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Old 12-05-2018, 06:53 PM
TeaguCal TeaguCal is offline
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Default Predator 212 Rings

I have had lots of blowby issues with this engine... it has ran for a total of 15 hrs with no break in. It foul's out a spark plug in about 25 seconds, and there is visible smoke in the exaust.
I took it apart, and the rings were almost nonexistent.
My question is how do I tell if the cylinder is oblong, and do I need to do anything other than slap new ring's on and go?
P.S. all the other items that could be worn are fine.
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Old 12-05-2018, 07:22 PM
mckutzy mckutzy is offline
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Hello and welcome... If its brand new... take it back, get a new one....
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Old 12-05-2018, 07:36 PM
J.S.@SMS J.S.@SMS is offline
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There are two ways that i can think of that are quick-ish and easy enough.
1. Remove the rings and rod and put the piston in the bore and hold it as close to dead center as you can. You should see an equal amount of space between the piston and the sidewall all the way around. Or.
2. Grab an accurate enough caliper and measure the bore. The numbers should not vary much.

But, if the engine is new (less than 90 days from purchase) take it back and exchange it for a new one.
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Old 12-05-2018, 11:36 PM
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Take it back. Why hassle?
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Old 12-06-2018, 11:43 AM
TeaguCal TeaguCal is offline
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I would take it back, bu I am not the original purchaser, and the engine is more than 2 years old.


Quote:
Originally Posted by J.S.@SMS View Post
There are two ways that i can think of that are quick-ish and easy enough.
1. Remove the rings and rod and put the piston in the bore and hold it as close to dead center as you can. You should see an equal amount of space between the piston and the sidewall all the way around. Or.
2. Grab an accurate enough caliper and measure the bore. The numbers should not vary much.

But, if the engine is new (less than 90 days from purchase) take it back and exchange it for a new one.
Thank you... that's exactly what I was looking for. Do I have to hone the cylinder or anything for proper ring break in? From what I understand, you can't hone an aluminum block due to a finish in the cylinder. I really don't want to ruin this engine.
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Old 12-06-2018, 12:15 PM
mckutzy mckutzy is offline
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You could try to take it back.. See if they accept it on the warranty basis.. Or why not get a new one... You'll spend just as much re building it, than just getting a new one for $100
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Old 12-06-2018, 02:00 PM
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You guys. It's real easy to measure the bore taper with out anything more than feeler gauges.

Take all the rings off the Piston. Put a ring in the cylinder and square it off with the Piston top. Measure the gap. Move ring up and down the cylinder and square it up and measure.

This is also how you measure ring gap by the way...
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Last edited by Whitetrashrocker; 12-06-2018 at 02:01 PM. Reason: Spell check is drunk again.
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Old 12-06-2018, 03:52 PM
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Quote:
Originally Posted by mckutzy View Post
You could try to take it back.. See if they accept it on the warranty basis.. Or why not get a new one... You'll spend just as much re building it, than just getting a new one for $100
Actually I replaced the valve seals, rings, gaskets (all of them), crank seals and carburetor on a GX200 clone for about $48 and some change. I honed the cylinder and the engine runs like new.

That motor had bad rings and the bore was too worn. And it had similar circumstances, about 20hrs of use and enough blow by that within 30 seconds you couldn't see the bike.

PS: I would recommend that if you replace the rings, you hone the cylinder. That will ensure a proper seat. And these engines have cylinder sleeves, which I believe are cast iron.
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Old 12-06-2018, 04:23 PM
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Quote:
Originally Posted by TeaguCal View Post
I took it apart, and the rings were almost nonexistent.
What does that mean exactly?

Quote:
how do I tell if the cylinder is oblong
Ideally you would measure it with a bore gauge. If you can see at least some crosshatching over the length of the cylinder's top and bottom sides, then it's probably not out of round nor tapered. Hone it and install new rings.

Quote:
Originally Posted by J.S.@SMS View Post
2. Grab an accurate enough caliper and measure the bore.
No calipers are accurate enough to do that and they won't fit down the bore. The equipment to do it right will cost more than a new Predator and it takes some practice to use them correctly.

Quote:
Originally Posted by Whitetrashrocker View Post
You guys. It's real easy to measure the bore taper with out anything more than feeler gauges.

Take all the rings off the Piston. Put a ring in the cylinder and square it off with the Piston top. Measure the gap. Move ring up and down the cylinder and square it up and measure.

This is also how you measure ring gap by the way...
Just be aware that the ring end gap is going to vary by a difference in the bore's circumference rather than diameter. The resulting difference measurement has to be divided by Pi to get an actual number representing bore taper.
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Old 12-06-2018, 05:07 PM
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Your right shelbyclone. But it's a way to measure with simple tools. More so just as a comparison from top to bottom to see how wore the bore is.
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Old 12-06-2018, 07:57 PM
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Absolutely, I didn't mean to sound like I was disagreeing. I just wanted to point out that it wouldn't be a direct measurement.
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