Had the bike out today despite the cold. Mixed some mmo in the tank (about 25 ml) shook it up. Things have not improved yet. Slow response, some popping and no power. It stalled on the small hill despite giving it everything in 1st and I had to turn around. Checked compression again when I got home and it was warm. 114 left and 118 right. Looked and smelled like oil vapor coming out the exhaust. Plugs look good (light brown)
'72 CL175 engine trouble?
- Thread starter echo
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I think it's running on both sides. It's a 2 into 1 exhaust but I can feel both headers get hot right away.
Correction from earlier today: my compression numbers were no good cause I forgot to open the throttle while I did it. Retest showed things have not changed since the 1st post. (L 114, R 129).
On a whim I dropped the clip on the needles to see how it would affect things. That and and turning in the idle screws a bit took care of most of the sputtering/popping, and seemed to give me a bit more go juice on the flat. Same story when I hit the hill though - the bike has trouble pulling me up the hill.
I will keep trying to take it out and run it to see if the rings and valves loosen up and de-crud. And we shal see
Correction from earlier today: my compression numbers were no good cause I forgot to open the throttle while I did it. Retest showed things have not changed since the 1st post. (L 114, R 129).
On a whim I dropped the clip on the needles to see how it would affect things. That and and turning in the idle screws a bit took care of most of the sputtering/popping, and seemed to give me a bit more go juice on the flat. Same story when I hit the hill though - the bike has trouble pulling me up the hill.
I will keep trying to take it out and run it to see if the rings and valves loosen up and de-crud. And we shal see
Well, running the bike with the marvel mystery oil unfortunately did not gain me one psi of compression so I decided to tear down the top end, if nothing else to satisfy my curiosity
It went fairly well and I feel my homework and investment in tools like the impact driver paid off. The motor came out easy enough - this one is light enough that I could pull it without a helper. Nothing got buggered up or broken, far as I can tell. I paid attention to sorting parts position and directionality.
I decarbonized the combustion chamber, piston tops and the bottoms of the valves. There was gritty deposits several mm thick. The crap on the valves was rock hard, but I was able to break it up with some persistence.
Once it cleaned up I noticed a lot of little gouges in the left combustion chamber and the left piston top. You can see in the photos. This was the cylinder that was giving me the lower compression issue, so that would make sense. The cylinder walls did not have any major gouged that I could feel with my nails, but I have yet to completely clean them up and spec them. With any luck maybe I can get away without overboring. The cam shaft and pistons od meet spec. Lots of work to do prepping these gasket surfaces. Seems like hundreds of little bits of old gasket on them.
One thing that happened was I was lifting the head and a cotter pin fell out. I'm not sure where it came from and I was hoping someone could Tell me what it goes to. See pic with the white background.
It went fairly well and I feel my homework and investment in tools like the impact driver paid off. The motor came out easy enough - this one is light enough that I could pull it without a helper. Nothing got buggered up or broken, far as I can tell. I paid attention to sorting parts position and directionality.
I decarbonized the combustion chamber, piston tops and the bottoms of the valves. There was gritty deposits several mm thick. The crap on the valves was rock hard, but I was able to break it up with some persistence.
Once it cleaned up I noticed a lot of little gouges in the left combustion chamber and the left piston top. You can see in the photos. This was the cylinder that was giving me the lower compression issue, so that would make sense. The cylinder walls did not have any major gouged that I could feel with my nails, but I have yet to completely clean them up and spec them. With any luck maybe I can get away without overboring. The cam shaft and pistons od meet spec. Lots of work to do prepping these gasket surfaces. Seems like hundreds of little bits of old gasket on them.
One thing that happened was I was lifting the head and a cotter pin fell out. I'm not sure where it came from and I was hoping someone could Tell me what it goes to. See pic with the white background.
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Valves need to come out to be lapped, but first test them. Put the plugs back in and pour kerosene or gas into the combustion chambers and see if it leaks out of the ports. Obviously with valves closed.
That pin is from the transmission and needs to be replaced and that means a complete motor strip to get to it.
The other thing you are going to look at is the rings and for that the barrels have to come off. We expect the rings to be stuck in their grooves.
That pin is from the transmission and needs to be replaced and that means a complete motor strip to get to it.
The other thing you are going to look at is the rings and for that the barrels have to come off. We expect the rings to be stuck in their grooves.
Teazer, thanks for identifying that cotter pin. So I will need to split the cases to put it back in? Where does it need to go? I wonder how it got out and got where it was...
I do plan to leak test the valves and lap them if needed. I'm going with new rings too after I spec the cylinders and deglaze.
Thanks for the feedback.
I do plan to leak test the valves and lap them if needed. I'm going with new rings too after I spec the cylinders and deglaze.
Thanks for the feedback.
I'm pretty sure that it is from the selector forks. There are three forks on one drum. Each fork has a roller dropped in that is retained by a small pin - just like that one.
