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Thread: Engine porting

  1. #1
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    Engine porting

    How people out their ,has had their engine ported?Is eric gorr
    the place to go ? ALL I ride are the woods.Would I have to use race gas ? The closes place to get it 2hrs away .If I did have it done what would I ship my cylinder in?
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  2. #2
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    First off my answers to your questions.
    -I've had bikes ported in the past with mixed results.
    -Eric Gorr is supposed to be very good, but I've never used him.
    -Whether you run race gas or not will depend upon what porting and head work you have done.
    -I've always had the work done locally so no comments on shipping.
    Question - What are you riding and what do you want out of the porting?
    Now an opinion.
    If you are riding an MX bike (CR, YZ, RM, etc.) and are looking for more low-end porting is going to be mildly effective. It's easy to open ports up for more flow, but hard to close and redirect them.
    '12 Honda CRF250R, '03 GasGas EC300, '75 YAMAHA TY80 <Since 2001> '71 Honda Z50, '00 KTM 380EXC, '03 KTM 65SX , '03 YAMAHA PW50, '06 Suzuki DRZ400S, '03 Kawasaki KX100, '08 YAMAHA YZ450F, '07 YAMAHA YZ250, '07 KTM 250XC-W
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  3. #3
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    Dave is correct. What are you looking to get out of it? I had my 98 kdx220 done by Jeff Fredette, I told him I was looking for more bottom end (at the time I also had a 95 kx250 torque monster), he recomended porting, boring the carb intake, and machining the head for more compression, while still being able to run pump gas. The result was a bike with NO bottom end, and all top end. Maybe good for some top level racer, but not me! I ruined by perfectly good bike! I ended up selling it 3 weeks later I was so unhappy, I'm not knocking Jeff's work, it just wasn't what I was looking for.

    So just be sure what you are looking for is what you will end up with.
    OK Brain, I don't like you, and you don't like me. So let's get this race over with, so I can get back to killing you with Beer!
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  4. #4
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    You see my signature? Notice the YZ is a 134?

    That's the work of Eric Gorr, and it ROCKS!!

    His work is excellent, and his prices are reasonable. He offers several discounts, so check out his website at http://www.ericgorr.com, or call him. He is very helpful.

    As far as shipping, I wrapped the cylinder in a bag, lined a cardboard box with another layer of cardboard, and padded it all with wrapped up newspaper. He returned it the same way, and there was absolutely no damage. (If you prepay by check, return shipping is free)

    Now, as far as how the bike runs? I use pump gas and I have no problem. The bottom end is increased a decent amount (still no 250) but the mid-top - Holy S**T!! This bike is great in the woods. The extra little bottom does help a lot, and once you hit powerband, ain't nothing stopping you.

    I'm no expert, but I figure the extra cc's helped my bottom, and the porting is what improved the mid-top.

    So far, I'm 100% happy with the work I received. Call him and ask him your questions. He'd be the one to tell you what he can and cannot do.
    Mark McDonnell
    ECEA B-200
    '01 KTM 200 MXC, '03 Yamaha YZF600R, '97 Honda Shadow Spirit 1100
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  5. #5
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    If you send it to Eric Gorr he will port it to what kind of powerband you wish to have and what type of gas you normaly use. So if you want more low end and you use premium pump gas, he will be able to port it to your needs and wants. I have no experience with any porting jobs, but I have heard nothing but praise for Eric Gorr.
    07 KTM 300 XC-W





    "A day without dirtbiking is like a day on a quad."
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  6. #6
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    Eric Gorr is the man. I had him turn my Honda CR125 into a 144cc. The thing was great. I asked him to give it "Mo Power", which is his phrase for all around power increase. It was exactly what he said. He is the lowest priced in the US that I have seen, and he is a great person as well. My next 125 will go to him before I even ride it.

    Also, he will ask you if you want to use race gas or not, and will modify the engine accordingly.

    www.ericgorr.com
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  7. #7
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    Thanks guys the bike I ride is a 2000cr 250.I have it set up for all low to mid wright now . FMF gnarley pipe, delta froce 2,two teeth bigger on the back sprocked than stock. I have been thinking about engine porting for awhile ,but I guess I just need to learn to ride better first ,berore I get more power .I am a c class rider.
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  8. #8
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    Hey, I missed this one. But here's my $.02

    It's really not that hard to get more bottom end from a modern two stroke. There are some basic things that can be done to shift power to the bottom. Most commonly done is cutting the base of the cylinder. From there the tuner can go in and raise the tranfers back up and lower the blow time. That's the time the from when the exhaust port opens to when the transfer open. KDX's have a pretty low blow time. You'll usually find a lot of carbon / burnt oil in the transfer ports of a low blow motor. Rule of thumb is, more blow time more top. Less blow time more bottom. This also gives a little longer duration on a cylinder reed induction motor, by lowering the intake port so it opens sooner. Another plus for more bottom end. The head may or may not need to be cut for this. It depends on the orginal squish clearance and if you want to run race gas. It may also allow the tuner to totally recut the head to get more squish area, which will help bottom. Or he might even cut the head for more top to help widen the power spread. Just depends on the motor, the tuner and how much R&D he's done with that cylinder.

    One of the more popular things of late is the big bore. These not only increase the size of the motor, but allow the tuner to do some more extensive reconfiguring of the port map.
    The neat thing about an increase in bore is if you look at the entry angles of the port tunnels, you can see that when you take the bore out a couple of mm you lower the exhaust and transfer port time / duration. The exhaust also gets smaller as it heads out the cylinder toward the pipe. So, you can also get a smaller port. These are all good for a big bottom end boost.

    Most guys looking at big bores are looking for more
    open class type power anyway, so this good. If the motor is already got tons of bottom ( some of the KX's ) and no top, you can raise the exhaust back up some and increase blow time and get some more top end or even spec a thicker or multiple base gaskets. Depends a lot on what effect the bigger bore has on that motor too. Then you just have to spec the head to fit the changes you made, which often can be just continuing out the stock squish angle to fit the new bore size. So big bores can actually make life easier for a guy like Egorr. Most of the work / desired effect, is done by the boring bar.

    One more big plus for the tuner is that it's a lot easier to port on a cylinder that's been stripped of it's plating, than one with it. That stuff is hard. It's also easier to create an edge that can start to flak away after prolonged use. So it's nice to re-plate it after you port. Most of the factory race teams get un-plated cylinders from the factory to use on their race bikes. Then thay can go in and do their mods and then have them plated afterwards. Don't want to have a plating failure and seize a motor just as your "million dollar baby" is about to launch off a triple.

    In the case of the '00 CR250 and more bottom end. You may look at contacting COMETIC and seeing about a thinner base gasket for starters. They can be pretty effective, but are often over looked in the quest for more bottom end. Typically they run about .010" to .015" thinner than the stock gasket. This lowers the port time, tightens the squish and increases compression. Usually not enough to need to switch to pump gas. And at about $8 they are a lot cheaper and easier than a port job.

    BTW- if you cut 2" off the end of you silencer you'll usually get a nice boost in bottom end too. Just like the $100 shorty silencers, but for free. And don't forget the head pipe spacers.
    Last edited by MTRHEAD; 03-04-2002 at 09:55 PM.
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