We had an 09 OTK chassis a while ago and apart from occasional attention you might expect for any brake system it was fine. BUT the following OTK's we have had 2011 & 2012's have all been high maintenance to keep the system either working at all or working well. This could indicate issues with manufacturing tolerance as noted earlier. When we replaced caliper pistons we have noticed a few with marks to the side indicating twist of the piston in the caliper body causing contact and marking possibly under side load during braking.
My advice is to check all your brake line connections first. Then replace all replicable items apart from maybe the master cylinder pistons. Replace master cylinder seals (make sure you get them the correct way round with the lips facing towards the pressure or brake lines), take care replacing them, better to pull the return spring off first to get the seal on that side. Clean out all parts with brake cleaner, a pipe brush etc, blow out. Replace caliper pistons, if the old ones are not marked keep them for emergency spares at the track. Replace caliper seals, again when the caliper is apart clean out everything. Make sure magnet in pistons are ok - not broken up if so replace. Use ONLY dot 5 silicone brake fluid - you don't need to use the OTK product just DOT silicone. Better to bleed with a bleeding tower. If you have time and it bleeds ok done with gravity is best, as alanrr says raise the rear of the kart.
I have modded mt bleeding tower by drilling a hole in the lid to take an interference fit Schrader valve tyre valve. Press that in through the hole - don't drill the hole too large the valve needs to be a tight fit. Take an old air line from a old knackered foot pump or similar. Connect that to the same valve so you have a double end air pipe with a air line tyre valve connector at both ends. Take the centre out of the valve in the bleeding tower lid. Connect the double ended air line to it. Take a kart tyre, rear is better, drop to about 5PSI or less. Make sure everything is connected and sealed - tower to master cylinder etc. fluid in tower. Connect line to tyre. This pressurises the tower bottle forcing the fliud through the system under pressure. Take care depending on the master cylinder piston position, fluid can be forced back up into the reservoirs if the lids are off. This is a good thing but take care not to allow them to overflow. Then put lids on and bleed the other way to the caliper, one side at a time until no air can be seen, use a clear pipe on the bleed nipple to view the air bubbles or not. Catch fluid in a small pot (indian takeaway little sauce pots work well they have a lid and are clear - you can look through the fluid to see it's condition), if you are just bleeding a system which has new fluid already in it, you can keep what comes out as emergency reserve fluid, mark the pot as used so you know what is new fluid and used. If the system has old fluid in it throw it. Most dot 5 silicone should be purple when new and goes dark when old.
The above pressure system idea came from 'easi bleed' been going years, works with this and is fast which is useful if you have a panic with the brakes between races. %psi is more than enough pressure, do not use more, you'll end up with fluid everywhere!!
All that said we picked up an OTK with a Kelgate brake - awesome and reliable!
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otk brake system by 'LisaBrown88' (21 Mar 2015 @ 12:06)
