Which way does the slant head go?

rockonp04

rockonp04

New Member
I am putting a slant head on my ride so I need to know which way should the spark plug should be facing? Also should I upgrade my spark plug because of the added compression?
 
I believe the plug points towards the exhaust port.... not 100% sure. but it would make the most sense. Someone probably knows better.
 
Makes no noticeable difference in our engines. One of my bikes has plug facing exhaust and another facing intake. Both run the same.
 
It's suppossed to face forward (for more frame clearance.) But I don't think it will perform any differently if backward.
 
as long as the fins and straight so air can run through them its fine i think air hits the dome of the head more if the plug is facing back but i cant remember atm. makes no diff just my little pet peeve. lol
 
any way you want it to face depends on how your feeling the day you install it feeling a little backward go backward feel like charging forward go forward ir your a side winder well run it sideways and it will run a little sideways but fine
 
It should face toward the exhaust for the best performance. But a spark is a spark and bang is a bang. I've noticed that better engineered slant head designs like Puch, Honda/Lifan have the spark face the exhaust. The Czechs have been making these since early 1900's, 1904 I think for 2 strokes on bikes. I think they have probably tried everything by now, they use slant heads facing the exhaust there must be a reason from experience and engineering.
 
If it faces the intake port would the combustion force be more inclined to stay in the cylinder a tad more rather than directed at the zorst port??
 
furament said:
dont put the plug in the rear it so dosent go there thats just wrong :):-||
Click to expand...
The part of the motor that always wears out first is the exhaust port. Unless the motor was uber tuned from the factory to pull 15000 rpms. Uh what I am getting at . The slant head has no squish band that was even properly made in the first place . Anything past 7500 rpms is going to make the cheezy designed roller bearing cage fall apart to begin with.

The very porting and breathing of these motors will not let them breath to rev like the big boy's. So in light of a timing perspective you get notta.

In light of the kernel from the spark starting so to speak in the rear I prolly saved my motor to begin with from wearing out prematurely. Having the slant head even side ways seams to have no effect on performance with our archaic motors. Do what makes you happy sir..
 
The reason for having a slant plug is for frame clearance.
I have a theory that it will also cool better if the plug faces forward because there are no cooling fins near the plug. If it's towards the rear there's less airflow moving across it & it can get too hot around the plug. Therefore, having the plug face forward will have better airflow across the part of the head that really needs it most.
 
I think as Goatherder said these little motors are pretty archaic and primitive in design, the test would be to use a thermal temp sensor (no touch type) to see if the head temp all acrross the head top is the same. Basicallly I think that the whole thing is 1 piece of metal thats only 4" across, I bet it is all one tempurature maybe 1 degree of differnce. It ain't really no big deal. Run what you brung... Since the head fits the studs forward or back do whatever gets you off. I'll stick with it facing the exhaust since clearance is not an issue for me and the german and Jap engineers that design slant heads generally have it facing the exhaust port. I really don't think it makes that much difference..wee. Some Honda/lLifan 4 cycles have it come in one side.
 
Last edited:
I have yet to warp a head or to see a warped head out of six motors. Not saying it could not exist. I suspect it may be a bit of a pita casting these heads. In such a case a flat piece of glass and sandpaper fixes that. Also I have yet to see the intake ports wear out ''any where'' near what the exhaust port does on these things. For those folks that don't know what torque feels like in their hands I strongly advise getting a torque wrench.

I kinda like the head fins in the front to gathers much air as possible on them like a heat sync in a computer. Being the heat is so much at the exhaust port on these pigs. A guy has to take into account that cold air is coming in from the back side on these pigs. The back half of the motor will be cooler by this wreckoning. Nobody takes into account how much wind this pigs draw inside them. Just thinking through the key board here. lol.
 
Last edited:
IMO The head faces forward...And anymore builds will be forward from now on.
The same piston is now lightly covered evenly with carbon as b4 it only had carbon on the zorst side of the piston. The 3 prongs on the spark plug have no carbon on them now (same plug, same fuel, same mix) whereas b4 1-2 of the prongs would prodominately do the work and the other 1 would have carbon covering it.
Just sayin..
 
Hmm I dont have any pics of how it was anymore but i can get one of how it is.
About 800km's. I can give a pic of the plug tonight if ya want but thats not really the whole story so I'll post the both up when I get home from work.
 
You must log in or register to reply here.
Back
Top