The pins are there to stop the roller from coming out. If the roller comes out, the fork could side side to side and engage two gear at once which would lock the transmission and pulling the clutch in would not free it. Not a risk I would want to take.
It is possible that the motor was rebuilt in the past and the PO may have dropped it and the question is did he replace it with a new one or is it missing. Do you feel lucky?
The damage on that piston and combustion chamber are common. It's foreign object damage. It may have been a broken ring or maybe just a stone sucked in at some point in the past. Use the old rings to clean out the ring grooves and check that they fully seat and are free to move.
By some odd coincidence, I happen to have a 175 motor apart so I checked the pins and they are a little different in this motor to that that one. I thought you found it inside the motor. Is so, maybe it's from the selectors and maybe the PO dropped it in when checking valve clearances. I would stip and inspect the bottom end just to be sure.
The pins are there to stop the roller from coming out. If the roller comes out, the fork could side side to side and engage two gear at once which would lock the transmission and pulling the clutch in would not free it. Not a risk I would want to take.
It is possible that the motor was rebuilt in the past and the PO may have dropped it and the question is did he replace it with a new one or is it missing. Do you feel lucky?
The damage on that piston and combustion chamber are common. It's foreign object damage. It may have been a broken ring or maybe just a stone sucked in at some point in the past. Use the old rings to clean out the ring grooves and check that they fully seat and are free to move.
By some odd coincidence, I happen to have a 175 motor apart so I checked the pins and they are a little different in this motor to that that one. I thought you found it inside the motor. Is so, maybe it's from the selectors and maybe the PO dropped it in when checking valve clearances. I would stip and inspect the bottom end just to be sure.
I will check with the PO to see if any work was done on the bottom end. I'm pretty sure he never opened up the motor (it only has 5000 miles). I'm not actually sure it came from inside the motor, I just saw it drop from the head when I was moving it. It may have been on the outside in one of the many nooks and crannies. If it fell from the headlamp, the head is a likely place for it to fall. Like I mentioned it has the grime you see on external parts. I'm gonna check to see if the cotter is missing from the headlamp when I get home. You got me worried a little bit though, I'm not quite ready to die yet 
Thanks for your suggestion on cleaning out the grooves with the old rings, I was wondering the best way to clean the grooves out.
If I do open up the bottom end, are the any critical inspection or maintenance items to look for? In riding it I did not notice any shifting problems, etc, so I was hoping to avoid splitting the cases...
Thanks for your suggestion on cleaning out the grooves with the old rings, I was wondering the best way to clean the grooves out.
If I do open up the bottom end, are the any critical inspection or maintenance items to look for? In riding it I did not notice any shifting problems, etc, so I was hoping to avoid splitting the cases...
That is all possible. How long is that pin?
If it becomes a problem you would know - not missed shifts as much as the whole thing locked up. If we can confirm it's not from the bottom end, the anxiety level goes way down. If you do have to split the cases, it is all very simple. What takes the most time is cleaning things up and chasing threads and painting etc. Strip and rebuild a bottom end is about 2 hours work or less. Probably closer to 45 minutes, but it takes time to clean parts and inspect them.
I don't recall that sort of clip in the headlamp of any of the 160/175s I have stripped. But on old bikes anything is possible. That's why most of us err on the side of caution.
Could you take some pictures of the sides of those pistons to see if there is any obvious damage, and how stuck were the rings?
With any luck the issue will be leaking valves. If not it's pretty simple to fit new pistons and rings, but you should inspect and measure the bores to see if stock pistons will still work with a glaze busting honing.
If it becomes a problem you would know - not missed shifts as much as the whole thing locked up. If we can confirm it's not from the bottom end, the anxiety level goes way down. If you do have to split the cases, it is all very simple. What takes the most time is cleaning things up and chasing threads and painting etc. Strip and rebuild a bottom end is about 2 hours work or less. Probably closer to 45 minutes, but it takes time to clean parts and inspect them.
I don't recall that sort of clip in the headlamp of any of the 160/175s I have stripped. But on old bikes anything is possible. That's why most of us err on the side of caution.
Could you take some pictures of the sides of those pistons to see if there is any obvious damage, and how stuck were the rings?
With any luck the issue will be leaking valves. If not it's pretty simple to fit new pistons and rings, but you should inspect and measure the bores to see if stock pistons will still work with a glaze busting honing.
It is quite possible that it had nothing to do with that bike and may just have been dropped off a bench or whatever. Back in teh day, they tended to use split pins rather than that type of R clip, so it's entirely possible that it's unrelated to your bike.
Looks like it could have been a seat pin clip. There is a smaller one just like it on part of the seat. And the main pin appears to have a cotter pin in it that does not appear to be original. I texted the previous (and only) owner about it and hopefully it'll be case closed.
