Changing Intake ports to a D shape for better flow.

One manifold brazed and done.
D manifiold done.jpg
 
If I understand this correctly, the port floor is pretty much straight and flat, until it curves down towards the bowl/valve head. And the short turn radius, as well as where the short turn actually starts, is the main factor in low lift vs high lift flow? And low lift flow helps low end/midrange power when combined with moderate cam timing. And vice versa, obviously.
I once saw some porting pics and other info, mostly related to 600 supersports bikes, i.e. early R6, CBR600, etc. That tuner sort of built up the port floor mainly in the short turn area, creating a sort of venturi shape. The idea being to increase the gas velocity in that area. Makes sense?
 
Any details you care to share on the motor set up Spungle?
The engine assembels of TM34 with ramped up alu manifold, Shell #1, 38mm headers, 750ccm 9:1 Europe 533 version, RD LiMa, Stainless Commando style exhaust. It's for street use, the goal is bottom and mid optimize. I will ride the head first with a standard cam and later the season with the Shell#1. I hope to get later to a Dyno. But it's real expansive, can take some time to save some money... I try my best to compare to a mostly standard xs. I had a friend who's xs build is finished in may I hope. He has a stock engine. Then here in my area I only know one more xs. I will try to compare to both of them.

If the results are good, and I think they are, then I try to copy the head. But I don't know if my skills lead to a comparable results. We will see.

I,ve asked Jack if it is ok for him if I share his head porting with other's who are interested. If a better skilled xs driver here around in Germany wish to copy the port for private use I will help with my head as an reference.
 
Last summer had complete tear down the engine. It was in a pretty good shape expect the Crankshaft, wich I changed for a renewed one with welded pins. Now the engine is reassembled and wait longingly for a good head and the winter is gone:cool: I hope the engine would take the extra Bums without a issue. My only concerns are the clutch. I hope it don´t slip:geek: And that the exhaust goes trough the German Hauptuntersuchung (formaly known as TÜV). Not even on such an old bike(1976) we are allowed to screw a nice exhaust on it. We have to have it registered by an Sachverständiger for some money. But the Sachverständiger can also be crosswise and refuse the registration if he either has no sense for old motorcycles or the volume is to loud. I hope my Sachverständiger has a good day.
 
The engine assembels of TM34 with ramped up alu manifold, Shell #1, 38mm headers, 750ccm 9:1 Europe 533 version, RD LiMa, Stainless Commando style exhaust. It's for street use, the goal is bottom and mid optimize. I will ride the head first with a standard cam and later the season with the Shell#1. I hope to get later to a Dyno. But it's real expansive, can take some time to save some money... I try my best to compare to a mostly standard xs. I had a friend who's xs build is finished in may I hope. He has a stock engine. Then here in my area I only know one more xs. I will try to compare to both of them.

If the results are good, and I think they are, then I try to copy the head. But I don't know if my skills lead to a comparable results. We will see.

I,ve asked Jack if it is ok for him if I share his head porting with other's who are interested. If a better skilled xs driver here around in Germany wish to copy the port for private use I will help with my head as an reference.
Hopefully the style mufflers you chose aren't real restrictive not allowing the engine to breath.
 
If I understand this correctly, the port floor is pretty much straight and flat, until it curves down towards the bowl/valve head. And the short turn radius, as well as where the short turn actually starts, is the main factor in low lift vs high lift flow? And low lift flow helps low end/midrange power when combined with moderate cam timing. And vice versa, obviously.
I once saw some porting pics and other info, mostly related to 600 supersports bikes, i.e. early R6, CBR600, etc. That tuner sort of built up the port floor mainly in the short turn area, creating a sort of venturi shape. The idea being to increase the gas velocity in that area. Makes sense?
The floor is flat with a slight radius in the corners to prevent or limit dead flow zones with this type of floor and tapers out to the corners of the valve head, this will help slowing the flow to make the turn over the short turn. Yes, the short turn radius has a huge impact on biasing flow in low, mid and high lifts with a stock XS short turn you don't have this option other than working the guide boss ,guide, raising the roof or enlarging the port to gain flow. Having the option to bais the flow in the low to mid lifts enhances throttle response, engine torque and engine efficiency but you also have to careful not to compromise top end pull or power, there needs to be a balance for the intended use of the engine. You could have several heads with different port shapes flowing the exact CFM but all them will impact power output and power range differently, again relating back to the intended usage of the engine. This D port to me is a well rounded port that delivers increased port velocity, no reduction in CFMs all with a smaller port volume and reduced spigot cross sectional area.
Yes to your last question, they build up that area to a D-Shape for increase velocity at the short turn to pack the cylinders tighter,etc.
 
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Are the Sachverständiger wise to Lollipops hidden in the pipes?
Those TUV guys are pretty bang on the money, most of the time. In some cases, only certain brands and types of tires are approved for a certain motorcycle model. Say, your bike is approved with certain Yokohama ir Bridgestone tires. Then Dunlop or Avon would not be ok. At least it used to be like that. Any change or deviation from stock needs to be entered into the vehicle documents, and have the required technical documentation from its manufacturer. Like an aftermarket handlebar, or aftermarket footpegs, for example. Pod filters would give an inspection fail, and so on.....
Have a look in the Kedo online catalog, pretty sure there is a lot of disclaimers regarding road legality of their parts .
 
Those TUV guys are pretty bang on the money, most of the time. In some cases, only certain brands and types of tires are approved for a certain motorcycle model. Say, your bike is approved with certain Yokohama ir Bridgestone tires. Then Dunlop or Avon would not be ok. At least it used to be like that. Any change or deviation from stock needs to be entered into the vehicle documents, and have the required technical documentation from its manufacturer. Like an aftermarket handlebar, or aftermarket footpegs, for example. Pod filters would give an inspection fail, and so on.....
Have a look in the Kedo online catalog, pretty sure there is a lot of disclaimers regarding road legality of their parts .

How does anyone ever manage to get a custom built bike on the road there?

Here in North Carolina inspections are no longer required on motor vehicles after they become 35 years old.
 
ArcticXS u are so right.



I've thinking of lollypops too. It's not legal, but hey, nobody see's it. But i will try to make that mufflers legal. I know where a good Sachverständiger works. will talk to him and we will see...

They're not legal here either but they are so easy to hide.
 
In Myrtle Beach, South Carolina the cops would slide their nightsticks up our pipes to check for baffles. If they hit anything we passed. So we would just run a single bolt in from the back and tighten it down. They never looked to see what their sticks were hitting.
 
In Myrtle Beach, South Carolina the cops would slide their nightsticks up our pipes to check for baffles. If they hit anything we passed. So we would just run a single bolt in from the back and tighten it down. They never looked to see what their sticks were hitting.
Never PO a cop that has his truncheon out.
 
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