'Round The Campfire > General Technical

High Performance Camshafts & Head Porting...

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J6G1Z:
A couple of ways to really increase the performance potential of a 4-stroke engine is to install a higher performance camshaft(s) & to port your cylinder heads.

Somewhere in my surfin' around on the internet, I had run across a camshaft grinder that listed camshafts for the VT500 engine. I thought it was MegaCycle. but there current brochure no longer lists it. http://www.megacyclecams.com/catalog/catalog.pdf
There is also Web Cam Inc: http://www.webcamshafts.com
Here is a primer on camshafts: http://www.oregoncamshaft.com/cam-basics.html

The FT500 Ascot is much easier to find a performance camshaft due to its close relation to the Honda XR/XL engines.

Now technically just about any factory OEM camshaft can be reground to a higher performance profile. This is done in several different ways. Probably about the simplest method is to reduce the diameter of the base circle of the camshaft. This in effect makes for a higher lift lobe profile once the material that was removed, is made up for by adjusting the length of the pushrods in that style of engine, or adjusting the extra lash out of the rocker arms. Another method is to weld additional material to the peak & surrounding area of the camshaft lobe, then grind the additional material to the proper new profile. After that is done, the camshaft is usually re-hardened or heat treated.

Another real trick modification to look into, is to install needle bearings at each end of the camshaft vs. a solid bushing & a thin film of oil. The needle bearings reduce some of the internal friction of the engine thereby releasing some additional power & throttle response.

Now for some type of modification that the average mechanically inclined person can perform at home. Some port & polish work. Now there are professional people out there that are highly talented at portwork & have a flow-bench to test their work with. If you can afford to have a "master" port your heads, you most likely will not regret it. But the average guy with a small hand grinder can still accomplish measureable performance gains with some study & some modest grinding/smoothing in the appropriate areas. The concept that we are after, is to try to "straighten" the port & to make any sharp radius less pronounced. Without the benefit of years of experience working with a flow-bench, you do not necessarily want to enlarge the port. For a street bike, we want to maintain a smaller port profile to enhance velocity of the charge. What the average Joe wants to look for, is casting flash that hangs down, or is rough. Something that obviously needs to be removed. Then try to imagine the flow of air, gas, or even the flow of water going through the port. We know that a charge that is moving doesn't like to change direction & will slow down. Now look down into your ports & try to see areas of the port that would resist smooth flow or transitions. Any sharp edges, machining marks, sharp radius with a peak to it, etc. We are not looking to redesign the port, simply make the best of what is already there. If there is a large protrusion around the valve guides, that is usually reduced to a minimum & tear drop shaped. Keep in mind while you are working that if there is more than one intake & exhaust port, you will need to match any changes that you make to one port, to the corresponding port. All intake ports should have as close to the same profile as possible & the same for the exhaust. I recommend that you start with the exhaust port as it will be less critical if you make a mistake. You want to pay special attention to the port "bowls" or "valve pockets" which is the area of the port closest to the backside of the valve. Most of your performance gains take place in the "bowl" & the valve seat area. A three-angle to a multi-angle valve seat really helps to improve the flow numbers. When doing your grinding/smoothing near the valve seats, you must excercise great care not to damage the valve seats. Often the valve seats are "high-lighted" with machinists bluing, or even a large red marker to make them easier to see.

These are some of my thoughts on performing some simple port work that can benefit your bike. The real beauty of port-work is that when it is performed properly, you can release large numbers of "free" power. Just think of the engine as an "air-pump". Anything that you can do to increase the amounts of air that is passed through the engine, or to reduce any frictional or pumping losses, will build power.

Below are several articles on performing port work.
http://www.diyporting.com
http://ascot500.com/index.php?topic=106.0
http://mototuneusa.com/power_news_--_think_fast.htm
http://mototuneusa.com/power_news_--_homework.htm
http://mototuneusa.com/power_news_--_the_2007_superbike.htm
http://mototuneusa.com/power_news_--_supersonic_nozzle.htm
http://mototuneusa.com/power_news_--_success_stories.htm
http://mototuneusa.com/thanx.htm
http://www.popularhotrodding.com/tech/0610phr_cylinder_head_porting
http://www.popularhotrodding.com/enginemasters/articles/hardcore/0412em_porting_cylinder_heads

I will add more to this topic as I run across more information.
J.

Dougie:

Ascot cams are still listed by Megacycle cams. Page 33

They are in with the 650 Hawk and Transalp which suggests that they could be interchangeable.

HONDA NT-650 HAWK (1988—1991) 500 ASCOT twin (1983—1984) .......................... (1983—1991) .......... 33

J6G1Z:
Excellent find! Thanks. 8)

J.

J6G1Z:
According to another forum member, this shop knows a thing or two about modifying the Ascots heads for some measureable power increases. http://www.hordpower.com

It looks like they do some excellent work on the Hawk engine & it appears that there may be some interchange possibilities. I noticed that they offer three stages of port work & install 2mm larger intake valves. They also offer big bore kits, highly worked over crankshafts, heavy duty connecting rods, etc. How much transfers over to the VT Ascot, I don't know. I will try to call them in the following week & see what they have to say.

J.

EDIT: I contacted Hordpower today & was able to speak to J.D. Hord. Unfortunately they do not provide any services for the Ascot.

Dougie:
One of the difficulties is getting above 600cc. In the USA it should be possible to fit a Transalp 600 engine in and fit the shaft drive output mechanism from the original engine in place of the chain drive.
650 head is quite different as the front exhaust port fouls the frame downtube.

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