too much compression?

[quadrcr87]

i just rebuilt a 250X engine. and it is making a pinging sound. i got a .20 over 12:1 wiseco piston. web mid to top cam, heavy duty valve springs. do you think i need a higher octane i run 93 pump gas. i already checked the valves adjustment and it is correct

[deathman53]

yes, you do need race gas. in general anything over 10.5:1 you should use race gas, 12:1 defintetly. I use race gas in my 11:1 ported xr280, it ran horrible on 94

[quadrcr87]

anyone else?

[powerslider]

Yeah you need race fuel or this motors gonna have a very short life....

[250xR#271]

I agree w/ deathman you have to run race fuel w/ that high of comp.
I believe (someone correct me if I'm wrong) that the pinging or knock comes from the fuel detonating early because the high comp. creates more heat. So when you run high octane it detonates when it is supposed to.

[TRX300X]

I also agree run race gas or at least a 50/50 mix of premium and race gas. You might be able to get away with mixing it but it's hard to say. I've been able to run 93 octane on my X engines with 11:1 compression but things like altitude and cam's and a whole bunch of other things can allow you to run different octanes.

[quadrcr87]

does anyone know what the pinging sound is like. cause when my engine runs its like tick tick tick............ or something like that
i thought it was valves but they were adjusted

[Hals250x]

I just rebuilt a 250X with a Wiseco 12:1 compression piston. It seems to run great on 93 octane and a little octane booster. Haven't heard it detonate yet. Maybe your ticking could be valves need adjusting or an exhaust leak.

[quadrcr87]

if you read my post it said i thought it was the valves but i checked them they are at the right clearences. and its not exhaust i put my hand near it to check

[shamisc]

I don't care how many times I adjust my valves, they still tick! I'm not that familiar with your motor but valves ticking is a good sign. No ticking means they are too tight, (too tight leads to burnt valves)and then I'd be worried. Try the race gas, if it still ticks, I'd bet money on the valves.

[thelegendarycd]

i have the same kind of ticking on my 250x but mine is stock. i don't think i have to worry about the compression so its probably the valves. if those are ok then try the race gas. i've heard of 250x's running fine on the 12:1 pistons with just pump gas and i've heard bad things. i guess it varies.

[Steven]

an audible ticking at idle is normal. this is the valve tapping against the seat.

if you get pinging (sounds like a hamer striking metal) under engine load, that is detonation and is super bad! To cure it, go up on the octane.

[400exdad]

With the price of fuel going up, you may want to swap out the piston. Sounds like toooooo much compression.

[zoom400ex]

i duno about a 250x but i am pretty sure you have ot run rac fuel. I know that the 400ex can go up to 11:1 without using race fuel........

[300exazzkikr]

i would definitely go to race fuel, the pinging is cause by not high enough octane.