smoking from new pistons.rings.jugs

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I think the key to doing a good job yourself is perserverance. If things don't turn out well research and do it again.
I've lost track of how many engines I rebuilt but to me the key is a good machinest. If possible take the piston in for him to look at before honing.
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I'm with you 100% pm this..... thanks for the feedback, all.
 
Best guesses here:

Rings not in right.

Rings didn't bed right, wrong oil (maybe a straight weight to break it in?) or break in procedure was wrong (did you wring it good?)

I wouldn't re-hone it, unless you put rings in that need it. There was some info on this recently.
 
compression test confirms my fears: 150 psi on right. plug is dry black (too rich mixture) .

left side: 90 psi which came up to 130 with a teaspoon of oil in the cylinder. Definitely some sort of ring issue: plug is oily and black.... my first guess is that right side rings were installed correctly and left side are reversed.......

School has started and I'm a teacher so I probably won't get to ripping it completely apart for a whle but I'll keep you posted.

kfh
 
hello!

my 2 cents......[haven`t read all posts here, so maybe it is mentioned already...]...when the engine smokes then oil is getting from the crankcase through the rings to the combustion chamber [as i know....so maybe someone knows other ways?]
i think the break in was too smooth so that you got glazing in your barrels. i think it is not normal with new rings and pistons that it smokes much when you broke your engine in well.
i do a hard break in so that there is lot of pressure on the rings and had always good experience with......strong engine, low oil consumption.

have a look at this site: there is a good explaining image what happens with a new honed cylinder wall at the break in:
http://www.ntnoa.org/enginebreakin.htm

i am not a pessimist, but rather a realist....i think your engine isn`t broke in. so i would re-hone it.
you won`t be happy with a engine that is not broke in well - you will feel the difference on a well broke in engine [at engine power and in your wallet....lower oil and petrol costs]

chris
 
71basketcase said:
compression test confirms my fears: 150 psi on right. plug is dry black (too rich mixture) .

left side: 90 psi which came up to 130 with a teaspoon of oil in the cylinder. Definitely some sort of ring issue: plug is oily and black.... my first guess is that right side rings were installed correctly and left side are reversed.......

School has started and I'm a teacher so I probably won't get to ripping it completely apart for a whle but I'll keep you posted.

kfh
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I haven't seen it mentioned so I will. The installation of the oil rings looks straight forward but if the rippely thing in the center of the set overlaps even one link that cyl will smoke. The wavy ring's ends must butt and never overlap (this from EMGO direction sheet). When you break it down pull them out slowly to see if that was the case altho the above missmatched compression sounds like a broken ring . Since there is no cross-over pipe on a 71 and you haven't mentioned it ... is one or both sides smoking? The compression diff and the black oily plug makes it sound like only the left side has the problem.
 
71basketcase said:
I think the key to doing a good job yourself is perserverance. If things don't turn out well research and do it again.
I've lost track of how many engines I rebuilt but to me the key is a good machinest. If possible take the piston in for him to look at before honing.
Click to expand...


I'm with you 100% pm this..... thanks for the feedback, all.
Click to expand...

I prefer doing all the work myself I hate to think what a CNW rebuild on an engine costs, also you learn as you go which I find quite enjoyable. For me one of the benefits of a bike like the Commando is that very few special tools are needed .....and its an easy bike to work on.
 
The installation of the oil rings looks straight forward but if the rippely thing in the center of the set overlaps even one link that cyl will smoke.
Click to expand...

as I said earlier, I'm busy getting the school year off and running, so no time to work on the bike: (which is a shame because the weather is gorgeous) but I'll be willing to bet this is at least partially the case but that doesn't explain the differential in compression.... as I said... I'm waiting for a bad spell of weather and a lazy saturday to figure it all out

thanks for all the assistance

Karl
 
Update on smoking from new rings/jugs. etc....

My last post was in August...and as I suspected, the fall turned into it's usual crazy time..... too busy with work, family, gigs (part time musician) and life in general.... Poor Strunzo waited patiently in the shed.

This weekend I finally got time to break down the top end: Here's the report:

***Cylinders... look good. shiny and even wear.

*****pistons looked good: no carbon, scratches, visible problems.....
**** Head/Valves: look fine... a little carbon on the valves BUT after reading the postings on octane, I think that I should definitely move up from mid-grade to premium and that will help with too much carbon (along with correctly fitted rings)

****RINGS ........ AHA!!!!!!!! compression rings were correctly fitted with 'top' stamped correctly. However, I don't think the left ring gaps were staggered correctly.

****oil ring......it's the 3 piece kind that I got from oldbritts..... on both cylinders there was an overlap in the middle serrated ring.....and on the left, the top/bottom rings were actually in the middle of the slot pressing on the serrated ring... no wonder the right one didn't smoke anywhere near as much as the left.....

given the info from you kind folks earlier in this post, it seems clear that the oil scraper rings weren't' doing their jobs at all, so naturally too much oil was getting past them.

