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dldavis_66

To Port and Polish or not to Port and Polish...

9 posts in this topic

That is the question that I have my dear, newly beloved friends at Thumper Talk...

***Ahem***

Yeah, well, I was talking to some dude at a Honda Dealership, I reckon he's one of the service techs, I don't know...anyways, I told him I was interested in P and P-ing my heads. He told me that P and P-ing is really a waste of money and it doesn't really add any significant increase of perfomance IF stock configurations of intake and exhaust are used on the 650L.

Since he called me at work during my lunch break and the breakroom was rather loud that instance with everybody talking at once, I really couldn't concentrate with talking to this dude and just thanked him for what info he gave me and hung up.

Anyways, I've been thinkin. I know that my exhaust config will definately NOT be stock.

As far as the intake, well, that's where I'm kinda confused a little bit as to if I am still stock. I will be using the stock carb, but peaked and tweeked a bit:rejetted [DynoJet Needle and jet] , Slide pressure holes drilled out , Pilot screw to 2 1/2 turns, , UNI foam filter, de-smogged and de-snorkeled. Sure doesn't sound like stock intake to me.

So, will I benefit with a Port and Polish? That is the real question. Personally, I think I will definately benefit with a P and P. But I am rather new to motorcyle upgrading and could use some different opinions.

Thanks in advance:ride:

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I wouldn't waste my $ on a port job unless you go all the way...big cam,piston,carb,ETC.ETC. Honda does their homework when it comes to flow in the ports.

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It will def. help. Just dont polish the intake to a mirror finish. It needs a small amount of rough finish for a complete mix of air/fuel.

I've ported/polished many RC nitro engines and a few auto cyl. heads. ALL with good improvements in driveability, mid range power. It cant hurt, unless you go too far.

Here is a good site for the DIY guy. It explains the basics, tools, etc. Anyone with some mech. skills can pull it off.

http://www.sa-motorsports.com/diyport.aspx

Good info in this thread also.

http://www.thumpertalk.com/forum/showthread.php?t=591357&highlight=port+polish+xrl+head

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I wouldn't waste my $ on a port job unless you go all the way...big cam,piston,carb,ETC.ETC. Honda does their homework when it comes to flow in the ports.

The only thing I can agree with you at the moment is the higher compression piston. It's one of the main reasons that started me to working on my top end in the first place, the other reason was I knew my pistons rings were beginning to take a dump on me and had to be changed.

As for the carb, I would rather stick with the stock and just tweak it out and dial it in. I know many people have had issues with dialing in the stock to their wanting. I guess for now I just want to take things at my own pace and see what happens.

The cam: I feel pretty much the same. more undecided about it in many ways and when indecision shows it's face I don't do anything, I leave things alone.

I know I should be starting a new thread for what I gonna write about below. I does pertain a little bit to the topic at hand though.

Just prior to writing this thread, I finished tweaking the carb off the '05 bike(the one I'm current working on with all the top end parts scattered all over the garage) with a DynoJet's main(165) and needle(130) and smaller Slide spring, plus I drilled out the 2 Slide holes to 5/32.

Then I went ahead and stuck it on my new '07 bike (yes...I have 2 Pigs) which is all stock except for a WB Pipe. I hooked all the smog junk back up. I wanted to take the snorkel off, but decided not to then (I'll do it later). After getting everything back the way it was, I turned the key, put it on half choke, just a little bit of throttle and she started right up when I hit the starter button. It idled on half choke really nice heh. Turned the choke off. Wouldn't idle. Put it back on half choke, started it back up, turned the idle up a little, unchoked it, idled on it's own . Revved it up for the first time, made a really loud POP. Too lean so I adjusted the idle and mix. Got it to idle really nice. Blipped the throttle again, popped a little bit. Turned the mix up a click or 2. Took it for a test drive. Quite a noticable improvement. Acceleration was VERY smoothe and responsive. Deceleration was quicker cuz of the enlargement of the slide holes, still a teeny bit of pop and burp(still on the lean side I guess...could be the smog too I reckon). Power wise...well there was some increase in HP. I really wasn't expecting any. But It did go 75+ mph up a hill that I could only get up to 70 mph (with a tailwind) on before.

Overall the bike ran ALOT better.

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Worth bearing in mind that a lumpier cam should work in harmony with a bigger or high compression piston. If you use a lumpy cam then its also best to increase the Comp ratio to get the most out of it and to account for the loss of compression due to more cam duration.

If youve got the engine apart then it makes sense to port the head a bit, but dont go out stripping the engine just to do that.

HTH

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Worth bearing in mind that a lumpier cam should work in harmony with a bigger or high compression piston. If you use a lumpy cam then its also best to increase the Comp ratio to get the most out of it and to account for the loss of compression due to more cam duration.

If youve got the engine apart then it makes sense to port the head a bit, but dont go out stripping the engine just to do that.

HTH

Thanks for the info crmc. Not quite sure what you mean by "lumpy" cam. I reckon you mean, in generic terms, a cam with more lift and duration, like the HotCam.

My thoughts are very simular, if not identical, to yours in regard to Compression ratio and a lumpy cam. If I were to get a HotCam I would definately get a 11:1 piston. I'm just speculating, but I reckon a 11:1 piston and a HotCam would probably be equal to a 10.25:1 piston and stock cam.

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Thanks for the info crmc. Not quite sure what you mean by "lumpy" cam. I reckon you mean, in generic terms, a cam with more lift and duration, like the HotCam.

My thoughts are very simular, if not identical, to yours in regard to Compression ratio and a lumpy cam. If I were to get a HotCam I would definately get a 11:1 piston. I'm just speculating, but I reckon a 11:1 piston and a HotCam would probably be equal to a 10.25:1 piston and stock cam.

That is my theory also. Being the 11:1 is not actually what it says, just under.

So if you put in a "lumpy" cam, the stock 8.3:1 dorps to near 8:1. So with the"11:1" piston, actual will be 10.25:1 to 10.5:1.

Again, just an educated guess.

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Keep in mind that the cam doesn't change the static compression ratio, but instead has a bearing on the dynamic compression. A big cam with more overlap and exhaust scavenging will show lower pressure on a cranking compression test assuming all else stays the same. However, once the large cam gets into its efficient RPM, the dynamic compression ratio will actually rise. the cylinder filling/emptying and scavenging is helped quite a bit by adding more static compression. In fact, it's possible for the dynamic compression ratio to actually exceed the static ratio. That means that the engine's volumetric efficiency goes over 100%, which is more often seen in maximum-effort, cubic dollars race engines and not the stuff we have. Then again, the crotch rocket mills like my F4i engine often hit 110% or more.....on 12:1 compression and 87 gas. :busted:

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