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Discussion Starter · #1 ·
just a discussion question. for science. trying to research how beneficial adding performance cams and a bigger throttle body are on a bike motor. assuming you upgrade the exhaust/air intake/fuel management and then change out cams for those with bigger lobes, would you also want to get a bigger throttle body as well? would you just be exchanging torque for HP with the wider air intake at that point? and if you do upgrade cams and throttle body, would you also want to do something about the exhaust port? why or why not? do people even mod that? multiple questions. go.
 

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when I wanted a bike with more power than my 650

I got a 2000 Royal Star 1300 V4 for $3000

the market for used motorbikes is so buyer friendly, I cant imagine tearing into an engine to get a few more HP out of it, and then needing to tinker with it for the rest of my life because it would never run as well as a bigger stock engine on a bike designed by engineers at Yamaha to be what it is.

I get the whole engine rebuilding / upgrading / camming porting jetting thing - If you like building engines thats cool too.

The cafe racer started that way in Europe, where engine size is limited by rider and insurance. taking a 250 or a 400cc bike and squeezing every HP you can out of it, without flagging the bike as being in a bigger class - thats kinda outlaw and subversive and has a lot of appeal.
 

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I would think if expense wasn't an issue if you were to go all out yes to all of it. To be able to get more air and fuel in you have get more exhaust out. It is all relative.
 

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Administrator - "Loose Nut" - Bandera, Texas
2001 Vstar 1100 Classic (sold), 2006 HD Electra Glide Ultra (totaled) 2006 Vulcan 900 (current)
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Fantastic topic, right up my alley. I'll agree somewhat with KCW, but reliable only goes down if you step over the line from streetable to race car. You can easily pick up 20% more usable power from head work without effecting reliability at all. Mass produced heads are designed with cost verses effectiveness. The best manufacturing process leaves rough casting and manufacturing flaws in the intake and exhaust of any engine. By cleaning these imperfections you make the engine preform as designed by the engineers. The time it takes to complete this process can not be recovered and keep the vehicles costs in line. I've personally ported hundred of heads thru out the years, performance and engine drivable has always increased. Let's get into some basics. Port matching is an easy way to enhance both intake and exhaust flow. The head, gasket and exhaust manifold are never exactly the same size. The difference will create a air to tumble disrupting the air flow. You remove material of the smallest, normally head, to eliminate the sizing issue.

91892


Sorry for next couple of pictures. These are heads on bottom of other parts in my shed and didn't want to move a bunch of stuff. First picture is stock exhaust port on a 351w. Second one is a port matched on a 351w. It will be hard in picture to tell the difference in size but look at bolt hole closeness to port in second picture. These are exactly the same head, before and after. The ported heads have 100k plus miles and hundreds of trips down the strip. My good heads are on car now.

91895


91896



The next step would be removing rough areas and imperfections on intake and exhaust passages from port to valve. You don't want too smooth a surface, still need a little turbulence to maintain fuel mixed in the fuel charge. Smoothing out any sharp bends or angles to a more rounded profile help a lot. It takes experience and time not to take too much off and get into a water passage, then you have an expensive paper weight. Yes you can weld it back up and start over.

91893


Next step would be a multi angle valve seat to enhance air flow. A normal valve seat is a single angle. A three angle is considered the minimum for performance engines with 4 and 5 angle valve seats for all out race cars. The angled valve job is the only part of building heads that I don't do. It takes special machines that are cost prohibited for the regular guy to buy, any machine shop can do it.

91894


All the above can be done without effecting reliability. I can do one head on a V8 in about 8 to 10 hours. I'm slow but very precise on what I do.

Now to cams. That will take research for what you want. Higher lift equals more flow. More overlap breaths better at higher rpm. Different ramp angles effect fuel pulse. Any good machinists can recommend the right cam, yes you can go too big and make an engine only effective at or near redline.

