dimple on top of piston? i dont think it was always ther...

[down4thakrown]

dimple on top of piston? i dont think it was always ther..(pic is posted).

i just rebuilt my picco .26. and i dont remember the top of the piston always having a dimple in the center of if. can any of you guys tell me if yours do. and when i turn it over it makes a chattering sound. but sound goes away when glow plug is out. do i need to add another shim? i reused the same 3 shims it came with. should i have bought new ones? or did i over tighten the head?

 

[beason]

could be the shims, or you could be missing the copper lock washer under the plug.

I've been told not to reuse them because the "crush" to seal. But i have reused them before with no issues.

 

[FrostByte25]

Sounds like your piston is hitting your glo plug...Check to make sure you have you're washer on your plug like beason stated...

FrostY

 

[HPI-Killer]

Okay, so the washer is important to that plug aparantly? How do you know if the plug you have is long enough for the engine your using or how to tell if you can ruyn plugs without the washer and be safe?

 

[Extreme RC Mods]

You should always use the washer for the glow plug, it helps make the seal. I have yet to see a standard glow plug come anywhere even close to a flat top piston on any nitro engine I have worked on ever. The dome makes it sit quite a distance away so contact could only be made if you were to screw a 1/2 long plug in lol. As long as you put all the stock head shims back in, there should be no issue. If you think the piston is hitting the head, you can take some silly putty and make a small very thin ring that you can put on the piston's outer edge, put the head back on and rotate. Then you can check the thickness on the out edge of the piston, it will be extremely thin on the edges but if it is hitting it will all be pushed away from the squish band. I hope that makes sense.

 

[down4thakrown]

i took the head off and took head button out and reinstalled them and tightend them a little at time. i think the first time i tightened the first bolt to tight and the head button wasn't sitin straight and the top of the piston was hitin the head. runs good now. ill post pics of it with my picco.26 and mgt pipe installed.

 

[down4thakrown]

heres my maxx with the mgt pipe and picco .26...(that I'm lookin for a new cooling head for) bout to upgrade to 17mm hex. just can't decide if i wana stick with 3.2 rims and tires or go with 3.8 rims and tires.