Topic: Broken cranks

[Old Goat]

So far this year, in 5 races, I've broken two cranks and my son broke one. All Briggs 31 ci.OHV single cylinder cranks. All three of them broke in identically the same spot. Take a look....

this is the first one, from my mod-x


One of these is from my pro-x and the other is from Mikes mod-x

[tjbryner]

Is this some thing like a small hint to ARC to get those billet cranks out? 

[Old Goat]

I hope so! They told me they would be ready last year, but I haven't seen any yet.  I'm tired of trying to keep these motors running. Too much work, time and money! It's a shame, because they do seem to run pretty good, when they're not broke! I might have to switch brands or else try another class

[The Tank]

Dang what kinda RPM's ya turning em OG?

[Old Goat]

3650????

[The Tank]

  come on now how hard

[WilliamEnglish]

Were those new cranks?...or out of some other engine...too much crankpin clearance will get you too....and ohv modified singles are probably the worst for vibration anyway.

[jerb]

so will too much timing....

[Mike's Dyno Tuning]

Dang..Broken at less than 4000rpm, Man those cranks are week! Is the rotating weight light? Has the cranks been balanced?

[matt175]

Mike, 3650 was a joke (thats stock RPM)

[Tazz914]

it would be bad if it was true

[Mike's Dyno Tuning]

I'm a little slow after a long work day!! lol you got me. I no nothing about the singles.

[matt175]

you can make a twin run though. I had to get ya on that one, you left the door wide open.  

[Mike's Dyno Tuning]

thanks bro, they are alot of fun. It's a hobby kinda thing for me. Something differnt. I've been building race motors (car) seems like most of my life. The mower motors give me something to stretch my brain. Never thought I would lay down at night and think of building a new mower motor..lol

[Gadgit]

lol thaught i was the only one that did that