grubee gt5 cylinder differant port map than others ???

hi everyone, i have a grubee gt5 that needs rebuilding and i have read that the grubee gt5 66cc jug has a differant port map than the standard pk80 or dax balanced motor.

my question is can i run a pk80 jug on a grubee gt5 ?

i know the pistons are differant as in the location of the wrist pin hole is lower on the grubee gt5 motor or is it higher lol i forget..... any way are all the jugs the same and the grubee just uses a differant stroke crank arm and thinner base gasket and higher wristpin hole than others to achive the same port timing or are the jugs differant as well ?

for instance i know the grub33 gt5 has a differant piston and stroke than my dax does

dax has a 110mm con rod and is 85mm hole to hole i think
and the grubee is 100mm and 83mm hole to hole ?? i am unshure here.

can i use a pk 80 jug on a grubee with some modifacation if i have to ?

for instance with a thicker base gasket and a differant piston ?

my dax has a 1.6mm base gasket and the grubee gt5 was far less like .5mm so right off the bat the dax has 1mm taller ports and the piston is differant also so w.t.f. ???

where can i get a grubee jug lol ? the only place i know of is arrow and they are all modded, i plan to save money and do the moddin and porting myself so spending 70$ on a grubee jug is out of the question ! all i can seem to find is pk80 type jugs for sale where can i get a stock grubee gt5 jug ?

or can i just use a pk80 jug and mod to get the correct port timing by raising or lowering the jug via gasket thickness and raising and lowering the piston via wrist pin location ?

the ports need to be fully open at BDC and the piston needs to come to the top of the jug for correct squish clearance at TDC, can i achive this with a pk 80 jug on my grubee gt5 motor using gaskets and piston swapping? or do i need a grubee gt5 jug ?

flybytaco said:

the gt5 piston is the b style the pk is the a style the wrist pin is higher up the skirt on the b piston.. you can get a gt5 jug at bikeberry or gasbike whoever sells grubees. ive always had good luck with a Skyhawk lower ends matched to a pk top end

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so running a pk 80 top jug on my grubee gt5 will esentialy raise all the ports ? given i use the grubee gt5 con rod and piston ? what size base gasket an even 1mm or should i use the 1.6 ?

if its true this setup would get better tranfer port timing and an nicely raised exhaust port that can be ported out a bit lower if desired, but i would have to lower the intake a lot with a good amount of port work to make it happy right ?

seems like a preformance mod for a grubee gt5, would be to add and mod a pk80 jug ?

so a gt5 lower and gt5 piston with a pk80 jug would need a lot of port work to correct the port timing

but a gt5 lower with a pk80 piston and pk jug would have ideal timing but the piston deck hight would bee to low due to the rod length and the jug would need to be decked ?

fly by taco.... can you elaborate some more on the combos of parts you have used with the gt5 lowers ? i have a spare gt5 motor with a scored up jug and piston and i am looking to do a long term full out high rpm racer build using the gt5 bottom end, think home brew arrow street racer.....

hey taco your right ! i do have the 38mm stroke full circle crank and the zaf 60 rod and with the pk 80 piston it does not work the piston comes out of the pk 80 jug but if i run the type b high wrist pin piston on the 60 rod and 38mm stroke crank it port maps perfectly to the pk 80/ f 80 40mm stroke top end but the jug needs to be decked down a bit to get the right deck hight as the f80 jug is a bit taller than the grubee gt5 jug

so with the zaf 60 rod and type b piston you can run a standard jug as long as u plan on decking it down a bit

The setup i am running now is the grubee gt5 38mm stroke with a juv from a dax, the jug ports are fuly open with a stock base gasket on the exhaust and transfers

Yeh the grubee jug i have seen all had angled transfers where as the dax and pk 80 style had a levle top

i do like the grubee motors and despite all the hoo ha about the dax and the gen v i have run all 3 i can say i stil like the grubee gt as a base motor for a fully moded engine

But damn its a pain in the ass trying to find a high wrist pin piston lol

I have ordered 2 high wrist pin grubee pistons now and bolth times got sent the low qrist pin lol

one had no maekings and one had a #2and an arrow however bolth pistons were exactly the same despite the markings

now if i can just get the right piston i can finnish my stuffed high comp midrange stump puller!