Cylinder head
#1
06-11-2014, 03:53 AM
Join Date: Jan 2013
Location: Las Vegas, NV
Posts: 1,422
Cylinder head
I'm going to be having some head work done to my bike, but I commute on it, and turn around time can be 2 days to 1 week, so if anyone out there has a complete head lying around that I could buy please let me know.
A big shop estimated me $600 for a port, polish, and larger intake valves
A buddy gave me a guy who works for thumper racing here in town and does head work as a side job. $250
yeah buddy!
A big shop estimated me $600 for a port, polish, and larger intake valves
A buddy gave me a guy who works for thumper racing here in town and does head work as a side job. $250
yeah buddy!
#2
06-11-2014, 01:26 PM
Be careful, you will be pushing the power range higher in the rpm range. The larger the ports get the more the intake charge is slowed down. Think about it, you turn on an open end garden hose and the water globs out the end. Neck it down with a spray nozzle and the flow speed increases. It is the balance between the ram effect of the intake flow packing the cylinder versus the size of the flow passage.
One tip, on the polishing, that used to be a trend - mirror ports. But unless the walls are straight, no waves, the turbulence may get larger and flow inefficiently. This was pointed out in some articles by Gordon Jennings years back. The tip was to smooth and straighten out the ports cleaning casing flash and such, then leaving a slightly rough surface. The small roughness (bead blast type finish) will have less turbulence and, in fact, the fluid flow of the intake charge can actually coat the intake, making for a smoother flow yet. The key is clean transitions from carb to manifold to head and into the cylinder, then from valves to head to exhaust. Matching the junction areas. Steps create huge turbulence, slowing flow.
Unless you have a seriously knowledgeable expert, there is a lot of risk in porting. Most just hog things out, figuring bigger is better. Not always true. I'd do a lot of research before I'd have head work done, finding what do some of the dirt trackers do with their 450s, just to try to get a handle on what is done and the gains. The dirt trackers are looking at max useable power.
These are just my thoughts from what I've read and learned over the years. When I was twenty I would have dived into something like this and hogged everything out. Now with a lot of reading and especially what has been done in automobiles (where actual work and results are published - motorcycles never get anything published) I'm seeing the balance factor. Cleaned ports with a fine bead blasted finish make a lot of sense, especially in cost. Bigger valves are like getting bigger cams, increasing flow - both ways - so there will be serious changes in the power band, likely pushing it up in the rpm range. At low rpm part of the charge will be pushed back out as the valves close.
Walk into head work very open eyed and well versed.
One tip, on the polishing, that used to be a trend - mirror ports. But unless the walls are straight, no waves, the turbulence may get larger and flow inefficiently. This was pointed out in some articles by Gordon Jennings years back. The tip was to smooth and straighten out the ports cleaning casing flash and such, then leaving a slightly rough surface. The small roughness (bead blast type finish) will have less turbulence and, in fact, the fluid flow of the intake charge can actually coat the intake, making for a smoother flow yet. The key is clean transitions from carb to manifold to head and into the cylinder, then from valves to head to exhaust. Matching the junction areas. Steps create huge turbulence, slowing flow.
Unless you have a seriously knowledgeable expert, there is a lot of risk in porting. Most just hog things out, figuring bigger is better. Not always true. I'd do a lot of research before I'd have head work done, finding what do some of the dirt trackers do with their 450s, just to try to get a handle on what is done and the gains. The dirt trackers are looking at max useable power.
These are just my thoughts from what I've read and learned over the years. When I was twenty I would have dived into something like this and hogged everything out. Now with a lot of reading and especially what has been done in automobiles (where actual work and results are published - motorcycles never get anything published) I'm seeing the balance factor. Cleaned ports with a fine bead blasted finish make a lot of sense, especially in cost. Bigger valves are like getting bigger cams, increasing flow - both ways - so there will be serious changes in the power band, likely pushing it up in the rpm range. At low rpm part of the charge will be pushed back out as the valves close.
Walk into head work very open eyed and well versed.
Last edited by klx678; 06-11-2014 at 01:28 PM.
#3
06-11-2014, 03:06 PM
Join Date: Jan 2013
Location: Las Vegas, NV
Posts: 1,422
Be careful, you will be pushing the power range higher in the rpm range. The larger the ports get the more the intake charge is slowed down. Think about it, you turn on an open end garden hose and the water globs out the end. Neck it down with a spray nozzle and the flow speed increases. It is the balance between the ram effect of the intake flow packing the cylinder versus the size of the flow passage.
