CMB 67 Greenhead

[John Seybold]

Hi,

I have a new CMB 67 greenie and remember reading a thread aways back about having to drill a hole to help fuel/oil keep the bearing from going bad.

Does anyone know where the hole needs to be drilled?

Thanks

 

[Samuel Hagan JR]

I was told by Stu to lapp the drum and housing and you shouldn't have to. I can't remember the compound we used.

 

[Ray Sametz]

John, Sam is right it was to lube the drum. Two choices hole or slot, I lapped the housing and drilled the hole.

 

[eagletwin90]

Do you need to do this on the 80 as well...

thanks James

 

[JeremyEdge]

I would, it wouldn't hurt. Plus it will be a mind easier knowing that it was stick for sure.

 

[Samuel Hagan JR]

I ran mine unlapped and you can see the damage being done. Then Stu told me what to do and it was much better.

 

[Don Ferrette]

Do you need to do this on the 80 as well...

thanks James

YES!

 

[Stuart Barr]

The holes and slots never really worked. I lapped with #15 diamond lapping compound and light oil. Finish with #6 compound.

Stu

 

[John Seybold]

Thanks for the replies. How do you lap a motor/housing. Any ideas where I can get the lapping compound.

Thanks

 

[Ray Sametz]

Thanks for the replies. How do you lap a motor/housing. Any ideas where I can get the lapping compound.

Thanks

McMaster-Carr for the compound. PM Stu Barr as to how and what to use.

 

[Glenn Gates]

John, I think the problem showed up when CMB went from the cast to the billet drum housing. Not enough clearance to allow the fuel/ oil mix to lubricate the bushing. I recently got a NIB motor with the cast drum housing and clearance was .0015". I have heard that the newer models with the billet housing had only .0005" clearance.

Please correct me if I am wrong Stu.

 

[Samuel Hagan JR]

I'm not sure how to Lapp the part. I had my Uncle do it. Ask a local machine shop maybe.

 

[Glenn Gates]

No offence Samuel, If you have no knowledge of lapping or honing parts perhaps you should "limit" your comments. I think John is a machinist( as was I for 30 years). I think the part could be easily honed using the proper stones and truing sleeves on a Sunnen hone. What I've learned about "lapping" over the years is that the harder lapping compound may inbed itself in the softer material(bushing) creating more problems down the line. A good honing stone like a Sunnen 57 series should work well.

Again, correct me if I'm wrong Stu.

 

[Tom Foley]

I also increased the chamfer on the end of the drum housing to give a "place " for oil to accumulate and disperse as well as opening up the housing and drilling the oil hole and adding two more grooves . Did this on the VAC 91 's as well but the most important mod is to open the housing up like Stu says .

 

[stan simpson iv]

I also increased the chamfer on the end of the drum housing to give a "place " for oil to accumulate and disperse as well as opening up the housing and drilling the oil hole and adding two more grooves . Did this on the VAC 91 's as well but the most important mod is to open the housing up like Stu says .

x2...

 

[Terry Keeley]

Here ya go:

http://www.intlwaters.com/index.php?showtopic=56099&hl=%2Bdrum+%2Bvalve

 

[Stuart Barr]

Glenn you are right on the clearance.

 

[Glenn Gates]

Thank you Stu and thanks to Terry also for a link to the original post. Clearance seems to be a problem. Not the lack of slots or holes.