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XR200 Over sized rings in std bore??

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So I messed up and got 66mm rings instead of 65.5 which I believe is the correct size rings for stock bore on a 1990 xr 200. Can I just gap to spec and send it or do I need to buy some 65.5mm rings?? Sorry if its a no-brainer but I hate to wait for more rings to come in the mail if there's no reason to. 

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You may be able to file your rings for a perfect fit. I used to buy the next size up rings and file for a perfect fit. The issue would be the “notched” portion. Only you can measure that to determine if it will fit around the little pin the rings need to center around. 

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The XR200R doesn't have pins in the ring groove like some vintage 2-strokes.

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4 hours ago, motrock93b said:

You may be able to file your rings for a perfect fit. I used to buy the next size up rings and file for a perfect fit. The issue would be the “notched” portion. Only you can measure that to determine if it will fit around the little pin the rings need to center around. 

Yeah no notch on this one. Think thats a 2 stroke thing. 

20201207_181205.jpg

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8 hours ago, motrock93b said:

You may be able to file your rings for a perfect fit. I used to buy the next size up rings and file for a perfect fit. The issue would be the “notched” portion. Only you can measure that to determine if it will fit around the little pin the rings need to center around. 

Hey there 93b....

You have been giving out a lot of advice in a lot of forums lately...

But a statement like this is something that can undermine all past and future postings...

Because it is something from Engine Basics 101...  

Only 2 strokes have ring locating pins... To keep the ring from rotating to where the ends can open up and snag in a larger port...

One of 2 things are apparent from your post.. 

1) you didn't know all pistons don't have ring locating pins

2) you didn't know an XR200 is a 4-stroke

As far as dirt bike tech guru status, either one of those things would move you waaaaaaaaaaaaaay down in the rankings....

Edited by mixxer

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10 hours ago, Clayton Skarke said:

So I messed up and got 66mm rings instead of 65.5 which I believe is the correct size rings for stock bore on a 1990 xr 200. Can I just gap to spec and send it or do I need to buy some 65.5mm rings?? Sorry if its a no-brainer but I hate to wait for more rings to come in the mail if there's no reason to. 

I have never done what you are asking here.... I'm sure it has been done, but I don't know the consequence, if any real one exists.

Rings are designed to have a target range of lateral force applied to the bore... In a perfectly circular fashion... With correct ring end gap for the bore size they are intended for...

I don't know how much difference there would be in lateral (bore) tension ... Or how much difference there will be in the circumferential distribution of that pressure with the small change in target bore size...

But for me personally, I would probably default to ordering the correct ring set....

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I certainly don’t know about all engines, but I was sharing actual experience I had with a kart two stroke engine. True story. I raced in a spec engine class, so detailed engine setup was critical to be competitive. My kart wasn’t very fast, and a mechanic at the race shop told me I should buy the next larger ring and file it for a perfect gap. I did this and instantly started winning races. It’s the only change I made. My engine was protested. All from buying the next larger ring and carefully filing. 
 

Of course, I don’t want anything to do with giving out bad advice, but the OP asked a question I had first hand experience with. It worked for me, and was suggested by a race engine mechanic. You obviously have much more intimate knowledge of this specific engine than I do. I was just directly answering a question that it may be possible, and added only he could determine if it would work for his application after measuring. 
 

Edit:  The image showing the large overlap wasn’t posted until after my reply. That ring is WAY more oversized than the one I worked on. I doubt filing that much material would be a great idea. Yes. I’d get the correct ring, as you suggest. I make no claim of being any sort of guru, I rely heavily on input from people with known knowledge when tackling technical issues I’m unfamiliar with. I know enough to be dangerous, so I’m careful. 

Edited by motrock93b

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4 hours ago, Clayton Skarke said:

Yeah no notch on this one. Think thats a 2 stroke thing. 

20201207_181205.jpg

Does not appear to be proper crosshatch angle. Almost looks like horizontal lines and deep? Maybe just bad pic?

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22 minutes ago, motrock93b said:

I certainly don’t know about all engines, but I was sharing actual experience I had with a kart two stroke engine. True story. I raced in a spec engine class, so detailed engine setup was critical to be competitive. My kart wasn’t very fast, and a mechanic at the race shop told me I should buy the next larger ring and file it for a perfect gap. I did this and instantly started winning races. It’s the only change I made. My engine was protested. All from buying the next larger ring and carefully filing. 
 

Of course, I don’t want anything to do with giving out bad advice, but the OP asked a question I had first hand experience with. It worked for me, and was suggested by a race engine mechanic. You obviously have much more intimate knowledge of this specific engine than I do. I was just directly answering a question that it may be possible, and added only he could determine if it would work for his application after measuring. 
 

Edit:  The image showing the large overlap wasn’t posted until after my reply. That ring is WAY more oversized than the one I worked on. I doubt filing that much material would be a great idea. Yes. I’d get the correct ring, as you suggest. 

A decent save...

But your "race mechanics" advice won't water as to any reason why it should work....

The lateral ring pressure of several pounds of force doesn't stand even the slightest chance of holding combustion pressure... So going up one size for any reason would likely be to compensate for a very worn bore ...

Combustion pressure is ONLY contained with the design on the ring and ring lands to facilitate combustion pressure to push the ring both to the bottom of the ring land AND outward against the bore...

The 6 or so pounds of lateral static ring tension can't hold the thousand pounds plus force of combustion in any way without using the combustion pressure to force the seal... So let's say that using one size larger ring cut to fit would go so far (it wouldn't) as to double ring static wall pressure .. from 6 to 12 pounds...

Still not a drop in the bucket to the combustion pressure added to the seal.... It would be the percentage of going from 1506psi to 1512psi lateral force... 

