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comnoz said:
That's the conclusion we came to for this service duty and space available.
We need to start talking about the next shortstroke build.
Head flow testing.
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That's the conclusion we came to for this service duty and space available.
We need to start talking about the next shortstroke build.
motorson
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One of my friends used to modify Honda XL125 heads back in the '70s. He would take out a bunch of metal and then just chop off the guide flush with the port. Of course he did that by just leaving it in there while he did the porting job and it ended up flush with the aluminum hole. The resulting guide was about 5/8 of an inch long. Sounds crazy but it lasted ok for racing and he won a lot.
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Just tossing out stuff I've come across and applied accidently. If no vanes to turn air flow then next best is vortex generators. Might try the 1007 head with a saw tooth or wire thread fiber gasket at the entry. Might try with just the lower half of gasket projecting VG's into flow - say 1/32 to 1/16" to get most the way out of boundary layer. Large scale aircraft/car size, orient the vanes 15% to the streamflow. That's why ya see V shapes in wide flat flow areas like the center of roofs but straight along body lines near roof edge because air flows up and back diagonally on its way to the lower pressure center flow. This draws fast air energy into the thickening boundary layer to get it moving further down steam bend, and against the high pressure back wash eddies formed on the down slope bend of rear window or short radius of intake.
Other shapes work too like sharp scales they not think even add thrust by increased back pressure.
Inside the head there's a thumb size patch I see inlet flow blasts against and then seems to ricochet to miss the exhaust valve. I wonder about trip tumble ridges or dimples there. One wants to see head surfaces all blasted clean of carbon.
Other shapes work too like sharp scales they not think even add thrust by increased back pressure.
Inside the head there's a thumb size patch I see inlet flow blasts against and then seems to ricochet to miss the exhaust valve. I wonder about trip tumble ridges or dimples there. One wants to see head surfaces all blasted clean of carbon.
Brooking 850
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Hi again, did mislead you a touch bike# 1 has a RH10 and bike # 2 has a RH4 head. Is the RH10 with a decent valve job the way to go with the JS keihins?
Regards Mike
Regards Mike
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ludwig said:
haha good one- and i think i know which cartoon! :shock:
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rvich said:
Epoxie can be used to build up the intake port and make it flow better. With modern pump gas it will only last for a while until the epoxy starts failing. It seems to last ok with race gas. At least long enough for racing. Welding in the middle of an intake port is pretty much out of the question.
That will not solve the cracking problem in an RH4 head. Fullauto cured that one. Jim
rvich
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Jim, I found the thread, and you gave the same comment there:
fullauto-head-combat-head-standard-head-t8478-30.html?hilit=intake epoxy
And I believe it may have been discussed in the earlier pages of this thread as well. My memory was that it got higher marks. It was another member who swore up and down it was the solution.
Russ
fullauto-head-combat-head-standard-head-t8478-30.html?hilit=intake epoxy
And I believe it may have been discussed in the earlier pages of this thread as well. My memory was that it got higher marks. It was another member who swore up and down it was the solution.
Russ
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rvich said:Jim, I found the thread, and you gave the same comment there:
fullauto-head-combat-head-standard-head-t8478-30.html?hilit=intake epoxy
And I believe it may have been discussed in the earlier pages of this thread as well. My memory was that it got higher marks. It was another member who swore up and down it was the solution.
Russ
Well I have certainly done a lot of JB weld port jobs- both on my bikes and other peoples. It is a lot easier and cheaper than welding or installing inserts. On my streetbike I would get one season out of it before pieces started flaking away. Usually around 8000 miles. I only consider it for racebikes anymore. Jim
Brooking 850
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thanks guys, will do a swap after giving the RH10 a thorough inspection and valve job, any advantage in changing the valve/seat size, or just leave them std and a good valve grind/lap?
Regards Mike
Regards Mike
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Brooking 850 said:
What I usually do for a good strong stock street bike is just a good 3 angle valve job. Keep the seat width down to 1mm intake and 1.5mm exhaust so they don't pack up with carbon and burn. Make sure the short side radius is steady -without steps as it turns down toward the seat.
Reduce the valve guide size to 1/2 inch where it protrudes into the port so it looks like a 750 guide to the airflow. Use Black Diamond valves and hard bronze guides.
On the 850 the best mod for the buck is to raise the compression up to around the 750 spec. 9.5 to 1. 10 to 1 will be ok if you ride solo most of the time.
There is a lot that can be done beyond that to raise the RPM level and make it more racy but for most street use I wouldn't go there.
Stick with a stock or very mild performance cam. Race cams get their horsepower from increases in RPM. Often times they end up with less torque in the RPM ranges enjoyed on a street bike. It takes a lot of time and money to make to make a Norton dependable when it's used at high RPM regularly. Jim
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