I’m out too

[scott bockingMember]

Trailboss wrote:

Quote:

Ollie wrote:

Quote:

did you get hold of the guy selling the bigbore kit scotty?

I wouldn’t do it Scott. And I can give you a long list of reasons why all with example cases. The gains dont out way the benefits. Seen , done it paid for it

TB

Is it a bad thing?

[GregMember]

I have had a XR250 go for two none stop seasons the next one fitted from new a 280 kit and it failed a little end twice

Bana’s DR destroyed a little end brg in a season

They are just two examples there are many more

You see a conrod and its respective brgs, crank, head bolts, head gaskets etc are all designed for work with a set weight reciprocating around the engine creating set stresses throughout the engine. When you increase the loads within the engine you decrease the reliability because of the extra stress within the engine

Forget all the emotion that this topic will create. I do this stuff for a living the above about extra engine stress for a component not designed for it is fact.

The gains aren’t that great, practice braking later good suspension good tyres will have a large nett gain on your riding then a big bore kit

PM me a land line number and a time you can talk and I will share what has happened to me and what I have seen with others

TB

[DavidMember]

Trailboss wrote:

Quote:

I have had a XR250 go for two none stop seasons the next one fitted from new a 280 kit and it failed a little end twice

Bana’s DR destroyed a little end brg in a season

They are just two examples there are many more

You see a conrod and its respective brgs, crank, head bolts, head gaskets etc are all designed for work with a set weight reciprocating around the engine creating set stresses throughout the engine. When you increase the loads within the engine you decrease the reliability because of the extra stress within the engineTRUE THAT

Forget all the emotion that this topic will create. I do this stuff for a living the above about extra engine stress for a component not designed for it is fact.

The gains aren’t that great, practice braking later good suspension good tyres will have a large nett gain on your riding then a big bore kit AND TRUE THAT TOO, DO BOTH AND ALL IS EVEN BETTER

PM me a land line number and a time you can talk and I will share what has happened to me and what I have seen with others

TB

[GregMember]

Oh and before rat goes bezerk about my statement I wont get into an argument here about it. I have some facts and figures about the stress on components for over size bores I can sent you Scott

TB

[DavidMember]

Trailboss wrote:

Quote:

Oh and before rat goes bezerk about my statement I wont get into an argument here about it. I have some facts and figures about the stress on components for over size bores I can sent you Scott

TB

Settle Petal , I was agreeing with you ya Dag

[DavidMember]

Trailboss wrote:

Quote:

Oh and before rat goes bezerk about my statement I wont get into an argument here about it. I have some facts and figures about the stress on components for over size bores I can sent you Scott

TB

You also know Friday is Berserker Day….we are safe now :laugh: :laugh: :laugh:

[DeanMember]

look out all you Husky 310 and KTM 280/350 :laugh: pilots Guess you will have to get a 300 2 stroke Scotty for those Hills :laugh:

IMHO if I had a 250cc 4 stroke one of the first things I would do would be the bigbore Kit

Ollie

[scott bockingMember]

Trailboss wrote:

Quote:

Oh and before rat goes bezerk about my statement I wont get into an argument here about it. I have some facts and figures about the stress on components for over size bores I can sent you Scott

TB

Cheers for the info TB. I was not in the market for a big bore kit but Ollie put me on to what is a good deal. In light of this info I will leave my bike stock. I have got it pretty well dialled right now and I don’t want to chance engine issues for a few extra cubes. Maybe I will start using 5th :laugh:

[drewMember]

if you’re still in the market for an up grade,

you can trade in on a Kwaka KV100,

and for your gear i’ll offer you

a 1.25L coke,

choc wedge

and a bag of natural confectionary party animals

and a Plane fare home

[Bruce CurtisMember]

TB and rat are right about more reciprocating weight, but I ave had some experience on Roadies using lightweight pistons, and while the sub-piston components do have to deal with higher combustion pressures I have found that if you have an over-engineered bottom end and rod kit the benefits are well worth it on certain powerplants.

Not arguing with the lads as I believe the 250/4Ts are pretty highly stressed to begin with leaving little margin for increased strain on internals.

Eric Gorr out of the states does some good complete big bore kits that take into account all of the issues with just upgrading the topend alone, not sure if he does many 4Ts though.

BC

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