Something else entirely is going on if that "trick" turned a slug into a dominant race engine...  

In recent years the push has been to develop lower static tension rings to lessen parasitic drag when the rings aren't holding combustion pressure...  Also the reason for the CRF's going to a single compression ring design... The higher the rpm , the bigger the loss to the parasitic friction of another ring ...

The whole goal is to have as little lateral force/ friction as possible unless the ring is actively sealing combustion pressure ...

So filing down an oversize ring to leap to race winning / protest inducing power would have to have a sort of voodoo associated with it... Like compensating for some other defect...

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1 minute ago, mixxer said:

A decent save...

But your "race mechanics" advice won't water as to any reason why it should work....

The lateral ring pressure of several pounds of force doesn't stand even the slightest chance of holding combustion pressure... So going up one size for any reason would likely be to compensate for a very worn bore ...

Combustion pressure is ONLY contained with the design on the ring and ring lands to facilitate combustion pressure to push the ring both to the bottom of the ring land AND outward against the bore...

The 6 or so pounds of lateral static ring tension can't hold the thousand pounds plus force of combustion in any way without using the combustion pressure to force the seal... So let's say that using one size larger ring cut to fit would go so far (it wouldn't) as to double ring static wall pressure .. from 6 to 12 pounds...

Still not a drop in the bucket to the combustion pressure added to the seal.... It would be the percentage of going from 1506psi to 1512psi lateral force... 

Something else entirely is going on if that "trick" turned a slug into a dominant race engine...  

In recent years the push has been to develop lower static tension rings to lessen parasitic drag when the rings aren't holding combustion pressure...  Also the reason for the CRF's going to a single compression ring design... The higher the rpm , the bigger the loss to the parasitic friction of another ring ...

The whole goal is to have as little lateral force/ friction as possible unless the ring is actively sealing combustion pressure ...

So filing down an oversize ring to leap to race winning / protest inducing power would have to have a sort of voodoo associated with it... Like compensating for some other defect...

It was a new engine, and the ring gap was larger than spec. So. I just assumed the advice I was given resulted in actually attaining proper compression. I didn’t have a compression tester at the time, but I can only guess closing the ring gap corrected a low compression situation, making it actually run as it should. My first time out with it put me on the pole for the first time ever. I didn’t alter anything else, so my experience lead me to believe it’s a viable option. I’ve never filed a ring since that experience. 

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That's still a big stretch... But I'm not interested in continuing this with you at the moment ....

Something is seriously wrong with a new engine that requires an oversize ring to achieve proper end gap... And the seal of ring to bore is more important for holding compression than an end gap...

Given that you are eager to add 2 stroke information... Of a wrongly manufactured 2 stroke in the first place... And didn't know that 4 strokes don't have locating pins (illustrating an enormous lack of engine experience/ knowledge base) ..it's pretty evident you are operating above your level with "information" you feel like handing out...

Now would be a great time to stop this current uncoordinated verbal dance with me..... I'm not really someone you want as a dedicated fact checker to your tech posts...

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1 minute ago, mixxer said:

That's still a big stretch... But I'm not interested in continuing this with you at the moment ....

Something is seriously wrong with a new engine that requires an oversize ring to achieve proper end gap... And the seal of ring to bore is more important for holding compression than an end gap...

Given that you are eager to add 2 stroke information... Of a wrongly manufactured 2 stroke in the first place... And didn't know that 4 strokes don't have locating pins (illustrating an enormous lack of engine experience/ knowledge base) ..it's pretty evident you are operating above your level with "information" you feel like handing out...

Now would be a great time to stop this current uncoordinated verbal dance with me..... I'm not really someone you want as a dedicated fact checker to your tech posts...

No dance. Just explaining a personal experience. YMMV. 

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2 hours ago, mixxer said:

combustion pressure to push the ring both to the bottom of the ring land AND outward against the bore...

  And that, boys and girls, is why you'll sometimes see little holes drilled from the top outer edge of a piston down into the ring grooves (to facilitate and/or enhance this effect).

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1 hour ago, Doogee57 said:

  And that, boys and girls, is why you'll sometimes see little holes drilled from the top outer edge of a piston down into the ring grooves (to facilitate and/or enhance this effect).

Gas ports?(pressure) 

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1 hour ago, adnohguy said:

Gas ports?(pressure) 

  That is indeed what they are called.

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10 hours ago, Mlessard85 said:

Does not appear to be proper crosshatch angle. Almost looks like horizontal lines and deep? Maybe just bad pic?

Ok if you two are done bickering like and old married couple, does anybody else notice the issue i brought up? 
45degrees? I think not

Chew rings

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That's not proper honing...

That looks like deep grooves from a bore job gone bad.... They look like that when there isn't enough meat left to do a proper hone to finish size...

I'd say use whatever you want for rings in there... It won't matter...😁🤘

Edited by mixxer

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4 minutes ago, mixxer said:

That's not proper honing...

That looks like deep grooves from a bore job gone bad.... They look like that when there isn't enough meat left to do a proper hone to finish size...

I'd say use whatever you want for rings in there... It won't matter...😁🤘

Blows my mind how much information yall can pull out of your rear ends based off a single cellphone picture thats badly lit and hardly in focus 😆. So tell me how .5mm oversized rings are too big for an "overbored cylinder with not enough meat"? 

@Mlessard85 Not sure who honed it since this is the first time I've taken this motor apart since owning the bike. But Guy before me said it had a new piston and rings when I bought it 2 years ago but it started to smoke a little so I figured I would throw some rings in it since I had to tear the engine down to replace the cam chain and gears anyways. I'm not too worried about my 2 year old hone not being exactly 45° cross hatch. Honestly I'll probably just throw the old rings back in and keep her topped off with oil till my compression is too low to start the bike again🤣

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