Hi, Just thought I would see if anyone has tried High Velocity porting on their SM's.
If you are not sure what it is, check out:
http://www.mototuneusa.com/homework.htm
Many Thanks in Advance
High Velocity Porting
Hi, Just thought I would see if anyone has tried High Velocity porting on their SM's.
If you are not sure what it is, check out:
http://www.mototuneusa.com/homework.htm
Many Thanks in Advance
I just read that entire site, top to bottom.
I'm going to be doing it on my supermoto honda, asap.
1988 Honda NX250 "Roxy" - 16" street rubber, +40mm front brake, flat black paint, reupholstered seat, barkbusters, uni pod filter, de-restricted exhaust, 20w fork oil/progressive springs, GSXR750 rear shock, EBC motoX clutch
Please let me know how it goes as I would be keen to see whether the bike performs better.
well im curious b/c i've alot in the past to keep the intake rough, but to polish the exhaust port...
93'XR600-http://www.bikepics.com/members/wornknobby/93xr600/
90'CR125-http://www.bikepics.com/members/worn...p?i=564495&s=0
87' XR200-http://www.bikepics.com/members/wornknobby/87xr200/
Agreed. ^^
There's some good, valuable content there. When I port and polish heads on the hot rod engines I build, "polish" applies only to the exhaust side for me. Some of the old school engine builders I learned from told me a long time ago that keeping the intake tract rough (to an extent) will keep the mixture in suspension longer.
All bets are off when I build mechanically-injected drag motors, though. EVERYTHING gets the glossy finish then...
The only ports that should be polished is the exhaust ports. That aids in combustion and carbon buildup (which you dont want)
If you have gas running out of your exhaust ports you need some serious other work besides port job.
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you need to remember this applies mostly to carbed motors. when you get a fuel injected motor with the injectors shooting right in the intake at the valve there isn't a advantage to a rough port anymore.
Now that is interesting. I wouldn't believe it, but his dyno and race results are pretty convincing. The only thing I'm wondering about is how the results would apply to a thumper turning at 5k-8k rpms rather than 10k. It looks like he gains power everywhere but the extremely low range.Originally Posted by benscrazy
Hi, Just thought I would see if anyone has tried High Velocity porting on their SM's.
If you are not sure what it is, check out:
http://www.mototuneusa.com/homework.htm
Many Thanks in Advance
Awesome find!
some of the super duper worked on civics I've seen actually take this theory and put little dimples in the inlet tract (like those on a golf ball) to speed port flow.
1988 Honda NX250 "Roxy" - 16" street rubber, +40mm front brake, flat black paint, reupholstered seat, barkbusters, uni pod filter, de-restricted exhaust, 20w fork oil/progressive springs, GSXR750 rear shock, EBC motoX clutch
Been involved in doing this to an F4i with positive results, ended up about +10 hp.
Also, a prof. who races sportbikes, I believe singles or twins, said this is rather common.
Sucked ya right in there didn't it.
I've read all his articles several times. They really make you think and you
get a much better understanding of what's what.
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The dimples are usually right after the fuel injector. This is to help prevent the fuel from falling out of suspension.
I did it on my YZF450. I have been filling ports since 2000 on all my 600's, with extremely good results, I usually had the quickest bikes in the class.
The current method, especially with todays 600's is to simply fill the top of the port and its basically a straight line from the valve seat to the top of the opening of the intake port, with some slight filling of the floor to make the shape smoother. Filling the floor only is seen as old hat in the UK, but works just as good, its simply more awkward !
On my 450, the ports are obvously no where near as straight, due to the carb orientation, so I had to raise the floor and fill the top of the port behind the valve guide. The valve guide (unground), was only just sticking through the filler, thats how much I did.
Did it work?
Well, the previous motor (with the same head) was a 480 big bore, the head was supposedly as works head (the bike was ex-factory), and it was quick, as quick as anything else.
I put it back to 450 when it cracked the cylinder, did the port work and hey presto, 4hp more, at low revs the same, but mid to top was much better, and from 30cc less.
Will see how it compares next weekend, as thats its first race since the rebuild.
Oh, and Belzona is the filler to use - expensive, but I have seen JB weld crack off on other bikes, so I darent use it, but I guess its all in the surface prep.
EDIT: i raised the port so much, that I had to fill the inside of the head near the valve spring seats (where all the oil is), and also the outside of the intake runner near the head mounting - if you have a YZF you will no what I mean.
Old hat? Its one of my favourite sayings !
OK, a picture paints a thousand words, so they say, so I have done this CAD image (ha ha, in paint can you tell?).
Anything in blue is what I filled, I also removed alloy from the roof of the port at the entry so it was straight and not hitting that nasty piece of casting thats on the Yams (the Hondas arent like this, but you the idea).
It aint to scale (obviously), but gives you a good idea of what I did.
I think I took out 9mm of alloy from the roof, at the entry point - but I have slept since winter, so cant remember. The blue near where I ground that out is where I had to fill it.
And if anyone says I have done it all wrong, so be it, I've heard it all. Every tuner has different opinions/ styles/ methods, I've been told what I have done am doing is a waste of time.....by the tuners of bikes I have passed, and then been accused of running big bore 600's !! Oh good times.
I have also been told the very best and quickest bikes use pretty much the same method.
I'll stick to what I know as I am only a skint engineer and racer, I darent risk anything new !!
Looks great. Thanks for your post.
Incidentally, did your mod work?
Sure did, read my first post.
Its not like the head before was bad, the tuner did a good job of porting it without filling it.
As far as I could see, the port was the best it could have been.....but could be a whole lot better by filling it !
Dont forget, porting the inlet/ exhausts, is only a small part of building a motor for race purposes.
When I first did this on my 2000 model R6, I had 112hp. I pulled the head, filled it up and without doing ANYTHING else it punted out 119hp on the same dyno.
Same bike had 101 standard, before I did any work, which was skimming, cams, bellmouths, etc..the usual crap.
I think I got one, maybe half a hp again by jetting afterwards, but that was all.
Many Thanks. I might give it go. What did you use as the filler? Was it pretty easy to do?
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Belzona 1111 Super metal.
http://www.belzona.com/prod1k.aspx
Good to use, its two part and its also not runny so its easy to work with..well, easier than other metal pastes.
I rough the surface and use a bent scriber to scratch it in once ive put it on, never had any chip off so far....touch wood.
that was superdiduper! Seriously who knew JB weld could do so much? Kick ass!
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