[smdl]

Hi, folks.

Okay, update for today (so far) contains both good and bad news. The good news is that both cylinders are now working! I won't say they're balanced yet, but at least they're both making a healthy contribution. For the first time, the left side is getting hot, the bike is revving more quickly, and it will now settle down idle RPM. So, obviously all my efforts to eliminate air leaks were finally successful! Now, of course, I need to get things in balance, and set the mixture, but I'll definitely call this part a win.

The bad news? My previously fluid-tight motorcycle is now apparently half swiss cheese, and half sieve, as it is leaking both oil and fuel (the latter prodigiously). I'm not worried about the oil, as that is just coming out of the cover over the stator and rotor, and I'm assuming that I just failed to tighten it sufficiently. Worst case, if the gasket there is damaged, I should have a spare in the engine gasket kit I purchased recently. The fuel is a different story, as it is literally pouring out all around the float bowl gasket on the right side, and at least some is leaking on the left side. The float bowl gasket is one of the few that I chose to still use from each of the crappy carb kits that I purchased, and the reason I did is that the originals were hard and looking like they were ready to start cracking. I'll check again to make sure that the gaskets are in their proper places, but I'll plan to change them out soon, regardless.

Two questions for the group:

1. Can anyone recommend a source for good quality carb kits?
2. Does the fact that the bowl gaskets are leaking indicate that the float level is too high, or that the needle an seat are leaking? Or, is there always the potential to leak there if the gaskets are bad?

Thanks again for all the help!

Shaun

 

[smdl]

Well, all the leaks have been taken care of through use of the original float bowl gaskets and tightening the screws slightly on the engine cover. I'm going to pause working on the carbs while I wait for proper parts. I have a few items that I need to order from David Silver Spares, so I'll have them throw in a couple of OEM gasket sets for me.

The bike continues to run on both cylinders, which is great, but there are other issues afoot. At anything over about 6000RPM, the engine starts missing, backfiring, etc. I'm suspecting a failing condenser based upon past experience, and this would seem to be supported by the very visible arcing that is occurring at the points.

Hopefully, people aren't finding the repeated posts boring or irritating. I just like to capture what I go through to resolve a problem in the hope that it might help someone else, someday. When I find the cause, I'll be sure to add the info to this thread.

Thanks again for the help on this. I'm enjoying working on this bike, even if it is giving me an interesting time!

Cheers,
Shaun

 

[ancientdad]

Shaun, everything is fine - mentioning more details rather than less is always better, you never know when it will strike a chord with someone who has experienced it before. As for carb kits, many here have had good luck with 4into1 kits but as with any kit, you should not use the brass parts as most aftermarket kits are notorious for improper sizing and/or length of parts. Gaskets and o-rings are the primary need, clean your jets, mixture screws and other brass and re-use them

 

[smdl]

Thanks for the tip, Tom. As soon as I get the replacement gaskets, I'll plan to return to the original brass.

Cheers,
Shaun

 

[Bownez]

Thanks for the tip, Tom. As soon as I get the replacement gaskets, I'll plan to return to the original brass.

Cheers,
Shaun

Hi Shaun,

I have fought for hours with the carbs off the two 175cc Hondas I have restored. Reading your posts could be entries into my shop notes....
Aftermarket carb kits are mostly trash. If you can use a third of the supplied parts you are doing well.
One other thing you might confirm is that the cam timing is correct. With one tooth off the bike will run, but not well.
I have a spare set of carbs if you come to the point that you need to try something else.
BTW, love your Guzzi lineup. I've been on the Italian stallions since 1993. (switched from BMW airheads).

Mr. Bones
Mpls

 

[smdl]

Thanks, Mr. Bones. This helps to put things in perspective, and gives me a couple of new paths to follow if the current one doesn't work. I'll update here as I progress, and I might just be in contact about the carbs of the existing ones don't work out.

