The Honda Corona Valve Job


Stoutblock: »If there are no Coronas left, I recommend walking carefully away from the bike, go watch football on TV, and redo ATS (all this shit) again in 24 hours.«

Vorweg: Martin Hansen aka »stoutblock« aus Seattle/USA, Honda CB-F-Enthusiast, Boeing-Mitarbeiter und inzwischen in Ruhestand, schrieb im Forum eine drollige Anleitung über die Ventilspiel-Einstell-Prozedur an Hondas frühen DOHC-Four-Modellen. Diese taugt uns so sehr, dass wir sie zum zweimonatigen Bestehen von nachdruck…. also hier einstellen, und zwar in der englischen Fassung, um Orginalität und Wortwitz zu erhalten. Die passende Illustration dazu hat Götz Richardt angefertigt (, der T-Shirts nach individuellen Wünschen im Cartoon-Style besprayt, gerne auch mit Motorrad-Motiven. Die Fotos der zur Ventilspielkontrolle notwendigen Werkzeuge bei den Bol d´Or-Bikes entstanden in der Werkstatt bei Honda Krapp in Mainz. Thank you, one and all. Und jetzt – enjoy a good read !!

It’s a rainy day here in the northwest, so I thought I would spend the morning writing this note to help my fellow CB1100Fers with the details of my recommended valve adjustment process.

I use the following special tools to adjust my valves; strong shop spot light, paper shop towels, a sitting stool, note pad, pencil, Honda wedge tool, Honda bucket retaining tool, 2 small-unworn screwdrivers, strong magnet, 1” micrometer, .002” to .010” feeler gauges, tweezers, ice cooler, and bottle opener.

Honda-Shims (Einstellplättchen), bucket retaining tool (Tassenstößel-Niederhalter), wedge tool (Ventilshim-Heber).

Only supplies needed; an assortment of valve shims (good luck here!), some gray gasket sealer, new valve cover gasket (if needed), a new stator cover gasket (if needed), ice, and a six-pack of Coronas.

If you don’t keep your engine clean, now is a good time to get any external dirt and grime away from the valve cover area. Take off your tank and clean the valve cover area real good. Blow off the area with compressed air.

Take your bike into a well-lighted, clean, secure area. You don’t want dirt and dust flying around and getting anywhere near your valve train. If you don’t have a garage, now would be a good time to go visit a friend who does. However, remember that the engine must be cold to adjust the valves and also if you include a friend you may need more Corona. Keep your hands clean as much as possible. I use a good supply of paper shop towels. These are the thick blue type and not the kitchen type. I keep a roll of these handy at all times while wrenching. They are convenient and help keep hands and parts clean. When they get used a few times I toss them. Nothing worse than re-using a dirty shop rags that may add more dirt where you don’t want it. I also use paper because it is a long time belief by some mechanics that paper fibers will go through the oil system and get trapped by the filter better than cloth fibers (not that you want anything to go through the system in any case). If you don’t clean your tools regularly, now would be a good time to clean all the tools you are going to use.

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Honda CB-F shims.

First, get a low workbench close to the bike on the stator side (if you have a motorcycle stand you probably don’t even need to read this post). I use an upside down cardboard box with metal tray (cookie sheet stolen from kitchen). Place paper towels over the tray and lay the roll on end next to the box. Lay out all the tools you will need on your towel-covered workbench. Place stool next to the bike on the stator side with your workbench off to your right (unless you are left handed). Place ice and Corona in the cooler and place it off to your left (unless you are left handed).

First step, open cooler, grab Corona with left Hand (unless you are left handed), reach to the right and grab bottle opener off the workbench, while firmly grasping bottle, apply upward pressure with opener and pop the top off. We will call this Corona activation or CA for short. Bring bottle up to your lips and take several guzzling slurps while being careful not to let excess liquid poor over your cheeks (clean paper shop towel comes in handy if you are messy…do no use dirty shop towels!). We will call this Corona Intake or CI for short. Place bottle on top of cooler, and opener on top of workbench. We will call this total process Corona Time or CT for short. CA does not have to occur on every CT but only when CI fails to deliver adequate levels of intake. CT is not a mandatory valve adjustment process step but is highly recommended. CT can be processed at anytime during valve adjustment operations and is totally at the discretion of the mechanic. However, if CT is utilized, it must be processed in its full cycle and at no time can CT be processed concurrently with any of the other valve adjustment process step. Also realize, that if CT is utilized too often, it may have detrimental effects on other valve adjustment operations.

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Remove tank, spark plug wires, and valve cover. Place clean paper towels in cam chain valley (to keep bottle caps from flipping down there which would put you In Deep Shit, IDS). Remove stator cover. Remove spark plugs.

(Note: All measurements and adjustments are done on the sparkplug side of the cams. If you want to do it on the other side of the cams you will fail and also run out of Corona supplies prematurely.)

Rotate crank clockwise using wrench on rotor bolt until two lobes are facing away from buckets. Measure clearance gaps between cam and shim with feeler gauges. You should find two exhaust and two intake valves can be checked per rotation. Write all the clearances down on the note pad. This step is called Rotate Crank and Record Clearance or RCRC. Repeat RCRC until all gaps are recorded. (CT is recommended prior to every RCRC cycle). For gaps that are .004”, I would check the gap at several locations on the back of the lobe again to make sure total gap is not less than .004” anywhere during rotation.

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If all gaps are .004 to .006 then remove paper towel and Put Everything Back Together (PEBT). Focus on CT the rest of the day.

