konrad

I've replaced the annotated schematic and ECU pinout in the first post with a document containing that information and much more. It's my first draft (I'm calling it version 0.8) of things I've learned about EFI OSSAs. It's information I've pieced together from notes to myself and emails to friends. But it's more than just what I've learned by reverse-engineering the system. In may places (perhaps too many, perhaps not enough?) I've tried to add justification and background to my thought process. I'm releasing it into the public domain without restriction. If you read it, I'd appreciate feedback – good, bad or indifferent. If you feel something needs additional explanation, please say so. If you think there are errors or omissions, I'm happy to discuss it (either publicly or privately). I want to make the document as useful as possible. I figure all of us who own these bikes need to support one another.

Canada280i, does ambient temperature have an effect on your bike? Mine seems more likely to start on 1 kick when it's cooler outside, 50 F (10 C).

My 250 almost always requires 2 kicks. If I stop and immediately restart, 1 kick will usually do. But if it's stopped long enough to walk a section, it will probably require 2 kicks to restart. One the other hand, if the bike has been sitting for months it may start on a single kick. My 280 is somewhat more recalcitrant. It probably takes an average of 2.5 kicks. I have some theories as to why this might be so, but I'm wondering if others have managed to make theirs a 1-kick starter. This really doesn't matter during practice or if ridden as a trail bike, but during a competition it saps my limited energy. Both bikes have Easy-Start kits. I'm a bit of a lightweight at 142 pounds (64.5 kg).

I am so grateful for the help I received with my gearbox I want to give something back to this forum. I'm a retired electrical engineer and a hobbyist machinist. I have done a fair amount of work reverse-engineering the TR280i's electrical system. Cheers. I have replaced the .PDF file with an entire website: https://www.ossa-efi.com/home It corrects some errors and omissions as well as providing greatly increased technical content.

Peter, that was hugely helpful! Thanks a million! I never would have "guessed" that solution. Here's a pic for the next poor ******* who has to tackle this problem. The grey screwdrivers eventually worked. The red and green were too small. It helps to have the gearbox held rigidly (I lightly clamped it in a vise) when first moving the circlip. I had to progressively move the circlip along the shaft as more and more wiggle room became available. Eventually, everything just fell apart. I tried the pallet knife shown between the circlip and the adjacent gear, but it was not helpful. I removed the circlip completely as I did not want it stretched while I wait for bearings to arrive.

I now see 3 circlip locations, but none look like they would allow any gears to then be removed. Much more information here: https://www.ossa-efi.com/home/engine/gearbox

This is great information, papapitufo! Thank you! I have a question and an observation. How do you remove the secondary shaft (where the drive sprocket attaches) to get to the point shown in the first photo? I see two inaccessible snap rings, and that's all. I believe there is an error in the second bearing part number. MT280232043 appears to be a Torrington bearing for the “clutch pump piston” (OSSA equivalent 173002RA). I think we actually want to also replace two MT280432039 (30x33x10) bearings while everything is apart. These are the bearings on which the clutch basket turns.