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Discussion Starter #1
Does anyone have a recommendation on where I can get head porting done?

Current engine mods include:
chimera intake
takegawa s cam
dual high mount exhaust
dynojet PCV

Thanks!
 

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I don’t have a recommendation, but I will be watching this thread with interest. At one time, I was very interested in either having my head professionally-ported or simply purchasing a head already ported and equipped with larger valves, etc. Here are a few of the observations from my own experience; your mileage may vary:

Grom FatherZ: Pretty much the gold-standard of head-porting and hopping-up Grom engines for maximal performance......but reportedly very pricey. Website doesn’t list prices for head-porting services, and no email. Communication very limited. They don’t seem to do email or phone. I wanted to send my head to these folks, but in the end, my questions (sent via PM on forum) went unanswered and I never even got a firm price quote. I think they primarily deal with much bigger wallets than mine.

JC Racing: Decent website. Moderate to high priced head-porting. I couldn’t find any Grom owners who had actually used their services, however. That concerned me. No response to email inquiries.

REN Motowerks: Nice website. They listed a new factory head which had been optimized, larger valves, etc. This looked like a really cool solution, but I think they have largely stopped doing business. Email inquiries went up-answered. Probably out of business.

DHM Racing: I liked this vendor; he re-flashed my stock ECU. Decent website. Like REN, DHM lists a new re-worked and optimized head, but has shown out-of-stock for months now. No reply to email inquiries. I think they may have ceased doing business.

Hard Racing: Extensive web-site, outstanding customer support. Promptly answer emails and — in a pinch — even phone calls. The issue for me here, however, is that Hard Racing just sells the Finbro heads, and those heads have had a number of pretty well-documented issues. While some folks have used Finbro products without problems, I don’t feel comfortable with a Finbro head from what I have seen.

This is about where I left off — essentially I gave up on the idea of having my Grom head ported. I will be curious if others can provide some more workable options.....maybe I’ll reconsider the idea one day.
 

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send it to GromFatherZ

REN motowerks is out of business due to California EPA coming down on him

or watch a ton of youtube video and do it yourself

I've done my own porting of the intake port and port/polishing of the exhaust port and also polishing the valves and port and polishing the inlet tube.
 

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DHM is activ3 (pun intended?) and going strong.
 

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DHM All Day, my man just got married and i believe a baby on the way. Best way to reach him is PM Activ3 or hit up DHM (David Hugh) on face book... He does not let his messages go un-answered and definitley takes the time to answer all your questions weather you purchase from him or not...

Pricing??? Hands Down reasonable

DEFINITLEY Not out of Business, the man is a Beast.
 

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Discussion Starter #7
I will try to message DHM (Activ3). Thank you all. Forgive the naive questions (I am trying to learn), but what else would I need to do?
Can I get away with JUST porting the head?
Should I grab a koso throttle body at the same time?
Do I need a new ECU map from somewhere after these changes?

What else is required (and or strongly recommended) if doing head porting?

Thanks!
 

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I know for a fact, porting the stock head, Grom fathers rev wedge, Koso 34mm throttle body, dual valve springs, TB cam, and more aggressive sprockets will make for a super fun Grom that will make power all the way up to 11K rpm.

Probably throw in a high compression piston and make it even better.
 

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Discussion Starter #9
In your guys' opinion, do you think head porting + koso TB is more reliable than say the takegawa 143 bbk?

I already have the chimera intake, dynojet pcv, after market exhaust, takegawa stage s cam.

Just want a little more oomph....
 

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In your guys' opinion, do you think head porting + koso TB is more reliable than say the takegawa 143 bbk?

I already have the chimera intake, dynojet pcv, after market exhaust, takegawa stage s cam.

Just want a little more oomph....
Increasing displacement is going to give you more low down "oomph". You won't have to rev the motor so high to get the power, compared to trying to get more power out of 125cc. The setup I mentioned earlier is going to feel dead under 6K rpm, but in a race - it'll smoke a 143cc bore kit mated to a stock head/stock throttle body with cam.

If you're going to do a bore kit, I suggest getting the 186cc kit. The 143-153cc big bore kits aren't worth the effort in my opinion. For the same amount of work, you can get a very noticeable improvement going with a 170-186cc kit. Reliability will be very good if you keep it "choked up" with the stock head, but I'm almost sure you're going to want to upgrade the head as well. Everyone does.... this is the point where cost starts going up exponentially.

If you go the souped up 125cc route, I think you'll enjoy it very much. Especially when you outrun other Groms with big bore kits.
 

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You can think of it like, Honda S2000 or V6 Honda Accord? One is more fun, the other is more practical. Just depends what you want.
 

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Discussion Starter #12
Is there any benefit to porting the head and keeping the stock rev limiter? I ask because I feel like the more you raise the rev limiter, the more likely you're going to break something. So does head porting only result in gains at higher rpms? ie - is it worth it with a stock rev limiter?
 

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I will try to message DHM (Activ3)....
Farmboy, I was curious if you were able to make any progress regarding your head-porting inquiry?

I was just thinking -- for someone who has the proper equipment and skillset -- this sure seems like a great small business opportunity: substantial demand, and virtually no supply.
 

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Farmboy, I was curious if you were able to make any progress regarding your head-porting inquiry?

I was just thinking -- for someone who has the proper equipment and skillset -- this sure seems like a great small business opportunity: substantial demand, and virtually no supply.
GromFatherz does a lot of porting work by request.
 

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Is there any benefit to porting the head and keeping the stock rev limiter? I ask because I feel like the more you raise the rev limiter, the more likely you're going to break something. So does head porting only result in gains at higher rpms? ie - is it worth it with a stock rev limiter?
You'll still see gains with the stock limiter. But you'll also be missing out on a lot of potential. You don't always have to rev it out to the max rpm if you to raise the limiter...you probably will tho cuz its so fun.
 

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You want all out power and beat the crap out of your friend's grom/monkey bike with out going to transplant 300cc engine than the engine I would recommend for reliability would be the old 170-2v ported head by BrianS which is no longer made, Finbro 183-2v with ported head or go big with Koso 170-4v or Takegawa 181-4v or Neo 181-2v.

all these BBK kit will need a updated ECU, cam, HD crank/rod, updated throttle body such as 34mm and updated F/I size, airbox, full exhaust system, external oil cooler, F/R sprocket combo change, and more

Speed cost, and if you short cut your build expect replacing and searching for the right combo of parts.
 

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I have a dhm ported head on my 143 built with the upgraded retainer and I love it! I rev this motor way past the stock limiter.

I also have a high comp 125 running a random ported head that runs pretty good also but over the winter Im gonna have david build me a head for that as well.
 

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Perhaps, but how does one go about making that “request?” My previous communication attempts have gone largely un-answered.
That has been my experience also.
Too bad, from what I have read he seems to do good work, although rather expensive. Although one must sometimes pay to play...
 
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