Blackmagic engines

[snowprozr]

I have an 2001 Arctic Cat, ZR. It originally came from Quebec and was raced in the snow cross league there. Not bad shape with all things concidered, When I ran the serial number it comes up as a 440zr snowpro but there has been some mods done before I got my hands on it. The engine's top end is Blackmagic if not the entire engine. It has plenty of power and has me wondering about the displacement. Is it a 440 or not?? Compression test last year revealed 185 and 190psi a side. Also I am having to run VP-116 which can get costly. I am not sure when i should pull the top end off to check for wear and what parts are still available for Blackmagic engine mods?? Any sugestions??

 

[raustincat]

185 and 190 psi eh... wow thats a boat load of compression but be a good yank to get it running. yea running race gas gets $$$ if ur just ditch banging it... i would pull the heads off take a look around measure it see what kind of displacement it is... just so u know... u could also look for some wear and tear on the top end... doesn't take much work to take a gander in there... my guess is that it is still a 440 just running wicked high compression and pushing the same hp as maybe a 700 would... just my guess... update us on what u do/find.

 

[snowprozr]

You bet it does take a good yank to fire it up!! Especiallywhen its 20 below!! Had it in Echco Cycle they did the compression test for me and relayed the numbers...thought they were a bit high but I am not a mechanic.
Had it out in Vale this past spring and it ran/hooked up well for a 136" trac. We are going up in December to see how it handles in real snow not the "Hero" snow from the spring trips. Thanks for the tips!!

 

[Modman]

I have an 2001 Arctic Cat, ZR. It originally came from Quebec and was raced in the snow cross league there. Not bad shape with all things concidered, When I ran the serial number it comes up as a 440zr snowpro but there has been some mods done before I got my hands on it. The engine's top end is Blackmagic if not the entire engine. It has plenty of power and has me wondering about the displacement. Is it a 440 or not?? Compression test last year revealed 185 and 190psi a side. Also I am having to run VP-116 which can get costly. I am not sure when i should pull the top end off to check for wear and what parts are still available for Blackmagic engine mods?? Any sugestions??

Running 116 with that high compression I would be checking that thing at least every few rides to ensure all parts and pieces are still where they should be. Measure bore when you have the head off and if you know the stroke or can measure the stroke then it is a simple calc to determine the displacement. Black Magic is no longer in business, the only parts available will likely be on Ebay, etc. Very well could be a 660 kit or something to that effect on the 440 bottom end.

 

[snowprozr]

185 and 190 psi eh... wow thats a boat load of compression but be a good yank to get it running. yea running race gas gets $$$ if ur just ditch banging it... i would pull the heads off take a look around measure it see what kind of displacement it is... just so u know... u could also look for some wear and tear on the top end... doesn't take much work to take a gander in there... my guess is that it is still a 440 just running wicked high compression and pushing the same hp as maybe a 700 would... just my guess... update us on what u do/find.

Well I pulled off the head last night and to me the cylinder walls look fine. I have attached some pic's. However i am not sure how to measure the displacement. Is there a easy way to do this?

 

[Modman]

Formula for displacement is

{(3.1416 X (bore diameter squared [^2] X stroke)/4000)} X # of cylinders

Maybe looks hard, is really simple. Here's an example of a 80 mm bore and 78 mm stroke:
80 mm bore squared [^2] = 6,400

{(3.1416 X (80 mm [^2] X 78 mm)/4000)} X 2
{(3.1416 X (6400X 78 mm)/4000)} X 2

6400 times stroke (78 mm)
{(3.1416 X (6400 X 78 mm/4000)} X 2
equals
{(3.1416 X (499,200/4000)} X 2

Now multiply 499,200 by 3.1416
{ (3.1416 X 499,200 /4000)} X 2
equals
{ (1,568,286 /4000)} X 2

divided by 4000
{ (1,568,286/4000)} X 2
equals
{ (392.07)} X 2
times # of cylinders
392.07 X 2
equals
784 cc

Or you can save the 2 mins of calcs and download the displacement calculator at Wiseco's website:
Calculators - Wiseco Piston Inc.

 

[raustincat]

measure diameter of cylinder so from side to side on the inner wall of the cylinder and then measure from Top dead center to bottom dead center and that is the volume of displacement... measure in centimeters if possible... use one of those micrometer measureing devices.. they are really accurate.. then just plug it into teh formula...

V=Pi*r^2*h

so whatever you find your diameter to be divide it by 2 in order to get your radius= r

and Pi is a constant = 3.1415

for example if Diameter of cylinder is = 6.25 cm then r = 3.13 cm
h = 7 cm

then V = 3.1415*3.13*3.13*7
V = 215 cc

so this is the volume of one cylinder... yours is a twin so double it and you get ur engines displacement .... this example would be 430cc

most often the actual displacement is slightly less than what manufacturer actually calls it... 600 = 598 or 599 type thing.

Hope this helps!

 

[raustincat]

opps modman beat me to it! his looks more professional anyways! lol

 

[snowprozr]

Very cool, Thanks for all the formula help fella's!!