For gaps less than .004” or greater than .006”, do the following:

Rotate crank until lobes are away from buckets. Rotate bucket with small screwdriver until notch is accessible on the spark plug side of the head. Use Honda wedge tool between cam lobe and shim to open valve. While using wedge tool the bucket will tend to spin and the bucket notch may no longer be accessible. If notch is not accessible then remove wedge and repeat. This takes a little practice to keep the notch where you want it but it can be done (CT recommended). This step is called WOV because I said so.

Place Honda bucket retaining tool between the two buckets. Retainer should be against the side of the closed bucket and on top of the edge of the open bucket. The retainer should not be on top of the shim but only on top of the bucket edge. Once you know the retainer is where it should be, remove wedge. IR process…

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Use the small screwdriver to pop the shim up using the bucket notch to get underneath it. If it does not pop up easily make sure the retainer is not on top of it. If the retainer is on top of the shim then repeat WOV and IR and CT is recommended. Once shim is popped up, utilize magnet and to pull it out from under the cam. Pushing up on shim from underneath and on the other side of the cam with a small screwdriver will help the magnet pull it out. Sometimes it will take two screwdrivers, one underneath and one pushing from the other side to get it out. The shim near the tack drive has to come out the other side of the cam and CT is almost mandatory at this location. You will find the magnet helps speed this step up. Remove Shim = RS

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Using mic, measure shim existing thickness and calculate needed replacement shim using this formula: EST – DC + EC = DST. Where EST = Existing Shim Thickness, DC = Desired Clearance, EC = Existing Clearance, and DST = Desired Shim Thickness.

Example #1: Your Existing clearance is .008”, your existing shim thickness is .100”, and you desire a .006” clearance.

.100” – .006” + .008” = .102

You will need to use a .102” thick shim in place of the .100” thick shim.

Example #2: Your Existing clearance is .002”, your existing shim thickness is .100”, and you desire a .006” clearance.

.100” – .006” + .002” = .096”

You will need to use a .096” thick shim in place of the .100” thick shim.

If you are having problems with the math…skip CT for a while and it will become clearer. Determine New Shim Thickness = DNST.

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Getting a shim that equals DNST is called LUCK. Trading Corona supplies with your local Honda parts guy may help. Make sure you use a micrometer to verify DNST for LUCK. You will notice there are useless numbers that are sometimes printed on one side of these shims. These numbers can have a correlation with the actual thickness of the shim and sometimes not. Sometimes you will have to use these numbers when communicating with a parts guy but my advice is to disregard these numbers and always verify DNST with a Mic. You do not need new shims and used shims are fine but verify the replacement shim is smooth on both sides and shows no signs of wear.

Clean shim with paper towel. Use tweezers to place shim on top of bucket with the useless numbers (if visible) facing down. Using fingertips, try to get shim started into bucket slot. Use wedge to push shim into slot but don’t force it with the wedge. It should go in with a little help from the wedge. Once shim is seated, use wedge between cam and shim to hold valve open, remove the retainer. Remove the wedge thus allowing valve to close. Insert Shim = IS. If during IS, the shim does not seat easily, repeat RS with appropriate tools, and make sure no foreign matter is between shim and bucket. Keep everything clean! If during IS the shim pops out, and goes somewhere you don’t want it to go, repeat RS, and repeat IS (CT recommended).

If the adjacent shim also needs replaced, repeat WOV, IR, RS, DNST, LUCK and IS for this location also. Do not repeat for any other valve location at this time. Rotate engine 720 degrees until cam lobes are facing away from these two valve buckets again. Repeat RCRC at these two locations. If numbers are between .004 and .006 then it is mandatory CT. If they are less than .004 or over .006 then repeat WOV, IR, RS, DNST, LUCK and IS. CT is not allowed again until clearance is corrected.

Repeat all this shit (ATS) for every valve location needed.

Honda CB750F, 1980

Once all clearances are correct PEBT and count the quantity of Corona supplies remaining. If there are five left you are probably thirsty. If four are left than you did a quick job and all went fairly well. If there are three left then you need to practice this more. If there are two left then you probably had a bad experience but for some reason it didn’t bother you. If there is one left, you might want to count your tools to make sure you didn’t leave anything inside the engine…make sure engine rotates freely before starting, and do not ride or drive for 24 hours (IDS possible). If there are no Coronas left, I recommend walking carefully away from the bike, go watch football on TV, and redo ATS again in 24 hours (IDS probable).

Honda CB900F, 1979

If you needed to change any valve shims, don’t worry too much about sealing the valve covers right away. Ride the bike for several tanks and then RCRC again. If all is well then PEBT but spend more time to seal the valve cover and you will not have to RCRC again for thousands of miles. If gaps are bad when you do ATS again, then CT and repeat ATS and ride for a few more tanks and check RCRC, etc, etc

Added complications:

Don’t check clearances on a warm engine or with warm Corona.

Don”t rotate cams without shims in place.

If there is no clearance, then you need to install a thinner shim until you can get a clearance reading to work from.

If LUCK is not possible for DNST in order to obtain DC then one of several things are happening. You need to adjust your DC between .004 and .006 until LUCK is possible for DNST. If DNST is beyond the range of the manufactured shim thickness sizes then LUCK is not possible and you are IDS.

Hope this helps…


Honda CB1100F, 1983

Text: Martin Hansen, Seattle/USA

Fotos: Buenos Dias, Honda

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2 Kommentare

  1. Avatar
    BlainetheMono on

    and because you scored that MASSIVE shim kit from Howie, you, and sometimes I, do not need LUCK


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