IBA4rt Posted December 7 Report Share Posted December 7 Well, after detecting a piece of metal on the magnet of my 2020 txt 300 gp, I opened the motorcycle and the result is a broken primary shaft sprocket. The half-moon needle bearings were beginning to break and have produced some very slight marks on the inside of another pinion and the primary shaft itself. The truth is that it seems like garbage design and bad materials. My question is, will changing just the bearings be enough or since there are brands, should I replace the primary shaft and the two pinions? Quote Link to comment Share on other sites More sharing options...
lemur Posted December 7 Report Share Posted December 7 I would be replacing any part that has visible signs of brinelling and once I had a new part in hand I would stroke a file against that failed bearing surface to see if it was ever hardened. If a file bites into the steel bearing surface easy then the bearing surface was never adequately hardened and that would indicate a defect in the parts manufacture. Quote Link to comment Share on other sites More sharing options...
lineaway Posted December 7 Report Share Posted December 7 I guess you never read through the gas gas forum. Ever since the pro motor came out in 2002 it has been the most defective transmission in modern motorcycle history. So much so they changed the cases to where you could fix the tranny without splittinv the cases. Usually its the kickstart gear or the shift shaft breaks inside the drum. You are just unlucky. Good luck. Quote Link to comment Share on other sites More sharing options...
lemur Posted December 7 Report Share Posted December 7 1 hour ago, lineaway said: I guess you never read through the gas gas forum. Ever since the pro motor came out in 2002 it has been the most defective transmission in modern motorcycle history. So much so they changed the cases to where you could fix the tranny without splittinv the cases. Usually its the kickstart gear or the shift shaft breaks inside the drum. You are just unlucky. Good luck. Then he might better reassemble it with as few replacement parts as possible and dealer trade it for something more reliable 🤔 Quote Link to comment Share on other sites More sharing options...
lineaway Posted December 7 Report Share Posted December 7 My son actually broke 2 gears in my front yard. He endo'ed over the bars. When the bike hit the ground the rear sprocket hit a brick that he had been using as a kicker. The engine was sill turning, knocked the chain off and wrapped around the front sprocket. One we got the chain off, we realized the tranny was locked solid. The next day which was a Sunday morning, when I split the cases 2 broken gears fell out. Monday I overnigjted the parts and wednesday I got the bike back together after work. We left Thursday for a 2 day event and my wife bought him a new bike on Friday! That should have been our last Gasser. I now have 2 more for my grandsons! 1 Quote Link to comment Share on other sites More sharing options...
IBA4rt Posted December 7 Author Report Share Posted December 7 Yes I know the gas gas. I have a 2014 racing that I repaired last year and I only had to change the ****ty half moon bearings. everything else was perfect. In my 2020 GP which I bought new and I have changed the oil (Nils clutch trial) every three months since I bought it, I have found the unpleasant surprise of having a broken pinion, and the primary one damaged, with some notches made possibly by the grind an idler, since an idler has disappeared from that bearing. hence my question. These bikes are getting worse, the materials are horrible. I will fix it and sell it since I have a Honda 4rt 301 that I bought precisely to escape these problems. What I did not expect is to have to undertake this repair on a motorcycle that is 4 years old and well maintained from minute 1. Quote Link to comment Share on other sites More sharing options...
lineaway Posted December 8 Report Share Posted December 8 We had a member replace the whole transmission at 7 months. I want to say it was a 2012. Always something with the Pro motor. Great motor when it is running! Quote Link to comment Share on other sites More sharing options...
IBA4rt Posted December 8 Author Report Share Posted December 8 The engine is great, and the cycle part too, my intention was to leave both motorcycles, the 4rt and the 300 GP, but the boxes are terrible, they always break no matter what and it is rubbish to have to open the entire engine for a design ****ty. I'm already psyched up so I rebuild, and in the process I put in the piston and all the bearings and seals of the engine, the primary shaft and the two broken sprockets. Quote Link to comment Share on other sites More sharing options...
konrad Posted Sunday at 12:30 PM Report Share Posted Sunday at 12:30 PM 20 hours ago, lineaway said: So much so they changed the cases to where you could fix the tranny without splittinv the cases. What year did that occur? Quote Link to comment Share on other sites More sharing options...
lineaway Posted Monday at 01:30 AM Report Share Posted Monday at 01:30 AM That`s long ago now, Maybe 2013. Quote Link to comment Share on other sites More sharing options...
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