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RB head mod question, or reviews.

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I looked into the RB Head mod shown here http://www.rb-designs.com/

It basically sounds like decreasing the cc of the head to maximize the compression while making sure that the piston does not cotact the head. Looks like the mod involves cutting the head down and then opening it up to match the squish. My question is, it it worth it to do the mod and where will the mod help out? Will it really make a diference? Will it help the low, mid or top range? How much will it affect the jetting? Do you need to change anything else to make the mod work? (For example, porting a cylinder will not really do much without changing the pipe too) It would be nice to here from people who had the mod done with some personel experience testmonials.

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Nobody? I have heard about head squish and such, kinda figured out what that meant. The I saw some posts about the RB head mod and head squish and also RB carb mod. And now all of a sudden, nobody knows about it? Come on, don't be shy. I just want to here if it made a difference on your bike and how it was affected. PM me if you don't want to make it public, I wont mind.

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I looked into the RB Head mod shown here http://www.rb-designs.com/

It basically sounds like decreasing the cc of the head to maximize the compression while making sure that the piston does not cotact the head. Looks like the mod involves cutting the head down and then opening it up to match the squish. My question is, it it worth it to do the mod and where will the mod help out? Will it really make a diference? Will it help the low, mid or top range? How much will it affect the jetting? Do you need to change anything else to make the mod work? (For example, porting a cylinder will not really do much without changing the pipe too) It would be nice to here from people who had the mod done with some personel experience testmonials.

Basically cutting the head intails getting the squish band to the optimal size for your gasoline of choice: race, pump or a mix.

Having the head cut gives you a more efficient combustion and should not waste very much raw gas.

Depending on how far off your current squish band is, it could be a drastic increase in performance.

I've never done it, as I've been putting out other fires and my stock squish band isn't as far off as most YZs. My bike's getting a new top end after this weekend's race, and I'm sending RB my head.

So if you're willing to wait until the season picks back up in late January, I'll let you know how she runs.:busted:

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My bike's getting a new top end after this weekend's race, and I'm sending RB my head.

So if you're willing to wait until the season picks back up in late January, I'll let you know how she runs.:busted:

Thanks for your reply. Not really wanting to wait. I would send mine out today if I had any reason to believe that it would help out my bottom end. Not that my bottom end is bad but before I do any mods, I really like to know how the bike will react. For example, some people think adding a pipe will give their bike more power. Well this is both true and not true. Many years ago, way before power valves, I had a port job and matching pipe added to my yz125. It had great power at the top but the bottom suffered greatly. Most people ride 125 at the top anyway, including myself, back then. I let a friend try it out and he thought it had no power at all. He rode it in the low RPM range. So more power at high, less power at low. I would like more power at low end but not change much anywhere else. I know that this is not always, if not rarely, the case. That is why I ask. I guess I could give him a call and ask.

Thanks again,

Mark

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I havnt used RB to have a head mod done but I had my squish corrected for 50/50 93 pump/110 race fuel for both my 125 and 250s by EG and it pulled harder everywhere! IDK if it was from the head mod or the porting, I got the "mid/top" porting option since I ride almost strictly MX so I would have to say that the head mod made the difference down low. Its one of the best investments I have ever made. In general I would say the bike just runs better and more efficiently overall. I wouldnt say that it gained any power down low but it def. runs more crisp off the bottom which makes all the difference in the world to me, def made it SCREAM all the way from the mid range until it signs off up top. The best part is even if jetting is slightly off from weather change, I get no spooge and no mess and the bike is less "touchy" about how much the jetting effects the performance.

Im not sure if this is the info your looking for or not but I thought Id give you a little info about how having the head worked can really help performance. As GMO said, if your squish is off to begin with it can really wake your bike up and make the bike run 1000x better.

Edit: I forgot to add, one thing he suggested that I do on my 125 since I had it ported for mid/top was to go up 1 tooth on the CS sprocket to give a little more torque down low since Im a bigger guy. It really helped down low and I didnt notice much, if any loss of top end power.

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We have a ton of info on the rb head mod. I imagine there is 20, maybe more, members here who have had it done.

Heres what it did for my 250. I'm not currently using it, but I ran it for several months. Low end power , or response was improved. Plus, I no longer had pinging when running straight pump premium.

The stock head is not designed very well, or at least not optimum. RB's mod takes care of that.

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I was thinking of doing this Roland, why are you no longer running it?

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Thanks for the responses so far. I did a goggle search and found some info on squish. The search ended up back here on TT. RC was very involved with that post. Thanks for that. I read all the pages and found some good info. I brought the topic back to life by posting on it as well.

