Head porting in Oregon

[Bratxschop]

hey guys question about who to take my head to to have it ported. I'm doing a rephased crank from Hugh. I want to also do a 700 kit and port and polish. I'm not sure I trust myself to do a port and polish on my head. Plus I want to get guaranteed horsepower. Anyone know of someone in the Oregon area that is experienced and good at doing a head job on an xs?

 

[DanielBlack]

I'm no expert, but I've been doing quite a bit of reading and research leading up to my own engine work. I believe it is pretty much accepted that the XS650 head does not respond well to the average port job. If you want guaranteed horsepower, my suggestion would be to go to the guys who've already figured out how to do it.

Purchase Craig Weeks' performance engine mod manual at www.650performance.com. Note the title of the first chapter. The Reality Of XS650 Cylinder Head Porting

Weeks works closely with Michael Morse at www.650central.com. Through him, you can purchase the CNC'd head Weeks talks about.

Note well, I am no expert. I'm just pointing out what I've found from my own research. Personally, I'm not looking for massive HP gains, just getting the best out of what MamaYama gave me. To that end, I'm going to do only a mild cleanup of the factory casting. Keyword: mild.

 

[Bratxschop]

I'm no expert, but I've been doing quite a bit of reading and research leading up to my own engine work. I believe it is pretty much accepted that the XS650 head does not respond well to the average port job. If you want guaranteed horsepower, my suggestion would be to go to the guys who've already figured out how to do it.

Purchase Craig Weeks' performance engine mod manual at www.650performance.com. Note the title of the first chapter. The Reality Of XS650 Cylinder Head Porting

Weeks works closely with Michael Morse at www.650central.com. Through him, you can purchase the CNC'd head Weeks talks about.

Note well, I am no expert. I'm just pointing out what I've found from my own research. Personally, I'm not looking for massive HP gains, just getting the best out of what MamaYama gave me. To that end, I'm going to do only a mild cleanup of the factory casting. Keyword: mild.

Ok! Thanks man I really appreciate the link. I'll have to get that manual! Im not trying to get anything crazy out of my xs. It would be very nice to gain some decent power though.

 

[Mailman]

I can tell you how to gain 25 horsepower and shed 50 pounds. Buy a Suzuki SV650! Haha, not trying to be a smart ass, it's just these motors are an old design, reliability trumps performance.

 

[Bratxschop]

I can tell you how to gain 25 horsepower and shed 50 pounds. Buy a Suzuki SV650! Haha, not trying to be a smart ass, it's just these motors are an old design, reliability trumps performance.

Lol did you just say Suzuki sv650 on the xs650 forum?? Man that's sacrilegious!

 

[Bob Kelly III]

Porting is easy it's not rocket science by any means....
the major thing to do is just smoothe the inside bores, I used Rotary files on my drill ....just remove any ridges and smoothe things up
the castings in the xs650 look so good, I wouldn't touch them BUT there the intake and exhaust connect you can do alot of improvement.
just make it breathe better....
as far as polishing ....the closest thing I would get to as a polish on the valves is what the rotary file leaves behind..... fairly rough !
WHY ? because if you make it slick you will get better airflow but the time involved is astronomical.... to make it mirror finish is silly
.... I remember Polishing a 250cc 2 stroke got all the ports enlarged and polished to a mirror finish , I was proud as hell of my work BUT
that bike loaded up so bad it was unreal it seamed the slick finish was being coated by the fuel at idle,... and it would only come off the walls at about 2500~3000 RPM and it did so with a vengeance !.... I pulled it apart and roughened the surface with 80 grit and that cured the problem
it seems that some turbulence is needed on the surface......
I suspect 4 strokers are the same , though the loading up wouldn't be as near pronounced as a 2 stroke machine because of the surface area
involved..... but if you try porting and polishing yourself do it on a different engine first not your baby
you may find it was better stock ! (their not dummies at the manufacturers!)
Porting and polishing usually means increasing valve size too, its really not worth all the hassle unless you do !
which means machining..... and in some cases you simply can't put in a bigger valve.... if you cannot buy a bigger valve face with the same stim diameter don't bother with porting , because you port because the valve face is bigger in diameter and the flow into that bigger face is restricted, by the old size valve and that needs to be relieved so it's not so restrictive to the flow. not all motors can benefit from porting !
( now that statement may rile some, but there is no sense in porting a 4 stroke unless you put in bigger valves...in my opinion! )
.....
think of your engine as an air pump and make the flow of air better and you will get a performance increase !
.....
for what it's worth , Remember I'm just a retired mechanic, not a professional in anything..... i learned by doing, so this is My opinion only.
Bob.......

