Topic: 1972 CL175 Project: Fire in the Hole!

[Scott S]

I was recently contacted by a buddy that I've done a little trading with. He was giving me first dibs on a '72 Honda CL175 on which he is throwing in the towel. Initially, I declined. Too many irons in the fire.
The bike is a nice looking little twin that he went through a couple of years ago. Tank lined, new petcock, sorted the brakes, tires, etc. He actually had it running and said it ran well.
Then the seemingly impossible happened: He lost spark in the RH cylinder. That, technically, shouldn't be possible on a Honda 175 twin.


He says he's tried everything; different plugs, coils, points, etc. Even had a guy that used to race CB350 twins take a look at it and he proclaimed "This isn't possible".
He drained the gas and oil and it has sat for two years. Complete, titled, once running bike. Now with a dead battery and a mystery "No Spark" in one hole issue.


After he got dicked around a bit when trying to sell it, he told me "Make and offer and I'll even deliver". I did, he accepted, I take delivery around Tuesday. I have yet to actually put my hands on it.
I will first check valve clearances, compression and maybe even the carb on the RH side. And a new battery, of course. He SWEARS it's a spark issue. But with one set of points, one condenser, and one dual output coil, that shouldn't be possible. You shouldn't be able to get fire in one hole but not the other.


While I await it's arrival, any guesses or suggestions on what to check?


And because everyone likes pics:

[tbpmusic]

You're gonna love that little bike - they're a LOT of fun to ride.

Make sure it's indeed doing what they claim (or not). Sounds unlikely to me as well, barring a bad plug cap or wire (or maybe even just a bad plug)......

[Scott S]

 I ordered a battery and he's actually delivering the bike today, between rain storms.

 Even if I replace everything from the points plate to the plugs, that's only about $50 or $60. Some fresh oil and a battery.... I could possibly make it run for ~$100-125. Fingers crossed!

[MoMo]

Does sound impossible unless, cap, wire or plug are bad.  You will like the bike, I got one running several years ago for a customer= I enjoyed the test ride ...Larry

[Johnie]

I had that bike brand new in 1972 in the blue. It was my first new bike when i was a senior in high school. Clocked a lot of miles on it with my girlfriend...now my wife. Great handling for a small bike too.

[tbpmusic]

It's almost the same bike as my CB200 - I'll ride that bike by preference, unless I need to go more miles than is comfortable.
It's a gas to ride........

[Scott S]

 It's here and in great, survivor type shape.  Tank.is solid and straight. Seat has no tears. Mufflers replaced with baffled pipes of some sort. Missing the mirrors but I probably have some.
 He said everything worked and it ran fine, then lost spark on RH side. I'm anxious to tear into it.

[jakec]

Nice bike. I have the same one, same year and color too. Very fun bike to ride around town. The thing about spark in one side is odd, I have had my share of spark issues when working on the 175, however everything you said about it is true, especially if he tried multiple coils and plug caps. On mine I have have a no spark issue pop up from bad caps, bad leads (have to replace the whole coil) and finally loose connections in between the coil and the points.

I think the explanation is probably that it's not that it's only one side, or if it will only run on one side, that it's fuel related (another problem I had).

[Scott S]

 Bike arrived yesterday and I'm very happy with the overall condition. The tank and side covers are still all original and in great shape. No dents on the tank at all, very solid with shiny paint and stripes and only a few minor scratches. Overall, the entire bike will shine up pretty well, I think.

 I adjusted the valves. They were all loose, by my standards. Adjusted the cam chain. I pulled the carbs and gave them a soak in Simple Green and hot water, followed by carb cleaner. Didn't find any smoking guns there. One of the floats was a little lower than the other (the floats look brand new, BTW). I set the odd one to 22mm to match the other and set the mixture screws to 1 turn out. Do those sound right, to you?

 Next up, I'm going to go over the ignition parts that came with the bike and bench test/ohm out everything. I'll try using what I have with the fresh battery, which should be here tomorrow.

