What is everyones take on better performance going to 331/340 displacement or going to 300cc and adding a set of aftermarket cams. I belive it would be cheaper to get a set of cams and a 300 jugthen to have the 300 jug bored out and replated.(I know that the bluebill sleeve is still probably cheaper than either). Just wondering if cams would be a better bang for the buck than full bigbore. The dyno graph that tremor posted with 300 and cams looked pretty good. I am really looking for good bottom and mid range as I don't really spend a lot of time a real high rpms, but I don't want it to fall flat on its face on the top end either.

 

Jeff,
If I had to choose between cams and big bore for bottom end grunt, I'd go with the big bore. Cams will compliment that improvement down the road if you want to do it and it's an easy next step to add them.
I've done both to my bike, using Web Cam Inc. When you do the cams, I'd use them for sure. Tell them I sent you.

Head work is also helpful. Luke Heaney at Luke's Racing ported my bike and lowered the compression ratio a bit. It was approaching 13/1 after boring, so he enlarged and cleaned up the combustion chamber some. It all works together to make a fine running bike.

Bill Dragoo
Norman, Oklahoma
KLX 331
FXDX, etc...

 

I'd have to agree with Bill. Big bore will give the most improvement to the bottom end.

 

+1 on what Shadetree wrote. If you are prioritizing, I would definitely go with large bore first. You could very well be satisfied with that mod alone.

As you go up in displacement, you will see the HP curve start to round off starting at about 8000-8500RPM.TheHP isstill increasingin that range but not like the uplugged KLX250whichhas a fairly linear curve. If you're mostly a trail rider, I wouldn't worry about it too much. It becomes an issue for motard guys who like to squeeze every ounce from the top-end revs. The difference is so small that I think we over-obsess with it sometimes.

I will beinstallinga 300cc kit withthe lighter than stock, Wiseco 292cc pistonas one of my winter mods and will be addingapair ofaftermarket cams to recover most of what is lost in the top end.I'm thinking the twomods will mesh together nicely.The camsspecifically target getting thetop end backafter you have installed a KLX250/D-tracker large bore kit.They are proven on the race circuits here in Japan. If you're interested,I canprovdethe grindnumbers to give to a company like web cams.


I know I sound like a broken record, but I recommend boring the 300cc jug and getting that nice, virtually no wear nikasil coating from Kustom-kraft vs the sleeve if you choose to gobeyond 300cc.

 

big bore it, no sleeve. use sprockets to target your sweet spot for power and save yourself a lot of money. from what I've read on here, no one has justified the investment for cams in the tiny KLX. this bike reacts to sprocket/gearing changes like crazy. I added the 13-tooth first thing and it was like a different bike. I then added a 45 to the 13 after I did all the mods including the full BigGun and it was again like a different bike.

 

Yep. When it comes to 'bang-for-the-buck.' the cams just don't compare with the added CC's. I would describesuch items as cams and different CDI'sas 'icing' fora cake that already pretty much stands onits own.

In theend, it all boilsdown toindividual preferences though, so I try to throw allof the optionsup there and letpeople make-up theirown mind.

 

I have the 300 Cylinder on my bike along with the Roesler Cam grind from Web cams (grind 101). They did open up the top end even better than stock which is hard to believe since even the stock KLX pulls nicely up top. However don't beleive Webcams when they say it increases power all over. You do lose some off the bottom which from your post is not what you are after. They do have a 293 grind which is supposed to pull low down.

However I'll join the others and say go with bore size increase over cams for your needs. Good luck.

 

Yeah, that's some pretty sensational advertising. Cams will either shift your power band up or down. It's the same advertising style they usefor some of the cams available in Japan. I actually had to make some phone calls with the grind numbers in hand when I looked at the Yoshimura cams.I found out theydidn't have enough intake/exhaust overlap, which results in the e-starter having to labor excessively without the ACR. I was fortunate enough to hear the e-start on aD-tracker with the Nassert cams and youcouldn't distinguish between those and the stock cams.

 

Does anyone know what the horsepower difference is between the 300 and the 331?

 

I think each step up gives you about 3.