Stroker vs Big Bore???


New Member
Jul 27, 2007
Auburn, New York
I'm curious as to see what people prefer, a Stroker kit or a Big Bore kit. I'd like anyone to list the pros and cons of them if they can. Also anyone with any experience running either are welcomed to comment as to which one they think I should get. But mind you I want to be able to run my Blaster on no more than 93 Pump gas NOT RACE FUEL.

As it stands I'm kinda looking into getting a Vito's 240 Big Bore kit so if anyone has any experience with it, feedback on it would also be much appreciated. I know the CT 240 kit is better but its just so much more money...
The vito's piston is nothin but sh*t, if you get the vito's 240 kit go with a wisecos 72mm piston. An by the way there is a cheaper solution to almost doubeling your HP instead of a 240BBK, it's called having the stock cylinder ported.

An if your going to have a stroker put in then you will need to have it ported to match the stroke.
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yeah, like blaster freak and me said the vitos are sh*t they overheat and melt so do yourself a favor get a wiseco they are the best hands down!
So is Vito's Big Bore kit worth buying, and using with a weisco piston???

Or should I just keep it stock bore with porting???

And do u have any knowledge/experience with a stroker???
Hi Master_Blaster, I see you’re in a dilemma about what to do. I’ll try to offer some advice. There are several problems with an oversized sleeve and piston in a stock barrel. When a barrel is bored to accept an oversized sleeve, the ports are cut and the timing is slightly changed (can be for better or worse, depending on the engine). The exhaust port in particular is changed because it is angled downward, and it is nearly impossible to move the exhaust port high enough to regain the port timing of the original engine. You can try using a base spacer and additional gasket, but the top of the barrel may have to be decked, depending on how much you raise the barrel.
An exceptionally large piston causes more heat to be built up in the engine especially at higher revs because of the swept area it gets in an undersized barrel. This can cause problems with the Blaster because it is an air-cooled engine. The larger piston also weighs more, and this causes slower revs, and it limits maximum revs as well. Also, on some two-strokes with small crankcases, increasing displacement can be bad news at high rpms. This is because there isn’t enough crankcase volume to effectively fill the cylinder, and this can cause the mixture to lean out and power to be lost.

But on the positive note, oversized pistons in the stock sleeve can yield neat results without the lost port timing of the big-bore. As horsepower is a function of piston area, more power output can be seen by boring out the stock sleeve and fitting the corresponding oversized piston. Just make sure to properly bevel the port windows when doing this, or the ports will act like scrapers to remove oil; the result, the new piston rings won’t last very long.

On a side note, the stock Blaster cylinder head is in a VERY mild state of tune. The squish band clearance is too loose to be of help. If you’re looking for some cheap horsepower, you can mill the head slightly to lower the squish band and put more mixture where it can be burned. If you have a shop do the barrel porting, make sure they give some thought to the cylinder head. If the shop knows what they’re doing, you can tell them what kind of riding you do, and they can cut a head and modify the barrel (if necessary) for the correct squish velocity. Just make sure they work on two-strokes and have enough experience to do this type of work.

Time for stoker engines. I think these can be best explained, with the advantages and disadvantages by reading this article from Group K It’s a little long and slightly dated with a focus on watercraft, but the theories and issues they faced are very real.

So I guess in the end, 01blaster_freak has a very good solution; porting on the stock barrel and removing casting flaws definitely helps output. A tuned/aftermarket expansion chamber and silencer work with porting to help output as well. If you’re interested in doing your own porting you can follow what the great Rick MacDizzy did here He really gets into the porting on Parts 6 and 8. Hope I’ve helped.
Basically if your going to run a big bore kit you need crank upgrades. I've found that the best crank with a 240 kit is a long rod, not a stroker crank. However people love the stroker crank because you tend to get power you didn't know you had. But in the end the cylinder starves for oil because of the side load from the piston is very great and just tears the cylinder up. Very strong and give you a longer stroke for low end power and once the big piston gets moving horsepower kicks in. A lot of people buy the 240 and just slap it on. To be honest without the upgrades your wasting your money because the engine is going to get tired real fast. There are pro's and con's to everything. You should follow blaster freaks advice if your on a budget because and get porting mods done. With porting mods you will be able to run a bigger carburator as well and we all know more fuel is more power as long as it has a path in and out of the cylinder. You will be surprised at a stage three port on a stock cylinder low 30's for hp. And have the head milled and run a blend of race fuel. I know you said you wanted to run 93octane but higher compression engines tend to put out more power and they need stable fuel with a higher octane rating.
so since i have a big bore kit is there something i have to do with it like porting
um well i bought the blaster already bored but the guy teaches deisel at the local vocational school and knows about engines ... the engine is being rebuilt right now so im gonna check the piston size what is the stock diam?
I beleive stock is 66mm. But If I'm wrong someone will let me know. I know my blaster has a 71mm. which would be equal to a stock cylinder bored
.200 over (bored 200 over). Some people say they don't make a piston that big for a blaster but if anyone don't beleive me I'll show you the paper work.
kk thanks did you know the amount of 0's behind the number2 doesnt matter unless it is before it? like .2=.20=.200=.2000 but .2 does not equal .02 and .002 and soo on just fyi
Yes I know that. I have a masters degree in Automotive technology. But when you refer to boreing and honing it is always refered to as thousandths, which is .000 . Did you know that? smart ass!
what BBK did you get? if you got a vito's there porting sucks i would deff rec. sending it to someone who can actually port.
sorry roccdeezy my bad yea i didnt know that wasnt trying to be a "smartass". well you learn something everyday