91898


For throttle body, for most street friendly engine a larger throttle body is not needed, for strip, yes. Larger injectors and an ECU remap to keep injectors open longer will do the trick. Want more info, just ask. I really, really, really like this topic. I can pretty easily take any stock engine, give you a solid 20 percent increase in power with adding cams, normally another 20 percent with cam, intake and headers. But you have to be careful, tranny, rear ends, etc, are not made for the extra power. Stay mild and all holds up well.
 

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Administrator - "Loose Nut" - Bandera, Texas
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Another way to enhance intake air flow is to undercut the valve stem next the head. Small things like this can make a huge difference.

91922


91923
 

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I haven’t seen a undercut valve in a long time you’re bringing back memories. What I’ve seen in the Yamaha line is the scarce parts for doing engine mods. Unless I’m just looking in the wrong places. They don’t seem to be to many offers out there that’s one reason I’ve bought a HD again. And do you do your own porting and polishing ? Still love my Yamaha though I don’t think I’d ever do any mods except exhaust and carb.

And if anyone has a site that offers high performance parts for Yamaha let everyone else know. As I’ve only seen stuff for dirt bike.
 

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Yes, I do all my port and polish work. I clearance blocks for stroker cranks. Picture below is one I did not to long ago, gasket covers up other clearances done. The only engine building items that I don't do is boring, crank balance and valve jobs, don't have the machines.

91927
 

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You can buy the valve seat tools pretty reasonable now days the set that I used were like $200.00 and they were adjustable for different size valve seats. And I think that it came with 5 or 6 different angles for the 5 step angle cutting. I’ve always used brand new valves in all my engine rebuilds just made life a little easier. It’s been awhile since I’ve been able to do the heavy work due to a work accident on black ice. But miss it a lot we used to do a couple motors a week. Lucky that around here we have some great machine shops for boring blocks and milling heads.

This is similar to the one I’ve used
Text Product Font Web page Screenshot
 

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Administrator - "Loose Nut" - Bandera, Texas
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I'll agree with you that valve jobs can easily be done. I'm normally working on old seasoned blocks, 60s - 70s, that need new valve seats. My engine machinist is good for working with me. Been using the same guy for years, gotten so I drop a block off and say "the norn". I do this on the side and have a very open time frame that he likes.
 

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Discussion Starter · #11 ·
lots of good info. primarily speaking to just upgrades to cams, throttle body, and exhaust ports - are you wasting your time/effort/money by just doing one of these upgrades instead of all 3? what are the HP/torque changes to just upgrading to larger cams? bigger throttle body? exhaust porting? is it too simplistic to say you will get some performance upgrade by upgrading cams, a little more by also adding a larger throttle body, and a little more by porting the heads?
 

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Administrator - "Loose Nut" - Bandera, Texas
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Upgrading cams to a streetable cam in otherwise stock motor you can gain about 15% more horsepower. Porting would be about another 10% and increase fuel delivery about another 5%. All three together would up that number as they compliment each other. Upgrading cam is always the highest initial gain but porting and more fuel complete the package. In fuel injected vehicles a tune to ECM is necessary for overall package.
 

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Port matching, port and polish exhaust and intake, increase fuel and better exhaust can be done on literally any bike and make big reliable power gains. Cams can be challenging on some models that don't have big after market support. You can get a cams custom made, but tends to be a little expensive.
 

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I haven’t seen a undercut valve in a long time you’re bringing back memories. What I’ve seen in the Yamaha line is the scarce parts for doing engine mods. Unless I’m just looking in the wrong places. They don’t seem to be to many offers out there that’s one reason I’ve bought a HD again. And do you do your own porting and polishing ? Still love my Yamaha though I don’t think I’d ever do any mods except exhaust and carb.

And if anyone has a site that offers high performance parts for Yamaha let everyone else know. As I’ve only seen stuff for dirt bike.

Patrick racing in Fountain Valley Cal.
Those guys used to run a couple of warriors when AMA/Prostar ran the hot rod cruiser class.

