220 head mod.

[cornishwrecker220]

ive been reading about the rb head mod & was wondering as a cheap alternative what the power gains / benefits would be if i just decided to skim the cylinder head say 15 tho..it would obviously increase the compression slightly thus giving a light gain in the lower rpm range,would this mod help the `squish`..has anyone on this site done anything similar,whats your opinion on this subject good idea or bad??

[zomby woof]

I'm not sure .015" would be enough.
If you have the head off, and can measure the chamber, you can calculate what the compression increase will be.

[canyncarvr]

ive been reading about the rb head mod & was wondering as a cheap alternative what the power gains / benefits would be if i just decided to skim the cylinder head say 15 tho..it would obviously increase the compression slightly thus giving a light gain in the lower rpm range,would this mod help the `squish`..has anyone on this site done anything similar,whats your opinion on this subject good idea or bad??

Bad idea.

1. A 'cheap' alternative? At $45, THAT is cheap to start with.

2. You would remove .015" based on....what? Why that number? What do you figure the % of chamber volume change to be?

3. You would remove the .015" how?

4. '..would this help the squish?' Help it....do what? A squish band is configured through the use of manipulating blending radius, band angle, depth, and width. Cutting the bottom of the head misses most of those.


Not trying to be smarmy about it, but the point of the question eludes me. You have two choices: Carve on the head yourself with all your head design knowledge, machining expertise, and thousands of hours of refinement and testing of the operation, or, spend $45 (plus s&h, yes) to have it done by someone that is aces in all of those areas, knows how to do it and will provide you with the positive effect you're looking for.

Please do consider that I don't even own a de-tuned KDX and I have no idea what .015" off the base of the head of a 220 would accomplish.

But...you did ask for opinions...and yanno...everybody has one of them, too.

[Julien D]

I would just quote Carvr, but that would seem to be just mean. I completely agree with everything he's said though. How much cheaper than $45 do you want to go??!! Could end up costing you a lot more if you paperweight that head :|

J.

[zomby woof]

$45 is only the start.
It would cost me at least $20 either way to ship it, so that's pretty close to a $100 bill.
I could machine it in under 5 mins at home.
While squish band is important, the bike runs well as-is (the stock one is not bad), and increasing the compression, but leaving it alone is definitely an option. With a few measurements, compression can be calculated, not as a percentage, but as a ratio.
Not trying to start a fight, but if you have the equipment, and some level of expertise, it's not a terrible idea - it's not exactly brain surgery.

OTOH, if you don't know what you're doing, you're probably best to just leave it, or send it to someone that does.

[Julien D]

$20 shipping each way for a little head? Who do you ship with? Personal courier by way of ferrari?

USPS flat rate will be about 5 bucks. That takes it all the way to 55 or 60 to have compression raised AND squish band re-configured. I'm not trying to start a fight either, just sayin. It's worth the investment to have RB do it. With some research I'm sure you can shave the head and pick up some compression for less money, assuming you have the proper equipment to do so. Any machine shop around here would charge $65 at a minimum.

[zomby woof]

I'm in Canada.
Trust me, I ship alot.
It's not cheap like it used to be.

[cornishwrecker220]

i understand what your saying & $45 is cheap..dam cheap, but i live across the pond & to have a head mod like the rb done over here would easy cost me £100-£150 of my english pounds atleast!..where as i could take the head down to my local marine engineering shop & get them to skim 15-20 thousands of an inch off for £15..i was just wondering if any of you guys on here had done a mod similar to what i`ve asked for on the cheap.i envey the U.S.A as you have so much more regarding tuning/engineering & aftermarket custom goodies than we do ..my country used to be called `Great Britain` but you probably know it better as `England`

[Indawoods]

Canada is the Capital of machinists! Surely there is someone there with the knowledge that can perform the procedure for you on the cheap! I don't think Ron is going to devulge any of his trade secrets as he has intellectual rights to them.


We still love ya England! After all you gave us Triumphs, Nortons and BSA's! Not to mention the Beatles, Rolling Stones, Judas Preist, Iron Maiden and many many others....

[cornishwrecker220]

ah yes ghosts of our past!!...but you guys had better rock bands..van halen etc although we did have heavier... black sabbath, deep purple!!.. come to think of it now you mention canada my 2003 kdx220 is a canadian import!

