Blaster piston slap?
- Thread starter mattsteibler26
- Start date
Blaner
Your Friendly South African Ambassador
i believe it is correct to measure about 10mm from the top edge of the piston, not the skirt, but these motors do not have a hectic taper on the piston so skirt should be fine.
Yes, then measure the bore, ideally with a bore gauge/inside micrometer, the use of a vernier caliper here can be misleading if there is a wear lip in the bore above TDC, the caliper will read the unworn part and not the worn part.
then do the sums: (Bore diameter) - (Piston Diameter) = Clearance
clearance should be:
Cast pistons (stock/proX/Namura/Vertex etc) = 0.04 - 0.05mm (0.00157" - 0.00196")
Forged Pistons (Wiseco/Wossner) = 0.06 0.08mm (0.00236" - 0.00314")
I like to run at 0.07mm with a wiseco (0.00275")
if you look on top of a new piston, you will notice it says for example 66.45mm, this means that it is actually a 66.50mm but leaves the 0.05mm for you to work out that the bore must be 0.05mm bigger than 66.45mm for clearance sake.
Yes, then measure the bore, ideally with a bore gauge/inside micrometer, the use of a vernier caliper here can be misleading if there is a wear lip in the bore above TDC, the caliper will read the unworn part and not the worn part.
then do the sums: (Bore diameter) - (Piston Diameter) = Clearance
clearance should be:
Cast pistons (stock/proX/Namura/Vertex etc) = 0.04 - 0.05mm (0.00157" - 0.00196")
Forged Pistons (Wiseco/Wossner) = 0.06 0.08mm (0.00236" - 0.00314")
I like to run at 0.07mm with a wiseco (0.00275")
if you look on top of a new piston, you will notice it says for example 66.45mm, this means that it is actually a 66.50mm but leaves the 0.05mm for you to work out that the bore must be 0.05mm bigger than 66.45mm for clearance sake.
ok,so judging by this thread and what you guys are saying..it seems to me 'piston slap' does not sound like a 'ring' 'or 'ching'..(like loose washers vibrating on a bolt)..but more like a 'tac' or 'clack' ?..am i correct? ..hopefully because that means i can continue hunting down the source of that dinging.
i thought maybe it was the brake rotor or the kick start lever..or 'piston-slap',but its hard to pin-point while riding.
i thought maybe it was the brake rotor or the kick start lever..or 'piston-slap',but its hard to pin-point while riding.
^ it seems like i notice it more about half throttle when letting off.I tried coasting with clutch squeezed (engine running)to see if it was terrain related if i could still hear it,like something was loose..i could not confirm.thinkin maybe something beneath the clutch cover,right side,like its in the bottom end..or just being noid.
You don't say if if that is mm or inches. Too tight if 0.02mm, much too loose if 0.020 inches.
There is another way to measure the piston clearance through the ports.
Put a dial indicator on the piston through the intake or exhaust port.
Wiggle the piston, and see what the dial indicator reads. That is your clearance.
Dead simple if you have a dial indicator.
i've never heard of that method before... i'm not sure thats exactly a trustworthy method... piston to wall clearance is measured without the rings in the cylinder. also your moving the piston on the wrist pin. for that method to be even near accurate youd want to move the piston against the wrist pin.. to take away the "tipping" factor of rotatin the piston on the wrist pin.
hudack said:
2 days is even and over estimation.. a break in is literally a couple heat cycles.. getting the engine warm letting it cool a couple times and checking fastener tightness.. one more heat cycle then beat it liek it owes you money. broke in TONS of engines... never lost one... my current topend has been in 4 years. 3 of which are unfriendly use.. clutch drops, constant shifts in over rev, hig rpm launches drag racing in the dunes.. no issues.. broke in this exact way.. the things you see on the internet are usualy overkill..
piston slap is kind of a clacking sound.. liek the 2 videos posted in the same link but it;s kinda tough to hear on a video. blasters are a noisey engine anyway.. if the engine is noisier than normal theres an issue.. base gaksets are cheap and it would be worth your while to take a half hour and slide the jug off. to check piston to wall clearance you need soem calipers and a snap guage.. measureing the bore at the top of the jug is no where near accurate.. a snap guage however is.. slide it in pop it open.. lock it and measure it.. i do it a few times and base it thta way... the piston needs to be measured near the wrist pin boss because this will be the part of the piston less prone to deflection or wear.. pistons wear on the sides where the piston can tip.. so the intake and exhaust sides will wear first. especially exhaust side due to high combustion heat and exhaust gases.. inadaquete lubrication in comparison to the rest of the cylinder again due to heat. i'd say pull the jug get your correct measurements and until thta time don't ride it or start it.. also if you have the oil injector.. remove it and mix your fuel. a good quality premix oil mixed 32-40:1 works great for topend life and no fouling plugs.. personally i run amsoil dominator at 40:1 and topend life is fantastic. i'm interested to see what you find so definatley post back with your results..
heres a youtube vid on snap gauge useage.. also known as telescoping guage. but anyone that uses them calls them snap guages
and heres a set on ebay.. sometimes youi can find the cheap chinese ones. they work fine too.. in fact my cheap chinese set reads dead nuts the same as the much more expensive mac set we have here..
MACHINIST TELESCOPIC ENCO INTERNAL GUAGE SET 5/16" TO 6" | eBay
and heres a set on ebay.. sometimes youi can find the cheap chinese ones. they work fine too.. in fact my cheap chinese set reads dead nuts the same as the much more expensive mac set we have here..
MACHINIST TELESCOPIC ENCO INTERNAL GUAGE SET 5/16" TO 6" | eBay
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don't just buy one.. spring for the whole kit. you'd be surprised how useful they are.. and like i was saying the cheapos are still fine. thats not somthing i say often... i prefer good quality tools... but theres not alot of accuracy to a t handle with a couple springs and 2 telescoping pins.. the accuracy come in with the caliper your measuring them with.. that said even a harbor freight digital caliper is pretty damn accurate..
