CamesJampbell
New member
My GasGas 300 is straight up gaslighting me
Hello all,
This will be my first post on this forum but I have spent an excessive amount of time looking through threads/posts. I purchased a 2003 EC300 (may technically be a DE300 because of all the features I have noticed) September 2025, and I have been desperately struggling to get it running since. I am starting to get burnt out on this project and I am hoping that someone here might be able to provide an idea of what the issue could possibly be. I am going to write a full chronological list of what has happened and I will also include a TLDR at the bottom because the timeline will be bulky.
Timeline:
Upon meeting with seller, I test rode the bike and it felt fine, aside from a poorly adjusted clutch (however I had not had much experience riding 300 2T’s at the time)
At this point, I shot a local mechanic $50 to give his input
I decided to go with an oversized piston after inspecting, honing, and measuring cylinder
-At all points after this, I attempted to start the bike after each change/fix, and it still did not start unless otherwise stated:
On trails:
TLDR:
Old paperwork on the bike from when a top end was done over a decade ago states that the bike had an intermittent float issue, which I’m thinking is the reason for the gas line issue.
My only hope at this point is that if I fabricate a longer hose from the reed to the carb and attach the airbox properly, then maybe some weird vacuum issue is resolved. Also could have been flooded from my most recent series of testing/diagnosing, that would be nice. (Spark plug was wet).
I am really running out of ideas at this point and I am hoping one of you folks can save me. It's a really unique and cool bike and it's somehow plated. I just want to ride though. So bad. Please send help. Thank you all in advance and have a great day!
P.S.
$2000 and it's yours if one of you can fix it. At this point I just want a functional bike for riding season without being $4k in the hole.
Hello all,
This will be my first post on this forum but I have spent an excessive amount of time looking through threads/posts. I purchased a 2003 EC300 (may technically be a DE300 because of all the features I have noticed) September 2025, and I have been desperately struggling to get it running since. I am starting to get burnt out on this project and I am hoping that someone here might be able to provide an idea of what the issue could possibly be. I am going to write a full chronological list of what has happened and I will also include a TLDR at the bottom because the timeline will be bulky.
Timeline:
Upon meeting with seller, I test rode the bike and it felt fine, aside from a poorly adjusted clutch (however I had not had much experience riding 300 2T’s at the time)
- I stalled the bike twice when test riding over the course of 20ish minutes, and when the seller demonstrated it after, it rode for about 5 minutes then died, at which point we were unable to start it
- Under the assumption of a fouled plug and the seller offering it to me for $2100, I bought the bike
- After further diagnosis (inspected spark plug, top end, reeds, and carb), I replaced the top end (with a size A piston), replaced the killswitch, and thoroughly cleaned the carb, after which it started.
- The first time I took it out to the trails, it ran for about half an hour, and then would not start again (kick or bump start all the way back from the trail).
- When I got back from the ride, I kicked it one more time and it started right up. After killing it again, however, it would no longer start.
- I discovered that my kill switch was a toggle on/off switch, which I did not know. Assuming that I may have left it in “off” I disconnected the switch to no avail
- After viewing a post with a similar experience on this forum, replaced stator and tested both stators vigorously, to no avail
- Bought a cheap amazon carb because I was running out of ideas, still no start
- Put the old stator back in
At this point, I shot a local mechanic $50 to give his input
- He tested compression @ 60psi (lower than expected given how well/power when ran
- In a very unhelpful manner and after looking at the state of the first piston I had removed, he stated that the only way I could fix my compression/get it running was getting cylinder re-Nikasil-ed
- At the time, I found the process/price of getting the cylinder recoated prohibitive, so I focused on other projects and purchased a used 250cc cylinder in the hopes that it might prove to be a cheaper process
- Decided to buy tool to measure bore, measured to be .01-.015 mm over factory
I decided to go with an oversized piston after inspecting, honing, and measuring cylinder
-At all points after this, I attempted to start the bike after each change/fix, and it still did not start unless otherwise stated:
- Installed size C Wossner (also inspected connecting rod and got no up/down play)
- Cleaned and adjusted the powervalve, valve itself and linkage
- Took off very dirty silencer to clean
- I left bike straight without silencer, switch back to OG carb, RUNS SECOND KICK
- Compression tested again: 165psi
- Cleaned and repacked silencer, reinstalled on bike, also reinstalled plastics, etc
- Bike will not start (again)
- I noticed gas not running from tank->carb
- Petcock clean, no vacuum from tank, and assume float is stuck
- Remove/disassemble carb; jets clean and float seems to move fine, reinstalled
- BIKE RUNS FIRST KICK
- Start it about 4 or 5 separate times at home before taking it out
On trails:
- Now sure that my only issue is sticky float, take bike to trails
- Bike dies after 10min of light but good riding
- Noticed gas was no longer in the fuel line, gas will flow when disconnected
- Layed the bike over to try and get the float unstuck, gas flows, bike runs for 2-3 sec
- Took carb back out, adjusted float height
- Notice that either side of the float was bowed inwards (towards the jets) and thought it might be catching there, so I bent until no hangup. Reassemble, bike won’t start.
- Switched to friend's carb which is tested/for sure working on 2009 KTM 250XC
- Swapped carb is shortbody version, so it will not reach/connect to airbox boot
- Jetted carb as per EC300 manual, and advice from this forum
- Tested bike without airbox/filter and new carb, no start
- Fuel line filling issue is gone with new carb
- Compression tested again, got around 160 psi
TLDR:
- Random symptoms at every stage of process that initially point me in opposite directions
- Bike can and has run, and run very well, for 2-3 short durations over the last 7 months
- Bike is getting spark
- Air intake/filter clean
- Reeds are good, no chips or cracks
- Carb is clean and no jets or passageways are clogged (both carbs)
- Most promising idea thus far has been stuck float, observed gas not flowing into carb
- Exhaust and intake passageways are clear of obstructions
- Electrical has been gone through with multimeter
- Probably forgetting something, but I have checked almost everything so just ask
Old paperwork on the bike from when a top end was done over a decade ago states that the bike had an intermittent float issue, which I’m thinking is the reason for the gas line issue.
My only hope at this point is that if I fabricate a longer hose from the reed to the carb and attach the airbox properly, then maybe some weird vacuum issue is resolved. Also could have been flooded from my most recent series of testing/diagnosing, that would be nice. (Spark plug was wet).
I am really running out of ideas at this point and I am hoping one of you folks can save me. It's a really unique and cool bike and it's somehow plated. I just want to ride though. So bad. Please send help. Thank you all in advance and have a great day!
P.S.
$2000 and it's yours if one of you can fix it. At this point I just want a functional bike for riding season without being $4k in the hole.
