Dax Balanced lower...?

This bottom end is the foundation for the strongest engine I have or have had, if you. Lost power Im gonna say you have something going on besides the lower.

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I had a solid running pk80 on the bike, pulling crazy rpms, the vibrations were hard to handle so I picked up the dax bottom end and now the bike hardly runs. All the other parts were swapped over, do all fingers point to the magnet? The plug wire was also swapped but the same coil was used?
 
Hard to pin point anything without more details other than it hardly runs.

Does it not hardly start?

Does it not hardly take off because it boggs down?

Does it hardly rev up?

Does it just have a lower top speed?

Remember the engine needs some miles on it to loosen up and get settled in also, " breakin "

Not sure that I can be of help but some of us may be able to point you better to some possibilities if we have some better detail on exactly what you mean by "it hardly runs".

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.wee.
 
I don't know what the stroke of the pk80 is but does the piston travel all the way to the top of the cylinder? Or it could be compression related, I would check to make sure it didn't break a ring.
 
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Greg58 said:
I don't know what the stroke of the pk80 is but does the piston travel all the way to the top of the cylinder? Or it could be compression related, I would check to make sure it didn't break a ring.
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I acttually thought about that also, the PK80 is a 40mm stroke if I remember right, the grube engines are a 38mm stroke im pretty sure.
I deff. Think it may be a good idea to make sure the piston is reaching correct TDC
 
When I say hardly runs. It won't idle at lower rpms, under 4k. It takes a lot more peddling to get started. I lost about 1500 rpms off the top speed and the torque is a lot less, small hills are now a big problem. While running it seems to be missing . The bike was pulling 9500 rpms 40+ mph. I'm not new to this by any means, I'm just stumped by what the issue could be. Thanks.
 
No problem we were just starting with the basics, the magnet is probably the last thing that could fail in my opinion. I would make sure the carburetor was OK and check the compression to start. Also if the pk80 was vibrating as you said the solders on the coil would be suspect also.
 
TwistedAlloy68 said:
When I say hardly runs. It won't idle at lower rpms, under 4k. It takes a lot more peddling to get started. I lost about 1500 rpms off the top speed and the torque is a lot less, small hills are now a big problem. While running it seems to be missing . The bike was pulling 9500 rpms 40+ mph. I'm not new to this by any means, I'm just stumped by what the issue could be. Thanks.
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No offense intended bro, Im not new either and I can tell you your problem is likely nothing to do with the engine lower.

Best wishes and Im curious to know what you find to be the problem.

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dnut
 
No offense taken. Miss interpretations are easy with text. Some more background on the bottom is it showed up with the studs busted off the front. Is that anything a hard hit could throw out I'm not thinking of? I noticed the crank is skinnier than the old one could crankcase pressure have anything to do with it? I know it's not the stroke. I appreciate the help I will post what is going on once I find out.
 
On my f-80 bottom end with the PK-80 top end, the jug has been decked by about 1 mm- This minor alteration will allow you to maintain proper squish clearance whether you are running one or two base gaskets.
 
Something i noticed on my GenIV dax lowers is that the transfer port ramp areas are smaller than on some of my other engines, if you had a pk80 with the larger ramps in the csae there could be a slightly less flow capacity and that could account for some power and speed loss possibly, on mine I did not enlarge those areas and I have had mine rev to 9400+ rpm.

If all the components from the other engine are still in top shape and the tune is good all I can think of that could causing your issue is flow restriction or lower compression.

Map
 
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