Yamaha FZ750 Valve Shim Inspection and Adjustment

Disclaimer- This document is for informational purposes only and the writer will accept no responsibility however caused for damage resulting from the use or misuse of these instructions. Use at owner Risk.

Note:

It is quite possible to complete the task below with imperial measuring equipment but please note that this will make calculating shims sizes that bit more difficult as conversion to metric will be required.

These instructions are not a substitute for the owners/workshop manual but are designed to be used with reference to the owners manual and give additional information and tips that will make the job easier to complete by the home mechanic. If something goes wrong for example they do not contain details of how to time the engine if reference marks are not made/or lost.

Tools required

Standard tool kit inc socket set, screwdrivers, spanners, etc

Micrometer (not always necessary)

Pen/paper/sticky tape

Calculator

Quality feeler gauge set

Bucket

White paint (tippex or like)

Impact driver

Small magnet

Spark plug extraction tool

An impact driver is essential for any sort of maintenance on Japanese machinery.

Recommended Torques

Camcover bolts - 10Nm

Spark Plugs – 17.5 Nm

Camchain sprocket bolts – 24Nm

1. Preparation

Yamaha Fz750 is 20-valve shim under bucket design, to replace any shims you will need to remove the relevant camshaft and therefore re time the engine. If you are nor familiar with this exercise please don’t attempt to change the shims. ENGINE DAMAGE will result if your motor is not re-timed correctly. The secret with this job is organisation. I recommend that you make up a quick chart like that shown below that you can record all your measurements and then calculate your new shim size. Any shims that are removed you should tape to the chart with sticky tape. Make your chart on a full size letter paper.

INLET (0.11 – 0.20mm)

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM__

R.SHIM

______

GAP___

SHIM___

R.SHIM___

GAP___

SHIM___

R.SHIM___

GAP___

SHIM___

R.SHIM___

GAP___

SHIM___

R.SHIM___

GAP___

SHIM___

R.SHIM___

GAP___

SHIM___

R.SHIM___

GAP___

SHIM___

R.SHIM___

GAP___

SHIM___

R.SHIM___

EX (0.21 – 0.30 mm)

1. Dissemble

Remove fairing lowers (you only need to remove one side of the bridging piece)

Remove air baffle plates

Remove Coolant cap

Remove LH sidepanel (for access to Header tank)

Drain coolant by removing hose clip below radiator (into bucket not garage floor)

Remove radiator and fan (disconnect wire at connector)

Remove LH engine (crankshaft) inspection cover and timing marks window

Remove cam cover

Remove spark plugs

2. Inspection

Turn the motor over to top dead centre (T.D.C) on No. 1 cylinder. Use the timing marks thru the inspection window or use probe down spark plug hole (turn over until the inlet valve closes and then the next time the piston comes to the very top is TDC on compression). You don’t need to be amazingly accurate on camshaft position.

Measure no.1 cylinder shim clearance between the shim bucket and the cam lobe. The cam lobe point should be facing away from the shim bucket. You will need to measure the 3 inlets and 2 exhaust valves on each cylinder. Double check your measurement.

Note the measurement down on the chart, in the correct place.

Repeat this for each cylinder, not forgetting to turn the motor over to T.D.C for each one. I always use the probe down the spark plug hole. Write the gaps down.

3. Adjustment – removal (If you are not fully confident that you are able to strip a top end and re-time an engine then you should leave the following to your dealer.) Reassemble the engine and pay a dealer to complete the work. At least you will know that the work needs doing.

It should now be apparent which shims will need replacing. The correct gaps are Exhaust 0.21 –0.30mm and inlet 0.10 – 0.20mm.

If the gap is above those specified you have a problem. Shims nearly always tend to close up (i.e. the gap gets smaller and the motor gets quieter!).

If no Adjustment is needed replace all the covers/radiator/etc and ride away happy. If you do need to adjust read on.

You will now be forced to remove the camshafts and extract the old shims. In order to calculate the new shim size you will need to establish what the existing shim is.

Turn the engine back to T.D.C on no.1.

Mark both the camshafts and camchain with a small mark of white paint or tippex. This is so you can replace the camshafts back to their exact position after the shims are installed.

