The International CBX Owners Association

Hi everyone,
I set all the valve clearances on my 1979 CBX less than 500 miles ago in the hope that they were the root of the tapping noise coming from the top end. Despite this and adjusting the cam chains as per the manual method described on this forum, the noise remained and so I checked the Oldham Couplers which were indeed worn. I've just replaced the couplers with oversized ones and I'm setting the valve clearances again however they are all less than 0.04mm which is the thinnest feeler gauge I have. All of the shim buckets turn so there is a gap on every valve but clearly it's less than 0.04mm. Looking at the adjustment worksheet I filled in last time, most of the valve clearances were at about 0.09mm so I've seemingly lost at least 0.06mm of clearance as a result of the change of couplers and removing and refitting the camshafts. I can turn the engine over no problem using the 17mm nut on the crank, the cam chains are tensioned correctly and it's all very smooth so should I be worried or should I just take each shim up by 0.1mm? Any thoughts / advice gratefully appreciated.
Best regards,
Mark

I've put in several sets of couplers but never had the valve clearance change. Are you sure your cam holders were torqued properly before? There is no reason to lose clearance. Aside from that, set them all at .004-.005 inch. The new couplers will fix your noise so loosen them up.

Dave

+1 on what Dave suggests.

Be sure to set the valve clearances to the wider end of the range (ie; .013mm) and you will be good to go for many thousands miles. Don't be tempted to run it as is, else burnt valves will definitely result.

In my experience, I have found removing and refitting the cam caps can sometimes result in a change in valve shim clearance, so your experience is not unusual. Many of the shims you already have in your engine will be correct for other valves, just a matter of taking it slowly and writing everything down.

You have the worksheet I created ages ago to help track before and after clearances and shim sizes on each valve?? If not, PM me your em address and I will send you the Excel sheet.

Cheers...Tony

A thought, NOT BASED UPON PERSONAL EXPERIENCE, would be that things do not get completely seated after changing shims, replacing camshafts, etc. Also, might be a bit of oil film build-up when doing so. Something I would try after removing/replacing cams and/or shims, etc. would be to remove spark plugs and turn the engine over 10 - 20 times using the 17mm 'nut' on the c/s end. Use a drill motor or old fashioned arm-strong. Don't spin it fast -- just turn it steadily. That should help completely seat things; and, possibly, set oil films to a 'normal' thickness. We're only talking 25 to 50 microns here -- not gaping holes.

As I said, have not tried it myself because I've not removed cams in the X. Thoughts and comments welcome!

Gents,

Many thanks for your thoughts and great advice on this subject. Since my initial post, I decided I couldn't take the risk of running the engine with so little gap and so I took the camshafts out again and refitted them ensuring once again that all the bolts were torqued down as per the settings in the manual and I manually turned the engine over a number of times to seat everything properly. The result; just the same as before i.e. less than 0.04mm gap on each valve but the shim buckets turn freely. I've therefore ordered the handful of shims I need to take the gap up to the higher value of 0.13mm as suggested and they should arrive next week.

It looks like the front camshafts at least may have been removed at some point prior to my ownership as I noticed that the number 4 and number 5 cam caps had been transposed (I assume Honda wouldn't have done that!) but other than that, I certainly didn't see anything unusual or damaged in any way. Glad to hear Tony that my experience isn't unusual and yes, your valve clearance spreadsheet has been a godsend thank you. I'll let you know the outcome once I get it all back together.

Cheers,

Mark

Hi,

Just to let you know that I've finally had the time to put the engine back together now after fitting the new oversized Oldham couplers. I received and installed the new shims to set the valve clearances to between 0.10 and 0.13mm and started the engine and the difference is remarkable, no more noise from the top end. I also installed the Six Centre oversized rubber kit on the clutch basket whilst I was at it which was reasonably straight forward and again, that's made a huge difference. I still don't fully understand why the valve clearances changed so much as a result of removing the camshafts and changing the couplers but it doesn't matter because as you can imagine, the engine sounds brand new now compared to how it was before.

Many thanks to anyone who took the time to read these posts and especially to those who replied, hopefully this experience will be useful to anyone else who may experience this same issue in the future.

Cheers,

Mark

Mark: I'm glad that you were able to again show that installing oversized couplers does indeed quiet these engines. Thanks for the update.

Dave

daves79x wrote:Mark: I'm glad that you were able to again show that installing oversized couplers does indeed quiet these engines. Thanks for the update.

Dave

+1

Hi, i would like to change my oldham. Is there differents size. i ask that because you talk about '' oversized ''.

thank's

didier

Aftermarket, oversize couplers are available. They are available in GB and Holland. Also here, I think: usedcbxparts@hotmail.com

Dave

Thank's Dave. But does that mean, i can buy any oldham coupler i find for CBX or specialy oversized, is there a difference ?

The aftermarket oldham couplers are oversized compared to the stock Honda couplers.
There is only one size of aftermarket.
http://www.sixcenter.nl/onderdelen/deta ... 5&start=14

Ok. It's clear. The thing is, how to know if they need to be changed or not ?

Only the noise or some measure. All my engine is in separate pieces now, i can measure what I want on it.

The mileage is 40000 kms

They never 'need' to be changed. But many, if not most CBXs develop a pretty busy 'sewing machine' noise from the valve train after some miles have piled up. It was discovered that the very slight wear of the couplers resulted in a slight 'rocking' back and forth of the cams at the joints, resulting in valve train noise. Many guys falsely assumed that tightening up the valve clearances would solve the problem. This is the last thing you want to do - have tightly shimmed valves. With the new couplers, you can shim your valves all to .005 inch and hear no tappet noise.

Dave

Shit, 65 € more :)