[Michael88R]

Neil,
This is just for discussion. I was reading an old issue of ATV Sport where they did the shootout between a 330R and the new LTR450. The LTR450 smoked the R in the shootout after they had removed the airbox lid and the muffler core. They quoted Allen Knowles saying that if Wiseco rings get really hot just once, you will lose 4 or 5 horsepower. Do you agree with that statement? Can you explain why that happens? And how hot is "really hot."

I might need a new piston and rings. I had a lean condition happening on my needle jetting one time and I got up to about 240 degrees F. I was only cruising the beach at the time, not running too hard.

 

[C-Leigh Racing]

I wouldnt say for sure, but that sounds just like Allen saying that. When in dought, a good compression gauge will not lie. Check the engine cold & then do it after its hot.

4 to 5 hp , thats a new one on me.
Neil

 

[Michael88R]

I think he meant that if it was overheated not just cold versus operating temp. I guess the only way to know is if you record the compression on a fresh top end and then monitor it as it wears and after any accidents happen, like getting it a bit overheated.

 

[deathman53]

I read that shoot-out, what a load of bs. They took a 250r setup for mx(short gearing and the rest) and compared it to a ltr450, that is very different. If they had setup the 250r for dunes, the shoot-out would have read the opposite. Also to take into account, the jetting on the r was probably way off, low-mid pipe. Not a fair comparism in anyway. They compard that 250r to the ktm525 (big bore and stroker) custom quad on a more level comparism and the ktm edged out, but not by much. I smell horse#### with everything about that shoot-out of the r vs ltr450.

 

[C-Leigh Racing]

After re reading this & thinking more about it & my years of working on 2 strokes, if an engine gets hot enough to cause the piston rings to not be able to perform their function, then theres more to worrie about than loosing 4 or 5 hp.
More than likely if that happens to a piston ring you could just about figure the whole engine would need rebuilding.
200 or even 250* shouldnt cause a ring to not perform.

One case in point.
A few years back when the 2 strokes still ran the national Pro class, my daughters boy friend was running a 310 that I built for him.
In one class main event race, he was holding 3rd place for 5 laps, then the center o ring on the Pro-x head gave up & started blowing out coolant, he ran for 5 more laps untill the engine just completely locked up & still holding 3rd place when it finely gave up.
If the rings had gave up once the engine started running hot, then for sure that engine would have started loosing power, but it didnt. Those rings were doing their job untill the engine just got so hot the piston & crank couldnt move anymore.

Whole problem in a nut shell.
He was just getting into the 4 stroke bike deal, early on when the 4 strokes were being pushed real hard by Honda & Yamaha, well the ol 250R, after all three heat races had been ran, it just sit there, nobody even bothered to check anything, like the coolant level, do anything to the tires or anything, everybody was so consentrated with the 4 stroke getting it right the ol 2 stroke was just kicked to the side.

I guess to some extent, it was a failure on my part because I should have took control & made somebody check it over, if not do it myself, because the end results it ended up making me look bad because the engine failed even though it wasnt my fault.

IF, if just one of us had looked, we would have found the coolant low & at least filled the system back up & then later found the o ring was the problem & corrected it before the next race.
Realy, it could have been the coolant was low after the reat races, not from the o ring failing but because he didnt run a catch tank & the system had just spit to much coolant out & then running it hard in the main the o ring just couldnt take it.
210 to 212 degrees coolant starts to boil & produce steam then you get steam pockets in the cylinder & head, so, how can a small o ring survive that.

I learned me a good lesson at that race that weekend.
Its just like the old saying, you can lead a horse to the water, but if he has not sence enough to drink, you have just wasted your time.
Some things you just cant do, one is trying to take a junk 250R & help somebody turn it into a Pro class bike & they dont have any money to start with.
If its going to run up front, better be ready to buy some new parts cause trying to use junk just aint gona cut it.
Neil