Airhead owners - I need your help.

[MotoRevive]

I've recently had some Cylinder heads reconditioned by a well known supplier/Workshop in the U.K.

New valves, guides and valve seats. It wasn't a cheap job.

On inspection, I have some reservations.

There seems to be A LOT of lateral play between the new valves and the new guides.

My mechanics intuition tells me this isn't correct. An airhead doesn't have stem seals and relies on a a tight clearance to prevent oil burning. However, the valve also does need lubricating.

I'm kicking myself for not measuring the old valves and guides for free-play. before I posted them off. (I didn't get them back).

The BMW manual spec for valve-guide clearance is 0.05-0.08mm for a new build. With an absolute service limit of 0.15. Which would likely be a smoker and burner.

The new Valve stems measure 6.93mm. BMW says valves should be 6.96mm. HMMM. They're not genuine BMW valves but the supplier does sell tons of these without issue.

The new guides have an ID of 7.0mm. Just as the book says they should. Perhaps even a little less than that.

So with those numbers, the stem to valve clearance is 0.07. Which is in spec. But at the higher end.

So I ask... Does anyone have a none smoking airhead in pieces that they can check if they have valve wiggle like in the video below.


P.S. I've checked valve wiggle in some old Honda and Yamaha heads I have in the shop. They also have a bit of wiggle. But they also run stem seals and they're not new engines anyway.

Many thanks. Ted

I have yet to contact the company. I need to get my facts straight first.

 

[Nin]

Doesn’t look right to me. But what do I know?

 

[MotoRevive]

Doesn’t look right to me. But what do I know?

At least your own shoe size. One would hope

 

[Stirlingmoz]

Obviously I’m going by eye, but with that much free play, if they were my heads, I’d be thinking about changing the valve guides.

I do mine at home (red neck engineering).

Heads in the oven - drift the old ones out and with the new guides coming out of the freezer - drift them back in.

It’s proper percussive maintainance but I’ve had considerable success with this method.

 

[Nin]

At least your own shoe size. One would hope

In both metric and imperial

 

[MotoRevive]

Obviously I’m going by eye, but with that much free play, if they were my heads, I’d be thinking about changing the valve guides.

I do mine at home (red neck engineering).

Heads in the oven - drift the old ones out and with the new guides coming out of the freezer - drift them back in.

It’s proper percussive maintainance but I’ve had considerable success with this method.

These are all new guides, valves and seats.

Fresh back from a machine shop.

Did you read the post ?

 

[snelly]

I've recently had some Cylinder heads reconditioned by a well known supplier/Workshop in the U.K.

New valves, guides and valve seats. It wasn't a cheap job.

On inspection, I have some reservations.

There seems to be A LOT of lateral play between the new valves and the new guides.

My mechanics intuition tells me this isn't correct. An airhead doesn't have stem seals and relies on a a tight clearance to prevent oil burning. However, the valve also does need lubricating.

I'm kicking myself for not measuring the old valves and guides for free-play. before I posted them off. (I didn't get them back).

The BMW manual spec for valve-guide clearance is 0.05-0.08mm for a new build. With an absolute service limit of 0.15. Which would likely be a smoker and burner.

The new Valve stems measure 6.93mm. BMW says valves should be 6.96mm. HMMM. They're not genuine BMW valves but the supplier does sell tons of these without issue.

The new guides have an ID of 7.0mm. Just as the book says they should. Perhaps even a little less than that.

So with those numbers, the stem to valve clearance is 0.07. Which is in spec. But at the higher end.

So I ask... Does anyone have a none smoking airhead in pieces that they can check if they have valve wiggle like in the video below.


P.S. I've checked valve wiggle in some old Honda and Yamaha heads I have in the shop. They also have a bit of wiggle. But they also run stem seals and they're not new engines anyway.

Many thanks. Ted

I have yet to contact the company. I need to get my facts straight first.

You always need a before and after when you have jobs like that done; but like you say unfortunately you did'nt do the before; your an engineering minded guy with the sounds of things so i imagine you have your own ideas of what you feel comfortable with;; yes it does look like it maybe a bit loose but once hot and expanded it could well be a good fit;; mikey boy would be the guy to advise you.

 

[Stirlingmoz]

These are all new guides, valves and seats.

Fresh back from a machine shop.

Did you read the post ?

I did. Sorry if my point didn’t come across very well.

What I meant was - had I not known these were new replacement valve guides - I would have changed them, just on the amount of wobble.

New ones I have done have virtually no discernible play.

Have you done the ‘pop’ test ?

 

[DrFarkoff]

I did. Sorry if my point didn’t come across very well.

What I meant was - had I not known these were new replacement valve guides - I would have changed them, just on the amount of wobble.

New ones I have done have virtually no discernible play.

Have you done the ‘pop’ test ?

@MotoRevive Ted if one came to me for work to be done ??

Hard to tell from a video, without having hands on ?

But I think that is at a stage I would be recommending guides !!

Actually I just remembered I bought Valve guides off a seller and they turned out of be out of spec and they took them back and refunded me and I fitted Genuine Guides!

 

[tofgasp]

With new valves and guides, you should have a 0,15mm play at maximum valve lift (+/-10 mm). It's hard to tell accurately from a video but there is way more than that on yours.

 

[Paradiso]

I had exhaust valves and guides done on an R65 in the last year and they were nothing like that. It does look like there's far too much lateral play. I'd be worried about oil consumption.

 

[DrFarkoff]

I had exhaust valves and guides done on an R65 in the last year and they were nothing like that. It does look like there's far too much lateral play. I'd be worried about oil consumption.

I would be worried about the heads falling off at Higher heat and RPM with them wobbling around like that!!!

 

[Mad Hatter]

I think they are massively loose!

 

[MotoRevive]

Thanks gents. They're going back.