carburator bogging at 60 mph By hitmusicinc (Read 1,940 times)

[hitmusicinc]

I have a cn 250 engine evrytime I start to got past 60 mph it starts missing and hesitating. PLEASE somebody help me. JIMM

[bhinch]

Need more info...miles....age of scooter....did you do a PDI .....have you adjusted the valves....changed the fuel filter...Yamaha 257.....Honda 244....sounds like it is running lean at speed.....do you smell gas....how does it react with throttle application...tell us what it is doing when this happens....like I said the Doctor ask you how you feel and where does it hurt..right....

[hitmusicinc]

its a 2009 jonway/Roketa YY250T my scooter shop just replaced the head and valves. It has a uni filter in the box which might b part of the problem I know these boxes are restrictive. A new carb was also installed he said he adjusted the screw 3 turns out. New voltage regulator, CDI,
iredium spark plug , rectifier, fan, muffler and belt, oh lets not forget the Dr puller sliders. Anyways once I'm on the interstate and hit 60 it keeps missing I have had this bike up to 70 before so I know it will do it(GPS speed check) it sounds like its just not getting snuff gas.

[ce]

Vac leak somewhere, not enough vacuum at WOT to keep the fuel bowl full.

Check all vac fittings, cut new end to line to air cutoff valve, check for pinched fuel line, and then you prolly need to up jet to a 120 main or raise the diaphragm needle.

[smokindawg]

I had this problem with my scooter but at just a slightly higher speed.

My top WOT speed was 60 and I was pushing it hard to get that. So I changed the main jet in my carb. I went from a 110 to a 114 and now can cruise at 60 no problem. I did however have one problem, I got the scooter almost too 70 and it began to sputter and die, I let off the throttle and it picked back up at about 45, the same also happened when I was climbing a hill and really had to get on the throttle.

I replaced the vac operated throttle with an electric one and now no more problem. I can run up to 70+ and no sputter at all. Cruising at 60 mph is no problem and it doesn't even seem to be working the scooter hard.

My fix was changing to the electric fuel pump. I also changed to bigger and better fuel lines too, as they seem to have been the original lines.

[Alleyoop]

It sure sounds like it is running lean at high rpms and not pumping out the mph like before due to not enough gas. Put in a bigger MAIN JET to get more fuel at wot.
Alleyoop

[smokindawg]

I also wanted to add that after adding the electric fuel pump, the scooter is easier starting and runs better when first started. Price for the pump at auto parts was $45 and well worth it in all aspects.

[scooteraddict]

When I had this problem, I found that if I adjusted the float to allow hold more gas, the problem went away. I believe that if you adjust it to 17mm, then you should be fine.

I can now manage to pass 73+MPH on the old chinometer.

[hitmusicinc]

Thanks all for your knowledge.I kind of hate to say this but I was so tired of always messing with this bike that I went out and bought a brand new Linhai 300 and now I'm in scooter heaven.

[mikecop]

I have a Roketa 250B with the 257cc Linhai engine. Do you know what carburetor and electric fuel pump I should get? Did you get your fuel pump at someplace like Advance Auto or O'Reilly's Auto Parts?
Thanks.

[Cruiser]

THIS is the fuel pump most people use in their scoots. No regulator needed because of low pressure output. Uses less than 1 amp.

[mikecop]

The 42S from Mr. Gasket didn't get very good on-line reviews. Most of the bad reviews were from people who used it in cars. Is it possible this unit works well with scooters, but isn't the right one for cars? Should this unit be installed by taking the original one out, or in addition to the original?
Mike

[Cruiser]

Here's the one I'm using:

www.pegasusautoracing.com/productdetails.asp?RecID=7535

Managed to scoff it off Ebay for $25. Mounted at the same level as the original vacuum unit. Angled the outlet at 45 degrees higher than the inlet. Do not use the vacuum pump if you are installing an electric (electronic) pump.







1800 miles with no problems.

[mikecop]

Thanks Cruiser. The pictures should help, as I have limited mechanical skills.

[smokindawg]

The Mr. Gasket is the one I used. But I used that exact one at first and it worked fine, till I took it for a ride. Made it about 1/3 mile from the house and it quit. Fuel pump had locked up. So I took it back and the only one they had was the 4-7psi. So I got that one and it's working fine ever since.