Blow Piston Ring?

LWalker

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Hey Everyone,

Happy Fall! I was bombing down a hill at WOT on a two week old 66cc/80cc bike engine when the engine suddenly died brining me to a complete stop. White smoke was coming out of the air intake. When I pulled in the the clutch to roll the bike back to my house, the sound of the piston moving inside the cylinder was VERY loud.

At first I assumed this was an overheating issue. Since the piston isn't directly exposed to the air, maybe it was hotter than the cylinder and expanded inside, making it difficult to move inside the cylinder. I theorized this would account for the loud metal-on-metal sound inside the cylinder, and could also account for the back flow of smoke out the air intake which likely created a fuel starvation condition.

After the bike had cooled for awhile, the metal on metal sound was gone and the bike started right back up. However, power was significantly decreased. Since it seems like a compression issue I tested for external air leaks with krylon spray and found none. Now I am worried I busted one of my piston rings. Does this seem likely? Is there something I should check first before disassembling my engine?

If it is a busted piston ring, can I just change the ring? Or do I have to replace the whole piston / cylinder set up

This is the engine kit I have been using except with an aftermarket shorty intake:

 
It seems VERY likely you damaged at the very least a piston ring if not more...Its 2 weeks old, hasnt been broken in yet using normal break in proceedures, (It varies but usual rule of thumb is approx. 300 miles at 20:1 gas/oil ratio and 32:1 thereafter), you were also not varying your speed as break-in requires, and here you were, going with WOT going for top speed "bombing down a hill", what were you thinking???

EDIT...The following is from F.A.Q from your link on that engine as to how long break-in proceedure should be, as well as the gas/oil ratio for that engine series. If your getting their "claimed" gas mileage of 150 MPG, your talking at least 225 miles...I use 300 miles as a rule of thumb, and thereafter go to 32:1 ratio.

DO NOT use synthetic oil for break-in as the rings will not "seat" properly, use conventional 2 cycle oil...Thereafter full synthetic should be fine.

Q: How long does it take to brake in the 80cc engine at 16 to1 oil ratio
Posted On: 2/27/2018 By: williamduty
A: Our BBR Tuning Racing Series Stage 1 66/80cc 2-Stroke Engine Kit requires a break in period of 3 gas tanks to be ran through the engine.

If that were me, I wouldnt even want to, let alone try, to do any rebuilding due to unseen damage that may also be there as well...save parts like exhaust, carb, CDI, chain and sprocket, etc. and order JUST a new engine, which will probably be cheaper to do in the long run, read the break-in instructions and follow them, and go from there...I wish you well...DAMIEN
 
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I was bombing down a hill at WOT on a two week old 66cc/80cc bike engine when the engine suddenly died brining me to a complete stop. White smoke was coming out of the air intake.


Yep, that'll blow an engine up for shore :oops:
 
It seems VERY likely you damaged at the very least a piston ring if not more...Its 2 weeks old, hasnt been broken in yet using normal break in proceedures, (It varies but usual rule of thumb is approx. 300 miles at 20:1 gas/oil ratio and 32:1 thereafter), you were also not varying your speed as break-in requires, and here you were, going with WOT going for top speed "bombing down a hill", what were you thinking???

EDIT...The following is from F.A.Q from your link on that engine as to how long break-in proceedure should be, as well as the gas/oil ratio for that engine series. If your getting their "claimed" gas mileage of 150 MPG, your talking at least 225 miles...I use 300 miles as a rule of thumb, and thereafter go to 32:1 ratio.

DO NOT use synthetic oil for break-in as the rings will not "seat" properly, use conventional 2 cycle oil...Thereafter full synthetic should be fine.

Q: How long does it take to brake in the 80cc engine at 16 to1 oil ratio
Posted On: 2/27/2018 By: williamduty
A: Our BBR Tuning Racing Series Stage 1 66/80cc 2-Stroke Engine Kit requires a break in period of 3 gas tanks to be ran through the engine.

If that were me, I wouldnt even want to, let alone try, to do any rebuilding due to unseen damage that may also be there as well...save parts like exhaust, carb, CDI, chain and sprocket, etc. and order JUST a new engine, which will probably be cheaper to do in the long run, read the break-in instructions and follow them, and go from there...I wish you well...DAMIEN
Wow there is a load of crap right there! Break in does not require 3 tanks or 300 miles nor does it require heavy oil mix or non synthetic to be used! Proper break in is heat cycles and load,you can do break in with the oil mix you intend to run right from the first start until it dies! 32-40:1 is the recommended ratio for these with 32:1 being best suited for more rpm/performance build's and 40:1 for lower rpm non performance builds. The load refereed to means no engine braking,no sustained rpm (fixed speed) rather getting it to pull you (load) to a point then pull in the clutch letting the engine idle briefly while the speed bleed's off and pull again and repeat for around 10 min which is 1 heat cycle in doing this the rings are forced to seat with the proper pressure behind them pushing them into the cylinder wall nice and evenly,this also prevent's the chance of glazing the cylinder wall and eliminates the chance of blow by! Three heat cycles minimum are needed and more can't hurt but generally are not necessary when done right. Running these engines down a hill pinned at wot will generally be their end as there is no rev limiter and the stock timing is WAY over advanced at high rpm which causes detonation and beat's the crap out of the rod bearings and piston top.
 
