I still wonder how these genuine bore kits get failed. 10 years back when I had the engine work of 2 stroke bike, I was there to witness every bit of work and I found that ring and pistons bought with the escorts company (can be said only compatible) and the the cylinder was bored and after the work done, the bike was awesome and never gave me any trouble until my 2T oil pump which was newly bought was at fault and the engine ran dry without the 2T oil. Here you have kits very much specially built for certain bikes and they explode after few k kms. Sounds funny and smelly.

The pic of the bore, it is very shiny, Looks like it was almost glazed over already, But that can be from the light present and the angle.

Piston has very short skirt, this means it will have more of a rocking motion than one with a longer skirt, Can't tell from the pic but is the piston intact? I guess it will be since you didn't report any broken piston pieces. Some minor scuffing on the side of the piston (normal) but the crown is very carbonized.
going by this I'll have to say the engine was run under some very rich settings.

Will you be able to remove the 2nd compression ring, squeeze it into the bore and use the piston to push it down about 20mm, Then take feeler gauges and measure the end gaps?, Push it about 1/3rd down and to the bottom of the cylinder where the piston's stroke would have ended.
This will tell you if the cyl is conical/tapered or square by the size of the endgaps, also if the gaps are very tight there is the possibility that they had butted up against eachother when they expanded and possibly was the reason why the ring snapped.

Can you also remember what the break in the ring looked like? Was it a clean break or fatigued? It may be too late as it may be in the bin but investigating and finding the cause and effects can tell you a lot about the engine.

Find the below image of the spark plug and those tiny scratches on the circular edge occurred while removing the plug. The overall tune seems to have proved what was expected out of it. The bike ran precisely 42Kmpl in city with occasional revving upto 11K RPM while I touch the highway very briefly. (Roads used in Chennai everyday: 4PM from Avadi - Ambattur - Chennai Bypass - Porur - Guindy - Velachery and vice versa at 2AM. Chennai members can calculate the traffic intensity)



Find the map used, ignition values are posted in my previous post. Today I have raised the ignition timings a bit steeper with richer values by 0.4 on fuel map to ensure perfect acceleration at high RPMs The lower RPMs were left untouched.



The highlighted area seen on the map, I mean the accurate TPS vs RPM is where I cruise in city or the area in which the engine is operated most of the time. The below video should help you understanding how the values are decided and how I achieve more power as well as fuel efficiency. Moreover this video was taken while operating the bike at neutral position and the TPS vs RPM differs with the power extracted at each gear on real road conditions, in simple words the bike will operate at higher TPS value at 5K+ RPMS in real road conditions, that is due to the load placed on the engine. Hope you will be able to relate it.

Just one thing, this is not a genuine bore kit. Its a aftermarket kit supplied by RC.

The bore is slightly glazed at certain places but other places had the cross hatch pattern intact. Pic is not very accurate. Yes, the piston is intact.

I will get back on this.

From what I remember, it was a clean break with sharp edges.

Had to bump in here to clear a lot of unwanted discussions.

@abhijeet - To you.
First off, it was clearly mentioned to you that a larger bore is going to give u bump in mid and increase torque right across, considering you still had stock valves. Also at one point u shelved the cam and exhaust, coz you didnt like the peaky nature. So knowing you and your riding style personally, you are not someone who loves a rev happy engine. Revving the nutts of an engine is not your way, so its more of mid that you needed.
Now coming to your existing prob, u lost compression, wondered why your engine was hardly moving.. Removed and found the primary ring to be cut! The primary ring on the bigbore is made of cast steel, while the one on your original R15 piston is made of steel. Reason?
The stock bore uses a coated liner - which is a softer compound. A bigbore always uses a hard steel liner. So in a cylinder - piston relationship, one of the components (either the rings or the liner) has to make way for the other to seal the gases. One has to be soft and the other hard. So here, the rings are softer than the liner. Ever heard of the Enfield fury? Has hard chrome liner and cast rings? Was known for breaking with wrong tune. Hard liners and hard rings cause friction and excessive cylinder wear. Increases oil temp and also engine temp.
Now why did your first ring break?
YOu always reported that you had richness and at one point the ECU tune was fine and later you felt it wasnt. A rich mixture causes hotspots in the chamber. The heat is directly transfered to the piston top. Which is passed to the first compression ring, which has the least lubrication of all the rings below it and has the hottest burning point, thanks to added compression load too. This makes the ring brittle and has cracked. While, IF you were to consider this as a defective kit, the piston would have warped, rings scuffed and the liner scored to extinction by now. The liner's harness ensured it still survived the broken ring. Some people think that a rich mixture cools the engine, while in reality its not true. At times adds to detonation and other resulting destructive factors. While we have a few xbhp members and others who have crossed over 30k kms on the same bigbore. I clearly like to state here that it was NOT a component failure, if it was 7000kms was too much then. In any case, you would call me a few times asking for an ECU retune, so why didnt you call me when this happened? I wont think twice for a replacement with the newer kit, coz I atleast personally know you. We have discussed so much in lengths about so many things and I have skipped my lunch once explaining a few engine concepts. Because this would make you a win the hearts of many a few bashers here and help you enter the "hall of fail" legion. Abhijeet, wasnt this a lot simpler with a phone call which you would otherwise do, so well?