Remove the cams be undoing the cam journals. TAKE CARE with the journals that are under load. One or more of the cylinders will have open valves, therefore the valve springs will be pushing up on the cam. There is a danger of DAMAGEING THE JOURNAL THREADS as you undo the bolts. A good technique is to ‘carefully’ use mole grips (vice Grips) to hold the cam down as the bolts are undone. Take your time and carefully remove all the journals. DO NOT MIX UP THE JOURNALS, they are individually machined and are numbered to the correct position.

To remove the cams it is necessary to remove the camchain tensioner to give enough slack to remove the cams. At TDC on No. 1 remove the two 10mm bolts holding the tensioner on. TAKE CARE NOT TO STRIP THE THREAD as the Tensioner will extend as the bolts are undone. It is also a god idea to strip and clean the tensioner while it’s off.

Do not be tempted to turn the engine over while the tensioner is removed as the chain will now slip over the cam sprockets and you will mess up the timing and be forced to re-time.

You should have enough slack in the camchain to withdraw a camshaft. Before you do this make a small mark on the chain and each camshaft sprocket so that you can put the cams back in exactly the same place in the chain. If you do not have enough free play then remove one of the camshaft sprockets (mark another white line so that you can put the sprocket back in the same position) and withdraw the cam through the sprocket. Remove the sprocket (and temp put it back on the cam).

Once both cams are removed (put a pencil thru the chain to prevent it dropping into the crankcase, you can extract each bucket for each out of adjustment shim.

Tip-use the magnet to pull the bucket out over the oil suction.

Remove each shim (it will be stuck on the underside of the bucket) and tape it to the chart in the correct box under shim____ heading. DO NOT MIX THE SHIMS UP or put them in the wrong box. Take your time! And you only need to remove the ‘out of adjustment’ shims, leave the others in place.

5 Adjustment – Calculate

Once all the shims that are out (EX and INLET) are taped to the chart. You are ready to calculate your new shim sizes.

The theory is that you need to calculate the new size shim that will bring the gap into tolerance.

TIP- If possible then always shim out to the maximum permissible gap (0.20mm for inlet and 0.30mm for exhaust) as the clearance reduces as the engine wears and this will give you the maximum amount of time until you need to re-shim.

The existing shim size is stamped on the side of the shim (other makes may find that the size is on the face of the shim and so wears off once the shim is used. If this is the case then you will need a micrometer to establish the size.)

For example if an inlet valve has a size of 175 stamped on it (ie 1.75 mm) and the gap is 0.05mm then the new shim required. is 1.75 +0.05 – 0.20 = 1.60. The required shim is 160.

Existing shim + Existing gap – required gap = required shim

1.75 + 0.05 - 0.20 = 160

Fill in the rest of the information on the chart.

TIP – Calculate all your required shims and then look through what you don’t need. There’s no point buying/exchanging a shim you already have. This can save you quite a bit of money especially if you have a good range of sizes.

TIP – A favourite Ducati tip is to sand a small amount off the shim (you will nearly always need a slightly smaller shim). Of course someone might have already done this and size stamped on the shim may be wrong. If you suspect the shims been tampered with then measure it with the micrometer. Your dealer may refuse your shims in exchange for this reason.

Once you have established what you need its time to go to the Yamaha dealer and exchange/buy the new shims.

6 Re-assembly

Place in the new shims on top of the valve stems and replace the buckets, in same place they came out.

You can replace the cams, making sure that the timing is correct, the marks you made earlier will enable you to put everything back exactly as it came out.

Replace the Cam journals (in the same place also) and taking care not to strip the threads of the bolt holes.

Replace the camchain tensioner. Hold some pressure on the tensioner to relieve the pressure on the threads.

Turn the engine over a few times (this will also make sure you valve timing is right before you attempt to start) then put it back to TDC on no.1 and check the gaps are now correct. Continue to check all the gaps are now correct (turn to TDC for each cylinder). If they are not you need to go back and re-shim and errors.

If everything is fine, replace the camcover, spark plugs, air baffles, radiator, Crankshaft cover/inspection and fairing.

Top up the coolant. Tip- I usually fill up thru the filler cap on the RH fairing and then run the motor to get any air bubbles out. Use a good quality Anti-freeze suitable for Aluminium engines.

Done.