BBK Crankshaft killer?

[flu]

Just trying to see how many people put a 50mm or 52mm kit on and had the crank fail on them. I keep reading that it WILL ruin a stock crank but I haven't read anyone posting that it has.

[buford1488]

talk to millsc...he will tell ya the diff between stock head and my heads-scrappydogs.......

[carasdad]

Originally Posted by flu

Just trying to see how many people put a 50mm or 52mm kit on and had the crank fail on them. I keep reading that it WILL ruin a stock crank but I haven't read anyone posting that it has.

We have 2 with them..one is over 5,000...the other over 6,000. What eats them up..is improper install. Folks will slap one on and end up with a compression of 240psi and have seen even higher Starter cannot crank it...and I could BARELY kick it over. Needles to say on both..the cranks did not last...nor did the pistons. The detonation..heat caused by it and super high compression made the flat top pistons bowl shaped excessively. When built ours we added an extra base gasket and head gasket. This kept the pressure about 180 psi...and not a single issue in their 5,000-6,000 miles.Bottom line...a little common sense and mechanical knowledge go a long way.

[inuyasha]

Originally Posted by carasdad

We have 2 with them..one is over 5,000...the other over 6,000. What eats them up..is improper install. Folks will slap one on and end up with a compression of 240psi and have seen even higher Starter cannot crank it...and I could BARELY kick it over. Needles to say on both..the cranks did not last...nor did the pistons. The detonation..heat caused by it and super high compression made the flat top pistons bowl shaped excessively. When built ours we added an extra base gasket and head gasket. This kept the pressure about 180 psi...and not a single issue in their 5,000-6,000 miles.Bottom line...a little common sense and mechanical knowledge go a long way.

Hi Glenn
Couldn't have said it better
I try to keep my BBKs compression to under 200 the last 2 where in the 190 195 range
Take care and ride safely dear friend
Yours Hank

[carasdad]

Originally Posted by inuyasha

Hi Glenn
Couldn't have said it better
I try to keep my BBKs compression to under 200 the last 2 where in the 190 195 range
Take care and ride safely dear friend
Yours Hank

hank...some folks forget that scoot upgrading is NOT Windows 95...where everything became 'Plug 'n Play' way back then. With scooters it is 'Fit...check..test...then recheck' to be sure...and by all means know what you are getting into and what the proper specs are. Kinda like my time with Second Force Recon and 8th Combat Engineers...the job should be easy...ya find a bomb ALWAYS cut the red wire cause that is how it is done on tv..and saves them all with 1 second left on the digital timer.. To hell with that..we just blew them in place. Anyway back to scooters. Performance upgrade parts installation is a skill..an art..a science..mechanical aptitude..but above all!! You must know the specs and boundaries...

[flu]

Thanks all for the responses! I had done a 47mm kit on my t3 before the crate motor it all went together and ran well with the jetting for the 50cc set up. It ended up blowing up literally after I ordered an #38 idle jet. The problem was I received a #50 but was too excited to notice until I had it in and all was not well. Spitting unburnt fuel out the exhaust and it back fired a few times. I didn't run it long like that but the damage had already been done. Since there was a giant hole in the bottom of my crankcase I decided to just get a crate 72cc from scrappy! I've been very pleased with that displacement for my t3 ,but I feel that my ruckus clone will need more umph! but of course don't want to tear up the bottom end.