"Patina" The 1973 CB175 Cafe Racer

Re: "Patina" The 1973 CB175 Cafe Racer

Alright after a mental break from this thing I'm back at it.

I put in the new floats. No leak!!!

My kickstand is at my welder getting a 5/8" slug added to it to lengthen it a bit. My lean angle was way too much. Not quite sure why but this will help.

Also, took it for a rip around with new plugs and got the following results:

Bike was responsive below half throttle. Anything above half throttle was really lethargic and choppy. Running at half choke helped slightly.

Here's my plug readings (I tried to keep it at full throttle as much as possible).

Right side:

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Left side:

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Looks to me like I'm running lean. The left much more so than the right.

So with that logic I guess I'll run it up a few sizes on the main jet?


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Re: "Patina" The 1973 CB175 Cafe Racer


1sttimer said:
Wha? Please enlighten me (after I just ordered 92, 95, 98 mains haha). How are you getting to that conclusion?
please go to the Dyno :)


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Re: "Patina" The 1973 CB175 Cafe Racer

Please forgive me I didn't know you were getting married when I said "go to the Dyno" happy wife happy life ;)


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Re: "Patina" The 1973 CB175 Cafe Racer


Texasstar said:
Please forgive me I didn't know you were getting married when I said "go to the Dyno" happy wife happy life ;)


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Haha no problem. Yep, less than a month. There is a reason this is project can't seem to come to a close :)

But, yes that's taking priority right now, and the fact work has me traveling for the past month.


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Re: "Patina" The 1973 CB175 Cafe Racer

Then again these just came in, so I'll see what happens. If Teazer is right, that is the most deceiving plug reading ever. And he's usually right :)

I'll order some 88s and 86s too just in case I gotta go the other way..

abb35127a30e009c8bc29a922b2effd8.jpg



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Re: "Patina" The 1973 CB175 Cafe Racer

Also, another small update. For some reason the geometry got wacked out so my lean angle when the kickstand was out was WAY low. So I cut the end off, bought some 5/8" stock and had my welder TIG in the slug. Lean angle when propped is much better. Doesn't look gorgeous but it works for me.

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Yep, those are confusing plug readings.

So let's start at the electrodes. No sign of heat on either the center or side electrodes that I can see in the picture. That suggests that either timing is slightly retarded or the engine wasn't run at full load or the mixture is rich - or the plugs are too cold (hard).

The tips should be more or less white at full load. Where we read mixture is down inside the plug and down there, it looks like the mixture ring is too wide which equates to rich IF it was run hard enough to burn off deposits and get to full operating temperature.

If it wasn't run hard enough to raise plug temperatures, than we can't read anything much from the plug.

The other things is that little Hondas seem to need smaller main jets if anything is done to make them more efficient. That's probably because they are running harder and that leads to higher gas velocity through through the venturi and that in turn pulls up more fuel.

And just because we expect to need larger jets doesn't always mean that's what the engine wants (with apologies to Thomas Merton).

That's why I suggested a short honeymoon trip to the dyno. They say start as you mean to continue...... :) Or not. as the case may be. :)
 
Re: "Patina" The 1973 CB175 Cafe Racer


1sttimer said:
Haha no problem. Yep, less than a month. There is a reason this is project can't seem to come to a close :)

But, yes that's taking priority right now, and the fact work has me traveling for the past month.


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two things..."marriage is a duel to the death that no man of honor should not accept!" GK Chesterton

The key is finding a worthy dueling partner!

Second your are 24 years ahead of me gaining motorcycle knowledge and 26 years behind in dueling. ;)


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Re: "Patina" The 1973 CB175 Cafe Racer


teazer said:
Yep, those are confusing plug readings.

So let's start at the electrodes. No sign of heat on either the center or side electrodes that I can see in the picture. That suggests that either timing is slightly retarded or the engine wasn't run at full load or the mixture is rich - or the plugs are too cold (hard).

The tips should be more or less white at full load. Where we read mixture is down inside the plug and down there, it looks like the mixture ring is too wide which equates to rich IF it was run hard enough to burn off deposits and get to full operating temperature.

If it wasn't run hard enough to raise plug temperatures, than we can't read anything much from the plug.

The other things is that little Hondas seem to need smaller main jets if anything is done to make them more efficient. That's probably because they are running harder and that leads to higher gas velocity through through the venturi and that in turn pulls up more fuel.

