motor rebuild questions

[hsi111]

I have a 2003 90 elpto that I have torn down. It has seized (stuck) rings on # 2. The damage to the cylinder wall is so minor that I think a honing may be enough but don't know yet til I get the right hone and try. I definitely need a piston. My questions are as follows: If by chance I need to bore the cylinders .015, 1) Do I have to get an over sized piston or just .015 over rings. 2) Can I bore 1 cyl and put .015 rings on it and re ring other two with std rings or is that being too cheap. (the reason for the question is that I have already bought std rings) Thanks, Rick

 

[canoemang]

Re: motor rebuild questions

You'll need to get .015 piston and rings if bored. Yes you can run one punched over and other stnd..

May want to get a bore gauge to verify it isnt that bad...

 

[hsi111]

Re: motor rebuild questions

Thanks for the info.

 

[Texasmark]

Re: motor rebuild questions

You said not too bad. Since you have it torn down you can't give me an answer but the compression on the other 2 cylinders would be interesting in determining a course of action. If they were above 120 it speaks of good rings and walls meaning a honing would be all that's required with new piston and rings. I prefer a ball type hone. Flex-Hone is the one I have used successfully. Unlike the 3 fingered stone type hones, being individual spheres and lots of them, they follow the contour of the cylinder much better allowing you to remove a minimum of material.

If you are going to bore one cylinder then I see it as upsetting the balance of the engine. Bore all or none as I see it.

I'd surely consider honing all 3 cylinders with new rings on all pistons. You can buy the hone for a lot less than you can pay for a boring job.

Go to BRM Flex-Hone, Industrial Brushes, Wire Brushes and when the home page comes up drop down to the second standard size hone pictured down the left side of the page. It's the "GBDFlex-Hone. Read the usage portal under the picture. It's the one made for what you want to do. Your bore is 3 1/2" so that's the one you want and type is "Abrasive" which is Silicon Carbide for your usage. Upper right of the home page has a "dealer" window to find a retail dealer. Don't take off any more material than necessary to kill the glaze. A minor scratch that you can't catch your fingernail on is not to be worried about. Be sure to follow their crosshatch pattern guide.

Good luck.
Mark

 

[racerone]

Re: motor rebuild questions

So if the cylinder is egg shaped and you use a ball hone the cylinder will still be egg shaped !-----A shop would have a proper hone that will true up the cylinder wall.------If the other 2 measure within specification it is accepted practice to bore just one cylinder.---A fact supported by many manuals.

 

[hsi111]

Re: motor rebuild questions

Thanks Mark for your input. Actually, that is exactly the hone that I have ordered online. Not here yet. The compression was 115, 30, 115. I have 3 new std rings already, just waiting to see what happens with hone. I can't really catch a scratch with my nail but can feel a little rough spot in one place with the flat part of my finger. I know you won't be able to tell much from a pic but I am attaching a couple. The piston is much worse that the cyl wall for some reason. Thanks, Rick

 

[hsi111]

Re: motor rebuild questions

Racerone....I have a good set of calipers and I am getting the exact same readings all around cylinder.

 

[racerone]

Re: motor rebuild questions

Vernier calipers is not the best way to " measure a cylinder bore " in my opinion.---------I use telescopic gauges and a micrometer + many years of experience in measuring techniques.-------What you see there is aluminum transferred to the cast iron cylinder wall.------Scrape that out / hone the cylinder / re-assemble with a new piston and new rings.-----------Now you must determine why this happenened !!---If not then you might have to do it over again.

 

[wrench 3]

Re: motor rebuild questions

The ball type hones are strictly a deglazer and they work very well for that purpose. But on a two stroke they tend to drop into the cylinder ports and jam up or brake.
The material that the piston is made of is a lot softer than that of the cylinder liner and has a lower melting point. Hence the increased damage to the piston. You may find that a lot of the damage to the cylinder is actually piston material deposited on the wall.
BTW have you determined what caused the failure in the first place.

