DR250SES Fuel Problems

Okay I've read a bunch of past threads and I think I have this down but need some confirmation as I am a relative newbie.  I bought a 1994 DR250SES third hand. It has an aftermarket Acerbis desert tank.  Ever since I bought it it has been sluggish starting in 1st gear, at least until RPM's are up.  A couple of months after purchase, and not a ton of riding, it started really hesitating, stuttering you might say.  I have pulled and cleaned the carb 3 times, inspected the diaphragm (fine) and each time it seems like its fixed, only to start the whole thing over again.  I have even removed the petcock and inspected it to see if the filters were blocked. They were fine.  Yesterday, on a dirt ride with my son, it really started acting up, but really only after it got hot.  It would stutter and hesitate on acceleration.  We hit the pavement for a return to the vehicle and it just flat out died, and no amount of holding the clutch in and revving would bring it back.  It seemed out of fuel.  I let it sit a minute or two, it started up, and I got it to the car at high speed, but it still hesitated in first gear when I started out.

So--I think this is my problem:  The aftermarket tank does not a have a vacuum line on the petcock and the vacuum port on the carb has been blocked.  The boggy/hesitation in first gear especially seems like a symptom of the lack of vacuum, since I understand that is what the vacuum line is supposed to address--giving a quick shot of fuel to the carb on quick acceleration when the carb can loose vacuum momentarily (is this right?).  As to why it seem to be more fuel starved after it heats up---I am at a loss unless it too is related to the absence of the vacuum line.

Am I right? 


So you ruled out electrical then ?

No I have not ruled out electrical.  This back was backed-into by a flat bed pick up, destroying the headlight/speedometer.  I have routed the ignition line to a 12v switch so it doesn't drain the battery when not used.  I have heard this could be a CDI problem as well?

If electrical, why would the the engine run worse when hot?

Could be the stator - has the symptoms of a bad stator


Could also be your Pulse Generator CPS - which is part of the Stator


Okay-will check the stator.  But could you explain why the problems are amplified when the bike is hot?

45 minutes ago, BoondocksUtah3 said:

Okay-will check the stator.  But could you explain why the problems are amplified when the bike is hot?

No  :excuseme:  :D

Heat increases electrical resistance.  If you stick your finger in the end of the exhaust does it come out black and sooty ? A rich condition may not show until the motor gets hot. Is the air filter clean ? The vacuum line was for an auto shut off petcock and nothing more.

Edited by JoeRC51

Okay-checked the stator--resistance within spec.  Air filter clean.  Next?

Is the end of the exhaust black and sooty inside ? How old is the spark plug ?

Also --the exhaust is clean.

Unkown age on plug

Try a plug , it needs it anyway. 

I should also note that this bike starts immediately--no problems there.

I will replace plug soon.  I live in the middle of nowhere and do not have easy access (hence the name Boondocks).

What does the plug look like ?

I can't get to it as I am not near the bike now.  But will pull it tomorrow.  Any other ideas assuming the plug is OK?

Finds specs on the ignition coil , the stator and the pulse generator , to ohm them out. 

Did that already--see above

Pulse generator and ignition coil too ?

May be tight valves too.

So to test the pulse generator test the resistance of the stator wires to ground --correct?  I have not checked ignition coil, and will do that tomorrow.  By the way, thanks for the help!:thumbsup:

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