Honda 175 break-in?

[Alex_V]

Finally got my '72 CL175 back under its own power last night. New standard pistons and rings (carefully assembled with attention to ring direction, clocking, cylinder lube, etc.) in bores honed with 320 grit (IIRC) stones after being mic'd up to .0002" under max. tolerance. All new top-end gaskets and valves lapped in by yours truly - didn't touch the cam or any bearings because it ran fine with even 130 PSI compression before the head gasket blew. Break-in oil is Honda brand 10w30 SL, fuel is 89 octane ethanol free, carbs. were in pretty darn good tune before the HG went so I didn't touch them.

After getting it to fire (4th kick

) and making sure it had oil to the top end (ran maybe a minute, gently/repeatedly revving up to 5 or 6,000 RPM most of the time) and sitting for about 10 minutes, the first drive was about 8 miles of hilly backroads, stopping once, and constantly varying load up to about 8,000 RPM several times (9K once, I think) with a few good hearty pulls. A friend was driving behind me and in his headlights I could see consistent, moderate oil smoke out the pipe that he said got better after I laid into it good and hard the first time. After shut-down I peeked in the cylinders - just a few vertical scratches but the crosshatching is extremely defined with no visible marks of where the rings stop and head back down. Combustion chambers are squeaky clean and plugs are pretty dark brown with the top half of the ground strap being lighter brown, no signs of fouling-type deposits. Consumed just over 1/2 of whatever full-add is of oil. Rode it about 10 more miles today, not varying speed as aggressively as last night, and it seems to only be running better - idles well at about 1,400, pulls harder than I remembered it doing before, has enough power to pull me (sitting up) along at 9,000 RPM on flat ground (didn't want to push it harder than that) when before it struggled to hold 8 grand under the same conditions. It was daylight but I can still see some oil smoke when I rev it sitting still.

Is the oil smoke expected this early on? What, if anything, should I do differently from this point?

 

[BrocLuno]

You have bores that are just under 0.002 of being to big. That means things are a bit loose. I would not have bored it either. But you can expect rings to take a while to seat if they are in a somewhat larger bore.

And, you said you did not touch the head other than to lap the valves. But did you mic the valve stems and guides? My bet is a bit is going past the rings and some is going past the valve guides.

I would not worry. But the brown plugs seems a bit rich. Tan is what I shoot for. Can't remember if that is CV Carbs or cable slide carbs ...

1,400 is a kinda high for idle. I usually idle my bikes around 700+. Will it idle down?

Rode through Cambellsville en route to a local MX race when I was stationed at Knox back in the '70's. Nice town. Good on you. Good country and nice folks

 

[Alex_V]

Actually, they were .0002" (two tenths) under max. - but that makes sense, and I won't be disappointed if it uses a little in the end. I bought new valves - never even thought to mic them, just lapped them into the old seats and gave them a careful "wiggle" just off the seat to make sure none had a lot more play than any of the others. They're slide/cable carbs., and it may be on the rich side. I had gotten them very close just before the head gasket blew - haven't decided whether I think the refresh should need a leaner or richer mixture. Is there a rule of thumb on this? Ha! I'd have to see 700 idle on this engine to believe it - book is 1,200 and it's gotta be just right to dependably idle there.

I like it here - lived here for 2 1/2 years now. Lots of good folks and things to keep you busy (in work and leisure) if you know where to look. One of my biggest uses for the bike will be riding to my part-time job at a vineyard on the South side of town.

 

[Langanobob]

Here is a link to a sometimes controversial site. His break in prucedures work for me.


Motoman

 

[Alex_V]

I can believe it, especially on bike engines. It makes sense that as long as conditions (heat, speed, etc.) in the engine stay within their intended parameters, very little gentle time is needed before you need to use what "bite" the parts have left to put them under real stress. He says he uses regular PCMO - as I understand it the main caution in using car oils is the friction modifiers not playing well with wet clutches, yes? But as far as the non bike-specific parts (pretty much everything else) will, let's say, VWB 10w30 promote better break-in than a 4-stroke conventional oil?

Looks like I'm in for some fun runs this afternoon.

 

[BigCahuna]

Just to stir the pot a little , motoman says he's done over 300 motors with his "breakin in" procedure. S&S probably the biggest aftermarket mfgr of motorcycle motors has probably sold over 10 times that many motors and this is their procedure for break in. I guess the main difference is if your motor blows up, moto man will tell you, too bad. While S&S will have to replace it at their cost. https://www.sscycle.com/tech-info/tech-tips/new-engine-installation

 

[Scout1]

I agree with BrocLuno, the smoke may be coming from your valve guides. I'm no expert but I once lapped some valves on a Chevy without paying any attention to the guides and when I put it back together it smoked badly. Had to take it apart again and have the guides knurled to get back to smoke free!

 

[ragtoplvr]

An extremely long stroke big bore engine with known propensity to blow cylinder head and base gaskets has little in common with a small bore short stroke used engine with slightly excess piston to wall clearance. Motoman it.

rod

 

[BrocLuno]

As far as oil, the shared sump means it needs a tranny/clutch/engine oil. To me that's one off the Allison List: http://www.allisontransmission.com/parts-service/approved-fluids/off-highway-fluids These fluids have been rigorously tested in combined sump systems and hold up well

 

[Alex_V]

Well, with about 55 miles on it (5-10 miles at a time) it's running pretty good. A little smoke, mainly just as you roll back into it from coasting, but I hope that continues to reduce with a few more miles. At <30 miles I changed out the Hondalube for Valvoline 4-stroke 10w40 and cleaned the filter - plenty of metal! Compression was 120 on both cylinders at that time. But aside from finicky idle and an occasional cut-out when rolling slowly into it, all looks good and it's stronger than it was. I sustained a solid 63 miles an hour home behind the wife this evening!

 

[ZeeOSix]

Originally Posted By: Scout1
I agree with BrocLuno, the smoke may be coming from your valve guides.


Didn't see any mention if new valve guide seals were installed. If not, then old hard valve guide seals could be letting oil past the valve stems.

 

[Alex_V]

Yes, valve seals were replaced - this engine only has them on the intake side. Didn't do anything to the guides themselves, though.

 

[Alex_V]

Up to about 500 miles so far, still running well. Found a vacuum leak at one intake manifold (that explains the light colored plug that I first suspected was an uneven float) and that I somehow had the timing retarded quite a bit. Double checked static and full-advance timing and was able to move the slide needles a notch leaner after that. It'll also think about hitting redline now, when before it hit a very defined plateau at 9,500 and would sputter above 7K if not under decent load. Waiting on 38 slow jets from the local bike shop to see if that'll darken up my plugs from the near-white they're now at with 35's.

I think I met and exceeded the thermal limits of the Valvoline 4-stroke oil on an 18-mile stretch of continuous 55 MPH running last weekend. Brother-in-law was behind me on his CM400 and said he noticed some occasional smoke later on in that leg. After pulling up at a gas station it didn't want to idle and the oil looked fairly dark with substantial vapor coming out the hole when I popped the dipstick, suggesting it had gotten good and warm. After that 140-mile day and losing about a half pint of oil the engine still ran strong and didn't use much more oil, but since then it puffed smoke at times suggesting the oil may have thinned out substantially and was slipping past the rings/valve guides. Draining it today it was pretty dark and not really translucent like I'd expect it to be - more cloudy like used gear oil. Amsoil 10w30 went in and it's giving much better vitals during and after a hard run!