 

[hsi111]

Re: motor rebuild questions

OK, Seriously? Why does the word "machine shop" sound so expensive? After the comment from racerone earlier, i went down to a local machine shop that does boat engines (been there 40+ years) and talked to them. They will vat and clean block and bore the cylinder for $50. Seriously? 50 bucks? I paid 80 for the hone. Luckily it hasn't shipped yet and just got a refund.

 

[hsi111]

Re: motor rebuild questions

Wrench3.....I have no idea what caused problem. I bought it this way. Actually I have two identical motors with exact same problem. Am assuming middle cyl may have been running too lean. Not sure what else would cause it. Water ports are pretty clogged with crap from salt water. It could have just not cooled as it should.

 

[Texasmark]

Re: motor rebuild questions

The ball type hones are strictly a deglazer and they work very well for that purpose. But on a two stroke they tend to drop into the cylinder ports and jam up or brake.
.

Funny, the site I mentioned specifically mentions marine engines. Getting the proper size is important. Time to deglaze vs "porting" the intake and exhaust ports is not an issue. Diameter of the honing balls is adequate. Never had one "break".

Deglazing will take any alum from the piston from the cast iron cylinder. Rings are chrome plated cast iron. If excessive grove is worn in the pistons then a full set will be required. Had that problem with a Ford Diesel tractor.

To each his own. You do it your way. I do it mine. HSI will do it his. This is a forum of ideas and experiences.

Mark

 

[wrench 3]

Re: motor rebuild questions

To each his own. You do it your way. I do it mine. HSI will do it his. This is a forum of ideas and experiences.

Mark

Just relaying my experience. But then I was using the one I had for four strokes.

 

[wrench 3]

Re: motor rebuild questions

Wrench3.....I have no idea what caused problem. I bought it this way. Actually I have two identical motors with exact same problem. Am assuming middle cyl may have been running too lean. Not sure what else would cause it. Water ports are pretty clogged with crap from salt water. It could have just not cooled as it should.

Around here it's usually the top cylinder that failles first, but we're a long way from salt water. It may be worth your wile to start a new thread on that subject and see if you can get some one with salt water experience.

 

[James R]

Re: motor rebuild questions

Why everyone messes with these jobs I do not know. Take the block to a good machine shop that does two strokes and have them measure and recommend and do the job. Once you know the finished sizes you can buy the needed piston or pistons and rings and do a proper job. If not then you stand the chance of blowing the motor again.

 

[wrench 3]

Re: motor rebuild questions

Why everyone messes with these jobs I do not know. Take the block to a good machine shop that does two strokes and have them measure and recommend and do the job. Once you know the finished sizes you can buy the needed piston or pistons and rings and do a proper job. If not then you stand the chance of blowing the motor again.

From post #10 it sounds like that's what he's doing, but he still has to determine the cause so that it doesn't repeat the failure.

 

[hsi111]

Re: motor rebuild questions

Yep, that's what I am doing. The shop is going to look at it Monday at tell be whether to buy 015 or 030 over piston. He said he would like to have piston before he bores. Below is a pic of crud around outside if cylinders. A lot of it has already fallen out. I didn't know it was salt water when I bought it. There is no evidence of it outside. Probably just occasional salt water. Actually I am just guessing that all that crud is from salt.

 

[Texasmark]

Re: motor rebuild questions

Don't rule out a pitted cylinder wall from corrosion and water intrusion as the root cause. That looks pretty corroded. I had a Scott Attwater 22 hp I sold a guy. Later I saw him with a different engine and asked him why. He said what I just said. I don't know if that engine had cast iron sleeves or was just bored cast alum. If just cast alum I can see intrusion. If cast iron sleeved, that means the corrosion had to penetrate the alum block and then the sleeve which I doubt....but I have nothing to substantiate either position.

Mark

 

[racerone]

Re: motor rebuild questions

I can not see a Scott Atwater with no cast iron sleeves in it.

 

[hsi111]

Re: motor rebuild questions

Thanks to all for your input. Block is now at machine shop. There have been some new developments since my visit to machine shop. I am going to start an new thread looking for input on root cause of failure. Please visit my new thread and offer any input that you have. Thread will be (Seeking root cause of my engine failure)