1968 CL175 repair and build

teazer

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Looks fine, but the mention of tight valves is not so good. Get a new set of valve covers and then get those off anyway you need to and set the tappets.

If you look carefully at the last picture, the left cylinder is on overlap and both valves are slightly open. On th right side, the motor would be firing and both valves should be shut tight. I suspect that valve seats may also be a touch rusty from being permanently open, so if it were mine I would pop the head off and remove and clean the valves and seats. You have to loosen the valve screws (tappets) to do that so go ahead and get those covers off.
 
Over a year later! I finally broke down after putting this thing back together over and over and took it to a local shop. They checked my work and told me I'd assembled everything correctly, but the cylinders and pistons had way too much clearance. They're suggesting I pick up some 50 over pistons and have the cylinders bored/honed to match. I'm fine with that since everything else is good.

Will CB175 pistons work? Any good sources other than ebay? I'm looking to just grab the pistons, rings, pins, and clips at once if I can.


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teazer

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Well, that's a classic good news-bad news story. Yes CB175 pistons will work. I used to get all mine off ebay.
 
And we're back in business! I got my scooter oiled and gassed up and put almost everything back together. The exhaust isn't totally mounted yet because I'm waiting on crush washers, and one of my bowl gaskets is messed up so that's on the way too. While dumping gas everywhere out of that carb, I was able to kick it and start it right up.

Made sure the back wheel is aligned and reinstalled the chain, and finally got it to move under its own power for the first time in who knows how long, even if it was only about two feet in my garage at like midnight haha.

Aside from the gaskets, I have to pick up bolts for the points cover, and that's the last bit.

One quick question for whoever is still listening haha, my clutch is a bit sloppy. The lever doesn't return all the way and there seems to be a ton of slack. I adjusted it at the handlebars as much as I could, but I'm thinking it's routed wrong. It should go in front of the fork, but where does it go after that? If I remember right it's down through frame where the coil is, and the just out to the left to the actual clutch actuator. That's how I have it now and it seems like I've got a good half inch of slop. May be that it's just stretched out and old, or I have it going through the wrong spot.

Pics coming when it's cleaned up a tad and all the way back together!

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I looked into the clutch cable routing and I have it right. I'm missing the little clamp that goes on the back of the clutch adjuster though so I'm looking for that but I can't find what it's called. EBay searching continues while the gaskets are on the way. I also found that the collar washers on my exhaust are too long, so I'm going to trim them down.

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I actually found it again in a box in the garage. It just sort of fell out of the case when I opened it up and I didn't know what it was, so I put it somewhere "safe" and it took quite a while to remember where haha. Just waiting on carb bowl gaskets now.

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Alright, got my gaskets, popped on the exhaust and the float bowl that was leaking and that problem is solved.

I've got some oil seeping from my tappet covers so I'm gonna get gaskets for those, looks like the shop that did the cylinders might have torn them up.

Also, I'm only getting throttle response when the bike is on the kickstand, which tells me maybe something is up with the right hand carb. I temp gunned the pipes and the one on the right is a bit cooler. When riding, the engine bogs under throttle so I'm assuming my carb adjustment is just way off.

How much will 50 over effect my tuning?

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teazer

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0.5mm oversize pistons should make no measurable difference to tuning. That's around 20 thousandths of an inch. Not an issue. Fitting 57mm or 61mm pistons might make a difference though. :)

Check tappets and try to get new pilot jets if they are available. And check carb synch and valve clearances too.
 
The carbs are synced, I checked that today. The shop did check valve stuff, so I'll have a look but I'm pretty sure they're fine. Because the bike responds great to throttle when it's tipped on the kick stand I feel like it's a carb issue. I'm going to open the carbs up and give them another good clean. It seems like when I'm trying to ride it it's just bogging down like it's way too rich or something.

I messed around a tad with the adjustment screws and didn't see any difference. I read somewhere that it's possible those circuits are clogged and it's just running from the height of the slides? I can't seem to find a labeled diagram of the carbs and I always forget which screw does what.

Also haha, I can't even imagine a piston that big in this little thing, that seems like way too much lol

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teazer

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We have a CL175 with 61mm pistons in it - along with a truck load of welding and machining.

If you look at the carbs, there should be 2 screws. One is just in front of the filter and that changes the amount of air drawn in through the pilot circuit. The one in front of that in line with the slide lifts the slide and is called the idle speed screw.

The air screw should be screwed in until they lightly bottom out and then back out one full turn plus a quarter turn. The idle speed screw start by screwing them out and then back in until they just contact the slides and start to lift and then add one turn. That should get you going.

Yes the carbs have some very small drillings inside and they have to be clean. Fortunately they are simple carbs. Strip them completely and spray carb cleaner (in a well ventilated space) into/through one drilling and then repeat on the other carb to be sure they are both similar. Those carbs have tiny holes in the floor of the bore at the front edge of the slide that are easily clogged and they have to be clear. That's where the pilot jets spray fuel out and if they are not clear, no idle.
 
