Cmb 21 Beta head clearance

[Danny King]

You didn’t answer if it came in a sealed box? Was it in the boat and advertised as new? Or was the motor in a sealed box. I have not seen a beta come without the shims Installed. And have not seen Cmb send shims that thin. And never seen .015” clearance without any shims.
So it appears someone had it apart.
I don’t use the solder idea. It’s always off. High but off.
It is very important you get it right.
You can run at .007” all day and the piston won’t touch until the bearings or rod bushing are worn out. But too low for a set up will be tough on plugs. Too high on a set up and you won’t make good power.
Patiently get this right or you’ll not have a positive experience.
A few things you have stated don’t add up.

 

[Mike lasorsa]

You didn’t answer if it came in a sealed box? Was it in the boat and advertised as new? Or was the motor in a sealed box. I have not seen a beta come without the shims Installed. And have not seen Cmb send shims that thin. And never seen .015” clearance without any shims.
So it appears someone had it apart.
I don’t use the solder idea. It’s always off. High but off.
It is very important you get it right.
You can run at .007” all day and the piston won’t touch until the bearings or rod bushing are worn out. But too low for a set up will be tough on plugs. Too high on a set up and you won’t make good power.
Patiently get this right or you’ll not have a positive experience.
A few things you have stated don’t add up.

Was new on the boat I got. Never had the sealed box. I had a talk with my father and I had my story mixed up. It did have 2 shims when we got it but it would not rev up in the water. Had a 1450 prop which was prob part of the problem. We took the shims out to try it but it got cold out so we had to wait till after winter which is now. This shims are measuring .001 and .002 on 2 different calipers. Measuring .015 on crushed solder. I know that’s not the best way but I would think it would in the ball park

 

[Danny King]

Good luck.

 

[Bradley Maglinger]

If it is a Gold Head Beta, there is a very good possibility that the water jacket(gold part) might be hitting the case not allowing the head button to seat all the way. Mine was doing that so I had to put shims on top of the head button as well so the water jacket would not hit the case when torquing down the head bolts. Dont forget to put a drop of oil in those threads everytime you pull those headbolts out or you will wish you did.

 

[Mike lasorsa]

If it is a Gold Head Beta, there is a very good possibility that the water jacket(gold part) might be hitting the case not allowing the head button to seat all the way. Mine was doing that so I had to put shims on top of the head button as well so the water jacket would not hit the case when torquing down the head bolts. Dont forget to put a drop of oil in those threads everytime you pull those headbolts out or you will wish you did.

Yes it is a gold head. I’ll have to check that cuz nothing is adding up here lol

 

[Terry Keeley]

If you look carefully the end of the solder will have a nub as that's the part that gets pushed into the chamfer between the head and cylinder wall.

Cut the last bit off with your x-acto knife and re-check it.

 

[timothy johnson]

If it is a Gold Head Beta, there is a very good possibility that the water jacket(gold part) might be hitting the case not allowing the head button to seat all the way. Mine was doing that so I had to put shims on top of the head button as well so the water jacket would not hit the case when torquing down the head bolts. Dont forget to put a drop of oil in those threads everytime you pull those headbolts out or you will wish you did.

Brad has a good point about the water jacket. Also I believe the very first Beta's that Stu sold had a head button issue where the HC was extreme. To correct this they came out with a new head button, the new head buttons had groves around the diameter. A picture of your HB may help. I believe the first engines had more HC for non nitro use. Danny for sure is correct no CMB engines came with that much clearance. Good luck.

 

[Mike lasorsa]

Brad has a good point about the water jacket. Also I believe the very first Beta's that Stu sold had a head button issue where the HC was extreme. To correct this they came out with a new head button, the new head buttons had groves around the diameter. A picture of your HB may help. I believe the first engines had more HC for non nitro use. Danny for sure is correct no CMB engines came with that much clearance. Good luck.

Here is the button

 

[timothy johnson]

Mike can you turn it so we can see the outside diameter! Does it have grooves?

 

[Mike lasorsa]

Mike can you turn it so we can see the outside diameter! Does it have grooves?

No groves from what I can see

 

[timothy johnson]

That is the groove I'm speaking about, that is one of the current HB.

 

[Mike lasorsa]

That is the groove I'm speaking about, that is one of the current HB.

Ok I thought you meant like little groves to help seal lol im not sure what to make of this then I wonder since it’s not broken in if the rod has to stretch some? I put a shim between the cooling jacket and button and got the same measurement

 

[Mike Hughes]

What size solder did you use? If it large it will give an off reading using that technique. You need to use the extra small stuff like Terry posted. You best bet is the turn the motor to TDC and remove the head. Measure sleeve to piston and then measure head button depth. Subtract the two.
Mike

 

[Mike lasorsa]

What size solder did you use? If it large it will give an off reading using that technique. You need to use the extra small stuff like Terry posted. You best bet is the turn the motor to TDC and remove the head. Measure sleeve to piston and then measure head button depth. Subtract the two.
Mike

Solder trick won’t work with this motor it keeps reading the dome part of the button. I measured sleeve and button im at .003 with no shims I’ll add until I am at .008

 

[Mike Hughes]

I shoot for 6-8 ish depnding on how much work I have to do. Had to sand a few sleeves down with the 320 and WD40 in a swirly pattern. Takes for ever sometimes.
Mike

 

[Mike lasorsa]

I shoot for 6-8 ish depnding on how much work I have to do. Had to sand a few sleeves down with the 320 and WD40 in a swirly pattern. Takes for ever sometimes.
Mike

I had a issue with it not wanting to rev up so Deff take my time and make it correct. Had a 1450 prop which I believe is to much for it

 

[brad nichols]

How about using plastic gage?

Brad