We have a ton of info on the rb head mod. I imagine there is 20, maybe more, members here who have had it done.

Heres what it did for my 250. I'm not currently using it, but I ran it for several months. Low end power , or response was improved. Plus, I no longer had pinging when running straight pump premium.

The stock head is not designed very well, or at least not optimum. RB's mod takes care of that.

I have a 2007 a YZ 250 which I plan on doing the RB head mod. I thought that the 2006 YZ's had a sensor for the detonation issues. If it did, I imagine that the bike just retards the timing a bit, which is just a band aid, I know.

I was thinking of doing this Roland, why are you no longer running it?

I too wondered why you no longer use the mod.

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I went to the Eric Gorr 300 kit, so I'm not using it. No other reason than that as the head is a fantastic product or mod.

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I went to the Eric Gorr 300 kit, so I'm not using it. No other reason than that as the head is a fantastic product or mod.

Did you need to do any jetting changes with the RB head mod? I can't seam to find anything about jetting here or on the net. All I see is trial and error with jetting. In other words, try a jet and see what happens. There has to be a better way. You seam knowledgable, what would you do?

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Its always trial and error. Giving specific jetting info is impossible since fuel is different, as is oil, and engines are as well. BUT, having a good head made jetting my bike a breeze compared to the stock bike.

I'm much leaner than most since I'm at 4500-5000 ft elevation.

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Have 2: #1- Reshaped dome= better everywhere.# 2- Higher compression but still for pump gas= big torque gains low-mid, this is the one I run cause it is so much better in the deep sand. I'll do business w/ RB again any day.

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Had rb do my 2006 yz 250 as Roland recommended it to help with spooge. Had carb mod done by him at the same time. Bike never ran right again, could not jet out the quirky transition from mid to high. Bike ran way better before. I am the exception but would not do it again. I always like to add "my bike ran great before I had it fixed".

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I did not try the rb carb. No reason really, I just did not ever get around to it. The head did not cause any serious jetting changes, but a carb mod might.

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Had rb do my 2006 yz 250 as Roland recommended it to help with spooge. Had carb mod done by him at the same time. Bike never ran right again, could not jet out the quirky transition from mid to high. Bike ran way better before. I am the exception but would not do it again. I always like to add "my bike ran great before I had it fixed".

Well, did it help with the spooge?

What gas/oil/ratio were you running before/after this?

Does RB have any recommended jetting to go with his carb mod at least as a starting point?

If not, where are most ending up with jetting after the carb mod?

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Great replies so far. I will do the test and send out my head and test samples after my piston kit comes in from TT.

RC, was it you that posted a jet kit or was that possibly William. Either way, which Jet kit would you recommend? I have Williams recommendations on jetting from another thread and will read through that. I read it before once but unless you are doing it, it could be hard to visualize.

I read somewhere that in order to know how to jet, you should start on a properly jetted bike and then screw it up. In other words, change the jets rich for example so it pops and make the rich carb engine noises. Then go the other way, carefully to see how it bogs. This way you know what to listen for when fine-tuning the jets. Have you guys heard of this technique? It sounds a little dangerous.

Sucks the one RB head and carb mod didn't work out though.

Thanks all.

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Well, did it help with the spooge? no

What gas/oil/ratio were you running before/after this? 40:1

Does RB have any recommended jetting to go with his carb mod at least as a starting point? 45

If not, where are most ending up with jetting after the carb mod?

tried everything between 40 and 50, all kinds of clip and needle changes as well as pilot and needle valve settings plus a new needle valve.

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I am using a jd jetting kit and its really cool. I woudl for sure buy it again.

I dont know about jumping into a carb mod for this bike as I dont believe I have any reason to believe it needs one.

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I've had none of the work discussed in here, but I did want to throw it out there that I stopped by RB designs since they're based out here in Portland Oregon, and the owner is a top notch guy and a really nice person. He helped me with some carb stuff, and is just an A+ person. I'd feel confident that if he's offering the service, it's worth paying for!

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I've had Ron cut several yz250 and kx250 cylinder heads, all i can say is don't hesitate any longer, you will not be disappointed! Easily the best and cheapest mod that we did to our 2 strokes. Actually got accused of running a big bore and protested at a track down south after beating their top A rider with our stock bore, stock port, RB head mod YZ250! He was screaming "there's no way a stock bore yz250 could pull away from me like that!" He retracted his protest when we pulled the tank and seat and started to drain the coolant.

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