We have decided to dub it a TRX85Z at least till the boy is ready for a 105 BB. For starters it took me about a year of gathering info on exactly how I wanted to execute this and what parts I wanted to utilize to get the best performance on the budget I had.
I had three main goals first install the motor in the furthest back position. Second be able to utilize an off the shelf expansion chamber. And third use the least amount of sources for the parts. All of the parts on the chassis are TRX 90, 300, or 450. Anything related to the motor are YZ85
I toyed with the idea of at first running a kids on quad frontend but didn’t like how the upper arms are just essentially clamped in place so that threw out the KOQ and the other kit which is no longer available. I’ve had others ask me why I didn’t go with the bolt on 300 stuff on eBay and here are a couple reasons. One they are not the correct geometry so bump steer is an issue. Two this thing is fast and in putting the most important human on this earth on it I need to be able to trust that he is going to be ok, or at very least minimize risk.
So all of that being said I went with the most expensive part of this whole build. After talking to quite a few dads running these frames an order was placed with Tom over at ATV Fourplay. Once I received these parts I was very impressed with the build quality. As a Pipefitter welder by trade seeing quality welds in my every day experience I was very impressed with the weld quality, these A-arms are works of art. My only complaint was with the swing arm, now mind you I had ordered these unfinished and when you order from tom with powder coat you will receive completely assembled arms with bearings installed. My problem was after being welded the main pivot tube was warped from welding and getting the bearings installed and lined up required some work. A call into Tom and all was sorted out as this was to be expected.
First things first are I decided to just start with a bare frame I didn’t own a TRX90 so a frame from an 02 on eBay for 125 shipped to the house with a good up to date registration was just the ticket. I cut out a lower tube, all of the mounts for seat, plastics, and welded in gussets around all of the shock mounts as well as any triangles.