I am going to have my machine shop guy give it a re-hone and perhaps have him look at the pistons/rings prior to re-assembling.

I somehow think that when I re-assemble it, the smoking with be cured (after a bit of a break in)

thanks for your continued support/encouragement.

Karl
 
Re: Update on smoking from new rings/jugs. etc....

71basketcase said:
I am going to have my machine shop guy give it a re-hone and perhaps have him look at the pistons/rings prior to re-assembling.
Click to expand...
Does it need a re-hone? Hopefully the over lapped oil rings didn't scrape the cylinder walls. The piston clearance should be checked, it'd be a shame to have to re-bore.
 
not a re-bore... just a re-hone: I bought the new jugs and they appeared to be honed... so I installed them with only a cursory honing with a cheepie hone. Hence the idea to have a pro hone it while I have it apart...... bores are currently smooth with no evidence of scratches or damage.....
 
Karl,

Before you hone....
post36944.html?hilit=hone#p36944
I felt quite smug about not honing my bores after reading this.
The reason I didn't bother is because I've always regarded honing as the last process in a re-bore to remove the machining marks which could snag a ring.
Just my opinion, based on time spent machining engine blocks for trucks many years ago.
 
excellent article, thanks much, B+....... you get an A from this shop teacher 8)

I think, given that I can clearly see the oil scraper rings were incorrectly installed, and that the barrels themselves look absolutely pristine, I'm going to re-install everything, fire it up... and see what happens. I'm itching to get a few rides in prior to the end of the riding season (which on cape cod can sometimes edge into December..... we have a few 50+-60+ days even this late in the year thanks to the gulf stream.....
worst case scenario, I rip it apart in the winter.... but I have a suspicion that my smoking problem is about to be cured.

thanks all.

KaRL
 
firing day approaches

this is the weekend....... I re assembled the jugs and pistons and once I get the package from OldBritts I'll have the head gasket and will assemble the head...... we'll see what happens to the smoking.....

question:

I'm reassembling with same piston rings in same cylinders etc...... should I follow a breakin sequence again or am I o.k. to just fire it and go?

thanks

kfh
 
"If a freshly rebuilt engine still smokes after 5 miles , I would be very worried ."


Yes, it should not smoke, however, are we sure it is not the valve guides or bad installation of same.
 
I'm reassembling with same piston rings in same cylinders etc...... should I follow a breakin sequence again or am I o.k. to just fire it and go?

You only needed to start the clock clicking again if you had rehoned, as you havent then you can count your previous miles towards the break in mileage.
 
it should not smoke, however, are we sure it is not the valve guides or bad installation of same.
Click to expand...

shouldn't be the guides because I had the head professionally rebuilt. all new valves/guides and machining. There's only around 500 miles on the valve job.

I'm pretty sure that things are going to be good: I double and triple checked the ring locations AND made sure that the oil rings were correctly situated. As I installed them I inspected them through the gaps at the bottom of the cylinders and all looked perfect.....

further report to follow.
 
71basketcase said:
I used a cheepie honing stone and probably didn't do as good of a job as I should.... figuring that since they were NOS new jugs... maybe that was a bit of a mistake.

I'm pretty sure that I installed the rings correctly as I double checked them a few times. H aven't installed rings in anything since I rebuilt a volkswagen in the early 70's but that went without a hitch.

I'm using castrol gtx: 20-50...... just about time for the first oil change.

I've been babying it: maybe jumping on the throttle up to about 1/2-way but for the most part, keeping in the low RPM range....... maybe I'll start gittin on it a bit......

as I said, it does seem to be getting less and less smokey but it does smoke a bit especially when the engine is hot: maybe if I go with a static 30 or 40w??, since I don't care about having to start it in the freezing cold.....

I'll keep you posted..thanks

kfh
Click to expand...
 
Did one say " Cheepie Honer" > :?: Normal ridge to quickly rub the top edge off the ring...worst than that,,,,break it :?: Hope the new valve seals fitted correctly...i had one pop off...and boy did she smoke on that side!!! :(
 
I have the carby's on my desk right now (to clean out the idle channel AGAIN ) and will be re-assembling/firing up the bike this weekend............ The good news about cleaning the idle circuit for me is that I'm a guitar builder, so I always have a bunch of .016 gauge wire (strings) around 8)

Hopefully, you'll get a happy posting from me on monday because: a. the bike doesn't smoke and b. the Patriots won!

kfh
 
STRUNZO IS CURED!!!!!!!!

I got Stunzo (the former 71 basketcase) back together yesterday anf fired him up....... afte about five miles of much reduced smoke, it stopped smoking altogether. and after about a 20 mile ride, I pulled the plugs to have a look-see.....

The plugs look absolutely perfect: like poster children for correct plug color etc.........

I didn't care if it was ony 45 degrees this a.m........ I rode to work! (I need to race home before the rain sets in)

so.... I can put strunzo (and this thread) to bed for the winter knowing that next summer we'll be putting some SERIOUS miles in

Thanks to all for your help, encouragement, and collective knowledge.

Karl Hoyt
 
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