Budget Big Bore 4mm Stroker

[robertg]

I just started building big bore 4mm stroker motor. I was going to send a 61X cylinder to Jetworks and let him do all the work but I think it will be more fun doing it myself.

So far this is what I have in to it:

New 4mm stroker crank, $411.00 plus $50.00 shipping
Northwest sleeve Big bore sleeves, $190.00
Wiseco 84mm pistons, $60.00
Machining the 61X cylinder casting to fit the sleeves, $90.00

I still have to get the cylinders bored and get custom domes made. I will update the cost when it is done.

I had the cylinder casting bored so the cylinders have a 0.005" interference fit and the sleeves are 0.005" above the deck surface. When I heated the cyl casting and dropped the sleeves in, I bolted a stock head on the cylinder. This way the sleeves couldn't move as they were cooling. i will have to get the cylinder decked also so the sleeves are flush with the casting. I can get that done for free.

With the Northwest sleeves the transfer ports are a lot lower then the 61X cylinder, and the exhaust is the same height. Every port is a lot wider also. With the stroker crank the exhaust port will open a few degrees earlier than stock and the transfers will be about the same. I have no Idea what kind of power it will have with this porting but I can allways get it ported later by someone who knows what they are doing. Hopefully it will have some decent bottom end, I'm sure it will be more than I need.

I am going to be using a Vilder ignition and aluminum flywheel, Novi 46mm carbs and V-force reeds. I am going to start with the B Limited chamber but I also have the mod, Blaster mod and a chamber that looks like a TNT.

I have the transfer ports 90% done but I havent touched the exhaust. I have to remove a lot of meat to make it match the sleeve.

 

[750SX]

where did you buy a new crank for 411?

 

[robertg]

where did you buy a new crank for 411?

I bought the crank and one of the pistons on eBay.

 

[#ZERO]

That looks like a nice project you have going. :biggrin:

Are you going to be using flat top pistons with your 4mil stroker?

 

[robertg]

That looks like a nice project you have going. :biggrin:

Are you going to be using flat top pistons with your 4mil stroker?

Just regular Wiseco pistons. It's not easy to find cheap flat tops and I think the porting has to be different for them.

 

[Matt_E]

Nice!!! I like seeing projects like these!
That's the kind of stuff I like & like doing myself. Thumbs up, I wish you good luck & will be checking this thread regularly.

Looking at your exhaust ports...where did you get the idea for the port shape? Are you using the Sport Port II template for that? (I ask because it has that shape.)

 

[sflsurfrider]

im guessing the nw sleeves are preported like that. he just has to do some matching

 

[Matt_E]

Upon further inspection, I appears I just don't look close enough.
I think you're right.

 

[#ZERO]

Hey Matt, here is a couple of pictures of those sleeves. :biggrin:

 

[Matt_E]

Thanks!

 

[#ZERO]

The reason I asked Robert if he was going to use flat top pistons is because of the information that they give you with these sleeves.

Also this will be a 4mil stroker engine so all this information will just be a starting point.

If these cylinders are to be used with Wiseco Kawasaki flat top pistons that are shorter than OEM pistons preparation for each will be as follows: for use in a flat top piston engine this cylinder sleeve will require machining approx. 2.5mm off the top cylinder deck and minor top edge port work to get the port timing where you want.

If these cylinders are to be used in an OEM dome style piston engine, the deck surface will only require light machining to match the sleeve tops to the deck surface. All transfers will need to be raised approx. 2.5mm (varies due to your desired port timing) and a supplied 1mm base gasket spacer plate installed.

 

[robertg]

I am pretty well done the porting on the cylinders. I just have to polish the exhaust ports and try to widen the transfer tunnels a bit more. I assembled it with some 83m pistons and checked the port timing with a degree wheel. The exhaust opens at 89 deg and the transfers open at 120-121 degrees. I might have to go with a thicker base gasket but I am not sure. The port timing is very close to stock 61X but the ports are a lot wider. Hopefully it will have good bottom end.

 

[Matt_E]

You'll have great port-time area while keeping stock timing. Nice!

 

[#ZERO]

Hey Robert, buy chance did you ever check the port timing on a stock 61x cylinder with the stock stroke?

From the picture it looks like you did a real good job matching the ports with the sleeves. :cool2:

 

[robertg]

Hey Robert, buy chance did you ever check the port timing on a stock 61x cylinder with the stock stroke?

From the picture it looks like you did a real good job matching the ports with the sleeves. :cool2:

I thought the transfers oponed at 120 degrees and according to this picture the exhaust opens at 90.48.

 

[#ZERO]

:bigeyes: Wow!... where in the world did you get all that information?

I've been trying to find stuff like this. :hail:

 

[RideItLikeYouStoleIt]

that is a sick diagram haha

 

[Matt_E]

Looks very nice. What tools did you use for the port matching? (Particularly the transfers)

Also, how did you get that surface finish on the transfer tunnels?

 

[robertg]

:bigeyes: Wow!... where in the world did you get all that information?

I've been trying to find stuff like this. :hail:

I think it came from the HPT web site. That site was George Grawbowski's.

 

[robertg]

Looks very nice. What tools did you use for the port matching? (Particularly the transfers)

Also, how did you get that surface finish on the transfer tunnels?

I just used a dremel, die grinder, and sandblaster.