Vr5fx Posted September 24, 2017 Share Posted September 24, 2017 This isn't my Baja, mine runs fine! One of my mates that I bash with recently got a new engine for his KM, "KM 4 Bolt Rev Engine 30.5Cc" from RCmodelz. We broke it in at my place, as I have a garden, and there were a few issues with it running, mostly it being rich and flooding every now and then, which I figured was normal. After the break in was finished, the needles were set to stock and away he went bashing. First bash....While doing WOT runs, after a few lengths of the field, the car cut out, and wouldn't start. The usual was checked, spark was good, bolts were fine, it wasn't flooded, it just simply wouldn't start, like the engine wasn't getting any fuel. Needles were reset, everything re-checked, air filter was off, but the plug was dry. An hour of pulling it out, and checking it, we sprayed WD-40 down the air intake (because the engine was dry), had the throttle wide open and after a few minutes of pulling it started to turn over, it would only start with WOT, and then it had to stay fully open for it to start running properly, tons of smoke (which suggests it was flooded, but plug was dry) but when it settled it was fine. Air filter back on, all back together and it was golden, after that the carb was swapped out for his old one that we know worked fine. Same thing happened last week. Engine cut out after a WOT run, was a right pig to start, but eventually started. Come to today, I didn't go out bashing, but got a message from him saying it wouldn't start at all. They tried everything again, even putting an electric starter on it. Ended up going over to his place with my trusty tools. Checked spark Checked bolts Plug was dry Plenty of fuel No leaks/residue on the gaskets Carb primes fine Choke made no difference I put a drop of 2 stroke down the plug hole to lube it, and didn't get anywhere, needles set to factory, nothing. Put the needles to a richer position, and nothing. The only way it would start was by putting my finger over the exhaust, and gave it about 10 fast pulls, then held the throttle wide open and it started to fire, probabaly took another 20 pulls for it to properly start to fire and stay running with the throttle wide open, when the revs increased I slowly let the throttle off till it would idle with no input Stayed running fine for a new minutes and then killed it, compression felt fine after it's brief run, as it had fuel in the engine,.Then came home to write this essay So, new engine, 2 carbs, same issue... I mean, is there something silly that's being missed? Cheers chaps for letting me pick your brains. Quote Link to comment Share on other sites More sharing options...
dalex Posted September 24, 2017 Share Posted September 24, 2017 All tight round carb and exhaust ? new plug with correct gap. correct coil gap. Whats the compression like, fuel pipes and tank filter, pipes correct way round , next step would be to drop off head and check ring and bore. Cheers Dave 1 Quote Link to comment Share on other sites More sharing options...
Vr5fx Posted September 24, 2017 Author Share Posted September 24, 2017 18 minutes ago, dalex said: All tight round carb and exhaust ? new plug with correct gap. correct coil gap. Whats the compression like, fuel pipes and tank filter, pipes correct way round , next step would be to drop off head and check ring and bore. Cheers Dave Carb and exhaust is all good, checked those today, New plug was used aswell, though unsure about the gap with that, but a stock replacement was used. I've not had the experience of checking the plug gap.... Coil was set using a business card Compression feels fine (same as my Baja) when there is some fuel in the engine, doesn't feel too great when it's dry. Fuel pipes were done a few weeks ago, as the old ones went stiff. My thoughts were to maybe take another look at the tune next week, and if it still plays up, we will inspect the head like you say Quote Link to comment Share on other sites More sharing options...
dalex Posted September 24, 2017 Share Posted September 24, 2017 Isolator blocks can warp too and give issues gap should be 0.3mm carb settings Quote Link to comment Share on other sites More sharing options...
KORB Posted October 6, 2017 Share Posted October 6, 2017 Have you adjusted the actual tick over screw ? That is the larger of the three as this sounds very similar to the problem I had with a new FG back in 2006 and which was reset by Mike from Mike's models in Birmingham. The engine wouldn't start no matter how much the plug and fuel mixture screws were adjusted and it was just simply the tick over throttle screw . Also worth checking the exhaust hasn't retained any fuel . Quote Link to comment Share on other sites More sharing options...
Vr5fx Posted October 14, 2017 Author Share Posted October 14, 2017 We changed a few things. But it looks like it was the fuel. After getting a fresh batch of rocket fuel and 2 stroke, it started straight away with no choke, and for 2 weeks, no issues. There is something great about starting a 2 stroke without choke. He had about 4 litres left of the old fuel, and gave it to one of the guys we bash with who has a ped, it ran fine for him on the day he put it in the tank, but the day after it wouldn't start. Definately something up with that fuel. No idea what though. Quote Link to comment Share on other sites More sharing options...
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