Coming to the ECU drama here. Both I and Race Dynamics Karthik, co-developed the R15 ECU maps and tune. The development started on our race bikes back in 2009 and it finally took the production shape in 2011. I have built the base maps, tested and developed various versions of the map for the R15. My maps for the various engine upgrades are my own developments based on test data and we still continue to. A tuning chart is like a sheet of paper. Your result is of what you plot there! You can now buy the same RR ECU which we released to the public a few months ago and can tune. Buy every person has his own level and pattern of tuning. I'm saddened over the fact that my maps are so wrongly interpreted. If the person who did has even one percent of common sense can clearly say that there is some nonsense. The map was plotted in the older version of the R-tune and now the smarter human has opened the same file in the newer R-tune format and displays some weird looking numbers to call me wrong and interpret wrongly. No engine on this planet can withstand any 3 digit ignition timing. Fail! This is a clear case of trying to insult someone's hardwork and reputation. Fail again. If you cant do it right, dont do it wrong!
A later apology wont do any good. The damage is beyond repair. All the reported information here have little truth and more assumptions. Offlate I have been having communications with a lot of members who are reporting that they are being influenced, persuaded and ill-talks have been happening about our offerings. I will compile such mails and chats and post screen shots to make clear why some-one be so hell bent to advocate their theories and put us down. Would TATA sell their cars, abusing Maruti?

This thread is just a clear bashing arena for all the lovers and haters. While the interest to reap the better, lies in the hands of the thread starter.
As much as this thread grows this way, we continue to develop and focus more on what we do. Helps us get stronger and work harder.
With the R15, we have seen ring land failure and run-in piston failure. I wonder if some can give me a theory as to why a few stock engines fail with barely 9:1 to 10:1 compression? We have seen plenty of stock R15s, RTRs and all indian engines fail. Why no threads? Did they come for free?
Intentions bring the better of the person inside you and the motive of this thread is clearly a sign of such intentions. If anyone here could understand the technical reasoning behind this and in this case its very much R15 specific as we have not had a single failure on any other engines. Now the result of anyone reading this thread is, spreading a viral that "bigbore is injurious to engines" message. Check with any member on this forum, who has any of our bigbores, besides the R15 if they have had an engine failure under normal useage? Open request!
The new R15 bigbore lineup ensures, all the haters enjoy it more. Do all that you can to break it! A lot goes under the knife and is tested on our race engines and then suitably adapted for street.

@PSR - Pls dont conclude anymore. The sleeve is NOT an insert. Those are cast with the block and finished at 59.97mm and polished off with a fine grit stone. YOu are free to verify any blocks that we give. None are inserts. From the R15, FZ, P200, P220 or RTR barrels, all are block casts. Nothing is a shoved liner and its cast with the block.

World-over on the internet forums, I now see there is a new trend of internet born tuners. I call them affectionately cyber - tuners!
This is the profile. First go to a reputed tuner, get abused with a bad tune/fate or report abuse and then win the hearts of most members. With all the bashing and calling everything out loud possible. Then come up with suggestive solutions. Then implement a few basic things and then say that they hit the jackpot with the tune. Claim that the reliability is now a million times better and the engine is a bombshell to even beat F1. Then suggest to the other members, that " We also can offer you similar services, if you are distressed" and start a business model. How far this can go, is also predicted. That I'll comment at a later stage. The trend is very much there on a few other Indian forums. I see most of the car forums taking the route. After 2 years you see the new tuner in the block was the "distressed kid" from the past and is now set to set new standards by selling an assortment of parts - parts peddling if I may call it. What - still, most or all dont get is that, swapping parts is not tuning. And tuning is not fitting. I'd love to see this trend grow, because this seperates the men from the boys!

Cheers

I am probably writing for the first time in this thread...

..All I can say is, any man who posts such a long explanation at 4:05AM in the morning is not faking. Not taking sides, it's just a feeling!

Good luck to everyone with future discussions here.

While criticizing about a new trend of internet born tuners we should not forget where we were born.... and the old Yamahat135.com that is where the punching a bigger hole gamble on R15 started, just by asking "Hey I picked an R15.....I know its same like vixion....can you help me with the after market parts..." If internet and vixion wasnt there, then there wouldn't be R15 with Rocket 165CC engines tuned at Bangalore. Very sincerely no offense to anyone, coz its his/her personal to post in any forum, but we should not forget the past and throw in words. We forget the same old concept that when you try to point a finger at someone four fingers point yourself.