 

[snowprozr]

One last question...What do I measure to determine the "stroke" dimension??

 

[Modman]

Bore is the measurement across the cylinder, stroke is a measurement of the vertical distance travelled by the piston.

To measure bore you need a set of bore gauges or a micrometer. To measure stroke you can use a number of methods.

Honestly, for just finding the rough displacement of whether or not this is a 440, 580, 660, etc., you probably don't need to buy a bunch of fancy tools though IMO. Measure in millimeters with a decent steel ruler. For the stroke, you need to determine if the piston reaches zero deck height or above (flush with the top of the cylinder, below or above). If it protrudes above, then you will need to set an arbitrary height above the top of the piston dome. (Refer to the "fancy" picture I drew in Paint to see what I mean ). Put two blocks of the same size on the top of the cylinder on either side of the piston so that when you lay a straight edge across it, it crosses the cylinder over the middle of the piston. Rotate the piston until it reaches top dead center (TDC) and place your ruler against the top of the piston and the straightedge. Check the reading for where it starts (for this example say it starts at 13mm on the ruler). Then rotate the crank until the piston is all the way down in the bore and reaches bottom dead center (BDC). Check the reading on the ruler now (for this example say it reads 93 mm). You simply subtract the initial reading from the final reading and that is your stroke ( in this case 93-13 = 80mm).

This is not the finite way to do it but with a decent ruler it will give you an idea of what your stroke is and enable you to calculate the rough displacement and determine what cc your motor is.

 

[snowprozr]

Excellent advise Modman, the pistons are flat tops and don't protrude past the top of the cylinder wall so I shouldn't need to utilize the block method. TDC to BDC to a straight edge accross the top of the cylinder. Sounds great!! I'll let you know how I make out.
Thanks for the help and the diagram.

 

[sumx54]

Great posting Modman, very helpfull stuff for us dummies :d :d Rep for you

 

[Modman]

Great posting Modman, very helpfull stuff for us dummies :d :d Rep for you

No worries sumx54. Just trying to help some fellow sledders out. That's what the sport is all about, keeping it simple and economical so that we can all go out and rip it up on whatever is hiding in the garage!!! You'll see my latest project coming in the next week or so. Trying to show that anyone can do it with a little elbow grease and time even if they are on a budget. Just get out and enjoy the sport.

There's no such thing as a dumb question. We all learn something everyday!

 

[snowprozr]

After all is said and done and using everyones tips...I came up with a 84mm-Bore and a 62mm-stroke=687cc's. Sounds a little odd to me so I checked the dim's and calc'c 3 times!! Now all I have to figure out is how to get my rig on pump gas to save some $$$$ but not give up much power!!:d

 

[Modman]

Your math is correct.

You can try and contact them and see if they made a big bore kit


Or Echo Cycle out of Edmonton was a distributor for them, maybe they have the last catalogue sitting around that shows what big bores they made for the 440.

I see a 66.5mm bore and 63 mm stroke listed so I would think that you are close with the measurements. Hope you find the answers!!

 

[snowprozr]

Thanks for all your help Modman, it sure helps having some technical advise for a novice like myself to use. I enjoy pullin wrenches and learning about sleds plus it also save's some $$$$ that can be put towards a trip to the mountains!! Cheer's

 

[ackid]

No worries sumx54. Just trying to help some fellow sledders out. That's what the sport is all about, keeping it simple and economical so that we can all go out and rip it up on whatever is hiding in the garage!!! You'll see my latest project coming in the next week or so. Trying to show that anyone can do it with a little elbow grease and time even if they are on a budget. Just get out and enjoy the sport.

There's no such thing as a dumb question. We all learn something everyday!

would he be able to run stoke heads to lower the compresion? or will the bore size mess that up?

 

[Modman]

would he be able to run stoke heads to lower the compresion? or will the bore size mess that up?

Don't know. If they are custom Black Magic jugs and head then the stock head might not fit or have the same cooling flow/bolt holes etc. Yes lowering compression would help but why would you want too??? So long as he takes care of it and doesn't detonate it, it may run for years. I know nothing about the motor port timing, state of tune, etc., so I really can't comment on that, it might be a case of being stuck with running race gas but its not that bad, just have to watch the fuel consumption cuz you can't siphon from just anyone's gas tank to make the trail ride back to the truck. He might be able to raise the cylinders with a thicker base gasket to lower the compression a little but then that screws with your port timing, it might be something that a guy could live with, it might make the sled run like crap too.

Unfortunately not having a supplier to go to doesn't help either. I would still try and give BM a call, there might still be someone around there for whatever reason. Ebay might have some parts too or a hardcore Arctic Cat forum may have a few guys that might know some stuff.

 

[Modman]

Thanks for all your help Modman, it sure helps having some technical advise for a novice like myself to use. I enjoy pullin wrenches and learning about sleds plus it also save's some $$$$ that can be put towards a trip to the mountains!! Cheer's

No worries man. I'm no technical wizard, just a dumb backyard wrencher that was very fortunate to have a smart father that taught me lots and I have lots of smart people around me.