Topic: Buttons or gudgeon pins {circlips}

[Retro Rocket]

Hi Guys, i was just reading a comment from another member about the reliability of Teflon buttons compared to gudgeon pins, the comment was that there are problems with the buttons and it suggested that they were not reliable. Whats the general consensus on Teflon buttons. I ask because i have 2 modern piston kits and both came with buttons, I'm trying to work out which would be better to use on my engines...  I would really like to hear from Mike Reick and Big Jay from APE...

[cbr954]

I have a set of RC 70mm pistons with alloy buttons, not Teflon.  I would like to hear some info about this also.

[Sam Green Racing]

See reply #159 in this thread, these are my piston with Teflon coatings. http://forums.sohc4.net/index.php?topic=106607.150#lastPost
If Teflon buttons and coatings did not work, why would people still be offering them for sale.
Saying that, back in the 60s, Honda had a 50cc twin cylinder race bike that reved to 24,000rpm with wire circlips.
What's the problem ?

Sam.

[johno]

 Like a lot of other forum members I have used both and they both work well,
My take on them is I used the teflon pads if the engine was a race engine and had to be rebuilt regularly I preferred the pads cos they are easy peasy to remove & install.
Otherwise I was happy with wire locks. 

At one stage I went through a phase chasing zero leadown and went to wire locks on the race motors only because I had spent a lot of time and money chasing a good bore finish , torque plate honed and all that kind of stuff and I was paranoid about something rubbing on my nice fine hone bore.  Just for interest it didnt make any difference though, hence the term "phase"
Cheers Johno

[HOSA]

I have been using teflon buttons for years,never any problems with racing engines. By the time the teflon buttons melt the pistons are already cooked.I now use nylatron on fuel engines, with gapless rings. For street use and the large variance in temps I suppose the circlips when seated properly would be best.

Just my opinion!

[Retro Rocket]

The reason i asked was because i googled teflon buttons {after reading another post} and there were a lot of people going against the teflon because they were saying it trapped particles in the teflon that wore grooves in the bore, this was in a street application. I found this in all 3 threads i read online...

[POPS 911]

Would not the rings up and down action at 7- 10,000 rpm's be MICRO honing the bore to a 65 R finish ? After the rubbing of the teflon plug ?  I wonder what NASCAR MOTORS use to run for 4 hours at high speeds.

POPS BK911

[MRieck]

The buttons always leave marks on the cylinders...something is going on there. I prefer not having objects rub against the wall. C clips work well (as long as they are installed properly).....I don't see a reason not to use them on the street

[Retro Rocket]

The buttons always leave marks on the cylinders...something is going on there. I prefer not having objects rub against the wall. C clips work well (as long as they are installed properly).....I don't see a reason not to use them on the street

Thanks Mike...

[Big Jay]

The "teflon" buttons will leave a mark in the wall that two strokes with the glaze breaker removes, so it is not making any kind of groove.

Years ago we did the aluminum buttons. Worked very well on both race and street engined.  Best part was the stepped part was a press fit into the pin, essentially making it an aluminum ended wrist pin. Just put pin in and drop the cylinder down over.  Never had to worry about a button falling in the motor.

Also the "teflon" required a full skirt piston as the end of the pin hole was what located the button.

Aluminum pressed in buttons could run in a radically scalloped piston with no problem.

When setting up a piston with any kind of button, be sure that the pin and both buttons come in .020" under the bore size. They are supposed to float and not put pressure on the cylinder.

[Retro Rocket]

Thanks Jay, that makes sense as well....

[Greg H]

In formula one they use circlips , nuff said 

[Greg H]

Formula one piston 

[cbr954]

Off topic but saw the F1 piston.  Here is piston out of my Honda CRF450R motocross bike.  Wonder where the technology is coming from  

[bwaller]

Ring holders.  Down side...don't expect 100,000 miles. 

[Retro Rocket]

Ring holders.  Down side...don't expect 100,000 miles. 

Can you add some more detail to that please Brent....

[MRieck]

Ring holders.  Down side...don't expect 100,000 miles. 

Can you add some more detail to that please Brent....