 

[grizld1]

Opinion, yes, everybody has one, but facts are generally more useful. As many guys have found out the hard way, the factory ports are already a bit oversized, and hogging them out won't improve things. If you're going to DIY, knock down the casting flash, leave intake ports roughed, and stop right there. Bigger valves? Talk to a few successful tuners about that, the motor has to be able to burn what you feed it. When you're thinking about motor mods, it's best to set a goal first; think about what you want the bike to do (example: a motor built for full-out drag racing will cause misery on the street). Think about the motor as a system; the pieces have to work together. Craig Weeks' performance manual is one of the finest and clearest pieces of technical writing I've seen.

Sacrilege, Brat? Ah, you're just getting to know us, nothing is sacred around here! Several members, myself included, own or have owned SV650s. Guys keep nattering about what a "modern XS650" would be like. Well, it would be a cheap, fairly simple, very reliable ride, with a lot of performance potential and a long production run. Sort of like the SV650 (19 years and counting) and the Kawasaki Ninja 650 (12 years so far). And Mailman, let's remember that the modern practice is to specify net horsepower, and back in the day the factories listed gross power at the crank with no clutch or alternator installed; the difference is probably north of 30 hp at the wheel. Reliability and performance aren't mutually exclusive in the XS650 motor if the builder knows what he's doing, as gggGary has proven on a couple of his long distance runs this year.

 

[grizld1]

One more thing, Brat. Don't pay any attention to recommendations from anybody who hasn't done exactly what he's recommending. For responsible information, enter the member name Jack in the search window and read a whole bunch of his posts. Porting may not be "rocket science," but the flow dynamics involved are complex enough, and a lot of what works is counterintuitive. Jack's research has been done hands-on at the flow bench. I don't know if he's taking on any new jobs or if you'd be interested in sending a head to North Carolina and exercising a lot of patience, but I can tell you (from experience) that Jack does beautiful port work.

 

[grizld1]

A couple more things (ain't there always?) Nobody can possibly "guarantee" a given power increase from a port job, there are just too many variables involved. Cam grind, valve timing, intake and exhaust tuning, and compression ratio are all factors that influence how well extra flow from port work will get used. Re. rephrasing, it will move vibration to another part of the rpm range, but it won't eliminate it, and in spite of the hype it won't give you a power boost. If you want to eliminate vibration, have the rods and pistons beam balanced and have the crank carefully trued. Yamaha spec allows .002" runout measured at the journals, but a good hand can get that down to none measurable at the journals with a quality dial indicator and .002" measured at the flywheels. Then have the flywheels tack welded to the shaft on the outside only. That's standard practice for race builders; having the flywheels welded on the inside as the crank is built up leaves you with Kleenex--use it once and throw it away.

 

[650Skull]

Here are Jacks pics for porting. there was a write up and pics over at the 650Garage but the pics are not available. I had saved them and reposted them in this thread with jacks permission. They aren't necessarily in the right order due to the change in order when i downloaded them. I have assembled them in order as i see them and what looks to be right. Intake port is left rough for mixture, outlet ports are polished.


Jacks XS650 Garage thread.
http://xs650temp.proboards.com/thread/119?page=1

Thread with the pics.
http://www.xs650.com/threads/jacks-information-on-head-porting.12301/page-2

Another link with good head/exhaust/porting info
http://www.xs650.com/threads/porting-pics-for-your-perusal.44711/