EC200 GasGas Big Bore Kit 236cc

Zman

Zman

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We had an EC200 that was in need of more power. I called up Eric Gorr who built the 327 big bore kit for my XC300 and I asked him if he could super-size the 200. He told me he would check it out so I dropped off a spare EC200 engine with him.

I always heard you could not do a big bore kit for the GG 200 engines so I was super excited when he told me he had it finished. Eric came up with a really cool kit that increases the stock bore from 62.5mm to 68mm so the new engine displacement is 236cc.

The cylinder and head turned out great and the install was straight forward. I used the 0.005? thin base gasket shim and the 0.011 gasket and the squish came out to 0.045? or 1.17mm which should work well with 93 octane fuel.
The bike has more compression than stock. It kicks over with a bit more effort than a stock 200 but it fires right up. The jetting was pretty close from before, but I needed to lower the idle speed a turn or two and richen the idle mixture slightly because it was jetted for 70F riding not the present 25F and snow.

I do not have a good place near my home to really ride the bike but from the 20 minutes of riding around the neighborhood it feels considerably more powerful than before. It has very good throttle response down low and still revs nicely. I really like that the bike kept the GG linear power deliver and that there was no added vibration. We are headed to TN for our spring break trip at the end of the month so I will have more details on how it works after the trip. This was his first kit for the GG 200 so I am testing it out the prototype and I will be giving him feedback after this trip. http://www.eric-gorr.com/

Here is a photo of an old worn out 200 piston next to the big bore piston. The new piston is 5.5mm bigger than a stock 200 piston and it is even larger than a stock 250 piston.
 

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Awesome.
I wonder why the holes in the piston on the exhaust side. Those are usually to lube the exhaust port with a bridge. Which the GG doesn't have.
 
Nice one,that should be a fun ride!
Best of luck getting it dialed in quick so you can give it a good thrashing!
 
200 gg

Thanks for the post gives me something to think about still working on my 325 thanks for all the info it helps a lot should have my top end back from mellinium plating soon
 
Nice work......lets hear more.....

noticed the same thing on the piston, drilled for a exhaust bridge..

is the piston a Weisco???

what about the power valve? Any clearance issue?? Are the power valves modified in any way?

crazy question......but the 200 uses crank stuffers to increase volume.....with the larger piston about the size of a 250 piston, are the crank stuffers retained?
 
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Eric said the piston is a modified Wiseco from a big bore TRX250R which is why it has the exhaust bridge holes. The bottom end is stock and did not need to be modified to clear. It is a 200 cylinder that is bored to fit the piston. Eric had to come up with a different power valve for it to clear the bigger piston. I had to readjust the power valve but it works fine. This combo should work pretty well since the bike came with the 38mm carb and the 250/300 pipe that came stock on the 200 .
 
Looking forward to the ride report. Both on the BB kit and where you're riding.

RB
 
For our spring break trip at the end of March we pick 2 or 3 locations and choose base upon weather.

This year we will try CRMA in TN and I think our back ups will be Royal Blue in TN and Highland Park in GA.
 
I wish we were already on spring break but we have to do that work thing for another week and a half. We should be riding on the 29th.
 
If you already have a GG 200 bike set up for your weight and riding style and you just want more power, this big bore kit offers another option to buying a whole new engine or bike.
 
This is why I've never bought a 200cc bike, though I've been tempted many times over the years.
I love them, but lots of times it's nice to have just a bit more grunt.

I find a 300 too much, so a 250 it is...
 
236 Big Bore Ride Report

We just got back from our annual spring break dirt bike trip. We had a chance to put some real miles on the GG EC200 with the Eric Gorr 236 big bore kit. We put the 236 kit on my friend?s EC200 that we have had in our group for about 5 years. The engine was originally stock and in good condition. We know this 200 pretty well and 4 people in our group of 6 have spent many miles on that specific EC200 or another similar EC200.

Right after installation of the kit, it was apparent that the bike was geared too low. We had it set up with 12/51 previously for tighter technical riding so I installed a 13 countershaft sprocket and that seemed about right with the additional power.

On this trip we rode CMRA and Highland Park Resort. My friend who has been riding the bike for the last 3 years said it had noticeably more power and he was able to easily ride the bike a gear higher than when it was a 200cc. I rode it for a while in the woods and I also took it on the MX-1 track at the Highland Park Resort. I was honestly impressed with the engine. First thing I noticed is that it has a nice increase in power across the rpm range yet it still kept the linear GG power delivery. It has noticeably more bottom end power, but I noticed a bigger increase in midrange and top end power. We found we could ride the bike easily and lug it (more than a 200) and we could also ride it hard and it seemed equally happy doing either.

I rode the MX track with my son who was riding his GG EC250. His 250 is set up for more midrange and top end. We switched bikes for a few laps and while I could tell the difference between the 236 and the 250 I would say the 236 feels more like a 250 than a 200.

For fun we did three standing start drag races on some dry unridden flat clay. The 236 was able to easily put the power to the ground and my son was have to manage between losing traction and wheeling. Either way the bikes were close. On the 3rd race my son found the sweet spot and we had a good race. The 250 had the 236 by a little less than 1 bike length by the time we hit third gear, (we ran out of room). Everyone that rode the bike said the bike was fun to ride and clearly had more power compared to when it was a 200.

Other bits and pieces. It was easy to jet (close to stock jetting), it takes a little more to kick it over (more like a 250) but still starts easily and the bike does not vibrate. It also sounds a bit healthier than a 200.

The 236 has very good bottom end and pulls strong with a meaty midrange and top end, but it did not have a noticeable ?hit?. It is a very easy bike to ride and it has more power where we wanted it. I think this is a great option for anyone with a 200 that wants more power across the board and still wants to keep the GG linear power delivery. Eric said he set it up to keep the same power delivery characteristics as stock, but I am sure he can modify the porting if you wanted to add more top end.
 
Questions.....
1. A new liner was installed in the cylinder correct?

2. Is the piston available in micro sizes to compensate for wear?

3. Does it run warmer / hotter than the 200??

4. Have you tried different pipes?? Say a 250 pipe??

5. Does the bike have a 2k2? Or 2k3??

Thanks
 
Nice write up. I'm glad to here this worked out as it gives us 200 owners options in the future for more power or a Oops.
 
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