notsed Posted August 1, 2012 Report Share Posted August 1, 2012 i have a 421 serval im trying to get running good, it has stock carbs with a 350 main, 30 pilot and stock needle on middle clip with a toomey 2:1 filter on 91 pump. im at 600 asl in 80* weather. ive done a leakdown test and its good. the compression is 157 160. my plug chop looks a lil ritch. my problem is when i do a couple wot runs 1-6 back to back or sometimes just one i get a high idle when i pull the clutch to stop, it takes about 15 seconds to idle down to normal. the question is what else would cause this if theres no leaks and it isnt lean? the pilot it def one to big. maybe it is deto? theres no signs of it on the plugs, is 160psi for a serval on pump safe? it only does it once its hot thanks Quote Link to comment Share on other sites More sharing options...
sprinklerman Posted August 2, 2012 Report Share Posted August 2, 2012 i have a 421 serval im trying to get running good, it has stock carbs with a 350 main, 30 pilot and stock needle on middle clip with a toomey 2:1 filter on 91 pump. im at 600 asl in 80* weather. ive done a leakdown test and its good. the compression is 157 160. my plug chop looks a lil ritch. my problem is when i do a couple wot runs 1-6 back to back or sometimes just one i get a high idle when i pull the clutch to stop, it takes about 15 seconds to idle down to normal. the question is what else would cause this if theres no leaks and it isnt lean? the pilot it def one to big. maybe it is deto? theres no signs of it on the plugs, is 160psi for a serval on pump safe? it only does it once its hot thanks Im going to guess that if you arent lean ( for any reason) jetting or air leak, that its your slides sticking. Try actuating the throttle a lot (with engine off of course) and see if either one tries to hang on you. Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted August 2, 2012 Report Share Posted August 2, 2012 Sounds like: 1. air leak 2. pilot jet is lean 3. slides sticking. Number 1 is easy to check for... start your engine, let it warm up and spray carb cleaner around all your gasket surfaces and see if you get anything... If that's good, then try a bigger pilot. Also, check and make sure that your fuel tank vent has been drilled out and that your fuel lines are clear and your petcock filters are good. You might have a fuel starvation issue. -Jared Quote Link to comment Share on other sites More sharing options...
Starwriter Posted August 2, 2012 Report Share Posted August 2, 2012 I assume that you're not talking about a run away. A run away is when the spark plugs get so hot from a lean condition that they act like glow plugs and the motor screams. When that happens, the kill switch will not shut it down. Just to eliminate that, hit the kill switch when it happens and see if the motor dies. Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted August 2, 2012 Report Share Posted August 2, 2012 I assume that you're not talking about a run away. A run away is when the spark plugs get so hot from a lean condition that they act like glow plugs and the motor screams. When that happens, the kill switch will not shut it down. Just to eliminate that, hit the kill switch when it happens and see if the motor dies. He said after about 15seconds it idles back down. Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted August 2, 2012 Report Share Posted August 2, 2012 My money is on Jared's idea of the vent cap not being gutted. It does sound like a starvation issue since it only happens after wot. Quote Link to comment Share on other sites More sharing options...
guns4children Posted August 2, 2012 Report Share Posted August 2, 2012 i would say your not getting enough gas. I have seen on here where guys say that the stock carbs are good till 70 hp or so. if that in the case then your prob right around the hp where you would want to think aabout getting new carbs. Quote Link to comment Share on other sites More sharing options...
notsed Posted August 2, 2012 Author Report Share Posted August 2, 2012 Thanks guys, never thought of the cap not letting enough air in, its an aftermarket cap so ill drill the hole as big as i can. I guess is better check the petcock screen to. This makes sence since i tried some 30pwk okos and had the same problem and the bike runs real good besides that Quote Link to comment Share on other sites More sharing options...
notsed Posted August 2, 2012 Author Report Share Posted August 2, 2012 so i drilled out my billet gas cap from 1/16" to 3/16" and checked my filter screen, it was clean. just took it for a rip and it still does it maybe not as bad. if i move the needle up a clip its to rich right off idle -3/4 throttle with the 30 pilot and 1.5-2.5on the air screw. basically no mater how i jet it so it runs good i still have this problem. if i dont hold wot for a long period of time it runs good and idles down fine. i set my floats to almost overflow. has all new gas line. pulled the lines off the carbs and turned the fuel on, had good flow out both. do i need dual pingel petcock? are the t5's holding to much heat in? something to do with elictrical-timing? do the stock bowls run dry often with a 360 main? Quote Link to comment Share on other sites More sharing options...
guns4children Posted August 2, 2012 Report Share Posted August 2, 2012 Oh my. I would DEFINITELY get a dual. Quote Link to comment Share on other sites More sharing options...
thomas h. Posted August 3, 2012 Report Share Posted August 3, 2012 Check the slides really good. Mine was having a hard time comming down too. HJR tuned the carbs and it was really good. He said the slides where not all the way down. Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted August 3, 2012 Report Share Posted August 3, 2012 so i drilled out my billet gas cap from 1/16" to 3/16" and checked my filter screen, it was clean. just took it for a rip and it still does it maybe not as bad. if i move the needle up a clip its to rich right off idle -3/4 throttle with the 30 pilot and 1.5-2.5on the air screw. basically no mater how i jet it so it runs good i still have this problem. if i dont hold wot for a long period of time it runs good and idles down fine. i set my floats to almost overflow. has all new gas line. pulled the lines off the carbs and turned the fuel on, had good flow out both. do i need dual pingel petcock? are the t5's holding to much heat in? something to do with elictrical-timing? do the stock bowls run dry often with a 360 main? Yes, get a pingel. Also verify that your floats are set correctly. Stock carb bowls are really small and will suck dry pretty easy. Quote Link to comment Share on other sites More sharing options...
notsed Posted August 3, 2012 Author Report Share Posted August 3, 2012 thanks a lot for the info, ill see how it works this weekend Quote Link to comment Share on other sites More sharing options...
Wheelman Chassis Posted August 3, 2012 Report Share Posted August 3, 2012 thanks a lot for the info, ill see how it works this weekend first check the above. Make sure you are fully on the idle circuit . What i mean is some times when the pilot is to big people will compensate and get it to run right by having the idle screw in to far to get it to idle.. what this does is when ya let out of the throttle it does not block all the air as it should resulting in the bike still pulling from the mains until the rpms get low enough for it to not pull from them. After it will return to the idle circuit but not 100%. In addition, with that size motor through the smaller carbs it will have a strong signal coming in, thus making it more of a fine line. The fix would be a smaller pilot, lower the slides down using the idle screws. then start it, move both idle screws in equally till it ldles on its own. Then while running adjust the air screws until you get the highest idle while still returning from a rev without hanging rpm.. after lower the idle screws to the desired rpm for idle. Make the same passes after doing this and see what happens. how far in are your idle screws? this will be the first sign that it could be doing what is stated above. Just my .02 Chris Quote Link to comment Share on other sites More sharing options...
Paulie B Posted August 3, 2012 Report Share Posted August 3, 2012 (edited) When I got my motor ported and put back together I had this problem. It ended up being too small of a pilot jet. Edited August 3, 2012 by Paulie B Quote Link to comment Share on other sites More sharing options...
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