Ok I have done some searching and if there is a post that I missed feel free to link it.

Ok I have some overtime money coming to me and I am thinking of pulling the trigger on the big bore. Now out of the 4 different sizes I can go with is there any disadvantages or anything. I want to go right to the 351 kit but I don't know if that is a good idea because of the thought of once you go to the max you got know where to go from there. And possible too much stress to the motor? Or maybe a heat factor? I don't know.
Also am I crazy to do this with me only having 2500kms on the bike. Seems wrong to tear a new motor apart. And should I send BB my cylinder to get done since it is so new or one he could send me just be the same anyway?

For the very little price difference between the kits 351 sounds good but I don't want to take away from the reliability of the bike either. Like I said it is brand new. Is there anything else I need to get to go along with the kit? I already have the stage 2 jet kit in there with a stock header and a fmf powercore4 slip on. Do I have to rejet again?

Any info would be great from the guys that have had these different kits installed for awhile. And agin sorry if this was covered in another post I know there is allot of them on here about the 351

 

I only had 1500 miles on mine when I did it. I don't think there is really much difference between the 331, 340 or 351. Obviously you will get a little more torque with each size you go up. The 300 and 331 don't get into the water jackets while the 340 and 351 do. I have had mine hill climbing up the side of a mountain in 98 degree heat and the worst that happened is the fans came on for a minute.

Also it is just a sleeve in the cylinder so if it ever does wear out, you could be BB or any machine shop to just re-sleeve it.

Leave the jetting as you have it now, it will most likely be pretty close. The big bore actually doesn't change it all that much. Then adjust it out if it is too lean or anything.

I have 2000 miles on my big bore and it runs great. One of the members here has like 17k on his big bore.

No regrets yet

 

Great good to know. What is the water jacket exactly? This stuff is kinda new to me.

 

I had 2,500klms on mine when I installed the 351cc. I have only put a few hundred klms on the big bore but so far all good.

I have had to play around with the jetting a little but im running a pumper and I would say that the standard CVK would be much easier.

Water jacket is the area around the cylinder where the coolant circulates to keep the temperature consistent. The 300 & 331 kits have "meat" around the sleeve where as the 340 & 351cc kits the sleeve is bored out into the water jacket. There has been lots of debate on the pros and cons of this but I haven’t seen any proof that there is any problems with the wet sleeve.

Install is pretty simple but if your not mechanically minded or if you don’t know much about motors I would recommend that you get it professionally installed.

 

this is also my next project...it would be helpful to get more information...i already have a jet kit, but i would like just a little more power...331 kit be more reliable and durable than a 351 kit?...would spending money to upgrade a carburetor greatly help the bike?...i was quoted $650 for a new carburetor upgrade and installation...

 

331 kit be more reliable and durable than a 351 kit?...would spending money to upgrade a carburetor greatly help the bike?

Ya exactly??

 

I ride when it is well over 100 degrees. How's 112+ sound? That's why I went with the 331...the water jacket is still intact. HOWEVER, I sincerely doubt Mr. Blue's 351 would have problems in this kind of heat, even though it is a "wet sleeve". I just am being extra-cautious in my decision to stop at 331...the largest "dry sleeve" that he makes.

Stock carb does fine with rejetting. See my signature for what my setup is. The pumper-carb guys love their setups, so, depending upon how deep your pockets are, or how NOT deep they are, make your choices! I don't think you'll go wrong no matter what you choose.

 

I would upgrade to the big bore 1st, before the carb. if money was an option. If you bought a jet kit already then you have the stuff you'll need if any. If you need more get a nice pumper and see what you can do.

 

I've been looking at this for a while, a couple of things are making me wait before I jump.
As mentioned, 300 and 331 don't break into the water jacket, 340 and 351 do. Now this may not be an issue, and I for one would not like to suggest otherwise.
As blackheart said, from a caution point, he stuck to 331.
Another thing that struck me is that in Japan (where I live), the largest kit I can find is 315cc, that made me wonder, the bike is designed here right? Japan is not short of engine tuning wiz-kids.... so why nothing larger than 315?
Then of course we get to the concept of the combustion engine, air in, air out. Sure a big bore will have a great effect, but when is it too much? 40% extra capacity with no work to the cylinder head to compensate? Full benefit for a big capacity increase would need bigger valves and p&p at least, IMO.
I would like to see power comparisons with the 4 sizes available, I'm inclined to think that there will be little difference between them, especially the bigger you go.
My opinion of course....

 

Some very good points here. That is strange you can't get a kit over 315 in Japan. I'm still up in the air on what to do. I want more power but.......? Hate to push reliability. Need to think some more on this I guess.