CMB Beta Evo Assembly

[avbrando]

Took my new .21 beta evo appart last night to inspect it before installation into my JAE rigger and , tried to reassemble it but i cant seem to get the rod over the crank journal, just not enough clearance to get the rod parallel the crank pin, ive been sucessfully rebuilding buggy engines for 15 years and never seen this prob before, any thoughts?, thanks in advance.

 

[Timbo Whalen]

Make sure everything is very clean and lightly lubed.... load piston/rod assy. through top

of case, WITHOUT sleeve/liner installed, carefully rotate to BDC, slide sleeve/liner in and

carefully rotate and correct, mid stroke, until piston enters sleeve, push sleeve/liner home

making sure alignment pin (case) and slot (liner flange) engage.

Hope this remedies your situation.

Tim

 

[avbrando]

tried but rod is recessed in a groove in the crankcase, cannot be installed at bdc.

 

[Walt Barney]

tried but rod is recessed in a groove in the crankcase, cannot be installed at bdc.

Make that TDC and wiggle the rod to try to get it on the crank turn the crank a couple degrees either way as your holding the rod with the end of your finger and when its perfect it will just fall on the crank, it will take several tries, until it goes on. Don't give up it will go on without forcing it.
Walt Barney

 

[avbrando]

Thanks Walt, man i tried for at least an hour, ive done a lot of .21 buggy engines and this one is tighter than any ive seen, all of the new machining is soo tight and the piston is at an angle when dropped in at TDC, it just wont go without force.

 

[Timbo Whalen]

Thanks Walt, man i tried for at least an hour, ive done a lot of .21 buggy engines and this one is tighter than any ive seen, all of the new machining is soo tight and the piston is at an angle when dropped in at TDC, it just wont go without force.

Yes, my bad, it's TDC... and it's easier to engage the piston with the liner at TDC, too.

My apologies...

Tim

 

[Toru Komatsu]

Hi avbrando,

I cannot see the oil groove/hole of the rod in your picture. I think that should face to the back plate (drum housing) side.

Toru

 

[Walt Barney]

Hi avbrando,

I cannot see the oil groove/hole of the rod in your picture. I think that should face to the back plate (drum housing) side.

Toru

Hold the engine up side down, put the piston and rod in from the bottom and bring it up as far as you can using the crank move to the top of the of the arc move it several degrees either way while moving the rod sideways a slight bit it will just slip over the crank ,in only one place ,as you get the rod just on the crank move it a slight bit as you try to get the rod on the crank, if takes a little learning but it will fit on and you will be surprised how easy it is once you do it make sure you have the rod in the correct direction other wise you will have to take it off and start all over again. if you want to call me that is OK 256-779-6472
Walt Barney

 

[Charles Dukes]

I have several of these motors and have not had any issues, if I use the procedure that Walt shares above. However(there is always a however), last week I was cleaning out and prepping a new CMB 21 Beta Evo for a friend and I had a devil of a time getting it back together. I think this latest version(or at least this motor) has slightly different dimensions somewhere. I was finally able to get it put together, but it took me a lot longer than usual.

 

[Brad Christy]

Thanks Walt, man i tried for at least an hour, ive done a lot of .21 buggy engines and this one is tighter than any ive seen, all of the new machining is soo tight and the piston is at an angle when dropped in at TDC, it just wont go without force.

Avbrando,

Start the crank pin insertion into the rod at mid stroke, with the crank journal at 3 or 9 o'clock. This will allow you to use the pivot of the rods in the piston to gain you the clearance you need. Rotate the piston/rod ass'y as you slide the rod onto the crank pin. As has been stated, when everything aligns, it will just slip on, with virtually zero force.

It went on there at the factory. It will go back on. I find that holding the case upside down, as Walt suggested, works well, with my middle finger supporting the piston, my thumb managing the rod and my other hand managing the flywheel.

Hope this helps.

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

 

[Timbo Whalen]

Avbrando,

Start the crank pin insertion into the rod at mid stroke, with the crank journal at 3 or 9 o'clock. This will allow you to use the pivot of the rods in the piston to gain you the clearance you need. Rotate the piston/rod ass'y as you slide the rod onto the crank pin. As has been stated, when everything aligns, it will just slip on, with virtually zero force.

It went on there at the factory. It will go back on. I find that holding the case upside down, as Walt suggested, works well, with my middle finger supporting the piston, my thumb managing the rod and my other hand managing the flywheel.

Hope this helps.

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

Isn't the crank pin still masked by the annular pocket at the 3 and 9 o'clock position?....

I haven't had my 21 Beta EVO apart yet, so can't speak from experience. My NR engines

encountered the same anomaly, and it seemed that loading the rod/piston first, engaging

crank pin at TDC, and then gently sliding the liner into place was what worked, similar to what

Walt stated.

I misstated such in my first comment.

Tim

 

[Brad Christy]

Isn't the crank pin still masked by the annular pocket at the 3 and 9 o'clock position?....

I haven't had my 21 Beta EVO apart yet, so can't speak from experience. My NR engines

encountered the same anomaly, and it seemed that loading the rod/piston first, engaging

crank pin at TDC, and then gently sliding the liner into place was what worked, similar to what

Walt stated.

I misstated such in my first comment.

Tim

Tim,

You may have to go a bit north of 3 or 9 o'clock to get away from the rod groove. Just so that the crank pin is off to the side so you can use the swing of the rod in your favor.

And, yes. All this is done with the sleeve out of the case.

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

 

[Timbo Whalen]

Tim,

You may have to go a bit north of 3 or 9 o'clock to get away from the rod groove. Just so that the crank pin is off to the side so you can use the swing of the rod in your favor.

And, yes. All this is done with the sleeve out of the case.

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

Yep, Brad....seems legit!

 

[Walt Barney]

Thanks Walt, man i tried for at least an hour, ive done a lot of .21 buggy engines and this one is tighter than any ive seen, all of the new machining is soo tight and the piston is at an angle when dropped in at TDC, it just wont go without force.

Did you get the engine togather???
Walt

 

[avbrando]

Did you get the engine togather???
Walt

Haven't got to it yet, but thanks to all who messaged and commented, gonna try again this weekend, looks like the concensus is i need to have the crankcase upside-down and install the rod at approx 11oclock or so, thanks again all!

 

[Timbo Whalen]

Haven't got to it yet, but thanks to all who messaged and commented, gonna try again this weekend, looks like the concensus is i need to have the crankcase upside-down and install the rod at approx 11oclock or so, thanks again all!

Like they say, the first time's the hardest...best wishes.

Tim

 

[rctinman]

One other thing that helps on a new/tight engine like this, is to make sure that your rod is slid over on the piston pin away from the crank pin you're trying to slide the bottom of the rod on.

Steve Ball

 

[Rob Pols]

I think te conrod is not right in position.
Looking from this side you have to see the lubrication hole of the conrod.
Also the countersank side of the bronze bearing must be faced towards the crank because of the radius of the crankpin.

 

[David Murany]

Its definitely backwards in the photo. Piston skirt goes towards the exhaust and oil hole faces toward the incoming fuel/air.

 

[Richard Hartley]

I think te conrod is not right in position.
Looking from this side you have to see the lubrication hole of the conrod.
Also the countersank side of the bronze bearing must be faced towards the crank because of the radius of the crankpin.

According to my just opened new motor this picture is correct