trickedcarbine Posted September 3, 2012 Report Share Posted September 3, 2012 Ok, so I was doing a little lock up tuning on my new passion 4mm set up and I noticed a MAJOR situation when I had the cover off. I swapped some springs and hit the whole thing wih some brake clean and went to blast it with the air hose. As soon as I blew off the primary gears on the crank shaft, the nut and thrust washer just fell right off. I looked closer and realized that this thing didn't just come loose and unthread, but the primary gear had pulled it self outward about 3/16 of an inch which just shoved right through the threads on the nut! The threads on the end of the crank snout out are great, but the nut needs to be replaced! I pulled the plugs and turned the motor by hand to verify that the crank still felt kosher and it was nice and smooth. No crunchy feeling from the bearings. I also tried to see if I could get the shaft to wobble and it stays nice and true. I feel that I got lucky that the nut let go and that it allowed the bearings to survive. There was no damage from the nut, it just sat on the shaft till I pulled the cover. Is it time for some straight cuts and what are the differences in the sets offered from Fast, No Limit, White Knuckle, etc.? I know there are ratio differences, but what are the quality differences and why are 2 gears so damn much! Quote Link to comment Share on other sites More sharing options...
gotta_goatsfast Posted September 3, 2012 Report Share Posted September 3, 2012 I can't claim to know the threshold to which spur gears are required.... but I run them on my 421 serval to eliminate one more weak point. Picked mine up from FAST racing. In all honestly, the spur gears are probably all manufactured by the same company. As for gear ratios, the stock setup is stock (duh) and they also offer a 2.68:1 (?) ratio for guys needing to pull more gear. So, instead of running a huge front sprocket you can simply spin the clutch assembly faster and get away with normal sized sprockets. If you were running on pavement it would be a good idea (drag racing and such). Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted September 3, 2012 Author Report Share Posted September 3, 2012 The bike definitely has decent power........ This is a case hardened chromoly steel sprocket from moose with about 15 hole shots. Quote Link to comment Share on other sites More sharing options...
gotta_goatsfast Posted September 3, 2012 Report Share Posted September 3, 2012 Yeah, thats a lot of torque and stress on your drive parts. It would be in your best interest to pick up some spur gears.... and maybe try a different sprocket Quote Link to comment Share on other sites More sharing options...
yamaha driver Posted September 3, 2012 Report Share Posted September 3, 2012 i see the problem for your sprocket. its got some dirt/grease on the side of it. clean it up it will work great Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted September 3, 2012 Report Share Posted September 3, 2012 The bike definitely has decent power........ This is a case hardened chromoly steel sprocket from moose with about 15 hole shots. You probably didn't tighten the crank nut to spec and it got loose, then as it rode around on the shaft it ate up the threads, which allowed the PTO gear to move and it just kept snow-balling. Did you install the compression lock-washer the correct direction? what did you use to tighten the PTO gear nut? As for the sprocket with broken teeth, that's no indication of power, its indicitive of a sloppy chain or mis-aligned chain, or junk sprocket. Hell, I run the primary drive sprockets on my 10mil and don't have a single issue with broken teeth. Quote Link to comment Share on other sites More sharing options...
okbeast Posted September 3, 2012 Report Share Posted September 3, 2012 You probably didn't tighten the crank nut to spec and it got loose, then as it rode around on the shaft it ate up the threads, which allowed the PTO gear to move and it just kept snow-balling. Did you install the compression lock-washer the correct direction? what did you use to tighten the PTO gear nut? As for the sprocket with broken teeth, that's no indication of power, its indicitive of a sloppy chain or mis-aligned chain, or junk sprocket. Hell, I run the primary drive sprockets on my 10mil and don't have a single issue with broken teeth. All of this is correct. Your bike did not eat the nut because of massive amounts of power Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted September 3, 2012 Author Report Share Posted September 3, 2012 You probably didn't tighten the crank nut to spec and it got loose, then as it rode around on the shaft it ate up the threads, which allowed the PTO gear to move and it just kept snow-balling. Did you install the compression lock-washer the correct direction? what did you use to tighten the PTO gear nut? As for the sprocket with broken teeth, that's no indication of power, its indicitive of a sloppy chain or mis-aligned chain, or junk sprocket. Hell, I run the primary drive sprockets on my 10mil and don't have a single issue with broken teeth. The sprocket is really only that bad because I kept beating it till I felt the chain totally slip, the bike has a round house swinger so it is nice and straight. I put a sunstar on it and beat it all day yesterday and it is fine. So I don't think I'll ever be using moose sprockets again. It appears that it was over hardened and made way to brittleittle when you look at up close where the teeth were. As for the nut and convex washer I had it the same way as the manual shows and I torqued it per clymer's spec with a Matco torque wrench. I just don't wanna put another nut on and have the same thing happen. It wasn't just some trail riding. It was repeated launching so it was certainly hard on it. The motor is definitely as bad ass as the motor in my sig so I worry that I may do some damage by choosing to run the helical gears again Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted September 3, 2012 Author Report Share Posted September 3, 2012 All of this is correct. Your bike did not eat the nut because of massive amounts of power I wasn't trying to say my motor is a mammoth beast that just Eats parts, just trying to show that it is not some weak spawn, and that it is at the level where all the weak links are being exposed..... All weak links haha Quote Link to comment Share on other sites More sharing options...
okbeast Posted September 3, 2012 Report Share Posted September 3, 2012 I see multiple 100+ HP motors on helical gears with no issues. These are bikes that are all drag racing. Yes straight-cuts are the best option, but something else might be going on here. Maybe you got ahold of a bad nut. Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted September 3, 2012 Report Share Posted September 3, 2012 The bike definitely has decent power........ This is a case hardened chromoly steel sprocket from moose with about 15 hole shots. You better switch sprocket manufacturers. I've got tons of launches on my PBI sprockets on my 18DM and none of them have ever done that. Quote Link to comment Share on other sites More sharing options...
dave5.0 Posted September 3, 2012 Report Share Posted September 3, 2012 (edited) My torque spec on that nut is always whatever my impact will get it to. After I goo up the mating surfaces with whatever I sealed the cases with. Never had an issue with my passion tweaked 4 mill stock cylinder. Edited September 3, 2012 by dave5.0 Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted September 3, 2012 Author Report Share Posted September 3, 2012 My torque spec on that nut is always whatever my impact will get it to. After I goo up the mating surfaces with whatever I sealed the cases with. Never had an issue with my passion tweaked 4 mill stock cylinder. I used to do it that way but Jim stressed the importance of step torqueing in sequence and not getting carried away with the air tools Altough the sprocket always gets a good impact Quote Link to comment Share on other sites More sharing options...
dave5.0 Posted September 3, 2012 Report Share Posted September 3, 2012 I used to do it that way but Jim stressed the importance of step torqueing in sequence and not getting carried away with the air tools Altough the sprocket always gets a good impact That makes sense. On the head and cases anyway. There's a torque sequence on the crank nut? News to me. I use an impact on the crank nut, clutch basket nut, and the sprocket nut. You definately wanna use the proper torques and sequences on the aluminum stuff. But the nut on the end of a shaft just needs to not come off. They aren't torque to yield. If they were we'd be throwin all this shit away everytime we started over. If Jim says I'm wrong I'll eat my words. He's pretty sharp and I dont think he'll steer you wrong. Quote Link to comment Share on other sites More sharing options...
okbeast Posted September 3, 2012 Report Share Posted September 3, 2012 The max torque on the crank nut should be 80% (or whatever safety factor you like) of what the yield on the threads of the crank are. Chances are the nut will be the weaker between the two. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.