One tip, on the polishing, that used to be a trend - mirror ports. But unless the walls are straight, no waves, the turbulence may get larger and flow inefficiently. This was pointed out in some articles by Gordon Jennings years back. The tip was to smooth and straighten out the ports cleaning casing flash and such, then leaving a slightly rough surface. The small roughness (bead blast type finish) will have less turbulence and, in fact, the fluid flow of the intake charge can actually coat the intake, making for a smoother flow yet. The key is clean transitions from carb to manifold to head and into the cylinder, then from valves to head to exhaust. Matching the junction areas. Steps create huge turbulence, slowing flow.
Unless you have a seriously knowledgeable expert, there is a lot of risk in porting. Most just hog things out, figuring bigger is better. Not always true. I'd do a lot of research before I'd have head work done, finding what do some of the dirt trackers do with their 450s, just to try to get a handle on what is done and the gains. The dirt trackers are looking at max useable power.
These are just my thoughts from what I've read and learned over the years. When I was twenty I would have dived into something like this and hogged everything out. Now with a lot of reading and especially what has been done in automobiles (where actual work and results are published - motorcycles never get anything published) I'm seeing the balance factor. Cleaned ports with a fine bead blasted finish make a lot of sense, especially in cost. Bigger valves are like getting bigger cams, increasing flow - both ways - so there will be serious changes in the power band, likely pushing it up in the rpm range. At low rpm part of the charge will be pushed back out as the valves close.
Walk into head work very open eyed and well versed.
One tip, on the polishing, that used to be a trend - mirror ports. But unless the walls are straight, no waves, the turbulence may get larger and flow inefficiently. This was pointed out in some articles by Gordon Jennings years back. The tip was to smooth and straighten out the ports cleaning casing flash and such, then leaving a slightly rough surface. The small roughness (bead blast type finish) will have less turbulence and, in fact, the fluid flow of the intake charge can actually coat the intake, making for a smoother flow yet. The key is clean transitions from carb to manifold to head and into the cylinder, then from valves to head to exhaust. Matching the junction areas. Steps create huge turbulence, slowing flow.
Unless you have a seriously knowledgeable expert, there is a lot of risk in porting. Most just hog things out, figuring bigger is better. Not always true. I'd do a lot of research before I'd have head work done, finding what do some of the dirt trackers do with their 450s, just to try to get a handle on what is done and the gains. The dirt trackers are looking at max useable power.
These are just my thoughts from what I've read and learned over the years. When I was twenty I would have dived into something like this and hogged everything out. Now with a lot of reading and especially what has been done in automobiles (where actual work and results are published - motorcycles never get anything published) I'm seeing the balance factor. Cleaned ports with a fine bead blasted finish make a lot of sense, especially in cost. Bigger valves are like getting bigger cams, increasing flow - both ways - so there will be serious changes in the power band, likely pushing it up in the rpm range. At low rpm part of the charge will be pushed back out as the valves close.
Walk into head work very open eyed and well versed.
I did a lot of automotive exploration before I was interested in motorcycles. The gentleman doing the job is very knowledgeable(asking my application, racing, usuable power on the street, street/strip etc.), we will be matching the carb intake to the head, it won't be a mirror finish, but rather a slightly roughed finish as you said. I just call it port and polish out of habit 
The large intake valves are supposed to help tremendously with the 351 kit (I'd rather have larger exhaust valves, but that is a no go) according to Bill (sourced from Japan customers who race supermoto). The intakes are only 1mm bigger, so the difference will be distinct, but not drastic imo.
Having the SF version, and I ride street and canyons, and I NEED that extra upper rpm power, it pulls hard up to 7k rpm, but lets be honest, it could pull harder, and keep pulling past 8.5k where it REALLY falls off.
I'll be sticking with the stock cams until I can get the ported head and pumper carb on the dyno and see if any gains can be made with 101 cams without seriously sacrificing lower end as you say.
I'm not being argumentative, just clarifying the vagueness of my first post
As always I appreciate the thoroughness of your post
#4
06-11-2014, 09:07 PM
You know what you're looking at. That is definitely a positive thing.
Amazing how all that stuff is out there for cars in the various media, but not on bikes. That is why I started subscribing to car magazines, to get that mechanical fix you can't get with bike magazines.
I look forward to hearing how it goes with the whole thing. with cams and the port work you should be pushing it up higher and not get hurt too bad down low due to the added displacement. Hot Rod just did an article relating to power generation by displacement, rpm, and boost. Interesting reading.
