UPDATED; want your cag engine quicker?

SKY_DANCER · #**121** (**permalink**) 26-08-2007, 05:33 PM

another simple mod for standard motor,( for those not wanting to spend much) , i fitted a NGK B6HS spark plug, this plug is @ 4mm longer than the std BM6A and gives a little noticable extra compression. doesnt foul o hit the top of piston. this is one of the first things i did on my 40cc stock cag motor.
::: would be better on motors with alloy starter :::

dylanpenhale · #**122** (**permalink**) 27-08-2007, 11:16 AM

I can't imagine that would have any effect on producing more power. The profile of the cylinder head is, or should be) specially designed so that the flame starts right at the top of the dome. I would be very interested if you could tell any difference from this mod. If anything I would imagine you would experience worse running due to hot spots/pinking, not to mention the coke build up on the threads falling into the engine every time you remove the plug.

SKY_DANCER · #**123** (**permalink**) 27-08-2007, 07:01 PM

cant really say if it did anything or not other than boost compression, (i haven't run the motor for almost a year). Bike is stripped completely now getting new paint and power plant

RD RACING · #**124** (**permalink**) 12-01-2008, 03:41 PM

sky-dancer is correct with saying the longer plug thread into the chamber has gained a slight bit more power. STOCK CYLINDER HEAD ONLY. dont try this with the 2 piece head kits or you will ruin your piston ect. with the angled sparkplug hole so to speak , the plug doesnt go directly straight down towards the piston crown instead it directs on the angle and does avoid piston contact, so when you think of this being some extra packing / filling that will reduce some internal volume in the combustion chamber, yes i will do so. as we say compression = power and compression comes from the cylinder head combustion chamber when the piston is at top dead center. just looking at the amount of guys that have viewed this thread that for some reason i started [ which i must say has been very valuable ] there have been over 20,000 views, beat that guys. ha ha.

dylanpenhale · #**125** (**permalink**) 14-01-2008, 08:48 AM

Hi RD

I will have to remain off the fence on that one I'm afraid. I know with other 2 strokes I have built and run they have been very particular about plug choice and I would never think about leaving the thread protruding that much into the combustion area. From what I remember about the combustion area design the size of the squish area and the dome are so critical to flame speed and direction that having the spark so far from the optimum distance is encouraging pre-ignition, an easy thing with coke build up. Also the heat rating the plug will be seriuosly affected as the threads direct interface to the head is considered when assigning the plug it's heat rating.

Getting A Head

I have heard that angling the gap toward the inlet ports by the use of plug washers/shims (which one in the case of the pocket bike multi-port inlet is anyone's guess) "could" be of some benefit but even that is subjective, I don't think there is any hard evidence to support it.

Dylan