 Oh, I also pulled the exhaust, mostly so I could install the LH side cover and check out the air filter(s). The LH filter has a torn rubber boot and it's been jury rigged with some rubber and a hose clamp. I might look around and see what's available out there.
 I also want to take a closer look at the tips/baffles someone has installed. Maybe try to come up with something a little better there, too.

[Bob3050]

I don't remember ever having a single cylinder spark issue on a 175 but we did have a lot of them with piston seizures due to overheating.  You can't lug that engine down or it will get hot in a hurry. So, any time you see a hill, down shift and bring the rpm up to keep it running freely and you won't  have any piston problems.
Bob

[Scott S]

 Fire in the hole! Fire in the hole!

 Cleaned a BUNCH of connections, including the main frame ground. Went through the standard tune up stuff. Re-used the stock coil because I liked the ohm readings on it better than the brand new coil. Fresh AGM battery. Set points to fire right on the F mark using my test light.
 Turned it over with each spark grounded on the head and I have fire!

  I also cleaned the carbs, and I ordered a replacement LH air cleaner since this one has a torn boot (and of course, it's the one you MUST put on before the header pipes).
 As soon as it gets here and I get the exhaust on, I'll add gas and see what happens.

 I have NOT tried to get spark with the points cover on...could be a short there, when it's installed.
 And, I found a double female connector right off the main harness that I'm not happy with. And it's for power to the coil and to the horn....Hmmm, possibly the culprit all along?
 It's split inside and even after I crimped it with pliers, the coil wire isn't as tight as I'd like. I'll probably dig through my stash and find a better connector to splice in.

[Scott S]

Well, I rode it today. It's DEFINITELY running on both cylinders now!

 It still needs some tweaking, though. I can't get it to idle properly. I have to use the throttle to keep it running. I tried changing the mixture screws (from 1/2 turn out all the way to 1 3/4 turns out) and the idle screws. I actually went all the way IN on the idle screws and it still didn't want to hold an idle. I also adjusted the free play at the throttle grip.
 One of the bowls is leaking around the gasket and...you guessed it...it's the LH side, the one behind the high pipes. I *THINK* I can install a new bowl gasket without R&R'ing the carb, but I also feel like maybe I should address the float heights again, too.
 I tried to sync them the best I could, by checking the gap in the closed position, W.O.T. and watching them open together.
 Just needs more carb work, I guess.

 I also feel like it would be wise to check the timing again now that I've had it running. And normal tweaking and tuning, too....clutch adjustment, etc.

[Scott S]

It doesn't want to hold an idle. I've tried several different settings on the mixtures screws, from 7/8 turn all the way to 1 3/4 turns. I thought for a minute there that it needed more turns out because of the nearly open (barely baffled) pipes, but it soon went back to doing the same thing. Occasionally, it will get stuck at ~3,000 RPM.
 I also tried going in on the idle screws until they were all the way in. I've now backed them out equal amounts.

 I've read about the slides being in the wrong side. I left the slides on the cable and kept them on their respective side of the bike. And when I was syncing (by using a flash light to check slide gap at rest and at WOT), I could see what looked to me like a normal small gap at rest. Now...it IS possible that someone before me has them swapped. I DID line up the long groove on the slide with the pin in the carb(s) and the wider groove with the idle screw. I guess it's possible to still have them on the wrong side?

 The air filters are old and dirty. I cleaned them off with a toothbrush (dry) and blew them out with compressed air, inside and out. They should still be OK, I would think.

 I also suspect the advancer, maybe? I checked it during the tune up and the springs *may* be a little on the weak side? But that should cause it to advance early and idle high, which it isn't doing. Ditto for air leaks.

 I set the floats to 22mm. I've since learned that they should be 21mm, but I don't *think* that 1mm would cause this. If anything, the fuel level would be a little lower, right?

 I did see a cracked throttle tube that I will replace. But...again...not sure it's the culprit.

 And while the LH bowl is leaking, the RH carb is fouling the plug.

