Checking Valve Clearances

DISCLAIMER
: Any of the words written or actions taken in the following post are not endorsed by 400Greybike and are the personal writings of myself. If you undertake any of the following processes you are responsible for your own actions, neither 400GB or myself will assume any responsibility. If you are not happy to undertake any of these actions please have a professional perform this task. Thanks you.

OK, so, as requested I have started on my write-up on how to check the shims, or valve
clearences on the NC30. First of all, let me say, it is not hard and is definately nothing to be afraid to do. This will also save you a few £100 now that you won't have to go to a mechanic to get it done. Before I start I want to put my thanks out there first before I forget. Thanks Rhory (castroljc) and Stu (Bunter) for having a laugh last night when we had our first attempt on one of Rhory's many NC engines but it all worked out fine, and also a big thanks to Rick Oliver for upplying the guide on how to do it.

Firstly this is what you'll need,
- Ratchet with a 10mm, 14mm and 17mm socket,
- Feeler gauge that can measure between 0.12mm-0.18mm and 0.21mm-0.27mm
- And possibly a flat headed screwdriver to carefully help you separate the cylinder head from the block.

OK, so you will need to strip pretty much all of the bike (this is where the dealer gets you in labour costs). So,
- Bodywork off
- Tank, airbox, carbs out
- Top radiator off (or dropped to allow you access to the front head)

(If you don't know how to do any of the above please consult the Haynes manual)

Your bike should now look like this (pic is from an '89 NC30 I re-built last year )

Now for the fun stuff. First of all remove the 4 bolts that holds the head in place. They are 10mm hex head screws,

 

Once removed carefully use a flat head screw driver to prise off the cam cover. Once off it will now look like this,

 

Looks scary don't it. Don't be scared, if you're lucky you'll not need to replace any of the shims. Next up is to remove the Timing Hole Cap. A 17mm socket will sort that out to allow you access to the Timing nut adjuster thingy (a very technical term, 'I will not buy this record, it
is scratched' )

Next up you'll need the 14mm socket to turn the engine over.

Turn until you get both of these marks lined up. T1 and the mark on the casing, and the other 2 lines to match on the top of the cam shaft.

And

The hard work is behind you now. Next up is to check the gap between the
shim and the camshaft (the long rod that has egg shaped things on it) When the lines are the same as the above pics you are then free to check the gap on cylinder no. 1 (rear left when sitting on the bike).

There are 4 valves/shims per cylinder (and there are 4 cylinders making the bike, yes you guessed it, 16 valve ) that need checking now. The front 2 are known as inlet valves and the rear 2 are exhaust valves. The tolerance for all the inlet valves
on the bike are 0.12mm-0.18mm so take out your feeler gauge and check it now. If it is within tolerance a gauge should fit in like so.

And the rear should be between 0.21mm-0.27mm and should fit like so,

Once you know what the gap is please use the following page to write it down for future reference.

Once you have Cylinder no. 1's gap it's then time to do cyliner no. 3 (this is the one to the right of no. 1. Turn the Timing nut again until you get back to T1 again and the cam shaft will now line up in the opposite way to the way it did on cylinder no. 1.

Once you are at this stage you can then start to check the clearance on cylinder no. 3. Again the front 2 are the inlet valves and the rear are exhaust valves and the tolerances are still 0.12mm-0.18mm on the inlet valves and 0.21-mm-0.27mm on the exhaust valves.
The following pics look the same as the ones above but believe me, thay are from cylinder no. 3. If you look really close you'll notice that.

Inlet valves

Exhaust valves

 

Courtesy of Viperbiker(400GB Forums)

 

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