Head, cam, springs and carb ?'s

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r_chez_08

New Member
#1
#1
Sorry, this is a newb question, but I could not find an exact answer. I am not running in a class, just a yard kart at home.

My setup-
6.5hp clone
Flat top piston
K+N filter
Billet rod
Aluminium flywheel
BSP-1 cam
Wiener Pipe + Muffler (will possibly change)

My questions-
1. My piston is approx. 0.035 in the hole. I was planning to mill it so I had .015 pop up, and use a gx160 head gasket, is this a good idea?

2. I was also planning to mill my stock 22cc head by .050. This will give me approx. 11:1 compression ratio. I am running on pump gas, can/ should I go higher? I was also going to remove any rough casting etc.

3. I have a BSP-1 cam, and was planning to shave the base circle with a toolpost grinder on a lathe. What cam lift would be good with my setup?

4. What valve springs should I use? I would like 6-6500 rpm if possible? I was thinking 14lb gx140, 16lb gx160 g4's or 18lb g200's?

5. Would I benefit at all from a 22mm mikuni or gx390 carb?

Thanks,
Rob
 
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SAFETYpin

New Member
#2
#2
Are you sure, your doing the math right on your compression ratio...? I haven't double checked your numbers but my initial reaction is taking of -.045 off the block, -.050 off the head would give you a lot more compression than 11:1. Especially considering you already have the flat top piston.

From the chart that I have just a flat top piston and -.050 off the head will give you 10.5:1

Nevermind, I got the gasket thickness confused, I see your planning on running the thick gasket....
 
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r_chez_08

New Member
#3
#3
Does 11:1 sound ok, and is decking the block worth it, or should I run .035 in the hole with a .010 gasket, and mill off .065 or so from the head?
Thanks
 
F

flathead59

New Member
#4
#4
r_chez_08 said:
Does 11:1 sound ok, and is decking the block worth it, or should I run .035 in the hole with a .010 gasket, and mill off .065 or so from the head?
Thanks
Click to expand...
.050 off the head would leave at 9-1 with a g160 head gasket which will run pretty good with a bsp cam and 18lb springs .and with that setup you can be in the 10-1 range if you use a gx200 gasket and thats without decking the block or using a longer rod . personally i wouldnt run much over 10-1 on pump gas !
 
1

1Bad Fox

New Member
#7
#7
r_chez_08 said:
Sorry, this is a newb question, but I could not find an exact answer. I am not running in a class, just a yard kart at home.

My setup-
6.5hp clone
Flat top piston
K+N filter
Billet rod
Aluminium flywheel
BSP-1 cam
Wiener Pipe + Muffler (will possibly change)

My questions-
1. My piston is approx. 0.035 in the hole. I was planning to mill it so I had .015 pop up, and use a gx160 head gasket, is this a good idea?

2. I was also planning to mill my stock 22cc head by .050. This will give me approx. 11:1 compression ratio. I am running on pump gas, can/ should I go higher? I was also going to remove any rough casting etc.

3. I have a BSP-1 cam, and was planning to shave the base circle with a toolpost grinder on a lathe. What cam lift would be good with my setup?

4. What valve springs should I use? I would like 6-6500 rpm if possible? I was thinking 14lb gx140, 16lb gx160 g4's or 18lb g200's?

5. Would I benefit at all from a 22mm mikuni or gx390 carb?

Thanks,
Rob
Click to expand...
The quickest...cheapest and prob most beneficial thing you can do is just take .070 off the head and run a 1.2 ratio rocker and use the Mikuni because its fully adjustable. 18lb springs. That should put you real close to 15hp.

The weak link though will be the valvetrain.
 
R

r_chez_08

New Member
#8
#8
Ok thanks. I will look into the rockers. Would that be ether than grinding the cam? And would the 18lbs not coil bind?
Any idea what rpm?
 
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