I think I will pull the carbs again and have my friend Rick at OldSkoolCarbs do his thing. And I'll verify slides are correct and get the fuel level/float heights correct. Other suggestions?

[Scott S]

 Started to drain the gas tank this morning so I could pull the carbs and take them to Rick at OldSkoolCarbs. That's when I noticed a couple of odd things...

 I noticed that I wasn't getting even flow out of the petcock outlets. And the one that was acting funny was the side that I was using to feed the RH carb.....Hmmm...
 Then, as I wiggled the lever around, I noticed fuel coming out of the petcock body. Also, Hmmm...
 Then, as I removed the crossover tube from the gas tank (hate those things), I noticed gas still in the LH side but nothing in the RH side. Triple Hmmm.....

 Pulled petcock apart and cleaned it well and tested it by sucking through the outlets and spraying carb cleaner. Didn't really find anything.

 Found the crossover tube nipple plugged up on the RH side of the gas tank. Fixed that.

 Then I moved on to the carbs. I wanted to check operation of the slides/cables. I also wanted to verify that the slides were in correctly. I kept them on the same side of the bike I removed them from. BUT, I had read several threads about the slides being in backwards causing a "no idle" issue. Pulled them out and, guess what!? Yep...in wrong. The throttle cable was also routed incorrectly.

 Fixed all that and hooked up my I.V. bottle for gas. Fired right up, I was able to adjust the idle and it revs MUCH better now!
 I'm still waiting on bowl gaskets and a new throttle tube.
 Inching closer and closer!!

[Scott S]

Just adjusted the clutch. I found the main, large worm gear screw all gummed up and tight. I greased it and worked it until I had full range of movement. I also found the lower cable adjustment all the way in. I set the clutch adjustment per the instructions on the Honda Twins site, did a short  test run with the fuel that was in the bowls, came back and did another adjustment, and WOW....what a difference.
 Between this and the carb stuff I've found, it's a completely different bike!

 Can't wait for the parts to show up so I can put it back together and go on a longer ride!

[Johnie]

Nice write up Scott...

[calj737]

I guess the PO upheld the PO’s Curse to the full extent... It was running fine, and I’ve checked everything...but...

I’m glad you’re getting it sorted out so quickly and easily.

[Scott S]

 He fully admitted to the carb slides. Says he never touched the clutch.
 And it has been sitting for two years since he threw in the towel.

[Scott S]

 Oh, yeah.... forgot to mention that I did a compression test, too. I got 135 and 136 PSI on a cold engine. Not too shabby.

[Scott S]

 This stupid thing is fighting me all the way. 

 I installed a new bowl gasket only to find out that it was leaking around the fuel inlet/line. I used Honda 5.5mm line but, when I pulled it off, I found that piece had a slightly larger I.D. Replaced that and fixed the leak.
 But the petcock still leaked. I had disassembled it and cleaned it. I tried flipping over the grommet and bending the spring for more tension, but no luck. Went to the local shop and found the grommet I needed in genuine Honda. Felt much tighter but still leaked. GRRRR!!!

 I also noticed something funny about this petcock. When I try to drain the tank, I don't always get fuel from both outlets. They're both clear, so I'm a little perplexed. I'm beginning to wonder if the RH cylinder dropping out had something to do with the fuel feed? In fact, I somewhat witnessed it while riding it around the neighborhood today. Especially when it goes on reserve. It's a genuine Keihin petcock with a new genuine Honda grommet. But something isn't right.
 I just ordered a new K&L replacement. I've had good luck with them on 350's. And when I can keep a constant supply of fuel to the carbs, the little bugger runs pretty OK!

[Scott S]

 Looks like the petcock may have been at least part of the problem. New K&L petcock installed and no more leaks and, so far, no more dropping a cylinder.
 I still haven't left the neighborhood yet, but it's running better and longer than ever.

 I'll probably tweak the clutch one more time and the rear tire has a (very) slow leak, but it's fine for now.
 Cool little bike, and it cleaned up well, too.



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