Engine quit while at constant rpm cruise!! By jetjock79 (Read 818 times)

[jetjock79]

Hey everyone.......took the scoot out for the first time today after putting her back together. Was going to take her on a half hour ride....which included some freeway. All was fine four about four miles or so.....speeds of 45-55, with an occasional stop at a light. Just before getting on the freeway,......I had been doing about 60 or so for a while at about 6, 000 rpms consistantly. Just as I was giving her gas to get on the on ramp......the engine just quit on me. I pulled over and tried to start her up again......no go!! After a little bit of cranking her.....she came back alive.

Could this be a fuel pump issue? She is a 2008 54 250B with 1000 miles on her with original pump. Four turns out on the a/f mixture, which seems to work better for cold starts (2 1/2 turns made for hard starting when bone cold). Thanks for any advice on this!! She rides great, and I was really looking forward to having her on the ride today. Had to take the Ducati instead.

[job]

Jetjock it could also be that your gas cap is not venting well. I changed fuel pumps and even tried an electric pump. The engine would just run out of gas on a long grade or when at a sustained higher speed. I finally drilled a very small hole through the gas cap and I was amazed at the change in high speed and acceleration. I hope you can get it fixed Job.

[jetjock79]

I'll have to surely look at that, job. There is a vent front the fuel tank, that goes to the charcoal canister though......wouldn't that be enough to vent out the tank? My issue sure sounds like fuel exhaustion from the carb bowl.......wish I had a screw driver with me at the time to unscrew the carb drain screw and see if there was any fuel left in her. As I cranked her though. ....she came back to life slowly....like when you drain the carb drain screw, and then try to start her again for the first time.

What pump did you replace yours with? I heard some people use the Mikuni DF44 as a direct replacement, but some use the DF52 because it had double the output.

[alleyoop]

I would try Loosing the Gas Cap first sure sounds like the gas tank was not venting. Those Vapaor trapping canisters if gas gets into the line and soaks the charcoal in the canister it will not vent and gas will not flow out of the tank when enough pressure builds up.

So First just crack open the gas cap from its locked position and see if that eliminates the problem. If so then take the vent hose coming off the gas tank where ever it is connected to and put a fuel filter on the end and tie it up HIGHER than your gas tank. Then plug up the Vacuum line going to the canister and after that you can take the rest of it off and have less problems and a cleaner less hose area.
Alleyoop

[jetjock79]

I just cleaned the carb today, and will be trying this out tomorrow. Already took the vent hose of the charcoal canister, blew into it with the gas cap off,....and could see that it was free flowing. I just ran into a slight problem that didn't allow me to take her for a quick spin today. A/f mixture screw is crazy loose, and keeps changing its position while the scooter is running. I'll post another thread about that,...but will post back on here about my venting issue when I get her out. Thanks again!!!

[jetjock79]

So that solved it!!! Took the vent line off the charcoal canister, added a fuel filter in the correct flow pattern, and set off into the sunset. Did 40 miles today with her around 5-6k rpms.....and she ran strong the entire way!! What a relief!! So glad it was a simple fix! Thanks again!!!

[jetjock79]

Back to square one everyone!! Can't believe this.....I must be loosing my touch on diagnosing this stuff. Used to be on point when I worked at the shop.....but years down the line now......I'm stumped! She cut out on me three times today. The first time made me think fuel pump because it took me opening the throttle halfway while cranking to get her to start sputtering. Made me feel like fuel pump wasn't delivering enough fuel to the bowl. She quit while I was letting go of the throttle after a 60mph run for about a mile. As I gave her gas again, I could feel her sputtering, then just quit.

The second and third time just happened tonight, both as I came to a stop at a light. Still took cranking with some throttle open to get her to sputter (indicating that fuel is starting to get to the bowl). What's going on here? I know it sounds like valves, but the previous owner said he adjusted them (I know, I know.....why trust his word). I just think that if it were the valves, I wouldn't have to crank her a few times with the throttle open, just to start her. She eventually does start just fine, but why cutting out?

I'm now running sea foam in this tank. I do have a slight issue starting her full cold, where I have to repeat my open throttle routine, but tonight,...she started via remote....so go figure. Any ideas ya'll??

[jetjock79]

I was thinking about this last night for a bit, and thought I should throw this in there to bring greater detail as to what may be going on; she starts ok, idles fine, and accelerates to 65 easy. Even after she cuts out, and I get her started again, the idle is pretty solid. Maybe fuel pump?!

[Barnie]

I would double check the valves for your own piece of mind. I had to switch to an electric pump to eliminate my fuel delivery problems. Did that 5 yrs ago and have never had a problem since that day. As these engines wear the vacumn output goes away also, and the faster you run the engine the vacumn output drops. You may be starting to experience fuel pump problems. The next time it cuts off, open the screw on the carb bowl drain hose and see how much fuel you get b4 trying to restart, that will tell you if u are starving the engine at high speed. At any rate, I would re-check the valves. Barnie

[JR]

Oct 7, 2013 8:25:03 GMT -6 jetjock79 said:

I was thinking about this last night for a bit, and thought I should throw this in there to bring greater detail as to what may be going on; she starts ok, idles fine, and accelerates to 65 easy. Even after she cuts out, and I get her started again, the idle is pretty solid. Maybe fuel pump?!

Have you checked the fuel filter and for the possibility of water in the fuel? Draining the carb will tell you if any bubbles of water is in it? These carbs hate water and mine did that just this past summer and I found I bought a tank full of water, had to drain it, replace the filter.

I'm not a sold out fan on the it's the fuel pump due to engine wear and the valves not seating like they should? Yes the valves need to be right for proper vacuum but at over 12k on my engine until just a month ago I was running with the Chinese OEM fuel pump and wasn't having any of the fuel issues people talk about all the time, in fact I never have had these issues and I own four scooters with two of them being the 250A and 250B with the linhai one being a 07 model and the other a 08. I replaced the fuel pumps on both just for kicks on a routine filter change not because I was having issues but because I had found a close out deal on some Mikunis for $5. They don't run any better.

JR

[jetjock79]

Ok,...so here is the update for someone who may read this later to get answers for their own situation: I agree that it could have been a valve issue. I was tired of dealing with the plastics and all, so I outsourced the work to a dealer out here. He fixed a small vacuum leak, and adjusted the valves. He said it was still cutting out after a long run at high rpm's due to not having vacuum to the accelerator pump. Also doesn't start without at least a few cranks of the starter (so can't use remote start). Suggested new carb. I told him to button it up and I'll just use her like that for now. Any thoughts on this?

[jetjock79]

Forgot to add.......we checked the fuel pump.......she is pumping! He said that he never has issues with the pumps on these things,.....but it sure is worth a try to drain the bowl if she cuts out on me again.