Drop in cams are designed to function within the constraints ofa stock engine ie. moderate compression ratios, limited valve travel conditions etc and only yield moderate performance gains. More aggressive grinds require valve springs and better keepers, sometimes guides need to be shortened and seat pressure needs to be right etc. Compression ratio should be raised to cope with lost cylinder pressure due to increased duration, is also a good time to consider increasing displacement.
..$$$$$
Portwork is another matter. Most engines are over exhausted anyway, 4:3 int/exh flow ratio is plenty. Cam timing and low flow numbers play a big role here as well.
Cylinder head porting will yield good power increase but there are things that must be done as well so it can be utilized. Did l mention $$$$$$$?
in an injected engine a big throttle body may be useful, although it may disturb the intake tract tuned length (diameter change where it shouldn't be), to big of a carb causes low velocity (weak signal) across the Venturi area. Then there's the exh system to deal with, the list goes on.
in short variable after variable.
And then there's the money thing, I have an oil cooled bandit that I have almost 5K$ in the engine (2200 in the head and over a thousand in the crank) and countless
hours in transmission, clutch work, ignition, etc and and it's a street bike.
if I had to do it again I'd just go buy something fast, at least it would handle better.
 

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Port matching, port and polish exhaust and intake, increase fuel and better exhaust can be done on literally any bike and make big reliable power gains. Cams can be challenging on some models that don't have big after market support. You can get a cams custom made, but tends to be a little expensive.
Port matching, port and polish exhaust and intake, increase fuel and better exhaust can be done on literally any bike and make big reliable power gains. Cams can be challenging on some models that don't have big after market support. You can get a cams custom made, but tends to be a little expensive.
Hi mate I realise this post is a little old but you seem to know what your talking about and I would like your advice pls ..do you know if you can port the heads on a Stryker or maybe even try larger throttle bodies ..any ideas

Patrick racing in Fountain Valley Cal.
Those guys used to run a couple of warriors when AMA/Prostar ran the hot rod cruiser class.

Drop in cams are designed to function within the constraints ofa stock engine ie. moderate compression ratios, limited valve travel conditions etc and only yield moderate performance gains. More aggressive grinds require valve springs and better keepers, sometimes guides need to be shortened and seat pressure needs to be right etc. Compression ratio should be raised to cope with lost cylinder pressure due to increased duration, is also a good time to consider increasing displacement.
..$$$$$
Portwork is another matter. Most engines are over exhausted anyway, 4:3 int/exh flow ratio is plenty. Cam timing and low flow numbers play a big role here as well.
Cylinder head porting will yield good power increase but there are things that must be done as well so it can be utilized. Did l mention $$$$$$$?
in an injected engine a big throttle body may be useful, although it may disturb the intake tract tuned length (diameter change where it shouldn't be), to big of a carb causes low velocity (weak signal) across the Venturi area. Then there's the exh system to deal with, the list goes on.
in short variable after variable.
And then there's the money thing, I have an oil cooled bandit that I have almost 5K$ in the engine (2200 in the head and over a thousand in the crank) and countless
hours in transmission, clutch work, ignition, etc and and it's a street bike.
if I had to do it again I'd just go buy something fast, at least it would handle better.
Another guy who knows what he is talking about so I will ask for your advice ,do you think porting the heads on a Stryker can be done ..your thoughts on gaining a couple of ponies would be really appreciated
 

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To try to explain is more than l can put in a post.
PM me a contact #
Thanks for replying mate I tried to pm you but it says as I'm. New user I have to come back later lol go figure

Thanks for replying mate I tried to pm you but it says as I'm. New user I have to come back later lol go figure
My email is [email protected] if that helps mate
To try to explain is more than l can put in a post.
PM me a contact #
I live in Australia otherwise I would give you my phone number
 

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Chances are the rev limiter will come on before the engine can approach the flow limits of the stock head.

Before doing internal engine mods l would recommend a quality exhaust system, a better flowing air intake and a power commander of some sort.
Significant performance gains can be had with bolt on stuff.

The other thing to consider is high performance engine parts availability. Building a big horsepower Harley is easy because you can get anything you need, not so much with a Stryker.
 
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