knocking?

[roadkill]

when i rev my blaster up as soon as it hits the power band it kinda taps a few times in what sounds like the pipe? it only does it then and no where else could it be the reeds fluttering ive heard of them doing that i dont think i need higher octane gas because it does that even when the engine isnt really that hot though i make sure to warm it up good before i ride and the crank bearing are perfect. any help would be great thanks

 

[blasterboy91]

could be anything from detination to piston slap...only way to tell for sure is to take your head off and find out yourself...

 

[Brute71]

considering its when the power kicks in, i'd have to say detonation. Give some higher octane gas a shot and see how it runs.

 

[roadkill]

ok thanks ill try the gas first then if it doesnt work ill pull the top end off. will i need to get new gaskets if i take the top end off?
thanks

 

[xjma]

Try running 91 if you don't already. That should help.

If you take the top end off, yes, you'll want a new gasket kit at the very least. Re-using top end gaskets is like just asking for a blown motor!!

If you're going to pull the top end, I would get a micrometer to measure the piston and the cylinder. If it looks in good shape and is within spec, have the cylinder honed (5-10 bucks at a shop) and put new rings in. Wash the cylinder thoroughly after the hone. You'll have to break in the new rings just like a fresh top end....which it will basically be minus the new piston. Also, check the rod bearings too while it's apart. If everything checks out fine, I would do the rings at a minimum. It should noticeably increase the power at least a tad.

If the piston and cylinder don't check out alright, bore it out to the next size and put in a fresh piston.

 

[phragle]

if it kind of sounds like someone is knocking on the inside of the pipe with a hammer..thats detonation. if you advanced your timing, put it back to stock, run 93 octane. if your head gasket etc. is not leaking, no need to change it.

Above all else dont keep riding it like that. It's really hard on the big end bearing and crank. more than likely octane will cure it so run premium 93

 

[roadkill]

right now im running 93 octane with the timing advanced so i will put the timing back and if that doesnt help ill let you know thanks

 

[roadkill]

ok so i put the timing back to normal and the knocking is now at lower rpms instead of when it hits the powerband and its a definate knocking that sounds like its in the pipe if i need to run higher octane gas would octane booster work because i dont know where i can get higher octane gas

 

[gsugarek]

Mine was doing the same thing when i first bought it. I rode it for a couple of days like that and all of a sudden it lost compression. I took the top end off to find a washer wedged between the piston and cyclinder wall. The knocking I heard was the washer bouncing around under the piston. I was lucky it didnt tear up anything else. I would recommend taking the top end off and checking the crank under the piston. Good Luck.

 

[roadkill]

how much is a top end gasket kit if i take the top end off

 

[blasterdude14]

octane booster will barely increase the octane, and gasket prices probably vary depending on what company you buy from just look it up on ebay

 

[gsugarek]

I paid like $15 for a cometic gasket kit. Look on bikebandit.com when you find a good gasket kit on bikebandit see if ebay has it for less. bikebandit is my first goto website to order parts for bikes. and if your real careful you can re-use the gaskets if they dont tear when taking off the top end, of course its recomended to use new gaskets.

 

[phragle]

I paid like $15 for a cometic gasket kit. Look on bikebandit.com when you find a good gasket kit on bikebandit see if ebay has it for less. bikebandit is my first goto website to order parts for bikes. and if your real careful you can re-use the gaskets if they dont tear when taking off the top end, of course its recomended to use new gaskets.

New Gasket set............................$15
New topend*bore/piston/rings.........$200

Causing $200 damage
from an airleak to save
$15.............................................Priceless

 

[roadkill]

so where can i get higher octane gas around where i am or can i run it if it is detonation could i try a cooler plug and will i blow up my top end if i run like that

 

[roadkill]

anyone? i really want to ride it but i dont want to damage it

 

[Brute71]

before you go tearing in to anything, what is the color of your plug? If it is on the whitsh grey side of things, you are running lean which could cause the detonation from increased combustion chamber temps.

Take a drive around town to the gas stations and see if anyone sells race gas at the pumps.

 

[roadkill]

i dont think any of them do. my plug is cardboard brown with a 280 main last time i checked but ill look in the morning

 

[1997blaster]

i dont think any of them do. my plug is cardboard brown with a 280 main last time i checked but ill look in the morning

then you probably have an air leak make sure the rubber boots around the carb are tight and the reeds and make sure the head is tightend to specs or thers a thread on how to make a leak down tester

 

[roadkill]

ok i took off the head and i found out i have .015 between the cyilinder and piston but the cylinder looks perfect no scratches nothing. so its gonna cost me 60 for the bore and 85 for the wiseco piston kit on ebay brand new how much farther can i bore it out if it has a 67.5mm piston with .015 between it and the cylinder just looking for an idea

 

[roadkill]

and i also found a major air leak cuz i forgot to tighten the cap on the carb but the plug was black so im way rich even with the airleak