Valve clearances... How much out of tolerance is too much?

CBRMAN94 · Nitrous Nuisance Joined: 10 Jun 2013 Karma :

Bike : Yamaha FZR400RR (16k miles)

Tolerance limits as per Manual :
0.0083-0.0118in Ex
Can't remember Inlets but they're spot on.
The exhaust valves however are reading 0.0060in which is a little on the tight side, Saying this the feeler gauges i have go from 0.0040in/0.0060in/0.0100in so i can't 100% sure exactly how far off the measurement is from spec but the 0.060in seems a little loose but the 0.0100in was far too big.

Reckon these will be safe enough for another year of use? First time i've checked in 2 years and only a little out of spec...

Cheers!
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Honda CBR-RW6 (Sold) - Kawasaki GPZ500s (Sold) - Honda CG125 (Project) - Honda CB750 Cafe racer (Project) - Yamaha FZR400RR

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

6 thou is very tight for a 8-12 thou range. You'll have to balance the reward of saving time and money against the risk of burning the valve lip from lack of cooling.
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Nobby the Bastard · Harley Gaydar Joined: 16 Aug 2013 Karma :

Look at it as the clearences are advising you to buy the correct shims and that you should be fitting them at the most convenient time that comes up in the next 3 months.
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CBRMAN94 · Nitrous Nuisance Joined: 10 Jun 2013 Karma :

Guess it should be done then... May as well while it's getting the winter overhaul, Better safe than sorry ehh?

Funny thing is, I've rebuild 125 engines and turned my hand to everything that needed doing on my bikes but for some reason, something this simple is scaring the shit out of me! Confused

How hard can it be though... Laughing

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Honda CBR-RW6 (Sold) - Kawasaki GPZ500s (Sold) - Honda CG125 (Project) - Honda CB750 Cafe racer (Project) - Yamaha FZR400RR

mentalboy · World Chat Champion Joined: 05 May 2012 Karma :

Fizzer Thou · World Chat Champion Joined: 06 Aug 2011 Karma :

If changing the shims on the 400 is anything like is needed on the FZR1000R,then the cam/cams will need to be unbolted so as to access the under bucket shims.But if you only need to sort the exhaust clearances then simply unbolting that camshaft from the carriers and rolling it forward without upsetting the cam timing should be feasible.

When I needed to replace certain shims on my R1,I bought the sizes that I needed from Wemoto,who have a good selection at a reasonable price.

You will need to check what size shims you already have inside the engine,so a micrometer will be handy so that you may well be able to swap around those that you have before having to buy replacements.

Do not forget to double check the clearances once the shims have been adjusted and ensure that you use a small scale torque wrench for bolting down the cam caps and the cover,as these bolts are easily sheared off if you are not careful Thumbs Up

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