And just because we expect to need larger jets doesn't always mean that's what the engine wants (with apologies to Thomas Merton).

That's why I suggested a short honeymoon trip to the dyno. They say start as you mean to continue...... :) Or not. as the case may be. :)
so miss your wit. Btw we got our first Bultaco two-stroke started!


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Thanks Tex. Someone said I only had half a wit - or something like that :) Good to hear the Bultaco is alive. That will have a little more get up and go than a small Honda, so watch that it doesn't bite Zeke.
 
Im not running the same carbs, or the same internals, but my jetting appears much sootier. I cant seem to ever get a good looking plug (like my sportster) on my Honda. My 175 always seems to have more usable power with a bigger jet at the cost of the sooty plug life. My next idea is to lower the main jet change and reduce the diameter of the needle.
 
Re: "Patina" The 1973 CB175 Cafe Racer

The plug is in the wrong location and for us it was a compromise. Victoria is better than Lucky because our squish clearance is right. Once you put it on the Dyno you will see where you want the bike to live. We were running WOT so that is where we wanted to Jet. I don't think it is feasible to get a great plug chop with our plug location. If you look at Hansen Racings Honda's they have relocated the plug to the center of the combustion chamber. One of the main purposes of getting the right squish is is for cooling but also for better flame propagation. Right now the fuel charge is igniting from the side of the combustion chamber.

When we pulled Victoria's head you could see what looked like a sideways mushroom cloud across the top of the piston.


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If you jet according to the plug it will be misleading IMHO we ran slightly rich at COTÁ and I am glad we did we were 27 degrees from detonation.

Your ignition timing comes into play if you switched to electronic ignition. If you are using the Manuals setting then your timing is probably too far retarded.

For example our points Bultaco Montadero is set 3.25" before TDC and Zeke's Montadero is set 2.75" BTDC because his has Electronic ignition.


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Re: "Patina" The 1973 CB175 Cafe Racer

Well I'm always out to bust up tribal knowledge :). So here's what I did. I put in the 95 mains for the heck of it yesterday. I had 90s in there before.

The bike came alive on the top end. No more slug over half throttle. I think it could be fine tuned and one day I will get it to the dyno to do that. It still has a sporadic idle which I'm starting to think has somethig to do with my EI idle timing.

Anyway, cruised for about 30 miles. Could go all day at 50 mph at 6k and 70 mph at 9k RPMs felt great.

I still get a little valve chatter when she gets hot and to Teazers point, I don't have any idea if any of this is efficient.

All I know from this is that I'm getting from point A to point B faster and with a bigger smile on my face.

Oh and holy crap do I need a thicker seat pad. Can't feel the boys after a bit. Ha.
 
That's good. Reading plugs is only good at WOT for a long run and if everything else is optimized and even then, all it tells us is what color the plug is. We need to know first what the bike needs on track or on a dyno and dyno is best for WOT running with instrumentation. Once we get the jetting and timing to what the bike needs, then we can pull a plug and see what it looks like just to see what that plug on that bike is like set up that way.

It doesn't always look like we would expect.
 
Time for a face lift. Glass From The Past style.

Going to repaint the tank, probably white, and paint the tail black with some nice white numbers wrapping the cowl.

Also will be swapping over to this new titled frame and keeping the inner fender, making a bigger electronics tray and more securely mounting this VINBTA seat.

6b89ebac046304d1448249626ff67abb.jpg
 
1sttimer said:
Time for a face lift. Glass From The Past style.

Going to repaint the tank, probably white, and paint the tail black with some nice white numbers wrapping the cowl.

Also will be swapping over to this new titled frame and keeping the inner fender, making a bigger electronics tray and more securely mounting this VINBTA seat.

6b89ebac046304d1448249626ff67abb.jpg

A larger electronics tray is nice, I just welded a flat piece of steel on the frame for mine. Why keep the inner fender? I originally did, and hated it so much that I eventually cut it out and had the frame repainted. Keeping it gave the bike a much more scooterish look IMHO
 
Re: "Patina" The 1973 CB175 Cafe Racer

Eh, not really interested in a scooterish look.

I took it out for my first go at the bike, and immediately regret it when I hit the road. I'm tired of cleaning off the back of my engine and swingarm, unnecessarily avoiding puddles...etc. This is an easy fix.


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