butlin boy Posted July 26, 2011 Share Posted July 26, 2011 HI GUYS I HAVE A REAL PROBLEM MY XS 250 YAM WILL START OK & WILL RUN OK FOR A FEW MINS THEN IT SEEMS TO JUST NOT WANT TO REV, LIKE ITS REALY STRUGGELING. I HAVE CHECKED THE FUEL IS GETTING THROUGH, THE ATU WORKS FINE THE POINT & PLUGS ARE GAPPED FINE SWAPPED THE CONDENSER FOR A NEW ONE & CHECKED THAT THE BATTERY IS CHARGING OK. DOES ANY ONE HAVE ANY IDEAS AS IM TOTTALY OUT OF THEM CHEERS. BUTLIN BOY. Link to comment Share on other sites More sharing options...
JimR Posted July 26, 2011 Share Posted July 26, 2011 HI GUYS I HAVE A REAL PROBLEM MY XS 250 YAM WILL START OK & WILL RUN OK FOR A FEW MINS THEN IT SEEMS TO JUST NOT WANT TO REV, LIKE ITS REALY STRUGGELING. I HAVE CHECKED THE FUEL IS GETTING THROUGH, THE ATU WORKS FINE THE POINT & PLUGS ARE GAPPED FINE SWAPPED THE CONDENSER FOR A NEW ONE & CHECKED THAT THE BATTERY IS CHARGING OK. DOES ANY ONE HAVE ANY IDEAS AS IM TOTTALY OUT OF THEM CHEERS. BUTLIN BOY. Have you done a compression test yet ? Link to comment Share on other sites More sharing options...
butlin boy Posted August 1, 2011 Author Share Posted August 1, 2011 YES I HAVE DONE A COMPRESSION TEST & ALL IS OK. ANY MORE SUGGESTIONS AS THIS IS REALY IRITATING. CHEERS. Link to comment Share on other sites More sharing options...
kindest Posted August 2, 2011 Share Posted August 2, 2011 r u sure it's not choked or something.. what rpm idle is it when you first start it up. Link to comment Share on other sites More sharing options...
butlin boy Posted August 13, 2011 Author Share Posted August 13, 2011 Hi it revs at normal speed & is not choked up. It appears to die when you turn the handle bars, maybe electrical but i dont have a spare loom to check this out. If anyone has a spare loom for a 250 special i could buy or borrow it would be greatly appreciated. I live near Taunton Somerset.Cheers. Link to comment Share on other sites More sharing options...
SPUDGUN Posted October 28, 2012 Share Posted October 28, 2012 I have just bought same bike and same problem. Leave it for 10mins or so and it goes better for a few minutes then starts to die. Did you solve the problem yourself??? I thought it could be the fuel petcock needing replacing??? About to order a replacement kit as o ring is pershed and I have put a generic tap after the petcock. Any suggestions would help. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted October 28, 2012 Moderator Share Posted October 28, 2012 open the pilot screws to 3 - 3.5 turns out. the "new" fuel doesn't burn as well as the old. carbs need to be clean and I mean really clean. if the bike has been standing over a month the fuel starts to varnish Link to comment Share on other sites More sharing options...
SPUDGUN Posted October 28, 2012 Share Posted October 28, 2012 Cheers for that. I also just read in an XS400 forum that it could be flooding so I'm gonna try the o-ring replacement for sure. I'll repost if it works. "Viton" is meant to be the unleaded proof brand to get. I tried the screws out at 2 full turns last night to try and keeps the idle speed down to under 1500 but they were out more like 3-3.5 when I bought it and it still happened but I'll try again. Is premium fuel the way to go??? BTW I'll clean the carbs again before I bother reposting as well. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted October 28, 2012 Moderator Share Posted October 28, 2012 depends on what age the bike is whether you have O rings or not (I assume pilot O rings) 1980 was a turn about year its not about premium fuel its about the ethanol in modern fuels. Link to comment Share on other sites More sharing options...
essexboydave Posted October 29, 2012 Share Posted October 29, 2012 Just a thought but is your air filter clean? A clogged air filter will allow the bike to start but then as it doesn't allow air through fast enough the motor will bog down and die. Link to comment Share on other sites More sharing options...
SPUDGUN Posted November 14, 2012 Share Posted November 14, 2012 Carbs. Plugs. Filters clean. Floats set at 28mm as it was flooding and I checked the level with a clear house it was a couple mm above the fuel inlet height in the bowl which I transfered to the outside. Petcock replaced but still leaks out slowly when ON position. Pri and Res full flow. mmm Still doesn't run after 5 mins it conks out. I'm gonna check timing next after I try the floats at 26mm. I went to check points gap but it has a solid state ignition module instead so I'll just have to rely on that being right once I check the timing. Dumb question do I need to drain the oil first before removing the side cover or not. I saw a guy on youtube running the engine whilst strobe timimg so wouldn't the oil come out when running or seize the engine if empty??? Link to comment Share on other sites More sharing options...
dt502001 Posted November 14, 2012 Share Posted November 14, 2012 Petcock nfg, the stator is dry no oil in that side. Link to comment Share on other sites More sharing options...
boon Posted November 14, 2012 Share Posted November 14, 2012 try it with the fuel filler cap open, could be a blocked breather vacuuming the petrol tank Link to comment Share on other sites More sharing options...
SPUDGUN Posted November 15, 2012 Share Posted November 15, 2012 I read on another site the petcock is meant to be connected to the carb inlet right hand side brass nipple so I got all excited as mine just had a cut off bit of red hose on it when I bought it and the two carb inlet ports were capped off. But it didn't work once attched to petcock. Infact now petcock flows full when ON position so I'm in the market for a NOS one. Anyway bought a tried the fuel cap open as well btw no change. Blew thru the cap to see if intake on cap was blocked but air came thru. SO now I'm gonna check the valve clearances and timing position (static) armed with a couple of CC and colas. I'm not gonna take it to a mechanic, I won't I won't. Have manual and feeler gauge ready to be bent up also multimeter for the coil check Link to comment Share on other sites More sharing options...
SPUDGUN Posted November 15, 2012 Share Posted November 15, 2012 Bought a multimeter from Supacheap auto and it didn't work. Good one Stanley made in China. I think my petcock is gonna gonna be donated to landfill. still dribbles when ON. I set the valve clearances though. Have another look at it tomoz. Link to comment Share on other sites More sharing options...
SPUDGUN Posted November 15, 2012 Share Posted November 15, 2012 Oh yeah right side 125psi Left 130psi after compression test. Not sure how to work out what its meant to be... anyone know? Link to comment Share on other sites More sharing options...
dt502001 Posted November 15, 2012 Share Posted November 15, 2012 Thats fairly good and within 10% 140psi would be like new below 100 time for a rebuild. setting the float at 26mm would alow more fuel in the bowl compared to 28mm ,,,30mm would be less fuel. The whole thing sounds more electrical than fuel check the pick up coil resistance right after it dies and the coil. Link to comment Share on other sites More sharing options...
jimmy Posted November 15, 2012 Share Posted November 15, 2012 Is premium fuel the way to go??? Any type of fuel. Drain some off into a can, remove the bike to some waste ground, pour the fuel over it and set it alight. Walk away without looking back. . . . . . . . . . . . .. . . . . Sorry mate. I had a very bad experience with an xs250cw back in the day (81-82) and still get a shiver thinking about the slug Link to comment Share on other sites More sharing options...
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