RB Designs Carb Mod for EC300 - Anyone had it done?
 

As the title says, has anyone had their carb bored and the divider plate installed on their EC300? I am going to get my head sent off to get the squish done and figure whilst their I might do this if it is worthwhile.

Has anyone had it done and if so what can you report?

Brendan,

This may not help you, but I had the RB Carb mod done to my KDX 200 and would HIGHLY recommend it - especially if you like low rpm smoothness and throttle control. I'll have Ron do my GG 300 ASAP :)

Jeff

Cool. I have heard KDX riders rave about it before and it seems like a logical theory (the dividing bit)...I dont see why it wouldnt also work on a 300.

Im looking forwards to getting my squish done too...between that, the carb mod and the new piston and ring im putting in my bike should fly.

When I got my 11 250 the jetting was off for where I ride. I was just like you, I was going to get my squish done by RB and decided to get the carb mod as well. With that being said, the bike was so much better. It came alive and was jetted spot on. It was like I was on a different bike. I can't can't say how much the carb mod itself made but the bottom and mid woke up and my mileage is much better than before. I love my bike now!!

Alan

I had the full carb mod as well as squish done on my 07ec300. That bike started out as a 250 and ran very well on top end but I missed the grunt on low end that my 01xc300 had so I switched the top ends over. My 07 was then a 300 and had good low end but simply would not rev out much on top. That all changed after Ron did his magic to the carb. After the mod it revved out on top like a 250 and would pull stumps on the bottom.

Thanks Guys,

I just found this thread in the products review part...

http://www.gasgasrider.org/forum/showthread.php?t=1140

Seems like many people reckon its worth doing. Head and carb are coming off tonight and tomorrow they will be on their way over the pacific to the US of A.

Brendan

you cant go wrong with that. If you just consider jetting time plus a JD kit you arevway ahead plus the added performance from the mod. It truly is a no brainer.

Update - got the mods done and the bike back together. Also put in a piston and ring at the same time. From the quick squirt I had on the paddock over the road I am very pleaseed. The bike absolutely hammers now...its like chalk and cheese. Hard to tell how much of the power gain was from Rons work and how much was from the fresh piston but the bike is very different now. I could immediately notice the extra power straight off idle, which I imagine is all thanks to Ron.

Havent had a chance to open it right up yet to test out the top end but am looking forwards to doing so. Just have to sort out a sticking throttle first...I near sh!t myself when I grabbed a bunch of second then tried to dial off but the bike hit band instead.

To test it, I did my bike in stages.

I had the head done first. Major power improvement.

Then I got the carb done. The biggest thing I saw was that I no longer had to go super lean up in Flagstaff, Arizona (9,000 feet) to keep the bike from blubbering. I also could go one size leaner down in Phoenix during winter.

Old jetting 175/45 for Phx winter and 162/38 for Flag in summer.

After the carb mod it is 172/42 and 168/38.

I could go leaner but I like the motor behavior when it's a little rich.

Final results are in - bike has more power everywhere. Its got at least 15kmh extra top speed, definitely has more grunt off idle and down low, and the mid range is heaps better with much more power over a bigger spread in each of the gears. Had a great ride on the weekend with it, including 40mins in the slowest most technical single trail I have ever ridden...and it didnt stall once. I would have struggled on this trail pre rebuild and mods.

Its also got tonnes more compression, which makes descents a hell of a lot easier due to the extra comp braking.

I finally sent my head and carb off to RB. It was delivered last week to him, but the weekend came between then and him closing shop on 3/8 - 3/13. He was kinda busy as well I think, so not sure if I have a bit more wait. Sounds like he'll be taking my compression up a bit based on my testing. I'm really anxious to try it out.

I've got about 20 hrs on the RB mods (squish optimization and carb mod). I have to agree with everyone, more lower end easier to adjust the jetting, no draw backs to date. I'd recommend to anyone. Ron got my parts on Friday, and had 'em shipped back to me the following Monday. He must be busy, and I wouldn't doubt it a bit.
Tim

Got my head and carb back from Ron and hope to get it back together in the next day or two and test. Visually his work looks top-notch. From everything I've heard I'm expecting great things here. I'll chime back in with my impressions when I get it back together.

I'll be waiting for the chime! :D

What is he doing to the new(er) carb?

What I can see easily is he put the divider plate in my AS II and bored it out to 39mm I assume. There is also a different jet block installed with the tower that the stocker didn't have. Haven't looked close enough yet to see if he modified the slide or low speed circuit, but those are still listed as part of the mod. He's still jetting with the CEK needle.

What is Ron Setting out for Jetting on ASI for a 300..

My 250 he sent:
cek # 3
42
178

Feels ok on my 300 a little fat on the bottom but very linear.

I await on how the mod affected motor performance (revs pre & post, for example).

He also cuts the slide.

Chiming back in on my results so far
 

I was able to finish bolting up my rb-designs mod'd head and carb yesterday and get out for a little rip. As I mentioned before the man's work just looks top-notch. The first thing I did was another compression test. It was 148psi when I sent the head out and it now tests at 150psi. I told him to set it up for pump gas, but I expected we'd be up a bit higher than that compared to other readings I've read about. I've got an inexpensive compression tester I picked up at Autozone, which I assume is consistent if nothing else. Whatever, I emailed Ron to let him know what it tests at now and he said it was fine, more about getting the squish correct. I just wonder if there is something more to be safely had out of it. What do you guys think?

I left all of rb's carb settings as is and just took it for just a quick little rip. The bike pulls strong and clean from about 1/8 and all the way up. No complaints there. I'd say it's as clean in this range as any jetting iteration as I had tried, which was quite a few (although not near as many as Jakobi!). His settings are a little rich down low, but I've got plenty of jets to play with including the ones he sent me. I didn't have any time to play with slow jetting yet and I'm really anxious to see if my air screw actually works now. I need to get out and put some time on it and post back.

The thing with compression testers is that the variance between testers is huge, they are good to measure changes, but cheaper ones are not always that accurate. We borrowed a compression tester from a friend with a sprint car shop and tested the engines at around 200psi. Borrowed another friends cheap tester and it measured 150psi on the same engines on the same day.

Point being, if your tester measures low, then the change from 148 to 150 seems like a waste of time, but it is more likely that the tester isn't accurate in the first place. :p

I assumed mine would at least be consistent if not accurate, but that may not be the case. I need to get my hands on a good one and get another test for comparison. Thanks

Also keep in mind that 300s have a compression bleed hole over the exhaust port for easier starting.

There is a difference between compression ratio and cylinder compression. One is the volume of the combustion chamber, the other is the ability of the rings to seal. Just changing the volume does not change the ability of your rings to seal.

Also, did you hold the throttle wide open when testing? How many kicks did you give it before you took your measurement?

Good points.. But you'd also expect a fresh engine with a higher compression ratio to have higher cylinder compression too.

The test I did before shipping the head off was with the carb off, so just the reed cage in place. I pulled the carb before I remembered to get a test. The test after I put the modded head back on was with the carb on, WOT. Each test I did several kicks until the gauge would absolutely go no higher.

I didn't read it was a fresh engine, I understood it to be a simple head swap and carb install. If, However, new rings were involved I would expect higher numbers after it was broken in.

Sounds like you got it right. If you didn't put new rings in then your numbers are a correction factor off, i.e.: right on the money. If you did put new rings in, you need to break the engine in and allow the new rings to seat before you test their sealing capabilities.

The engine only has about 16 hours on it. I was only able to ride enough last season to break it in really.