I put my first mile on my yz250f 300 gasgas swap bike!!!

Kbowen4

New member
Hello forum members, (my first post but like most ive been lurking for a while)..first off I would like to say thank you for the wealth of information that this forum provides.

Iong story short I bought a 05 ec300 a few months back and was very happy with it. I knew it needed some various bearings and eventually I realized there were huge chips in the fork sancions from steel studs flying out of the winter tires which were causing lots of leaking.

A few pictures will be up today or tomorrow. It's been very cold here so my power washer isn't an option. I rode it yesterday but with the carb open to air I don't want the pressure blast water in it so she's a little dirty.

I set off to buy a set of kayaba sss forks instead of Messi g around with the stock forks. I arrived at the guys house to pick the front end of a blown up four stroke and the guy didn't take them off of the frame as promised. He was an older Guy (I need to find out what all of these 55 plus guys in eastern PA are eating/doing to stay in riding shape...the guy I bought the gasser from was 65). He was drinking with his buddies on a Saturday when I got there and didn't feel like messing with it I guess so he offered me the rest of the rolling chassis for $100 more.

So I said worst case I could sell the rest of the chassis and essentially get a free set of forks. I got home and started measuring and realized that I might be able to pull this off.(I bought a TIG welder last year but I'm very inexperienced with aluminum, never have I done a swap like this). After thinking some more the yamaha chassis is much easier to get parts for, lighter and seems to have the slight edge on suspension.

So I cut the stock mounts from the frame, had the rear swingarm bolt hole in the case machined 1mm larger and went to town. I got the pipe to fit through the chassis without cutting the y section out. The pipe goes through the spot that the oil cooler is on on the yz250f. At the top of the y section I had to shave off about 5mm of the edge to clear the pipe flange, the pipe springs I moved slightly by simply drilling new holes.

Lots of small adjustments and fitting changes later and here she is, all that is left is to fit up an air boot. It almost looks like it was made this way.
 
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I should be able to get a few pictures up today or tomorrow. It's been too cold here to power wash the chassis and until I get the air boot sorted out she'll be pretty dirty
 


All that is left to do is mount the computer better, put my handgaurd on, see if I can get the old gasser airboat to work, and clean up the wiring.
 
Thank you, anytime I see a thread like this there doesn't seem to be much info on what had to be done to fit the engine in a frame once I get home from work I'll give anyone reading this more details on what had to be done to get the engine to sit low enough for the pipe to clear the factory Yamaha Frame y area and engine mount details. It wasn't too bad really well we'll see about the air boot situation soon
 
I have not put it on the scales yet I just finished or I should say partially finished it yesterday the scales will come in the next couple of weeks. I do have one question for you gas gas guys the newer gas gas bikes don't have the upper head stay mount and I didn't fab one up yet, I was wondering how many of you guys that have older gas gas 300 that are running without the upper head mount bracket?
 
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Looks like you need to find an 18" rear wheel now. Nice work.

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Well today at work I ripped most of a fingernail off and then rolled my ankle quite hard shortly after. We'll see if I can wobble my way to the garage tomorrow for more pics because tonight I can barely walk
 


While I sit inside and stare ate the garage wishing my foot wasn't swollen here is a pic I took before cutting off the stock yz250f engine mounts. The pipe flange almost fits through there even though the mounts are holding it about 2 inches higher than it should be. One thing that I didn't mention is that I choose to cut the swingarm down to match the engine so that I don't damage my 300 block just in case the whole frame thing did not work out. So the spacer between the two swingarm roller bearings was taken out and I put the roller bearings closer together to make the gap between the swingarm about 12 millimeters Wider total.
 
Still no weight yet

Well hopefully tonight I can get this rubber air boot seated into the air box properly tried to do it last night and thought about burning the air boot after fiddling with it for about an hour. Looks like I'm going to have to grind part of the frame off for the YZ250 air boot to fit around the shock area. I found a member of another Forum that did the same thing and it almost looked like it was like that from the Factory. Hopefully I can get the air boot sorted out tonight so that if the weather cooperates on Sunday I can take it for a real ride and report back and hopefully power wash it so I can get some nice shiny pictures up. :)
 
It's normal to have to heat the airbox boot with a heat gun to make it fit on a GasGas. It's probably even more necessary on your setup.
 
Well I got the yz250(not 250f) airboot to fit with some grinding to the frame. Made the Reed side carb boot just a hair longer using a car gas filler neck tube cut to the right size. Took it for a bit longer ride today. It feels like a yz250 with a better engine (go figure). The suspension is a little less plush than the gasser stuff but with much better bottoming resistance. Tomorrow I will be putting a few hours on it and cleaning it up for pictures after. Makes me wish I was a better rider to really utilize this beast.
On a side note I absolutely love the light clutch pull on these bikes.
 
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