Ok, I know the topic of big-bore kits has been discussed and brought up almost as often as jetting questions on here. But that said, I got curious (and a little suspicious) when seeing a couple "new" BBK listings on ebay. So I did a little homework.
We all know that Vito's Performance and LA Sleeve offer viable 240 big-bore kits for the Blaster engine, but this company, Parts Depot ATV, is a new one on me.
Here is their 240cc listing:
Blaster 240cc 72mm Big Bore Kit Sleeve Piston Triple Port Cylinder Head Wossner | eBay
This kit is honest. You send in your cylinder and head to be re-sleeved and modified, and they send you back a ready-to-bolt-on-and-run top end. Simple enough. Ken O Connor Racing and many others have built their own version of this kit, and it seems reliable and effective.
This is the listing which got me suspicious. It is for a "260cc" 4mil stroker kit.
Blaster YFS200 72mm 260cc Ported +4mm Hotrods Hot Rods Big Bore Stroker Kit | eBay
First of all, the formula for calculating the displacement of any engine is: (Bore x Bore) x .7854 x Stroke x # of Cylinders. (The .7854 constant is obtained by dividing pi by 4.)
Therefore, when applying this formula to a stock Blaster engine with a 66mm Bore x 57mm stroke, you simply plug in numbers and do the calculations. Be sure to convert mm to cm before multiplying.
(6.6 x 6.6) x .7854 x 5.7 x 1
=
43.56 x .7854 x 5.7 x 1
=
195.00 cc
There ya go! You end up with the known-factual 195cc displacement of a stock Blaster engine. Now that we know the formula works, let's plug in the numbers of Parts Depot's "260cc" kit and see what we get!
(7.2 x 7.2) x .7854 x (5.7 + .4) x 1
=
51.84 x .7854 x 6.1 x 1
=
248.36 cc
Oops! We're just a LITTLE short there!
This "260cc" kit is a lie! With a 72mm piston and a 4mil stroker Hot Rods crankshaft installed, you come up 12cc short of a fulll 260cc kit. Plus, nowhere in the listing does it mention Parts Depot installing the 4mil crank. Apparently, you are on your own when it comes to trenching your cases and installing the crankshaft. All Parts Depot wants is your old cylinder and head for the sleeve mod. They claim "no other work is needed" for this kit to bolt up!
Parts Depot also offers a resurrected version of Trinity's old 265cc kit which used to be floating around. This is the same size kit that HJR successfully ran on a dune Blaster for years before somebody blew it up. Here's their 265cc kit:
Blaster 265cc 75mm Big Bore Kit Sleeve Piston Triple Port Cylinder Head Wossner | eBay
Lets do a little more math and see how this kit measures up.
This "265cc" kit comes with a 75mm piston and sleeve set (thats a helluva big sleeve to stuff into a stock cylinder IMO). While Parts Depot does mention the need for your bottom end (cases) to be bored to accept the large sleeve, this 265cc kit does NOT come with a stroker crank. They offer the 4 mil crank, of course, but it costs extra.
SO, figuring out this kit just as Parts Depot has it listed:
(7.5 x 7.5) x .7854 x 5.7 x 1
=
56.25 x .7854 x 5.7 x 1
=
251.82 cc
Uh, oh! About 14cc short of a full kit! X(
Let's assume, for a moment, that you've already got a Vito's 3mm stroker kit installed or on order for your build. Let's re-calculate, figuring in the 3mm stroker crank.
(7.5 x 7.5) x .7854 x (5.7 + .3) x 1
=
56.25 x .7854 x 6 x 1
=
265.07 cc
Bingo! There's your 265cc kit! BUT, you'll need a 75mm piston and at least a 3mm stroker crankshaft to get there. And I bet a piston that big runs rather hot, especially sitting in a stock cylinder housing.
The math doesn't lie. People will claim anything to try and sell a part. Buyer beware. I:I
We all know that Vito's Performance and LA Sleeve offer viable 240 big-bore kits for the Blaster engine, but this company, Parts Depot ATV, is a new one on me.
Here is their 240cc listing:
Blaster 240cc 72mm Big Bore Kit Sleeve Piston Triple Port Cylinder Head Wossner | eBay
This kit is honest. You send in your cylinder and head to be re-sleeved and modified, and they send you back a ready-to-bolt-on-and-run top end. Simple enough. Ken O Connor Racing and many others have built their own version of this kit, and it seems reliable and effective.
This is the listing which got me suspicious. It is for a "260cc" 4mil stroker kit.
Blaster YFS200 72mm 260cc Ported +4mm Hotrods Hot Rods Big Bore Stroker Kit | eBay
First of all, the formula for calculating the displacement of any engine is: (Bore x Bore) x .7854 x Stroke x # of Cylinders. (The .7854 constant is obtained by dividing pi by 4.)
Therefore, when applying this formula to a stock Blaster engine with a 66mm Bore x 57mm stroke, you simply plug in numbers and do the calculations. Be sure to convert mm to cm before multiplying.
(6.6 x 6.6) x .7854 x 5.7 x 1
=
43.56 x .7854 x 5.7 x 1
=
195.00 cc
There ya go! You end up with the known-factual 195cc displacement of a stock Blaster engine. Now that we know the formula works, let's plug in the numbers of Parts Depot's "260cc" kit and see what we get!
(7.2 x 7.2) x .7854 x (5.7 + .4) x 1
=
51.84 x .7854 x 6.1 x 1
=
248.36 cc
Oops! We're just a LITTLE short there!
This "260cc" kit is a lie! With a 72mm piston and a 4mil stroker Hot Rods crankshaft installed, you come up 12cc short of a fulll 260cc kit. Plus, nowhere in the listing does it mention Parts Depot installing the 4mil crank. Apparently, you are on your own when it comes to trenching your cases and installing the crankshaft. All Parts Depot wants is your old cylinder and head for the sleeve mod. They claim "no other work is needed" for this kit to bolt up!
Parts Depot also offers a resurrected version of Trinity's old 265cc kit which used to be floating around. This is the same size kit that HJR successfully ran on a dune Blaster for years before somebody blew it up. Here's their 265cc kit:
Blaster 265cc 75mm Big Bore Kit Sleeve Piston Triple Port Cylinder Head Wossner | eBay
Lets do a little more math and see how this kit measures up.
This "265cc" kit comes with a 75mm piston and sleeve set (thats a helluva big sleeve to stuff into a stock cylinder IMO). While Parts Depot does mention the need for your bottom end (cases) to be bored to accept the large sleeve, this 265cc kit does NOT come with a stroker crank. They offer the 4 mil crank, of course, but it costs extra.
SO, figuring out this kit just as Parts Depot has it listed:
(7.5 x 7.5) x .7854 x 5.7 x 1
=
56.25 x .7854 x 5.7 x 1
=
251.82 cc
Uh, oh! About 14cc short of a full kit! X(
Let's assume, for a moment, that you've already got a Vito's 3mm stroker kit installed or on order for your build. Let's re-calculate, figuring in the 3mm stroker crank.
(7.5 x 7.5) x .7854 x (5.7 + .3) x 1
=
56.25 x .7854 x 6 x 1
=
265.07 cc
Bingo! There's your 265cc kit! BUT, you'll need a 75mm piston and at least a 3mm stroker crankshaft to get there. And I bet a piston that big runs rather hot, especially sitting in a stock cylinder housing.
The math doesn't lie. People will claim anything to try and sell a part. Buyer beware. I:I
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