has anyone attempted this themselves or had it done?
i did search but i really wanted to know how porting affects these motors and how much the port was enlarged durring this process. I may try it on a head later on but i was trying to get a guess as to what percentage to enlarge the port for otimal power as i wont have access to a flowbench to test it
I am going to do this - will let you know.
I have been making mods and then dragging the bike, logging my ET at every step. I'm going to try to get out to the track this week to see what a Supertrapp gained me. It'll probably be another month before I get around to porting the head. I always post my ET improvements with the subject "RACE REPORT" so you can search for that.
Hit me back in 3-4 weeks.
a supertrapp off ebay?
Quote from: bcutrufellii wont have access to a flowbench to test it
It almost can't be done without a flow bench - if you're actually looking to improve flow. Many a "port job" has resulted in less flow. You might start with just matching the ports to the intake manifold and exhaust header.
I recently read Kevin Cameron's book, "Sportbike Performance Handbook" - highly recommended. At several points, he mentions that factory tuners have had to reduce the port sizes on certain superbikes when building them for racing.
I saw a "tuner" 30 years ago blow cigar smoke into the intake ports to measure his progress with the grinding tool. :o
Polishing the intake ports probably will end up hurting. Cleaning up the casting marks will help though. The rough texture will aid with the atomization of the fuel. Like oldsport said, matching the manifolds to the ports is a must. The castings are terrible.
As you increase the diameter of the intake port, the velocity decreases. This is where the problem comes in as less fuel may be drawn in. Since the exhaust port is much smaller than the intake, enlarging may help. Polishing them will definitely help.
Necking the valves is also a good thing to do.
Quote from: quinnbozza supertrapp off ebay?
I saw that one...a few weeks ago, right? I thought about buying it but those things are dang loud.
The Supertrapp was not off ebay a few weeks ago (I know the one you are talking about though - I bought the race plastics). I bought it probably a year ago and just got around to the project. It sure did make a big difference in power. I rejetted too because it was WAY lean (I went from 135's to 150's).
I can't wait to run it!
Quote from: dgyverPolishing the intake ports probably will end up hurting. Cleaning up the casting marks will help though. The rough texture will aid with the atomization of the fuel. Like oldsport said, matching the manifolds to the ports is a must. The castings are terrible.
As you increase the diameter of the intake port, the velocity decreases. This is where the problem comes in as less fuel may be drawn in. Since the exhaust port is much smaller than the intake, enlarging may help. Polishing them will definitely help.
Necking the valves is also a good thing to do.
You mentioned necking the valves - have you ever talked to anyone that has done this on a GS? I just got ahold of a valve facing machine and have been ITCHING to tear into the GS head. I am waiting on a gasket set to get started.. I was planning on doing a standard 3 angle and then putting a nice backcut on the underside of the valve to see where that got me for starters.
I also just got access to a 3 axis lathe and am going to mill the head 30 thou to start.
When I did the supertrapp I found that the stock exhaust inlet (to the header) could be improved A LOT with a die grinder. I noticed (think I did at least) a difference before vs. after. I don't know if I'll make it out to the track on Wednesday - I'm trying to get paint on my Pinto so the GS has been inactive for a week or two. Gotta get back to it.. :cheers:
Necking the valves is nothing major. Easily done a lathe, even on my old lathe. I have done several sets of them. It just reduces the cross sectional area of the valve stem that is is the port. A multi-angle valve job is something different.
Here are 3 GS valves, from left to right:
Stock Intake --- Necked Intake --- Necked Exhaust
(http://img.photobucket.com/albums/v64/dgyver/GS500/GSneckedvalves01.jpg)
so this necking gets you what in terms of performance? round estimate...how much would this cost for a machineist to do?
I do not have a performance data. A flow bench or dyno run would be the only way. Necked valves by themselves would really not gain that much. It would have to be part of other mods to have noticeable gain. It is kind of like taking 1 mod that gives a 1% increase but do 10 mods that each have a 1% increase, then you will see a difference.
Not sure the cost of having a machine shop do the work.
Quote from: DomQuote from: quinnbozza supertrapp off ebay?
I saw that one...a few weeks ago, right? I thought about buying it but those things are dang loud.
Yaha i was first to find it but, once it got down twords the end i was gone a bid again but it got to rich for my blood :x that allways happens :lol:
( maby i'm just a cheapscate) :mrgreen:
well :cheers: everyone
Quote from: luke1645so this necking gets you what in terms of performance? round estimate...how much would this cost for a machineist to do?
Well not really a lot by itself. But if you neck the valve, put a back cut on it, massage the seat-to-port transition, smooth out the casting flash, blend things in a bit... You can pick up quite a bit if you pay attention and do some poking. As others have mentioned, the intent is not to just hog things out. You want to pay attention to detail, keep the flow up, and not get carried away. I haven't flow tested any heads I've done but the engines are much snappier and really really responsive..
I believe this link may have been posted here before. Articles 16 - 20 cover ideas on porting.
http://mototuneusa.com/thanx.htm
i have looked at mtototune before. I dont know how keen i am on reducing the intake ports via jb weld. He also states that you will loose power iby enlarging the ports. There are alot of variables when deciding to narrow or enlarge or just smooth castings. The mototune guy also recomends a hard break in on the motor not sure if i trust that either. 1
:dunno: you try it let me see some dyno numbers
QuoteI dont know how keen i am on reducing the intake ports via jb weld
JBweld might be ok, i know Marine Tex is used alot, seems to have the elasiticity to handle the expansion and contraction. Machinist used it on my Nissan Pickup head to reshape some of the waterjacket ports and some electolisus (sp?) on dead end ports. then milled the head for warpage. he said it should be good for another 6 years. intake ports arnt dealing with the pressure NOR the high temps found on the hotsides of the valves. you want to have the volume to fill the chamber with little effort, but too big and the speed of the air flow (velocity) would be too slow to properly mix. the only way to retain velocity with biger ports is to lengthen the stroke. Boreing would have to be a major jump in size to do the same. building a stroker motor you can have ports bigenough to toss a cat through.