My Beta has an engine knock when going up steep hills,also seems to be a bit down on power. Would a top end rebuild be the answer to this problem. If so can anyone advise how much this would cost if .I took it to a bike shop. .I live in the North East,any good bike shops that would be recommended. Thanks.

Edited February 7, 201115 yr by stephen1967

Hi

you dont say how old your bike is? or if the problem is a sudden one or has developed over time / getting worse?

engine knock under load likely to be 1 of 2 causes:-

1. Pre-ignition (pinking) under heavy load
   
2. Piston Rattle (however this is mostly heard under no-load at idle)
   

Its worth looking at the pre-ignition side of things before launching into a top-end rebuild

• Ignition timing... has it moved or been moved
  
• coked up plug, wrong plug, coked piston or blocked/coked exhaust
  
• overheating due to low water, damaged water pump, faulty fan, leaking cyl head joint etc.
  
• overheating due to running weak, blocked jet/s, check the plug colour, clean the carb, blast with compressed air
  
• Air leak somewhere at the inlet... usualy indicated by poor idling / slow to return to idle
  
• damaged reeds (difficult to start?)
  

Another thing to check before top end rebuild is the cranking compression.

I dont know the healthy compression for your bike, but i suspect it will be 150 - 200psi.

This is really easy to do, and a good trick for checking ring wear is to put a little (1-2ml) neat 2 stroke oil down the plug hole and re-check.

If the compression goes up enourmously (it is normal for it to go up 10-15%) its likely rings.

If none of this is conclusive.. its barrel off time

Good luck

Engine knock under load is usually a low grade fuel problem. Beta's like octane since they have rather high compression ratios. If the bike has seen over four years on a set of rings a new set will liven it up but will raise the compression making the the knock worse if it's fuel. Get you hands on some race gas if you can and see how it runs on the good stuff first. Don't trust the octane numbers on the fuel pump at the local station as they are often far from the truth.

The bike is a 2005 model and the problem has been getting progressively worse. I forgot to mention in my original post the compression when kicking over is really high and makes starting really hard as i am never sure when the kick -start will "bite". Is there a cure for high compression ?. Thanks.

please check your timing first befor doing anything else