Sounds good! I'll be trying to get into it a little on Friday probably. The bike idles just fine, and when it's leaned on the kickstand it revs right up if I rip the throttle, but if it's upright like I'm riding it it just bogs down. I'm also going to check the petcock, and maybe swap carbs and see if the problem follows.

Does that 175 have the same stock crank in it? Is the stroke the same and the chamber is just bigger?

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teazer

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If it revs faster on the side stand, it could be that the right carb float level is too high or it's flooding.

Yes. Our 240 motor has a more or less stock crank. Stock stroke but I probably selected the lightest crank and that may have been a 160 crank. Can't remember now. Stock sloper 175 is a good motor. That motor has a Cb200 head with seals n all 4 valves and the combustion chambers were welded up into more of a bathtub shape with low crown pistons to improve flame propagation.

I do have a lightened 180 degree crank here but not in a motor until I work out a better way to control cam chain whip. I'd like a gear driven cam but will probably just use modern bike tensioners and guides to calm things down.
 
So it turns out I'm missing this screw. It seems to block the passage to a tube in the bowl of the carb. What does that screw do? I was looking at parts fiche blowups and it's just listed as a screw, no name.

Here's hoping that's the problem. Gonna try to find something close enough tomorrow.

Edit: my bad, circled the wrong thing. I'm missing the screw pictured, but it goes in the other hole on the carb missing it.

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teazer

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That hole in the bottom carb is probably closed. Carbs are often cast in a way that allows the same casting to be machined for left side or right side fitment. If that hole is not open to the throat, then it's OK. That's where the air screw fits and there should be one only on the left of tht left carb and right of the right carb.

That light colored screw in the top carb is a blanking screw and closes off that passageway. It will be a fine thread and it blocks off that passage that could be used for a Power jet. On some early carbs, Keihin fitted a power jet to make teh top end richer for more power at the top end, but not all crabs were drilled and tapped. I believe you will find that there is a jet inside there.
 
teazer said:
That hole in the bottom carb is probably closed. Carbs are often cast in a way that allows the same casting to be machined for left side or right side fitment. If that hole is not open to the throat, then it's OK. That's where the air screw fits and there should be one only on the left of tht left carb and right of the right carb.

That light colored screw in the top carb is a blanking screw and closes off that passageway. It will be a fine thread and it blocks off that passage that could be used for a Power jet. On some early carbs, Keihin fitted a power jet to make teh top end richer for more power at the top end, but not all crabs were drilled and tapped. I believe you will find that there is a jet inside there.
Right. The big screw in the carb on the top blocks off a passage to a tube that goes into the bowl. I'm missing the corresponding screw on the other carb, I just took the picture like a spaz haha.

Would that screw missing from the other carb be causing me problems? I'm gonna try to replace it anyway, but I hope that'll solve the problem. The bike only likes to start with the choke on right now.

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Alright more weirdness! I put the carbs back on and can start the bike with the choke on.

I lost the bar that goes between the choke levers somewhere so I just open them both manually. The left jug wasn't getting hot after a couple minutes of running, so I killed the bike and pulled the plug to check for spark, which I'm getting plenty of. After I put it back together again I started the bike and if I choke the left carb the cylinder gets hot, but if I don't choke it it doesn't run.

I seated and backed the fuel mixture screws out to like 1 1/2 turns each to start, and the slides are synced so I don't even know now haha. I know it's close, and I'd really like to scoot around but this is driving me nuts.

Gonna open up the left carb and check the floats and float valve /again/ I guess.

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teazer

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The bike will suck air if that top aluminum screw is missing.

See if you can get one from CMSNL. The best way to set fuel level is to look at FUEL level and not float level. You need a spare float drain screw. Drill it and insert a thin tube and connect that to some clear tube. Fuel level on both sides should be the same and around 3mm below the gasket face.

like this https://www.kzrider.com/media/kunena/attachments/6412/cleartubecombo.jpg

http://ww2.justanswer.com/uploads/MO/motoforge/2012-11-25_010502_float_level_adjustment.jpg
 
Hey guys! Mostly Teazer who seems to be the only one following along haha.

Since my last post I've been working three jobs and didn't have time for scooters.

Found a little break after moving and balanced and tuned carbs, replaced plugs, did valve lash, and got this little thing to run. I was getting some surging and dying and it turns out my left float valve was stuck, probably from sitting for a while, but it's fixed now. Also adjusted the floats again to spec, they weren't far off, but a little fine tuning and I was happy.

She's alive! Still pretty smokey under heavy throttle, but after a little 3 mile ride I'm pretty confident I've got a working bike.

I didn't think to take any pics during the little tweaks, but here's how it looks now. I just need to grab the right hardware for the points cover and replace the stator cover gasket and I'll be set.

That helmet is about nine thousand years old haha but it'll protect my noggin for now.

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