gt5 new jug and piston

[HeadSmess]

felipe. check your ruler. 48's and 66's both have 38mm strokes. all mine have anyways... though back in the early days i DID measure 40mm, even on the 48's... i checked my ruler!

ok. anyways.

the 66 cylinder will not fit a 48. the "spigot" at the base is bigger.

a 48 cylinder will not fit a 66. the stud spacing is different, and 48's use m6, 66 uses m8 threads.


but. as you said, the wristpin/gudgeon is out on the piston by 175 thou... so that is the problem. the piston. NOTHING ELSE BUT THE PISTON. so, either machine the piston, machine up a "shim" plate, or return the piston and get a replacement and hope that yours was just a QC evader... tech line could easily measure and tell you if so...

 

[IbedaYank]

headmess
pistons are within .05 in height
cylinders are within .25
will post pics of gasbikes solution and all parts

 

[IbedaYank]

quote from gasbike email........

Sent: Wednesday, August 24, 2011 5:47 PM
Subject: gasbike

Hey fred this is josh from gasbike, send that piston back and i will send you the correct piston the one with the lower hole, and it is the piston for the super rat/gt5a motors write your order number on the box and note that you want to exchange for super rat piston

 

[HeadSmess]

^^^^theres the answer there^^^^^

.175 of a inch on wristpin location

^^^^and there^^^

 

[IbedaYank]

problem is the original piston the wristpin is higher in the piston making it have less stroke than with the replacement piston
I have the regular GT5 not the superrat or GT5A

would make it a WHOLE lot easier if grubee gave all the parts a specific part number
to order replacement parts

measured from top of piston
motor is at work because i order all my stuff from online/ebay through work
i will try and get pics of both pistons next to each other today

 

[HeadSmess]

cool

its something to keep in mind, that theres two styles of engine out... "deck height" of the piston is different... a useful thread

which one has the longer conrod? or is it just that the cylinder sits higher/lower on the crankcase?

longer conrods equal more power

reminds me of this thumpstar i had. went to soup it up and found that it had a conrod 10mm longer than any similar engine. therefore the cylinder and studs where 10mm longer... guess what i snapped? then the following tapping out to m8 studs and dealing with oil galleries ...grrrr.

stroke stays exactly the same. thats equal to the crank circle. unless thats been changed?


these things must be found out and stickied somewhere!

 

[IbedaYank]

headmess

as far as i can tell there are 2 cranks for a grubee motor one uses a 202 bearing the other a 203

the anglehead motors have a higher compression due to the combustion chamber being smaller
i do have the anglehead GT5
as far as i can tell by using a dialcaliper there is no differance in the cylinders
Boss already sent the piston back this morning so no pics...

guess the smart thing would be if ordering a piston would be to measure it before ordering

 

[HeadSmess]

two cranks and two crankcases

6202 15 35 11

6203 17 40 12

so once again... is it the stroke, conrod, and/or cylinder to crank height thats different? and what other changes are there? hmmmmms.

 

[IbedaYank]

without a few to tear down and mic not sure how we can answer that...lol
As far as ordering replacement pistons. measure old one and contact before ordering to make sure you get the right one

 

[IbedaYank]

two cranks and two crankcases

6202 15 35 11

6203 17 40 12

so once again... is it the stroke, conrod, and/or cylinder to crank height thats different? and what other changes are there? hmmmmms.

cylinder is the same... heads and pistons are differnt