my parts are prepped and ready to go back together. Hopefully will be assembled today. That being said, nothing good happens when I am given time to think. I hate hate hate the stock cb frame. Now being that in 2-3 hours the 175 will be done, I was about to start another project building a new frame for a cb100 motor, and even have some of the tube bent up. The goal was to just do some stuff I haven't done or seen done, and then maybe use what I learn with a larger displacement machine. More of a showpiece project than rider but who cares.

All that being said, I'm thinking I may drop the 175 into this new frame, if my design works. So I figured I will build the frame up to where I have to make a decision, and see how much I want to keep it for myself haha. Oh and the idea is a lean and low prostreet rigid, with a raked out cr125 inverted front end. I will have to revalve it to work better more raked out, but it's a hell of alot cheaper than buying something else. Definitely not built for comfort, but should catch an eye or two.
 
Re: '75 cb550 and '71 cb175 double build!


jag767 said:
Little update.

All my parts are prepped and ready to go back together. Hopefully will be assembled today. That being said, nothing good happens when I am given time to think. I hate hate hate the stock cb frame. Now being that in 2-3 hours the 175 will be done, I was about to start another project building a new frame for a cb100 motor, and even have some of the tube bent up. The goal was to just do some stuff I haven't done or seen done, and then maybe use what I learn with a larger displacement machine. More of a showpiece project than rider but who cares.

All that being said, I'm thinking I may drop the 175 into this new frame, if my design works. So I figured I will build the frame up to where I have to make a decision, and see how much I want to keep it for myself haha. Oh and the idea is a lean and low prostreet rigid, with a raked out cr125 inverted front end. I will have to revalve it to work better more raked out, but it's a hell of alot cheaper than buying something else. Definitely not built for comfort, but should catch an eye or two.
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Man that sounds like a cool one to follow. Best of luck to you but it seems you have the fabrication stuff down pat. I'm excited to see it!

If you happen to find your CB175's mikunis sitting on a bench unused for any reason let me know :)

Looking forward to the project!
 
Re: '75 cb550 and '71 cb175 double build!

1sttimer said:
Man that sounds like a cool one to follow. Best of luck to you but it seems you have the fabrication stuff down pat. I'm excited to see it!

If you happen to find your CB175's mikunis sitting on a bench unused for any reason let me know :)

Looking forward to the project!
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Haha making a frame, no problem. Engine work, problem. LOL. I'm not sold on the exact front end yet, but I will have a frame done this week assuming I get one quickly. I knw a guy with 30-40 complete front ends good to go would just have to grab one.
 
Re: '75 cb550 and '71 cb175 double build!


jag767 said:
Haha making a frame, no problem. Engine work, problem. LOL. I'm not sold on the exact front end yet, but I will have a frame done this week assuming I get one quickly. I knw a guy with 30-40 complete front ends good to go would just have to grab one.
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There's a guy on dotheton that's got a 175 build going using an Aprilia RS125 inverted front end that looks sweet. They're dirt cheap on ebay. Harder to find the triples for them than the forks.
 
Re: '75 cb550 and '71 cb175 double build!

1sttimer said:
There's a guy on dotheton that's got a 175 build going using an Aprilia RS125 inverted front end that looks sweet. They're dirt cheap on ebay. Harder to find the triples for them than the forks.
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Interesting, I'll have to look for it. Might have to put a hold on those plans as closing the garage I just broke 3 fingers on my dominant hand. :mad:
 
Re: '75 cb550 and '71 cb175 double build!


jag767 said:
Interesting, I'll have to look for it. Might have to put a hold on those plans as closing the garage I just broke 3 fingers on my dominant hand. :mad:
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Holy moly man! Sorry to hear that... No surgery I hope.
 
Re: '75 cb550 and '71 cb175 double build!

1sttimer said:
Holy moly man! Sorry to hear that... No surgery I hope.
Click to expand...

Thanks man, no surgery just braced for a month. I did a little work on the frame, or at least what I could. Have most of it figured out, I think I will stick with the cb100 motor for it after all. Once I have frame made it'll get a separate thread.
 
Re: '75 cb550 and '71 cb175 double build!

Small update:

Everything on the top end is ready to be reassembled, should get done in a day or 2. Also, not sure if this is common knowledge or not, but if you ever have a really stubborn gasket, don't even bother to fight it, just scrape off the outer layers, then spray some extra strength easy off oven cleaner. I let it set for 20 mins, the took the part and sat it in boiling water for another 20. After that I lightly scraped with a razor blade while still wet and it all easily came off. I was amazed. I should point out one of my side jobs is tinting windows and I'm quite used to having to be careful with a blade, individual results may vary, lol.
 
Re: '75 cb550 and '71 cb175 double build!

FYI,

Clymer is wrong. Gaskets almost always go on dry both sides. On a motor or case that come off often such as a race bike, it's easier to grease one side of the gasket and glue the other side, but other than that, it's dry all the time.

Copper head gaskets DO need Copaslip or something similar to seal them properly.

130PSi isn't all that low, but check the valves for leakage. Turn the head upside down and if the valves are closed, pour acetone or wd40 or gasoline into the head and if it seeps out of the ports
 
Re: '75 cb550 and '71 cb175 double build!

teazer said:
FYI,

Clymer is wrong. Gaskets almost always go on dry both sides. On a motor or case that come off often such as a race bike, it's easier to grease one side of the gasket and glue the other side, but other than that, it's dry all the time.

Copper head gaskets DO need Copaslip or something similar to seal them properly.

130PSi isn't all that low, but check the valves for leakage. Turn the head upside down and if the valves are closed, pour acetone or wd40 or gasoline into the head and if it seeps out of the ports
Click to expand...

Thanks Teazer.

Here are the pictures you asked for. I think its all set right but i never turn down an experienced eye!
 

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Re: '75 cb550 and '71 cb175 double build!

Rotate it one full turn please and check the other side of the sprocket too for the "o" mark. I just checked a few CB`160 and 175 cams and the O is often easier to see on the side away from the points but on a couple I could not find the mark.

With the O at the top, the drive pin for the points will be pointing straight down.
 
Re: '75 cb550 and '71 cb175 double build!

teazer said:
Rotate it one full turn please and check the other side of the sprocket too for the "o" mark. I just checked a few CB`160 and 175 cams and the O is often easier to see on the side away from the points but on a couple I could not find the mark.



With the O at the top, the drive pin for the points will be pointing straight down.
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Ahhh success!! Here is the o mark at a lower angle, and where the rotor is to match.
 

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Re: '75 cb550 and '71 cb175 double build!

That's what we are looking for. In the upper picture it looks good, but where was the crank/rotor at that time? Is the second picture the point it jumps to? Use a wrench on the crank nut to hold it if it is jumping backwards.
 
Re: '75 cb550 and '71 cb175 double build!

Yes that's where it jumps to. I just did what you said, and the bitch sat right down on the t and now the o went from where was it is in the pictures (slightly to one side) to dead on center.

does this mean I am good and can close it up?
 
Re: '75 cb550 and '71 cb175 double build!

Teazer also its worth mentioning i rotated the engine over a few times and the valves seem really loud. I did not do anything but adjust then to spec, could this just be louder than i am used to since they are dry?
 
Re: '75 cb550 and '71 cb175 double build!

Yea I'm an idiot, sound was the results of improper cam chain routing, has been fixed. Engine is all sealed up, and back in the bike. Should be able to get it fully put back together today. Maybe I'm wrong but the feel kicking it over seems way better than before I tore it down, much stronger pop sound through the compression stroke also.
 
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