Yes, definitely a Guzzi addict, but I have managed to get down to an even four. I can't see a time when I won't have any, but I am enjoying the little Honda, as well.

I've included a recent Guzzi pics for interest.

Cheers,
Shaun

 

[Gluman]

I have been monitoring this discussion with interest. I have a 1971 CL175 and for a while struggled to get both cylinders to sing the same song. Because my bike was missing the original carburetors, I was forced to use OEMSTD aftermarket Chinese carburetors. I work on a lot of bikes and usually use vacuum ports to balance everything out. These 175 motors do not have vacuum ports so I decided to add my own. I drilled and taped the intake manifolds and inserted brass tubes along with rubber vacuum caps. Now I can use a Twin Max meter or mercury sticks to balance everything out. What a difference that made! The motor now runs perfectly. Other improvements included replacing the points with electronic ignition and installing a window in a spare timing cover so I could use a timing light to set the spark timing.

If any one has any questions, please let me know.
Cheers,
Steve

 

[ancientdad]

If any one has any questions, please let me know.
Cheers,
Steve

Steve, the input is nice but we still don't know anything about you, since this is only your second post and you never properly introduced yourself to the community. Please do that here and read this link below
Critical - READ BEFORE YOUR FIRST POST

 

[smdl]

I have been monitoring this discussion with interest. I have a 1971 CL175 and for a while struggled to get both cylinders to sing the same song. Because my bike was missing the original carburetors, I was forced to use OEMSTD aftermarket Chinese carburetors. I work on a lot of bikes and usually use vacuum ports to balance everything out. These 175 motors do not have vacuum ports so I decided to add my own. I drilled and taped the intake manifolds and inserted brass tubes along with rubber vacuum caps. Now I can use a Twin Max meter or mercury sticks to balance everything out. What a difference that made! The motor now runs perfectly. Other improvements included replacing the points with electronic ignition and installing a window in a spare timing cover so I could use a timing light to set the spark timing.

If any one has any questions, please let me know.
Cheers,
Steve


View attachment 307676

Nice bike, Steve, and great information on the work you have done. I was thinking about adding vacuum ports, too, and the timing cover idea is interesting.

Cheers,
Shaun

 

[smdl]

Just a quick update. I finally received my parts order from David Silver yesterday. The US operation was waiting for parts from the UK for some time, and finally just sent what they had. No complaints on my part -- they certainly can't be held to blame for the pandemic.

Anyway, got out into the shop today, and decided to try the new condenser first as that was what I thought was most likely at least one of the issues. Quick to change out, and I'm pleased to say that I noticed an instant improvement afterwards. Visible arcing at the points is greatly reduced, and all the backfiring at high revs has disappeared. I'll count that as a win!

The bike is still not running how I want it to, but I feel pretty confident that I have removed an outlying problem, and can now proceed down a more standard path of tuning to bring it back to the best it can be.

What I am finding now is that the bike is enough better that I am actually able to get up over 40mph for the first time, whereas it was maxing out at 30-35mph before (even on a slight downhill!). It's still not eager to rev over about 6000rpm, and seems to pick up power a bit when I close the throttle slightly. At the moment, I still have the air filters off for access to remove and reinstall the carbs, so I'm not surprised if it is running a bit lean. Interesting thing, though, is that it didn't seem to respond to the choke much. Oh, well. Next, I'll be pulling the carbs to install the original brass (save for the new OEM needle & seat) and the OEM gaskets. Wish me luck!

Cheers,
Shaun

 

[smdl]

Hi, folks.

Happy to say that I continue to see improvement, but I'm hoping for a bit of advice with regard to the advance mechanism.

First, an update: As foreshadowed in my last post, I went through the carbs again, using the new OEM gaskets and float needle/seats, as well as returning to the original brass, otherwise. That seemed to incrementally improve things, with the result that both cylinders seem to be pulling their weight now (both running warm). Once I got the air filters back on, the bike was more eager to rev, and quickly surpassed the ~6000rpm point at which it struggled before. However, when trying to rev beyond that, it seems to now hit a wall at about 7500rpm, at which point it begins to hesitate and backfire. That pointed me in the direction of the mechanical advance mechanism, and when I pulled the breaker point plate out, I found said mechanism to be totally seized up.

