Cam timing Mod with 331 BB kit.
 

Guys ,
Quick question.
Is it worth doing the KLX 250 ( 300 ) camshaft mod by Marcelino
With the 331 big bore kit ?

Cheers
George

Oh no, not again.. lol

To repeat myself - If it turns out that the stock ports, valves, cams, (and perhaps CVK) all combine to "choke off" a BB way before redline (say 8k and up) - and even a full exhaust and lidless setup can't bring the top end "alive", then IMO, you might as well do the MCM after verifying that your BB maintains stock valve-to-piston clearances - we already know the 351 kit does and works just fine with the MCM..

In this scenario, the MCM would further "kill" top end power levels over 6.5-7k but enhance TRQ below that.. The enhancement would likely be fairly radical - if fueled correctly - and create freakish power from idle to around 7K with likely a quick tapering off of power above that..

Hopefully soon, we will start accumulating data on BB's (dyno charts), to make better determinations about such things..

Until then, IMO, the best overall power curves are probably going to be lidless setup+full performance exhaust without MCM. The stock cam timings make top end power - which probably helps a BB to extend it's "brutality" some into the upper ranges..

Thank you for your help, Yes i did read the posts about the valve clearance worries on the 351, but i didnt hear anything about the 331. Any way , i am going to continue the build with standard timing for now. My head was ported and larger intake valves fitted by Bill Blue. so perhaps the restriction would be less. I am going to check the valve clearances in 5000km so will decide then whether to try the MCM. Thanks again and sorry if you had to repeat yourself.
Much appreciated.

No problem..

The 351 kit has been run with the MCM by two members. One ran it hard (revving up to redline) before deciding to go back to standard. He was running stock intake and exhaust and wanted to try to get more top end..lol

He realized the MCM didn't help with that..

Actually none of this (using the MCM) applies to your ported/big valved heads + 331..
You should be set for biggy power everywhere with standard timings..

I wouldn't bother, mid range power is fine with the 330, the top end(over 8k) needs more attention than the mid range. Your ported head should work really well. How much is Bill charging for those?

Complete rebuild with bigger inlet valves and porting $750.

My 2nd hand head was $400 ,
Import fees and shipping .

Total has cost me around $1500. (just for the head)

I have spent alot on the bike as you cannot really buy anything bigger than a 250 here in Indonesia. There is a luxury Tax on anything above 250cc (300%)

Makes big bikes crazy price.

I just hope the Juice box can supply enough fuel to it.

Fingers crossed. (This may be the next battle to come across)