2015 ec300e
 

I'm new to Gas Gas having worked on Jap bikes, CanAm's ATK's and KTM's. I'm in the process of rebuilding my son's 2015 Gas Gas ec300e that he bought from G Aaron. It was a Mag test mule and I have no idea how much time is on the motor. His complaint is while it has great bottom and mid it has NO top end. I'm in the process of tearing it down a little at a time due to the garage temps (triple dig and can only work for a half hour to an hour at most). My question is, what brand of piston was used in the 15 300 and is it a forged piston. How much does the billet head from RK tech help performance? I know I'll be coming back with more questions on this engine. Thank you in advance for any advice given.

Please try JETTING the bike first...

Yep, jetting. I’ve heard that Geoff loves jetting his bikes super lean. I imagine you will find a tiny main jet in there. Get yourself a N3CH needle, a 42 pilot, and a 178-180 main. Report back and thank me later


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Awsome!!!

My son has has already been playing with the jetting and the PV settings. My son is 41 years old and not some kid. The only reason I'm working on it is between his job and my grandson he has no time while I'm retarded er retired and have plenty. He's had the bike for about 2 years already and it's only recently that he's noticed that the top end power isn't what it was. I'm thinking the PV is carboned up and not opening all of the way. He doesn't use the top end very often but wants it to be there when he needs it. He used to be the one everybody used to bring there bikes to him to fix as I said, he has no time now. Is there a difference between the 09 and the 15 300 as far as pistons or gaskets are concerned?

Same piston mate.

Have you checked the PV settings? 2,5-3 turns out just to see if its there

The powervalve on my 15’ seized up after setting for 2 months. I had to send the cylinder off to get it unstuck


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Pulled the pipe and the PV moves freely. The rings are showing blow by, at least where the exhaust port is but won't know until I pull the cylinder. The cylinder wall on the intake side as seen from the exhaust port still has the cross hatch showing so the cylinder isn't wore out. Yeah I know, I've been taking my time but as I said with triple digit heat and unfamiliar with gas gas I'm going to take it slow. I also found out he installed a JD jet kit in it set for the 3000' to 8000' elevation we ride at.

Finally got the head off. Hate the factory hose clamps!!!! Cylinder looks good but the piston is loose. Will measure after I get the cylinder off which by the way, can the cylinder be pulled with the engine in the frame? I've never had to pull the engine on any of the KTM's I've rebuilt but the PV chamber on the left side looks like it will hit the radiator.

Thank you!

Found out he wasn't just talking about the top end power but being down on power which figures as the piston is worn out. Been trying to get the inner clutch cover off but so far no joy. I've gone over the case looking for any bolts left in but haven't found any. Removed the impeller but not the seal yet. I've been tapping on the cover with a rubber mallet and the part of the case by the kick starter will come away from the center cases but not the front near the water pump. Is the water pump seal holding the case from coming off? On the KTM's I've worked on the whole water pump comes off with the case.

There are metal alignment dowls on opposite sides of the cover My bet they have rusted, causing the issue.

My son did say it was jetted very lean.

That was my guess but didn't know if I had missed something. Thanks

That bastard dowel is always rusted as shite, the threaded hole is open at the back so it rusts from the out side in. Get a new on when you get the cover off and smother it in anti seize. Then seal the hole with silicone when assembled. You?ll thank me next time it comes off.

very true

Any suggestions on how to get it off? I've been thinking heat as the Alu will expand much quicker and farther than the steel. The cover near the back came away from the center cases so was able to put some feeler gauges between the mating surfaces as far forward as I could then tighten the case screws near the back and the case popped out a little ways in the front but is still held in place. Might try that again but nervous about breaking the case. I've had flywheels be real stubborn coming off and when I finally got it off made a sound so loud it sounded like gun shot going off with me only 2 feet away from the engine. Ouch!!

Just tried to find the picture I took of the setup I used but no joy.

Got the cover off using a little heat and a 1 mm feeler gauge to lightly persaud the cover off. Metal gasket???

Latest and greatest problem. The damn bolts holding the exhaust manifold won't loosen even with an impact driver! The manifold is hitting the frame and blocking the cylinder from being removed. That bike is bound and determined to make me remove the engine. Hoping heat will loosen the bolts up. Anybody have a metal inner case gasket on their engine?

I pulled the cylinder off my 15 without taking the exhaust spigot off. Just pull it up off the studs and then twist it to the side a little and she pops right off


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Ended up doing the same thing but didn't want to have to remove the radiators. Guess I'm spoiled by my old 91 KTM. Even the 04 KTM 300 I worked on was a pita!

Messaged RK Tech to ask if the their head mod will work on a 2015 300 Sat. and not a peep so far. My son wants more power without losing bottom end and I feel that head work is the only way. All they listed was the 2018 and 2019.

Most likely very similar.

What piston is Gas Gas owners using in their 300's? Checked Wosiner and Wiesco and neither of them list a piston for 2015 300. I use forged pistons when ever possible as I feel they are a much stronger piston. If the cylinder has S3 21113 047 # stamped in the base surface is that a stock cylinder part # or one from S3?

S3 makes the cylinder .

I just put a weisco piston in my 15 300. Got it from Halls Cycles https://uploads.tapatalk-cdn.com/201...415440c9ef.jpg


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Chris, how was the tko??

Is that the Pro X one? wiesco lists a forged piston for the Gas Gas 300 ATV but only list a Pro X cast piston for the EC300

ATV should be the same motor.

Hardest one yet. My effort was dismal at best. Lack of preparation and lack of seat time really reared it’s ugly head. I was about 2 miles from the end of TKO 1 when the track workers convinced me that continuing on was not a good idea.


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Came in a wiesco box. Might just give Halls Cycles a call and they will set you right up


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https://www.ebay.com/itm/TOP-END-KIT...gAAOSwX99Zn9Ha

This is the route I usually go. Great kit with everything you need for a good price.

Piper, kicking ass on pricing again!!

Better safe,than sorry 6 feet under.,

Thanks!! That's what I'll use as my son is going to sell it after I get it back together. Thank You again!!

Putting it back together so far has been way easier than trying to take it apart. Just as a side note, my son is selling his 15 Gas Gas EC300E. It's registered for the street in Kali which is rare. PM me if any are interested and I'll supp;y the info. By the way, the main reason he's selling is he wants a 2018.

Well this ISN'T going to plan. The damn ring locating pins are in the wrong place. The pins are so close in the clocking as to be right over each other. I already installed on the rod and there's a few surface scratches from trying to install the pin clips though they're not on any surface that contacts the cylinder. I was too trusting that it was the right part and didn't check it out before hand. Damn Ebay!!

Here's the original and the new one. There's a booster port located right where the locating pins are.

Do the rings pass over the booster port at BDC?