[RBD]

cornishwrecker220,

If you deck the top of your cylinder, you will probably need to shorten the pivot bushings that support the sub-power valves also.

Ron

[Julien D]

I'm in Canada.
Trust me, I ship alot.
It's not cheap like it used to be.

Ah yes, that is a totally different situation. Shipping to/from Canada is a bear. I failed to take that into consideration. My bad.

An undeniable truth is that you WILL gain compression by shaving the head or decking the bottom of the cylinder. Either one should have similar result. Wether or not you will get a desirable change in performance while still being able to run pump gas is the question....

[cornishwrecker220]

cornishwrecker220,

If you deck the top of your cylinder, you will probably need to shorten the pivot bushings that support the sub-power valves also.

Ron

..i had figured that ron,thats why i just thought by skimming the head a little would be less time consuming & hassle..expect i`ll just dump a wiseco piston in & see what she runs like..i had an 06 525exc before & nothing compairs

[canyncarvr]

cornishwrecker220,

If you deck the top of your cylinder, you will probably need to shorten the pivot bushings that support the sub-power valves also.

Ron

..i had figured that ron,thats why i just thought by skimming the head a little would be less time consuming & hassle..expect i`ll just dump a wiseco piston in & see what she runs like..i had an 06 525exc before & nothing compairs

This is getting pretty scattered.........


Reducing volume of the head is not the same as removing material from the bottom of the cylinder. The former doesn't change port timing, the latter does...and not in a way that would generally be considered to be a good thing.

I missed where decking the top of the cylinder came in..but the bushings do fit fairly close to the top. Don't know how much room there is for the top of the subport drum itself..and how much you could remove from the head before that became an issue.

Most of the 'bad idea' opinion of mine comes from what I've found all too often to be true...The Law of Unintended Consequences is just waiting to bite you in the arse. It's just too often that one thing leads to another...whether you want it to or not. 'Fer instance...you take .020" off the head, reduce the thickness of the squish (btw..what I meant when I used the word 'depth'), you end up with increased pressure on the piston crown at the ring land, little bits of the piston start to ping away, you end up with a mess.

Will that happen? I have no idea. I'm making up a Law of Unintended Circumstances example..and saying I've seen it way too many times.

[Julien D]

Good point. Decking the cylinder DOES change port timing, shaving the head does NOT. I guess decking the top of the cylinder wouldn't either, but that opens a whole nother can of worms, as has been discussed.

[canyncarvr]

For anyone who maybe wants to maybe learn a thing or two.

Considering the bad LUC you could have, note the info on squish config, boundary layers and stuff.........

Food for thought anyway.

[zomby woof]

Canada is the Capital of machinists! Surely there is someone there with the knowledge that can perform the procedure for you on the cheap! I don't think Ron is going to devulge any of his trade secrets as he has intellectual rights to them.

I am a machinist.... specializing in cylinder head work

Mostly automotive, and always 4 stroke

My head's not going anywhere. The bike already has more power than I have riding skill.

[canyncarvr]

Not trying to start a fight, but if you have the equipment, and some level of expertise, it's not a terrible idea - it's not exactly brain surgery.

That's not a particularly fair statement, being a machinist.


Nothing one knows how to do (and can) is brain surgery...including brain surgery.

I know how to do a lot of things quite well..none of them are hard...and NOone would EVER pay a decent wage or sum of money for me to do them.

Concoct (and drink!) a good rum mix? Yep.

Lose stuff? Yep.

Attain a critical mass of crap in any vehicle I drive? Yep.

Sit on my butt for LONG periods of time with a throttle in my right hand? Yep.

Have no patience 'fer crap from most of the species? Yep.

No money in it, though.

[cornishwrecker220]

For anyone who maybe wants to maybe learn a thing or two.

Considering the bad LUC you could have, note the info on squish config, boundary layers and stuff.........

Food for thought anyway.

...yes deffo interesting read on the effects & benefits of reducing the squish band (page 2)...my question has been answerd .

[canyncarvr]

Read all of it.

This:

It (squish reduction) is one of the few "all gain with no pain" modifications one can carry out on racing or even street motorcycles.

..I'm not saying isn't true. But it has to fit and work together with aspects of turbulence increase, increased burn rate, and keeping the boundary layer intact.

..drastic increase in cylinder pressure has increased the local temperature (and molecular speed) so high that it has reached the ignition temperature of the fuel.

Or...ping-o destruct-o.