Well, told a thousand times not to compare stock R15 parts and relaiblity with after market parts. No matter how much or how many shouts from the hill hole, nothing can match the stock reliability and quality coz its from a factory which does the job and does it well for over 50yrs. They know what they are doing and have enough machinery and techniques to tell them where they stand.. instead here we just add cheap hair color to natural hair and say its ton times better than the actual hair in all aspects and it seems even certifications will be given very soon. Anyone with his senses in place would always know about Yamaha before owning one, or at-least after owning one and would decide accordingly. (Sadly I am not)

In Straight words all these modds, be it mine or anyone's cannot stand a chance in front of a stock R15,

Anyways, Thanks to all for your comments......

A big thanks to everyone for the new concepts,and applications which had broadened my understanding .

Thanks for clarifying this which was running on my mind for a very long time Joel in-spite of my 220 not with me anymore, as couple of us have moved into 2'strokes, the concept of big bore is always a liner insert to us...with added Wiseco's

P.S. Any chance of you helping us with the same for RX - 135's??

Since you have replied on this thread, a very simple question to you. Please answer it.

An after market setup which was perfected by you on the race track still faced engine failure due to wrong ECU maps. Why did this happen? All components on my bike were RC parts only. There was no external factors at play here. Both of us being located in B'lore, even the weather/altitude and such factors can not be blamed in this case. So why?

In light of the fact that I changed the maps twice from you and the map was still not perfect, can I conclude that you were experimenting with the ECU maps on my bike? That you still did not have the correct maps ready when you sold me the kit?

To you, All parts were from RC, like what the full engine?
You had the bigbore and an airfilter only. And at a later stage, you started fiddling the maps and you got your prize!
I kept tuning the ECU as per your feedback. BAsed on what said worked well and what didnt. At one point you said the setup was spot on. You need to consider than open loop system IS subjective to climatic and barometric changes. This is not a closed loop system.
We ofcourse have the maps and the first map what I loaded to you was for the bigbore. Then you kept asking me to change it. Which is what I did.
You asked and I dished it out. I dont call this as map failure. This has nothing to do with the maps. This is more to do with your own feedback of how you wanted me to tune the ECU. At once you said you wanted leaner, then richer.
On a race track, the engine is tuned specifically for the given day and time of the race. Factors change over hours, let alone days, weeks and months.
At a later point, you decided to play the maps on your own with the tuning cable, so am I fault?
I have your maps here and can prove to you that it could not have caused it, unless you played along with the values. The first base map that I loaded runs fine on a lot of engines. How come abhimanyu, who is Mumbai runs a pig-rich map and still does not blow the rings? And why you?
COunter argument! Coz he does not fiddle with anything. Checks with me and then I send him maps accordingly.
Rohan cleared mentioned over the phone that you guys have been exchanging the cables and tuning the ECU on your own. So holding me responsible is a very safe thing to do, on a bashing thread like this. A few things that can cause engine failure are wrong ignition chart, wrong ignition dwell time, incorrect fuelling etc.

@joel

Im trying to reach you mate. Cant get through your phone or email.

Now we have come full circle. The blame finally goes to the guy who has once been a customer of RC. Wow! How convenient.

The customer says rich and you tune it rich, the customer says lean, you do it? Really? Is this why you have spent hours base-lining maps? So that any tom, dick and harry can ask you to put any values on it? Seriously Joel, who tunes the frigging bike? You or the customer!

A map is not like salt in a dish man that the customer can have as he wants depending on his taste!

And the first map? So rich that the engine chokes on the unburnt fuel after a km. I had been telling from the first day the maps are too rich. Don't tell me that's your baseline map!

Weather changed so much at a single location (Bangalore) that the engine blew? LOL! Nice one.

Prove this. FYI, I still have that ECU. Do you want to check what values are there on it? It has the same values that you have put on it. I once asked Rohan to read the ECU to see what values are there on it. It was not readable as you had locked the ECU. That all I fiddled with the ECU. Also, all this AFTER the engine blew. Other than this I have not even touched the engine for 7k kms.

Any please don't bring others in the picture. Why the maps you have works on XYZ's bike does not bother me in the least. It has failed on mine. Cause - poor metallurgy or incorrect design/map parameters. End of story. If you have something concrete, by all means post it. Else, don't bother with the mud slinging game.

In the end, I feel I am correct in my decision not to go for the replacement bore from you.

Guys seriously am no one to tell nor do i have any of the fantastic technical knowledge u guys have, but would like to suggest few things- See whatever happened or is happening - Its not helping to either of you guys to reach for the conclusion of the work undertaken, what i would suggest is that put the figures on table (i dont mean here) sort this out meeting each other and sort the problems more in a gentleman's way. blaming, replying, posting harsh comments wont help anyone at least here. Come on, we at least know whats the problem with the work undertaken or we might be able to understand the problems, but for these we must stop talking and start working isnt it? brothers.
Well my comments doesnt mean any offence to anyone here so aplogy in advance if my post is going somewhere else. Takecare

@ HarishK, You are contradicting yourself.

At one place you say that stock items are reliable and at the other stage you do the modds even after you have been bitten several times. From all this we understand that it's your bad luck and also few misinformation from your side (hidden truths) which has made you gone through all these situations and have bad mouth towards Joel. Few Fz-s are getting modded in a month and also few which have been recently. We will give you the real true report. Just wait..........