Amazing how all that stuff is out there for cars in the various media, but not on bikes. That is why I started subscribing to car magazines, to get that mechanical fix you can't get with bike magazines.
I look forward to hearing how it goes with the whole thing. with cams and the port work you should be pushing it up higher and not get hurt too bad down low due to the added displacement. Hot Rod just did an article relating to power generation by displacement, rpm, and boost. Interesting reading.
#5
06-12-2014, 02:59 AM
When I grenaded the crank and had to tear the engine apart I did some work on the head while I was waiting for parts. I'm with Mark on the idea of diminishing returns for port work. I have spent a good bit of time massaging ports over the years-started with simple files on my KX125 rotary valve screamer back in the day and progressed to a 8 sec. nitrous Mustang when I had my auto business. After looking at the KLX head I'd say that the choke point is going to be the port design on the exhaust-trying to get good flow around the kink exiting the head will be tough.
I think that adding larger intakes couldn't hurt but at some point it would be easier to switch to something else that was designed for a higher output from the start. I just matched the flange and cleaned up the throat transition on the intake side and laid back the chamber around the valve perimeters to allow better low lift flow. The exhaust is a compromise no matter what you do-hard to get good flow on a 90 deg elbow compounded with a air injection port in the stream.
I'm pretty satisfied with the performance of the engine in its present state and I think that I have maxed out any more economical gains.
The old adage still applies-how fast do you want to spend???
I think that adding larger intakes couldn't hurt but at some point it would be easier to switch to something else that was designed for a higher output from the start. I just matched the flange and cleaned up the throat transition on the intake side and laid back the chamber around the valve perimeters to allow better low lift flow. The exhaust is a compromise no matter what you do-hard to get good flow on a 90 deg elbow compounded with a air injection port in the stream.
I'm pretty satisfied with the performance of the engine in its present state and I think that I have maxed out any more economical gains.
The old adage still applies-how fast do you want to spend???
#6
06-12-2014, 03:25 AM
Join Date: Jan 2013
Location: Las Vegas, NV
Posts: 1,422
After looking at the KLX head I'd say that the choke point is going to be the port design on the exhaust-trying to get good flow around the kink exiting the head will be tough.
I think that adding larger intakes couldn't hurt but at some point it would be easier to switch to something else that was designed for a higher output from the start. I just matched the flange and cleaned up the throat transition on the intake side and laid back the chamber around the valve perimeters to allow better low lift flow. The exhaust is a compromise no matter what you do-hard to get good flow on a 90 deg elbow compounded with a air injection port in the stream.
I'm pretty satisfied with the performance of the engine in its present state and I think that I have maxed out any more economical gains.
The old adage still applies-how fast do you want to spend???
I think that adding larger intakes couldn't hurt but at some point it would be easier to switch to something else that was designed for a higher output from the start. I just matched the flange and cleaned up the throat transition on the intake side and laid back the chamber around the valve perimeters to allow better low lift flow. The exhaust is a compromise no matter what you do-hard to get good flow on a 90 deg elbow compounded with a air injection port in the stream.
I'm pretty satisfied with the performance of the engine in its present state and I think that I have maxed out any more economical gains.
The old adage still applies-how fast do you want to spend???
I got my big bore kit for practically nothing ( bought it used uninstalled with a tm34 pumper for $500, sold the pumper for $300 then the old cylinder back to bill for $175), so I figure $300 for pumper and $300 for headwork, I can get close to 35hp klx for only $750 ($150 slip on). I say that's pretty darn good
#7
06-12-2014, 03:49 AM
Join Date: Aug 2011
Location: Phuket, Thailand
Posts: 516
The top end performance is really appreciated on a SuperMoto setup, the real peak power curve is lifted by almost a 1000rpm! My bike will pull hard to 9000rpm & will easily hit the 10.5K redline in 6th gear when required with 14/39 gearing.
#8
06-12-2014, 05:17 AM
Join Date: Jan 2013
Location: Las Vegas, NV
Posts: 1,422
I was very pleasantly surprised with the 101 cams. The cams to me felt like they beefed up the low/mid range grunt with snappier stronger torque range.
The top end performance is really appreciated on a SuperMoto setup, the real peak power curve is lifted by almost a 1000rpm! My bike will pull hard to 9000rpm & will easily hit the 10.5K redline in 6th gear when required with 14/39 gearing.
The top end performance is really appreciated on a SuperMoto setup, the real peak power curve is lifted by almost a 1000rpm! My bike will pull hard to 9000rpm & will easily hit the 10.5K redline in 6th gear when required with 14/39 gearing.
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