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...because every day is MotoGP day when you own a CBR 125r...
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PostPosted: Sun Apr 17, 2016 2:45 pm 
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Joined: Sun Mar 23, 2014 9:21 pm
Posts: 535
Location: Parksville, BC, Canada
Canada
The other day I got a 'new' bike - my buddy's old CBR 600 RR. He picked up a brand-spanking new Triumph Street Triple RX (2016) - which is just what the doctor ordered. I grabbed his 600 at the same time.

The bike's got 40K on it. It's straight. Thing is, I don't know the maintenance history on it. The factory red-line is 15K and it doesn't like to go there. After some research I found out that it's a common issue and it can be tracked back to the fuel pump. The fuel system on these things runs at a whopping 50 psi!

I also found out they, apparently, have timing chain tensioner issues and also the ram air intake typically means the air filters plug up pretty quick.

As you can guess, I'm looking at doing some service on it. I've got a new pump on the way, a new toolkit (it was missing), a new owner's manual (also missing) and a new service manual so that I can work on the thing.

It's quite a bike. You can really tell that Honda puts a lot more effort into the CBR 600. And they should, it's their second-best bike with the CBR 1000 being the top dog. It's also a direct street port of their MotoGP 2 bike, so it's a big deal for them to make sure it's great.

Anyway, I'll be putting new plugs in it, a new air cleaner, a cam chain tensioner and....lashing the damn valves. This bike is a 4-cylinder and it has 4 valves per cylinder. This means it has 16 valves and each one needs to be checked.

Where this bike is very different is that each valve does not have it's own lock nut and adjustment screw. They use a design known as 'shim under bucket'. This means that the camshaft actuates the 'bucket' (really, a lifter) and underneath that lifter is a precision shim. The width of that shim is what determines your valve clearance. It's a very, very good system as it does not tend to go out by much at all. With the 125 you really should look at your valve lash in the first 5,000k or so and then probably every 15k after that. With this system, once you do the first adjustment and things have worn-in, you're probably damn near set for life :laugh:

Problem is, I don't know if it's ever been done and with the new fuel pump and other maintenance I'm expecting the engine to bounce off the rev limiter at 15,000 RPM pretty easily. I don't want to be out there beating on it and wondering if the clearances are off or if one, or more, of the 16 valves are going to fall into the engine! That would be very costly on an engine like this. You can't just walk into the Honda store and buy the parts for a total rebuild for anything reasonable and you certainly won't be able to build the engine in an afternoon as with the 125. It would be very costly and very time-consuming to scatter this engine.

At any rate, I set out yesterday to check the valve clearance and then adjust as necessary. As it turns out, you pretty much need to strip everything off the bike to do it. Even the throttle body has to come off. Here's some pics is anyone is interested.


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Best & Thanks!
Marvin Miller
cbr125world Store

...because every day is MotoGP day when you own a CBR 125r...
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