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Author Topic: 1968 CL175 repair and build  (Read 15081 times)

Offline medicalmechanica

  • Posts: 104
Re: 1968 CL175 repair and build
« Reply #130 on: Feb 15, 2018, 04:00:03 »
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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Offline teazer

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Re: 1968 CL175 repair and build
« Reply #131 on: Feb 15, 2018, 11:05:05 »
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.

Offline medicalmechanica

  • Posts: 104
Re: 1968 CL175 repair and build
« Reply #132 on: Feb 15, 2018, 14:52:51 »
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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Offline teazer

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Re: 1968 CL175 repair and build
« Reply #133 on: Feb 16, 2018, 17:14:14 »
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.   
« Last Edit: Feb 16, 2018, 17:17:22 by teazer »

Offline medicalmechanica

  • Posts: 104
Re: 1968 CL175 repair and build
« Reply #134 on: Apr 01, 2018, 19:02:17 »
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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« Last Edit: Apr 01, 2018, 19:37:45 by medicalmechanica »

Offline teazer

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Re: 1968 CL175 repair and build
« Reply #135 on: Apr 01, 2018, 19:25:56 »
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.

Offline medicalmechanica

  • Posts: 104
Re: 1968 CL175 repair and build
« Reply #136 on: Apr 02, 2018, 14:22:32 »
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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Offline medicalmechanica

  • Posts: 104
Re: 1968 CL175 repair and build
« Reply #137 on: Apr 02, 2018, 22:41:41 »
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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Offline teazer

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Re: 1968 CL175 repair and build
« Reply #138 on: Apr 03, 2018, 00:31:19 »
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

Offline medicalmechanica

  • Posts: 104
Re: 1968 CL175 repair and build
« Reply #139 on: Jun 26, 2018, 23:52:09 »
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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