Whe i bought my bike about 2 months ago, when i bought the bike (rev3 250) it was piston knocking so i de-coked the piston etc, I reduced it by loads but it has started knocking again!

I have noticed the carbon is back, But im sure it shouldnt be this bad only 2 months later?!?!?

What could be the cause???

that looks wet rather than carboned up. the carbon would be like charcoal that you can scrape off with a plastic ruler or a credit card.what does the insid eof the cylinder head look like is it dry or wet

if you say its knocking i suppose you mean like someones tapping the top of the piston with a hammer as you roll off the gas and the revs go down to idle then it should just need leaning off . what does the plug look like. is it dry or wet

Edited May 31, 200917 yr by totalshell

that looks wet rather than carboned up. the carbon would be like charcoal that you can scrape off with a plastic ruler or a credit card.what does the insid eof the cylinder head look like is it dry or wet

if you say its knocking i suppose you mean like someones tapping the top of the piston with a hammer as you roll off the gas and the revs go down to idle then it should just need leaning off . what does the plug look like. is it dry or wet

is that clockwise on the mixture screw thngy? lol

I honestly don't have a lot of experience with trials bikes and was hoping that someone would respond to your listing - but I have 35 years of experience with chainsaws and motocross bikes and I really don't think the carbon deposit looks unusual and is pretty typical - I suspect the droplets are just coolant leaked out when the head was taken off. I really don't see that you need to keep taking your head off to decarbon the piston and cylinder head......you are going to wear yourself out taking the engine apart to keep the carbon off as it happens quickly in a two cycle engine. There should not be an interference between the piston and head with the small amount of carbon build up on the piston.

Are you using a good full synthetic oil mixed at the recommended ratio? I don't know about your Beta - my Sherco is mixed at 80:1. Find someone that is familiar with your bike and see if your bike knocks louder than theirs......maybe it is time for you to get a piston or rings if the knocking is caused by excessive clearance between the piston and cylinder.

I honestly don't have a lot of experience with trials bikes and was hoping that someone would respond to your listing - but I have 35 years of experience with chainsaws and motocross bikes and I really don't think the carbon deposit looks unusual and is pretty typical - I suspect the droplets are just coolant leaked out when the head was taken off. I really don't see that you need to keep taking your head off to decarbon the piston and cylinder head......you are going to wear yourself out taking the engine apart to keep the carbon off as it happens quickly in a two cycle engine. There should not be an interference between the piston and head with the small amount of carbon build up on the piston.

Are you using a good full synthetic oil mixed at the recommended ratio? I don't know about your Beta - my Sherco is mixed at 80:1. Find someone that is familiar with your bike and see if your bike knocks louder than theirs......maybe it is time for you to get a piston or rings if the knocking is caused by excessive clearance between the piston and cylinder.

Took the head off a Rotax engine which had been run 32:1 for decades, virtually no carbon build up !

is that clockwise on the mixture screw thngy? lol

Further in the screw the richer your mixture, screw it all the way in then back out 1.5 turns max. Use a good oil Rock Oil/Putoline/Repsol, 70cc per 5 litres of unleaded, don't use superunleaded. Suggest you use a BPR5ES plug, should be a light sandy brown colour when your mixture is spot on. (black and oily it's too rich, white deposits generally suggest too lean)