Street Ryderz says:
"Wow there is a load of crap right there! Break in does not require 3 tanks or 300 miles nor does it require heavy oil mix or non synthetic to be used!"

!st off...If you wish to be able to exercise the use of a warranty offered either by the manufacturer or the distributor/agent, you had better adhere to their break-in requirements...I worked for Valvoline Oil Corp. for 20 years before retirement...The labs were regularly sent parts and sometimes whole engines when wrong oil types, wrong viscosities, etc. were suspected in warranty issues and were granted or denied based on lab reports relieving the manufacturers time and time again of any responsibility.

2nd off...No one knows the item built better than the initial manufacturer of said product...If what you say is true, that would mean that we can all take anyones manufacturer instructions and just throw them straight out the window and disregard them entirely, because of course we are all engineering geniuses and thus can dispense with all of the manufacturers R & D efforts.

3rd off...
For what it is worth, I worked for Valvoline Oil and subsidiaries for 20 yrs before retirement...NEVER break in with synthetic oil...NEVER.... Always use any GOOD brand, conventional, motor oil for break-in period and then and only then, AFTER break-in, Use a GOOD quality, full synthetic oil thereafter...Valvoline synthetic, ELF synthetic, Amsoil synthetic, are all great choices...Im running 2 cycle engines myself and using Amsoil 2 cycle full synthetic since Valvoline doesnt make a FULL synthetic in 2 cycle version, (only semi-syn), and i havent found ELF at all where i now presently live...I personally never use any semi-synthetics at all or even Mobil One so-called full synthetic in anything, since it really isnt a full synthetic as claimed...it is derived from what is called a "cracked hydrogenated" process which in the rest of the world, only qualifies it to also be just another semi-synthetic.

Thats all i have to say on the subject,...DAMIEN
 
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"No one has done R&D in 60+ years."

So i guess there has been no improvements in porting, also no more inovations such as ceramic lined cylinders such as mine, or 40mm crank stroke, 40mm bore, and 40mm intake improvements from the old standard 36mm to 38mm.

R & D is still ongoing, elsewise, no one would be bothering with the newer engines being offered and even being used competitively with, yes the user community contributions, but based on manufacturer improvements and innovations that are still ongoing...If we were still using the same 60 year old argument, would we even consider using synthetics which the 60 yr old design was never intended for...try using synthetics in an original Model A Ford and see what happens...DAMIEN
 
Street Ryderz says:
"Wow there is a load of crap right there! Break in does not require 3 tanks or 300 miles nor does it require heavy oil mix or non synthetic to be used!"

!st off...If you wish to be able to exercise the use of a warranty offered either by the manufacturer or the distributor/agent, you had better adhere to their break-in requirements...I worked for Valvoline Oil Corp. for 20 years before retirement...The labs were regularly sent parts and sometimes whole engines when wrong oil types, wrong viscosities, etc. were suspected in warranty issues and were granted or denied based on lab reports relieving the manufacturers time and time again of any responsibility.

2nd off...No one knows the item built better than the initial manufacturer of said product...If what you say is true, that would mean that we can all take anyones manufacturer instructions and just throw them straight out the window and disregard them entirely, because of course we are all engineering geniuses and thus can dispense with all of the manufacturers R & D efforts.

Thats all i have to say on the subject,...DAMIEN
Dude I've been racing and building 2t's for over 40 years and been a sponsored team rider working with the engineer's whom would just laugh at you're reply! These are China crap engines with little to no warranty and the Chinese suggested break in procedure is unrealistic,I also am a certified mechanic authorized to service Sthil,Bosch,Polan,Toro and various other 2 stroke equipment and they too would say you're wrong,none of my race bikes had more than 3 or 4 heat cycles on them before being put on the track and run the hardest they could without issue so using this method for a regular street bike is a no brainier! I talk with engineer's and world championship engine builders every day and none of them would agree with you!
 
Your entitled to your opinions...but keep in mind, im not at odds with you over how you use these china girls on track...they are entirely disposable to you after a few races...im talking to those who are using these in regular everday situations and expect them to last a while and do not have the financial resources of race teams at their disposal...DAMIEN
 
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