What could cause this?

A little back story first, I have a 12 nytro mtx 153 that I bought brand new in march 2012 and since purchasing have been slowly modding it, mostly handling upgrades and only mechanical upgrades are mpi 180 turbo, ulmer clutch kit, and pc5 pti from oft racing. At about 600ish miles I came across a good deal on ebay for the turbo and pulled the trigger on it. Once I received it I debated having my dealer install it or doing it myself, I consider myself fairly mechanical savvy but didn't want to hurt the motor any so I asked my dealer how many turbo kits they've installed and they said they had did one like seven years prior on a rx1 so I decided to do it myself, figuring I can read instructions just as well as them and not pay the labor to do it. With the help of here the install was very straight forward and actually easier then anticipated. Machine ran great other then clutching from ulmer took some tweaking.

Now for my dilemma, towards then end of the first season with the turbo I noticed a strange idle condition developing where it would idle rough and low rpm's at first start up of the day and once warm ran normally. Figured it must have been a vacuum leak/ spark plugs. Over the summer started diagnosing problem and hit a dead end/ put it on the back burner. Come beginning of this winter I decided I wanted to up the boost and contacted Oft Racing for their spooled up kit, after several communications with rick decided to go for it, and turned out things were slow for him and he actually offered to install the headshim/spooled up kit. So I loaded it up and took it to him for install. Once he finished he had informed me when he was removing the head and installing arp head studs that he had to drill a few of the stock head bolts to get them out, which would indicate it had overheated before, but everything visually looked fine as far as head/pistons/cylinders. Had me puzzled considering the temp light had never came on and im diligent about using scratchers. Since it was only November at this point and still no snow decided to take machine to a dealer to diagnose the idle issue. Not same dealer I purchase from this one has lots of experience with turbo nytros, and upon checking all vacuum connections/ electrical with no avail they did a leak down test and two of the three cylinders had over 25% leak by, and they said it could be valves or rings which broke my heart considering at this point the sled on had just over 1000miles!!!!

Upon my approval they tore the engine apart to locate the issue. They had the head and the block sent to a machine shop to have checked out, which led to all new valve seals and all valves reseated. The block was within spec and all cylinders were round and not ovaled no scoring or gouges. At this point the dealer installed new piston rings and reassembled. Upon firing up the machine still idled like poop, they did another leak down test and center cylinder was still around 25% ish leak by and I believe it was mag side was around 20% ish leak by. Needless to say at this point every one involved was baffled and the next course of action was to order a new block and pistons$$$$$$$$$$$ I had asked them at this point if Yamaha could do anything for me be it good will some parts or discounted parts price, but..... of course was denied. So now the bill is up to $5k in parts/labor to repair a motor that only had 1000 miles on it.

Once turboed the machine was only set at 6psi boost and always ran premium with half a bottle of torco accelerator mixed in. Installed gauges same time as turbo and was always spot on afr and boost.

My question would be what could have caused this/ how to prevent it in the future.

Sorry for such a long post but trying to be thorough.

As far as compression #'s was never given those from the dealer just the leak down rates.

When first researching the odd idle all indications were leading to a vacuum line popped off/cracked around the throttle bodies or a bad idle air control solenoid which would cause an irregular idle. After inspections from me and dealer all hoses were connected correctly and no tears/cracks, also IAC solenoid checked out and was functioning properly

O2 readings when I still had the sled before all this were always 12.5:1 or less when rideing and 14:1 or less at idle. Except when the strange idle condition started happening at first cold start of a day the o2's would be rich around 10:1 but just off idle they would go right to 11.0-12.5 and stay that way the rest of the ride. fast forward to this season when I would first cold start the sled the 02 would be extremely lean around 17:1 and rpms would be low around 900-1000 rpm and sounded like it was running on only 2 cylinders, but as soon as I would bring the rpm's up to around 1800-2200 the o2's would go back 12.5-13.5 and the machine sounded/ran normally and from there the higher the rpm the better the o2's would get 11-12.5.

Never tried unhooking the pc5 but the map in the pc5 does nothing until 3000 rpms so idle and just off idle would still be controlled by the stock ecu. Didn't run the doebeck box but just for a couple rides after installing turbo before switching to the PC5 PTI.

Fuel pump and injectors were still stock at that time, but never checked the fuel pressure, and I know the sock had never been changed/altered.

When dealer suggested a new block and pistons I scoured ebay looking for a used engine but all that could be found were from 08's for around 2500ish and hope I wouldn't be getting a 6-7yr old can of worms.

thamax said:

Fuel boxes can cause strange problems go back to all oem system and tell us if it still does the same problem!

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Right now the sled is still at the dealer, been there since around Nov 18 to present and they should be reassembling the motor with the new block,pistons,rings and reworked head this week. Hopefully with no other surprises it should be good to go.

With my original post might have been a little to drawn out, the answer I was hoping for was what could have caused the block to be shot after only 1000miles 400 boosted. The dealer said there was no signs of detonation internally and this bad motor was a first for them and is a conundrum considering the low boost levels and always running the torco, they said this motor should have never done this. At this time its pretty much being chalked up as a fluke failure.

I was hoping to try and get a root cause as to not have history repeat itself.

Dealer said it should be around 3-5% no more then 7% leak by

RACINSTATION said:

A couple points to ponder.

Were the cylinders honed and was ring end gap checked?

A.) Not sure if they honed the old block, and they said they double checked ring end gap and clocking.

If that all checked out, how many miles and/or hours are on the new rebuild? Your rings will not take a seat until you have some run time on a new rebuild and you could have some leak at the rings until they seat.

A.) When they did the second leakdown it was on the redone head and new rings with zero miles on them.

Next questions. A leak down test is great, but where is the leak taking place? Rings, valves, or gaskets? The dealer should know this and this is a very important part of any leakdown test. It the leak is at the valves, then as Jullio stated you may have some carbon build up, incorrectly adjusted valves, or a bent valve. First thing to find out here is where is it leaking?

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A.) Dealer said it was leaking by rings into case.

fc8464 said:

What I dont understand is in your first post you said they sent the block out to have it checked and that the cyliders where in spec. Then they put new pistons and rings in (Assuming then they did rehone the cylinders to break in the rings) , how do they still have excesive leakage past the ring? Fred

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When they got it back from the machine shop they put in the old pistons with new rings and it still leaked by and had them baffled which lead to ordering new block and new pistons.

They had offered to do just new pistons or new block and pistons but being the machine is out of warranty I didn't want to have to pay all the extra labor if new pistons didn't solve the issue.

Update. Called the dealer today and they got everything back together and running, but not running smooth, which is looking like one of the new injectors that came with my Oft Racing spooled up kit ( with zero ride time on them) is bad. They put stock injectors in, unhooked pc5, and removed my yamaha rollover tether and it runs like a swiss watch. Then they put the larger injectors back in along with pc5 and it ran rough again and was the center cylinder. While I was on the phone with them the mechanic was swapping the injectors around to see if the problem followed the injector, or if it is the pc5. They also highly recommend that I swap out the yamaha roll over valve for a better unit, they said they've seen nothing but problems with the yamaha valve. That's where it stands now hopefully done soon.