|
|
Post by scooterted on May 9, 2018 10:41:03 GMT -5
So ive been thinking about installing 47mm bbk. I was thinking about the piston rings. Most kits people buy probably have cheap rings. Will higher quality (like nataku) rings fit the piston properly?
I cant tell. There are no specs i can find.
Or would it be beneficial to use an entire quality piston that may be lighter? i cant fknd specs for this eithe.
Edit: i know the rings need to be 47mm. But im wondering about them fitting properly with the piston.
|
|
|
|
Post by GrumpyUnk on May 10, 2018 14:10:46 GMT -5
I suspect that the ring dimensions along with the piston land and groove dimenstions, are set in the GY6 or 139QMB specification. In order to manufacture, and use the 'label', you must comply with the specification.
Do they? dunno.
Order some along with a micrometer and feeler gauge set, and measure. Thickness, depth, diameter, and then the ring lands and grooves. Weigh the pistons (see site measures in technical forum area) and see if they compare.
I got a piston from one place, cylinder from another, and rings from a third supplier. We shall see if it all works together but I am relatively confident they will. I won't bet the farm.
tom
|
|
|
|
Post by scooterted on May 10, 2018 14:22:44 GMT -5
Thats kinda how i figured. I made my purchase. When i get them ill take the measurements and ill post them up here to add to the collevtive forum knowledge.
I found one post online about the same thing but they didnt post numbers.
|
|
|
|
Post by scooterted on May 17, 2018 15:03:25 GMT -5
So i recieved my 47mm goofit bbk. And my 47mm naraku piston (p/n nk100.63). Both pistons very similar.
The only differences are
1. Obvious machining differences.
2. Weight. Piston only the goofit is lighter at 57.1g with the naraku being at 61.4g. Piston, rings, wristpin and clips the goofit is lighter at 85g with the naraku at 87.2g. The naraku rings, wristpin and clips are actually lighter than the goofit.
3. The compression ring grooves on the goofit piston are machined slightly larger than the naraku. The naraku is .039" while the goofit is just a hair larger but .040 wont go.
4. The goofit compression rings are narrower than the naraku rings. Goofit rings were .038" and .036" thick while the naraku are both .038".
5. Iner diameter (radial dimension?) of the goofit compression rings are roughly thr same as naraku but with looser tolerances.
Naraku rings should fit on a goofit piston no problems. Im going to use the naraku piston because the tolerances are a little tighter.
|
|
|
|
Post by scooterted on May 24, 2018 15:18:23 GMT -5
Just as an fyi to compare. I weighed the stock piston. It was 36.7g as a naked piston. With the wrist pin, rings and clips it was 59.5g.
That is all.
|
|
|
|
Post by GrumpyUnk on May 25, 2018 10:53:40 GMT -5
sooo. the mass goes from about 60g to about 90g. A 50% increase. The force on the crankshaft rod journal is higher... Wonder what the 50mm and 52mm kits come in at. Either way, when using a BBK, pay attention to higher rpms as being 'killer' for the whole assembly. I'd suggest staying closer to the factory recommended rpm limit in the high-8k range. Running a 50/52mm BBK at 10k seems to be asking for it to punch a hole in the block...
tom
|
|
|
|
Post by scooterted on May 25, 2018 11:17:49 GMT -5
Yup. I dont intend to run mine past 8k much(unless i find a bunch of speed there). Ive settled on a spot that im currently happy at (ill do proper tuning later). I acellerate around 7.5k and can accellerate to my top speed of about 8k under my own power after that.
Im not convinced its real wise to be running 45mph on a tiny scoot anyway.
|
|
