piston 1.7mm in cylinder

[damann33]

if I buy a akunar piston, the piston will be about 1.7mm down in the cylinder, and about 4.3mm of the dome will stick out from top. Will it be alright runing the engine with the piston that low in the cylinder? or would it throw timing off and a whole bunch of other ****?

 

[motoXXX]

mmm not to sure mate wait for cactus jack or mack or some1 that know's what they are talking about to come they will tell you

 

[damann33]

yup, well see what happens

 

[Mack]

The pistons position in the bore does not affect cam timing. It will effect squish and compression. It is not ideal setup to be running the piston so far from the deck but will not hurt anything and will run fine providing you still have reasonable compression, which I suspect you will with the dome. You have to measure the ratio and see where your at. The akunar pistons have all different size domes.
The 140 is not an easy build for the inexperienced as there are no pistons specifically for this engine. Your best bet is to order a complete kit from Akunar. They will supply you with an alloy cylinder and piston with various base plates to help set the ratio you want. You might as well go 57mm if you do this.

 

[damann33]

i just wanna run somethin rather then the stock piston I took off, but dont want to spend that much in terms of buying a new cylinder. The dome on akunar piston is 8.5mm minus about 1.3 (after using glue instead of paper base gasket) which means the dome will stick out about 7mm. The head gasket is 1mm thick, and the head dome height is 13mm. There is also valve pockets on each side of the piston for a lil more clearence. The piston probably will give me the higher compression, its just clearence that I am worried about, especially if I were to run the 28/24 valves. I know with the stock flat top piston, clearence wont be an issue using the 28/24 valves, but when the dome sticks out a bit, there is a risk. They have another piston with a 6mm dome height which will stick out 4.3mm, its not a coned dome, but a rounded one. I was thinking about which one to get, if to get them, and if I get them and the valves hit, I was thinkin about juss using a dremel on the spot the valves touch the piston.

 

[Mack]

The only people can answer your questions are Akunar themselves...they should know what piston of theirs does what? I don't think you'll find many who have replaced the stock piston with same size for a 140 on this forum.

I have experience with bigger than stock pistons, but all the domes are different for different sizes and ratios change with size and dome and deck height, so way too many variables to guess if it all is gonna work from a few specs off the Akunar site. You will find the pistons themselves can have great variations. I have had a few from Akunar where the valve reliefs were a mile off centre and had to be totally recut. Like I said before the 140 is not straightforward but Akunar does do a complete kit they make sure will work for you. You'll only be paying a little extra surely for the cylinder? You then get alloy cylinder, better squish and compression, 57mmm if you want, a piston checked for suitability by Akunar...

 

[damann33]

yea I see what my options are, I can see exactly what your saying. I think that if I get a 28/24 valve head, ported/polished and keep the stock piston and cylinder, that would be the best for now, as a bolt on BBK kit is supposed to come out for the 140cc soon, or is this basically a complete kit from Akunar? I have been making contact with him in terms of the piston etc... but I will ask him about the cylinder, 57mm piston and neccessary gaskets. I guess the cylinder I get will have to be matched to the stroke of the stock cylinder, but the piston they send me may still contact the valves.

 

[Mack]

the kits I think you will find are Akunars...alot of the online stores have been stocking Akunars kits for a while now. Notice Akunar getting bigger and having a much better range of stuff for China engines in the last 12 months? The 28/24 valve heads getting round are mostly theirs also.
The only cylinders available are your stock one (then the deck height is too great) or the alloy 78mm (then the deck is too short) and you need spacers. Akunar will send a 2mm and 1mm spacer for you to set the rough height you want with an alloy cylinder and a piston to suit.

If you want the easy and cheapest option with the stock piston...then get a .5mm copper gasket from DRATV or run no gasket at all.

 

[damann33]

is the 2mm and 1mm spacer for the base gasket in order to raise the cylinder up? I have emailed him and I will find out how much he wants for the cylinder, gaskets and 57mm piston. Then I will have to hope that the valves wont hit the piston. If the price is too high for the kit, ill go with a thin copper head gasket.

BTW is this set up what le garage did in the how to section?