Irishchris Posted October 7, 2011 Report Share Posted October 7, 2011 I have a 421 Serval with maybe 20 hours on it. Last time I had it out it started running rough and sputtering unless I was high in the rpm's and eventually it shut down would not start again. Now it wount idle, I can get it started and keep it aroud 2500 just fine but as soon as I try to get it to idle it starts running really rough and shuts down. It will start right back up on the first kick and do the same thing again. It seems like when its cold it will idle and when the engine warms up is when it wont idle. I took the carbs apart cleaned them really good and put a bigger pilot jet in but it did not change anything. I have 30mm OKO carbs with 165 mains and 60 pilots. The compression is 150 on both sides. Any suggestions on what I should do next to try and fix this? Quote Link to comment Share on other sites More sharing options...
SuperMex Posted October 7, 2011 Report Share Posted October 7, 2011 Pretty sure your pilot is way way too big. Whats your elevation? I'm at 800ft and running a 48 pilot on my 421 Serval with 34pjs Quote Link to comment Share on other sites More sharing options...
coryv4 Posted October 7, 2011 Report Share Posted October 7, 2011 Pretty sure your pilot is way way too big. Whats your elevation? I'm at 800ft and running a 48 pilot on my 421 Serval with 34pjs yeh a 60 seems kinda big i am running a 75 in my alky bike with the same carbs and alky requires twice as much fuel as gas Quote Link to comment Share on other sites More sharing options...
Irishchris Posted October 7, 2011 Author Report Share Posted October 7, 2011 yeh a 60 seems kinda big i am running a 75 in my alky bike with the same carbs and alky requires twice as much fuel as gas yeah I was just seeing what if it was going to make a difference. I usually run a 55. I just took the carbs apart again and cleaned them again they still look brand new inside. The thing will start and run but anything under like 2800 it will just die like its running out of gas. I can see there is gas getting to the carbs because i have see thru lines. And the left side plug looks wetter than the other side.I already switched the coil wires and the carbs around. Any other suggestions? Quote Link to comment Share on other sites More sharing options...
SuperMex Posted October 7, 2011 Report Share Posted October 7, 2011 Whats your elevation? 55 still is huge bro Quote Link to comment Share on other sites More sharing options...
coryv4 Posted October 7, 2011 Report Share Posted October 7, 2011 Whats your elevation? 55 still is huge bro 55 isnt massive for a pj id try a 48 or a 52.. Quote Link to comment Share on other sites More sharing options...
Irishchris Posted October 7, 2011 Author Report Share Posted October 7, 2011 Whats your elevation? 55 still is huge bro Like 1000 ft but its already getting cold here. If the pilot was too big would that cause it die? I ran a 55 for the last month without any problems. I do have a set of 50s I can throw in there to see. Quote Link to comment Share on other sites More sharing options...
Nutwood 472 Posted October 7, 2011 Report Share Posted October 7, 2011 Like 1000 ft but its already getting cold here. If the pilot was too big would that cause it die? I ran a 55 for the last month without any problems. I do have a set of 50s I can throw in there to see. i'm at 420 ft above sea level and i run a 52 in pwk 35s and its still rich,but idles great and never have to use my choke,starts on first kick,and can lug around in first gear and never has to touch the gas,lol put 50s in it and it wont stay idleing,it will die after awhile,but will idle for ever with the 52s in it Quote Link to comment Share on other sites More sharing options...
gotta_goatsfast Posted October 8, 2011 Report Share Posted October 8, 2011 Id be looking into the ignition. A weak spark will essentially "blow out" at a given rpm but ignite the fuel fine below that threshold. The second clue is it ran fine and now is acting up. Test and try easy stuff first like continuity through all wires, plugs, spark plug boots, coil, you get the picture. Quote Link to comment Share on other sites More sharing options...
2004LEBanshee Posted October 8, 2011 Report Share Posted October 8, 2011 Check for a wire rubbing bare on your frame. Quote Link to comment Share on other sites More sharing options...
Irishchris Posted October 8, 2011 Author Report Share Posted October 8, 2011 I jetted it down to 50 and put a new coil and new plugs in it and now it will idle fine. One question though I let it idle with new plugs for maybe 15 minutes on and off and pulled the plugs out and they still looked new. They were still white, does that mean now its a little too lean? Before even with new plugs they would be brown in only a few minutes. Quote Link to comment Share on other sites More sharing options...
gotta_goatsfast Posted October 9, 2011 Report Share Posted October 9, 2011 The brown plugs could have been result of a weak spark from a bad coil (which is also why it wouldn't get into any real rpm). The plugs might not have been hot enough to burn off any fuel. Generally, it is good practice to change one variable at a time and then test. You should only have replaced the coil or the jets, not both. Now you do not know what change produced what results. Quote Link to comment Share on other sites More sharing options...
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