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Had my Honda motor re boarded with new over sized piston & rings. After putting it back together it runs but a lot of smoke & not much power. Any suggestions?

First reaction is its bored too much for the ring diameter. You are bypassing oil, giving smoke. Bypassing compression in to the crank case, losing power. Oil from the crank case breather at all?

Would try making your air/fuel bit richer would be running lean I u haven't adjusted

How would I do that? I thought that mixture was pre set and couldn't be adjusted.
I had it professional boarded out, with the correct cylinder to piston clearance.

I think fist you should look into an compression test

Tip the oil out.
Go to Walmart and buy a quart of the cheapest oil you can find.
run the mower who in heavy grass to put a load on the motor.
This will help seat the rings which would appear not to have happened.
If it does not clean up in 10 to 15 minutes take the engine back for warrante repairs.

Boring/piston fitting is an exact science. I have been burned at a so called "pro shop" which could not hold the proper tolerance. I hope this is not true in your case. Careful measurement accross the piston skirt must be compared to the true bore diameter. There used to be some clearance checks made with a feeler gauge inserted between bore and piston. A spring scale hooked on the feeler gauge must show the specified withdrawal force. I only mention this so the professionals can comment and perhaps save you a tear down to measure the piston. If you are "sure " of the piston diameter you should get someone to carefully measure the bore and compare. No thicker oil film will solve an overbore problem IMO.

Every time I take an engine for boring I also take the specs from the manufacturer with me so they know how to measure the piston skirt, cylinder clearance. If they don't measure the clearance according to the manufacturer they can really screw stuff up.

ILENGINE said:

Every time I take an engine for boring I also take the specs from the manufacturer with me so they know how to measure the piston skirt, cylinder clearance. If they don't measure the clearance according to the manufacturer they can really screw stuff up.

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I gave up on geting them bored and now do it myself.
Problem is very few people get mowers bored so very few shps have the faintest idea of how to do the job and in particular how to mount the cases.
Most car engines are bored by bolting down either the sump or the head so when confornted with a mower engine rather than make up an L block closing plate to bore the engine they just fit it by the head bolts and you end up with an oval bore.

My first question is, did you check the ring end gap in the newly bored cylinder before installing? Your cylinder my be bored correctly, but you received and installed the wrong rings. Second question, are the rings installed in the correct order and proper edge facing up? Third, did you replace the piston also? Can you post the following info:
1. All numbers for the engine.
2. Part number for the ring set.
3. Part number for piston.
4. What diameter was the cylinder bored to?
5. Was the block washed and cleaned multiple times before reassembly.
6. Are you sure the rings were staggered when install?

This will help us diagnosis possible problems.

bertsmobile1 said:

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I gave up on geting them bored and now do it myself.
Problem is very few people get mowers bored so very few shps have the faintest idea of how to do the job and in particular how to mount the cases.
Most car engines are bored by bolting down either the sump or the head so when confornted with a mower engine rather than make up an L block closing plate to bore the engine they just fit it by the head bolts and you end up with an oval bore.

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I have one bored about once every two to three years. Usually just replace the engine, unless there is no other engine option, or too expensive to replace, like the $3000 kawasaki engine for a JD gator, or one of the older JD's with the K series engine with no replacement option available.

I looked around a bit and found that the feeler pull technique seems relegated to antique or older engines. And the discipline described is all the way from "a feeler gauge" pulled by hand to "a 1/2 strip of shim stock pulled to inch pounds or foot pounds," depending upon the manufacturer. So that approach does not really help - too imprecise. Best to make careful meaurements which probably involve a tri-point bore gauge. Perhaps a motorcycle shop "might" be the best source, if a good one can be found. Rivets tips on rings includes end gap filing to manufacturer spec. Reringing should be seen by newbies not as a solution in itself , like o ringing a leaking faucet. Won't work.

DavidG said:

Had my Honda motor re boarded with new over sized piston & rings. After putting it back together it runs but a lot of smoke & not much power. Any suggestions?

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Have you done a compression test?

Shot in the dark..... what oil are you running in on?...that is assuming you've done the valves etc

To clarify my post, I do not recommend filing rings to change ring end gap. I wanted to know what the end gap was of the new rings. If the rings installed were not the corrected ones for a newly bored cylinder, the end gap would have been too large, allowing oil to bypass. Also, if new oversized rings were used, but not an oversized piston, the same problem would occur.

Rivets said:

My first question is, did you check the ring end gap in the newly bored cylinder before installing? Your cylinder my be bored correctly, but you received and installed the wrong rings. Second question, are the rings installed in the correct order and proper edge facing up? Third, did you replace the piston also? Can you post the following info:
1. All numbers for the engine.
2. Part number for the ring set.
3. Part number for piston.
4. What diameter was the cylinder bored to?
5. Was the block washed and cleaned multiple times before reassembly.
6. Are you sure the rings were staggered when install?

This will help us diagnosis possible problems.

Click to expand...

When I first read this thread this was my thought. I agree with this post. Ring gap and if the rings were installed right???

Rivets said:

To clarify my post, I do not recommend filing rings to change ring end gap. I wanted to know what the end gap was of the new rings. If the rings installed were not the corrected ones for a newly bored cylinder, the end gap would have been too large, allowing oil to bypass. Also, if new oversized rings were used, but not an oversized piston, the same problem would occur.

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Sorry Rivets...the filing end gap is my statement. Still hold to it, however. And a slight chamfer on the outer edges of the ring ends. :ashamed: