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Author Topic: 1971 Honda 175cc Cafe Build  (Read 23623 times)

Offline dcbryan

  • Posts: 25
Re: 1971 Honda 175cc Cafe Build
« Reply #50 on: Jul 10, 2012, 15:49:58 »
Hey guys, sorry I got behind on posting here. Good news - the bike is up and running!




Bad news, still have a lot of things left to do. As you can see I have about 12 inches of extra slack on the cables, so I need to get them shortened.

It's also been smoking out one one cylinder, which I hoped would burn off, but it doesn't look like it's going to. So I'm guessing that could be a potential major problem.  Still have to paint the seat hump. The carbs are pretty far out of tune as well, but hey at least it's running.

I'll get some more pictures of soon.

Hey how do those CL pipes fit on that SL frame. Im building a CB/SL mash up. I want to run the high pipes but was not sure if they would fit or not. Could you sho a picture of how they clear the frame in the front? Bike is looking good.

CL pipes on the SL tube frame clear it just fine. Had to weld a custom mounting spot, but that was it.


Offline Booligan

  • Posts: 155
    • My build page
Re: 1971 Honda 175cc Cafe Build
« Reply #51 on: Jul 20, 2012, 00:53:45 »
I definitely want to see where this goes. We need more little bikes on here, lol.

Offline dcbryan

  • Posts: 25
Re: 1971 Honda 175cc Cafe Build
« Reply #52 on: Aug 27, 2012, 14:43:21 »
Hey guys, just thought I'd throw a quick questions on here. I'm gonna pull the engine out of this bike tonight.

Ever since I rebuilt it, there's been white smoke coming out of the left cylinder. Not to bad on idle, but when I rev it, it really shoots out.  The plug doesn't really get too fouled, but I have pulled that exhaust pipe off, and right where it meets the engine, it's all oily and black.

Thoughts on what the culprit might be? I was thinking maybe I broke an oil ring? Any other ideas?

Thanks for the help.

Offline 56_oval

  • Posts: 77
Re: 1971 Honda 175cc Cafe Build
« Reply #53 on: Aug 27, 2012, 16:08:32 »
Hey guys, just thought I'd throw a quick questions on here. I'm gonna pull the engine out of this bike tonight.

Ever since I rebuilt it, there's been white smoke coming out of the left cylinder. Not to bad on idle, but when I rev it, it really shoots out.  The plug doesn't really get too fouled, but I have pulled that exhaust pipe off, and right where it meets the engine, it's all oily and black.

Thoughts on what the culprit might be? I was thinking maybe I broke an oil ring? Any other ideas?

Thanks for the help.

It's most likely the rings.  Does the smoke have a blue tint to it?  Generally white smoke is from coolant burning off and blue is from oil, And my best guess is that your little beast isn't water cooled.  Anther thing that is a possibility, but not likely would be look valve stem guides or bad seals, but I'm not sure these motors have seals on the stems.  Did you rebuild the engine? 

Offline kieferocks

  • Posts: 48
Re: 1971 Honda 175cc Cafe Build
« Reply #54 on: Aug 27, 2012, 17:15:35 »
Did you "clock" the rings when you installed them? The gap on each ring shouldn't line up with the wrist pin or a gap in another ring. Having gaps line up gives oil a direct route into the combustion chamber. Just a thought.

Offline SeekingZero

  • Posts: 419
    • Seeking Zero
Re: 1971 Honda 175cc Cafe Build
« Reply #55 on: Aug 27, 2012, 20:02:58 »
When an air cooled engine exhausts white smoke, this is an indication of engine crankcase oil burning.  Make sure the amount of oil is correct, the type of oil is correct, and then rings are your likely culprit.
"The less horsepower a motorcycle has, the more it can teach you. -Ben Bostrom

06 Ducati 999
66 Ducati 250
88 Honda Hawk
12 Honda CRF250R
03 Suzuki DR650

CB175
Ducati 250
SeekingZero.com

Offline dcbryan

  • Posts: 25
Re: 1971 Honda 175cc Cafe Build
« Reply #56 on: Aug 28, 2012, 03:32:50 »
It's most likely the rings.  Does the smoke have a blue tint to it?  Generally white smoke is from coolant burning off and blue is from oil, And my best guess is that your little beast isn't water cooled.  Anther thing that is a possibility, but not likely would be look valve stem guides or bad seals, but I'm not sure these motors have seals on the stems.  Did you rebuild the engine?

I'd say yeah, maybe there is a little blue to the smoke.  I didn't replace the valve stem guides...I'm pretty sure I remember just putting the old guides back in. I did rebuild the motor, just the top end. new rings, honed the cylinders all new gasket set.


When an air cooled engine exhausts white smoke, this is an indication of engine crankcase oil burning.  Make sure the amount of oil is correct, the type of oil is correct, and then rings are your likely culprit.
Well since one cylinder has never smoked at all, I'm assuming amount and type of oil isn't the issue.

Did you "clock" the rings when you installed them? The gap on each ring shouldn't line up with the wrist pin or a gap in another ring. Having gaps line up gives oil a direct route into the combustion chamber. Just a thought.
I did set the gaps on the rings at ~120 degrees apart, my only guess is I broke one and didn't notice, which seems unlikely really.

I didn't get to this tonight, trying to get my xs650 running. It's got some unknown mysterious ghost of a starting problem. 



Offline 56_oval

  • Posts: 77
Re: 1971 Honda 175cc Cafe Build
« Reply #57 on: Aug 28, 2012, 13:12:34 »
I'd say yeah, maybe there is a little blue to the smoke.  I didn't replace the valve stem guides...I'm pretty sure I remember just putting the old guides back in. I did rebuild the motor, just the top end. new rings, honed the cylinders all new gasket set.

Well since one cylinder has never smoked at all, I'm assuming amount and type of oil isn't the issue.
I did set the gaps on the rings at ~120 degrees apart, my only guess is I broke one and didn't notice, which seems unlikely really.

I didn't get to this tonight, trying to get my xs650 running. It's got some unknown mysterious ghost of a starting problem. 




Just pull the top end again and check to see if there is a broken ring.  If you rebuilt it with new rings and the honing was to spec, then you shouldn't be smoking.

Offline 56_oval

  • Posts: 77
Re: 1971 Honda 175cc Cafe Build
« Reply #58 on: Aug 28, 2012, 13:14:16 »
When an air cooled engine exhausts white smoke, this is an indication of engine crankcase oil burning.  Make sure the amount of oil is correct, the type of oil is correct, and then rings are your likely culprit.

Also make sure it's not over filled...

Offline timbutterfield

  • Posts: 106
Re: 1971 Honda 175cc Cafe Build
« Reply #59 on: Sep 18, 2012, 20:12:59 »
Been following this thread.

Get the motor out and apart yet? Curious as to what's causing the smoking.

Hope you get it figured out quick and finished up soon.
1995 honda nighthawk 250

1972 honda cb175 project bike