In attempting to get the advance unit moving again, I have tried to gently persuade the flyweights to shift, but to no effect. So, I thought I would remove the mechanism to work on it off the bike, but it doesn't seem to want to move. I have removed the small bolt and washer at the end of the points cam, by it just doesn't seem to want to move. Is there something I'm missing, or do these units just end up rusting to the cam? Or do people usually just try to free them up with penetrating oil in place? How much pressure can you put one these things without endangering them?

Any input would be helpful.

It doesn't look too bad in there but I don't have much to compare it to. I have attached a pic for reference.

Thanks again, folks. This forum has been very helpful!

Cheers,
Shaun

 

[smdl]

So, I decided to use some WD40, which should be safe for the electrics, and then left it to soak for a bit. After about 30 minutes, I came back and started gently manipulating the mechanism with the blade of a small screwdriver. After a few moments, it started to move, and gradually loosened up to the point of normal operation. Once I had everything back together, I started the bike, and instantly noticed a big difference in how it revved. Quick jaunt out on the road, and I was amazed! 9500rpm was easy (that's the highest I took it), and I'm really impressed with how quick this little bike is! Very pleased, finally, but I can see why the previous owner decided to move the bike on. There were several things impacting how it was running, and I could tell that he was frustrated will not being able to get it working the way he wanted. It has only been through my stubbornness and the great support of this forum that I got through all the issues that were holding this bike back. The major issues were:

• Tight valve clearances
• Resister spark plugs in place (not sure if this impacted ignition performance or not)
• Carbs needing rebuild (partially done before, but I think the ultrasonic cleaning helped)
• Faulty spark plug cap
• Points pitted and needing filing (see next)
• Failed condenser
• Seized advance unit

Anyway, now that the bike runs well at speed, I can go back and do some carb tuning . Currently, it doesn't seem to want to idle once warm, but I should be able to figure that out now.

Will report back once I get it all sorted.

Cheers,
Shaun

 

[ancientdad]

Shaun, the advancer is simply stuck on the end of the camshaft, much like the unit itself was gummed up or slightly rusted and was stuck itself. No need to pursue it further as long as it's working properly at this point. Good to hear it's running well... and yes, these engines like to rev when properly tuned - that redline isn't just for looks

 

[smdl]

Shaun, the advancer is simply stuck on the end of the camshaft, much like the unit itself was gummed up or slightly rusted and was stuck itself. No need to pursue it further as long as it's working properly at this point. Good to hear it's running well... and yes, these engines like to rev when properly tuned - that redline isn't just for looks

Great - thanks for the confirmation!

Cheers,
Shaun

 

[smdl]

Hi, Folks.

Now that I have the ignition sorted, I'm noving back to the carbs. I'm fighting air leaks again, likely because all the on/off has compromised the paper gaskets I made. When I was disassembling things again, I was closely inspecting the insulators, and noticed that one had cracks in it (see pic). Being that the cracks are only visible on one side, and that the cracks only go from the inside edge of the bolt holes to the intake passage, is it likely that this might affect how the bike runs?

Secondly, the only source I have found (so far) for these insulators is CMSNL.com, and they are priced at 19 Euros each. I'll pay that if it is the only option, but it seems high. Are there any other sources? I didn't find any on eBay or at David Silver.

Lastly, I have the equipment to make these if I know what the material is. I'm assuming something like Delrin, but wondering if anyone knows for sure?

Thanks in advance for any information.

Cheers,
Shaun

 

[chili]

Hi Shaun, did you ever get this sorted out? I'm dealing with a nearly identical issue and would love to know how things ended up.

Cheers!
John