Factory headpipe boring????

Y

yamaslut

Guest
What is the best way to get the disired size and have everything line up.
Also, what size should I bore to... Its at 42mm now... I was told 49mm, is that correct????

I'm assuming you bore the headpipe first, mate the surfaces and spray some paint or something in there to see where it lines up????
 
Y

yamaslut

Guest
oh yeah..

760 LPW ported motor
w/ dual 44mm mikunis (stock mani, carbon tech reeds, stuffers)
MSD enhancer
2 degree advanced (static)
 
N

njfl

X-H2
Although I would expect Paul to be the best to tell (for your particular motor)you since he built the motor, you can also give Chuckie a call. He usually does that on the motors he builds.

I would suspect that everyone on the board should not jump and bore their headpipes to the max size possible (although you likely could benefit from a little larger opening than 42mm).

Have any of you ever built a 350 Chevy with street specs and then put on 2" primary tube headers? You lose a lot of bottom end because of reduced flow speed due to the larer runner volume. I would suspect that some of that holds here in the two-stroke world as well.
 
Y

yamaslut

Guest
yeah... I always confirm everything w/ him... he is busy and I don't like to bug him w/ ever little detail. I always like to hear what everyone has to say first...
 
Frosty

Frosty

New York Crew
Location
Western New York
I just got mine back from Chuck... I can measure tonight when I get home if you like. He bored the exhaust manifold and ported the head pipe and matched the head pipe gasket to the new ID. Did a great job... can't wait to get it back in the water.

Although, mine is running on a ported 701
 
Jr.

Jr.

Standing Tall
Staff member
Site Supporter
Location
Hot-Lanta
every motor is different, there needs to be a degree of back pressure.
Most of the BB motors, like yours, work best at 46.5mm for freestyle,
a race, high rpm motor would like the 49mm as suggested.

ski ya, Paul
 
Y

yamaslut

Guest
Jr. said:
every motor is different, there needs to be a degree of back pressure.
Most of the BB motors, like yours, work best at 46.5mm for freestyle,
a race, high rpm motor would like the 49mm as suggested.

ski ya, Paul
Click to expand...

werd.... I'll shoot ya a call today...
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
I trimmed the gasket hole to 47mm and used it for a template on the exhaust manifold and head pipe. I heard that you can run little more compression with this ported out too.
 
Y

yamaslut

Guest
yeah... talked to Paul on the horn last night... he did mention that running the smaller 42mm outlet could cause detonation. So that makes sense to me about the compresion... I need to hone my cyls tonight install new rings, port that mani/headpipe and slap my motor back in...

got a smaller base gasket too... so I should have a little more punch w/ that and the ported pipe​
 
RiverRat

RiverRat

.......
Location
Louisville, Ky
I think I bored mine out to 45mm. But I am going to send it to Paul this week and have him bore it out even more. My lamey cylinder was a race cylinder and is magerly hogged out on the exhaust ports. I am thinking taking it out to about 48mm may help it out throughout the rpms. I am running 48mm carbs as well and I have heard that the exhaust outlet should match the carb size on the intake side on the motor.
 
Jr.

Jr.

Standing Tall
Staff member
Site Supporter
Location
Hot-Lanta
Depends a little on what chamber? But 45-45.5mm for your bore sizes.
Keep in mind also water injection screw setting & stinger water also figure into this. But those vary a lot with ambient water temp.
 
You must log in or register to reply here.
Top Bottom