I believe Brent means don't expect longevity out of the those parts Mick. He is correct too. I have done some CR heads and the Ti intake valves hammer themselves into the seat ( even with the soft spring) which eats up lash clearance. Next thing you know the thinnest shim is to thick and it is time for a rebuild.
 That piston is nice. Very light with a nice design. Unfortunately the lack of skirt makes it more unstable which allows rocking which wears the rings (all 2 of them) and skirt.
 I think the big problem is guys ride those things like 2 strokes which means they pin the throttle over jumps etc which has the engine constantly banging off the rev limiter.
 All that said the 4 strokes are more reliable than the old 2 strokes IMO. They make great power, rev up real nice and are fun to ride. There is always a price to be paid for that kind of performance.

[Bill/BentON Racing]

4 of those 250 pistons for a badazz build. Rt,not long life? Bet it would rev tho! Bill
What size is the pin?

[cbr954]

I just had my head rebuilt this spring and threw a piston in at the same time.  I didn't know you worked on them I would have contacted you! I grew up riding the two stroke CR's and now ride the four stroke CRF.  I know what you are saying about them riding them like a two stroke but for the life of me I dont know why, they have so much torque you dont have to ring them out.  Mine has been dead reliable for about 60 running  hrs till the valves wore out.  From what I read and heard the problem has a lot to do with the Ti valves being incompatible with the seat material, the other manufacturers dont have AS much of a problem as the Hondas do, but I cant say for sure all I ride is HONDA

Bill mine is a 450, piston is 96mm, pin size is 19mm

[/quote] I believe Brent means don't expect longevity out of the those parts Mick. He is correct too. I have done some CR heads and the Ti intake valves hammer themselves into the seat ( even with the soft spring) which eats up lash clearance. Next thing you know the thinnest shim is to thick and it is time for a rebuild.
 That piston is nice. Very light with a nice design. Unfortunately the lack of skirt makes it more unstable which allows rocking which wears the rings (all 2 of them) and skirt.
 I think the big problem is guys ride those things like 2 strokes which means they pin the throttle over jumps etc which has the engine constantly banging off the rev limiter.
 All that said the 4 strokes are more reliable than the old 2 strokes IMO. They make great power, rev up real nice and are fun to ride. There is always a price to be paid for that kind of performance.
[/quote]

[754]

 I think the main reason the Teflon buttons came about is to speed up top end changes at the track..like Jay said push them out with your fingers.

[MRieck]

I just had my head rebuilt this spring and threw a piston in at the same time.  I didn't know you worked on them I would have contacted you! I grew up riding the two stroke CR's and now ride the four stroke CRF.  I know what you are saying about them riding them like a two stroke but for the life of me I dont know why, they have so much torque you dont have to ring them out.  Mine has been dead reliable for about 60 running  hrs till the valves wore out.  From what I read and heard the problem has a lot to do with the Ti valves being incompatible with the seat material, the other manufacturers dont have AS much of a problem as the Hondas do, but I cant say for sure all I ride is HONDA

Bill mine is a 450, piston is 96mm, pin size is 19mm

60 to 80 hours sounds right to me. There is a lot of debate about the Ti valve and seats. There are also folks that change out to stainless valves BUT there is a reason Honda used Ti. I have also seen people use a stainless valve with the OEM intake spring which is just plain dumb.
 Suzuki has used Ti intakes for years now on street bikes and there haven't been problems. And they don't run bronze or copper beryllium seats. Dirt bikes just get the crap beat out of them in general.
 Luckily the Honda Ti valves are not that expensive @ 50.00 or so(cheaper than many Kibblewhite stainless valves).

[Retro Rocket]

Ring holders.  Down side...don't expect 100,000 miles. 

Can you add some more detail to that please Brent....

I believe Brent means don't expect longevity out of the those parts Mick. He is correct too. I have done some CR heads and the Ti intake valves hammer themselves into the seat ( even with the soft spring) which eats up lash clearance. Next thing you know the thinnest shim is to thick and it is time for a rebuild.
 That piston is nice. Very light with a nice design. Unfortunately the lack of skirt makes it more unstable which allows rocking which wears the rings (all 2 of them) and skirt.
 I think the big problem is guys ride those things like 2 strokes which means they pin the throttle over jumps etc which has the engine constantly banging off the rev limiter.
 All that said the 4 strokes are more reliable than the old 2 strokes IMO. They make great power, rev up real nice and are fun to ride. There is always a price to be paid for that kind of performance.

Thanks Mike...

[Jim F]

guess I am old school but Give me my KTM500 smoker any day

[Big Jay]

We have the fix for those CRF Honda heads. http://www.bigborethumpers.com/crfheadkits.html

[BLUE71TURBO]

Thanks Jay, that makes sense as well....

   Yep.  I'm gonna use buttons on my kz turbo engine.