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Author Topic: 1968 CL175 repair and build  (Read 17661 times)

Offline medicalmechanica

  • Posts: 105
Re: 1968 CL175 repair and build
« Reply #60 on: Feb 22, 2017, 17:11:13 »
Oh man it's been a while. Finally have the time to get into this little engine. I ordered a camshaft today, piston rings, and a whole gasket set. Hopefully next week I'll be able to replace the cam and all the gaskets and my little scooter will be back on track.

Question for anyone interested, I've never replaced the cam in a bike before, anything to watch out for? I'm a little worried it'll be a tooth off or something when I'm done. I'm planning to put the left piston at TDC and just pop the cam out and replace the new one in the same position I guess.

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Offline medicalmechanica

  • Posts: 105
Re: 1968 CL175 repair and build
« Reply #61 on: Mar 03, 2017, 15:02:41 »


Engine out! Only one deep wound under the fingernail, calling that a success. Just have to pick up a chain breaker and I'll be at least popping the cylinders off, if not getting everything back together tonight.

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Offline teazer

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Re: 1968 CL175 repair and build
« Reply #62 on: Mar 03, 2017, 19:34:44 »
Please pick that motor up and place it on a table of some sort to keep the dust out of it.

Cam timing is easy and is spelled out pretty well in the service manual. Take the time to check the timing and ask questions if it's not clear - before you bolt it all back together.  good luck- and mind your fingers.

Offline medicalmechanica

  • Posts: 105
Re: 1968 CL175 repair and build
« Reply #63 on: Mar 03, 2017, 19:36:42 »
Oh the motor was on the ground for about ten seconds. I taped up the intake and exhaust before I even took it off the bike and now the motor is on a table in my living room.

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Offline medicalmechanica

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Re: 1968 CL175 repair and build
« Reply #64 on: Mar 04, 2017, 02:08:46 »
Well, looks like I'm screwed. I got the rings on and was able to slide the cylinders back down onto the pistons but only about halfway, and now they won't go down any further or come off. Not sure where to go from there.

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Offline teazer

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Re: 1968 CL175 repair and build
« Reply #65 on: Mar 04, 2017, 13:31:07 »
That's unusual.  Daft question, but are you sure that the cam chain or tensioner or something else isn't in the way?

Are both pistons in so that all rings are in the bores? or is it cocked to one side?  It's really hard to trouble shoot without seeing it.  Can you post a picture or two?

Offline medicalmechanica

  • Posts: 105
Re: 1968 CL175 repair and build
« Reply #66 on: Mar 04, 2017, 15:49:27 »
The chain and tensioner are out of the way for sure, I can move them around freely right now because the pistons are at TDC. I've been able to see that the right piston moves but the left one is completely stuck.

Also Teazer, I heard you were a 175 expert, can you tell me which cranks will fit? I'm fine with tearing all the way down and replacing the crank, pistons, and cylinder and I'm like 90 percent sure the cylinders are interchangeable.

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Offline teazer

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Re: 1968 CL175 repair and build
« Reply #67 on: Mar 04, 2017, 17:18:42 »
Any 160, sloper 175 and vert 175 crank will drop straight in.  Some have different crank drilling etc for lightness/balance but all will work.  CB200 would work but the rods are too long and the drive pinion splines are different, so avoid those.  The crank can also be rebuilt with C90 rods IIRC.

Any 160 or 175 barrels will drop straight on.  Same height etc.  Vert 175 have different fin shapes than the slopers but I doubt that anyone else would notice.

Same with heads.  Any head will fit BUT 160 has a tiny combustion chamber, sloper and vert 175 have very different ports.  Vert head has ports cast much higher in the head and are arguably a better head but take work to make them work correctly.  The best valve guides are CB200 which have modern seals and smoke less.

It sounds almost as if the barrels are on at an angle and have cocked on one piston.  Check and see how square they are and lightly tap them up on the low side.


Offline medicalmechanica

  • Posts: 105
Re: 1968 CL175 repair and build
« Reply #68 on: Mar 04, 2017, 17:38:30 »
Dude you're amazing, I spent hours Googling around and got about half that information haha. There were some fins broken off when I got the bike so I'm going to replace the cylinders anyway. The head is in great shape, and with a little cleaning I think it'll be just fine.

I've found a few cranks with rods on them so I'm going to just take the whole mess out and start fresh, and now I have an excuse to open the whole thing up and clean the 50 years of gunk out.

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Offline teazer

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Re: 1968 CL175 repair and build
« Reply #69 on: Mar 04, 2017, 22:10:55 »
You're welcome.  That was the cliff notes version.....

When we built our first CB160/CL175 race bikes I collected every cheap motor I could get my hands on and stripped them and measured parts and even had a couple of heads cut into cross sections to see the differences. Fortunately there are a lot more new parts available now that when we built that first motor. 

We even have one with highly modified Wiseco Kawasaki pistons and the cylinder head welded up and machined into a different shape.  The one thing I never finished though was a decent blade cam chain tensioner design to control chain whip.  One of these days....

Check out what Michael Moore did with his 216 motor or racers like Byron Blend. there's a large pool of knowledge available now on those bikes - including guys on this forum  like Zeke and his dad Patrick who have spent many hours inside those motors and trying different things.  They even had the Bostrom boys ride one of their bikes right at 100 MPH.
« Last Edit: Mar 04, 2017, 22:14:09 by teazer »