Bad Carb??? By usmarine112 (Read 2,727 times)

[usmarine112]

Okay guys I'm back to square one!!!

My scooter remains losing what seems to be fuel at 60+ mph... I'm mean really lose fuel!!! I'll be cruising for a bit and all of a sudden, while I'm still holding the throttle, it'll just stop accelerating and bogg all the way down to the point it seems like there is nothing coming from the throttle pull... Here's what I've done this week and still no good results:
-Installed Mikuni fuel pump
-Replaced all fuel and air lines (twice in 3 months - just to be sure.
-Disassembled Carb and soaked it in Carb cleaner for 24 hours.
-Removed Fuel tank and cleaned it completely out.
-Another valve job.
-Added seafoam to fuel.....
-Adjusted float in Carb
-Adjusted fuel / Idle for Carb

All this and still absolutely no difference!!!
Is it possible that I just have a bad Carb??? Has anyone ever experienced this and tried all the above but still got nothing??

My wife is ready to kill me because of the time and money I keep spending on the scoot... But she knows I love it and it is a great fuel saver, when it's running, to and from work (76 miles round trip)...

Now for those of you that don't know, I have a JCL MP250A with the Linhai engine..

Also, if anyone has purchased a decent carb please let me know where you got it from... I don't want to buy a cheap carb because chances are I'll have the same problem in the future..

Oh yeah, silly me never measured the carb size that I need.. Can someone tell me the correct size I need... Thanks for all your help guys... Scoot currently has 5300 on speedo...

[ce]

Check the diaphragm for leaks.

[speedracer]

USMARINE I feel your pain. I know you spent hours trying to resolve this issue but to no avail. Is your plug OK? A fouled plug will act up at higher speeds. Also what about the coil and cdi?

My wife is a lot like yours. She just can't imagine all the time I spend in the garage because of the scoot.

[ce]

If you adjusted your float wrong it won't work at WOT. Adjust it to allow more fuel.

You have a 30mm carb.

[Alleyoop]

Are you sure it is not getting hot and seizing on you. When it starts to Bog have you tried backing off the Throttle a little and see if it comes back to life. If it does then it is a Fuel Delivery problem. In that case it could be the Float is set to low shutting off the fuel to early.
Alleyoop

[widehide]

Did you look at the fuel filter, you may have more than one, be sure you have a clean, new filter mounted in the correct direction. Also It is possible the fuel cap is not allowing proper venting and can cause a vacuum in the tank. Try riding with the fuel cap loose or off. When this happens immediately stop and check the bowl drain, open it to see if fuel runs out from the Carb Bowl.

[usmarine112]

wide hide, yes I do have fuel running out of the carb bowl when I drain it and the fuel cap is tightly on.... That's normal correct??? I will try to ride with the fuel cap loose or off... I heard someone talk about this vacuum in the tank problem before... Is there a remedy for this or do I just ride with the cap not so tight??

[usmarine112]

Just a thought, after reading several postings of other topics related to the carb, I saw a picture of one of JR's postings of a carb... I noticed on the side of the gas port of the carb, just below the enricher, there was a plastic or rubber cover on one of the ports... I looked at mine and did not see that, just an exposed brass port... Is there supposed to be a cover on it?? While searching for new carbs, I also noticed there was something covering that port.. What is it for and does it need to be covered?? I can't remember if it ever had one on it to begin with and maybe it fell off... Anyway, please let me know what this port is for and if it should be covered.. Thanks for the help and I'm going to try the gas cap technique tomorrow..

[Alleyoop]

Usmarine112,
Put up a picture of the Left Side of your Carb. Or does it look like this one:
Anyway some scoots tank have a hose coming from the top by the Cap and some have a Filter attached to the end of them. Some have the hose going to a canister to trap the fumes. Others just have a tiny hole on top of the Gas Cap which can get clogged with the paper element they put inside and those you can clean out the logging paper element out so it can breath.

But you should try the following:

This Trick is very accurate to tell you what kind of fuel delivery problem you are having.

1. When it starts to stumble or bog, Back off the Throttle a little and Hold It There:
a. If it Speeds up and or Settles Down you are running LEAN.
b. If it Stumbles and Then Settles Down you are running RICH.
c. If it Settles down then IF you crank Open the throttle to Wide Open Throttle and it Speeds up and runs good for a little bit THEN Bogs Again. That is a good sign that your Fuel Bowl is NOT filling up to the Proper Level. Which could be several things, Wrong Fuel Filter(to big), Float is adjusted to Low, Fuel Pump is not keeping up, Tank Not Venting.

Alleyoop

[widehide]

Great info, both of my 257cc scooters have never been able to run over 65 mph wide open. I will need to look at my carb diaphragm. I could use more speed. If I remember correctly you also drilled a small hole in the top of your gas cap to prevent a fuel tank vacuum lock. Adios

[usmarine112]

I am looking at the two plastic pieces that sandwich together... If I take my fingers around it, it spins freely... Is it supposed to be spinning or is it supposed to be tightly in place... Also, where do I put the blue silicon??? Is it on the top or the ring around it touching the diaphram and also on the bottom... basically filling the gaps of where it sandwiches??? Or do I try to separate the two rings and then put silicon around them sandwiching it back together??? Please help, I'm thinking this is where the problem might be... Thanks!! Also, the gas cap on or off did not make a difference...

[usmarine112]

Okay, I think I figured it out...again....lol..... I just looked at the tech section and was just curious about the spark plug area.. Maybe at high rpm's my coil wasn't working.. So I took the bike apart and took the coil off the plug... I had an extra plug laying around and hooked it up to see if I saw a spark.. I saw a spark for a split second and then nothing... Cranked it again and same thing... I played around at the coil connectors and all was tight and looked pretty damn good... But here it is, I was tugging at the coil just above where the cap goes over the plug and all of a sudden with the slightest and I mean slightest tug...it separated.. I looked at the wire that came out of the plug and all the little gold colored wires looked as if they separated a long time ago!!! I gues it was just connected with a little pressure and when I would cruise at 65mph + it would not be a good connection... So Jr or anyone else, could this have been giving me the problem??? I go back to day one with the scoot when it had 0 miles on it... I remember doing a PDI and replacing the plug, I'm pretty sure that I didn't tug the cap off the plug by the cap, instead by the wire leading to the cap... This is where I probably began separating it... Because I do recall that in the beginning, after cruising several miles, I would get a slight loss of throttle response but not as bad as it is today... And after replacing the next spark plug, I'm sure I pulled the wire again trying to remove the cap from the plug...thus separating it some more and throttle response / power was being lost even greater at cruising speeds... So, If this makes sense to anyone please let me know... I'm going to order a new coil.. Jr, do you know of a place to order one for the Linhai version?? I've seen some for the CF version and they look the same, would that work?? Thanks guys for all your help on everything... At least now I know how to completely take apart the scoot in no time!! lol....

[Alleyoop]

Usmarine112,
I believe you have found your cutting out. Good find and a simple fix at that. You can just get a New Cap and not the entire Coil. They only cost about $3.00 bucks or so. If you have a Dealer near you they would have them they are usually NGK caps they are good I got 4 of them last time I bought them. I always carry spares a CDI, Entire Coil, Spark Plug, Fuel Filter and Plug Cap.
Alleyoop

Here is the Coil Cap:
www.buggypartsnw.com/home?page=shop.product_details&flypage=flypage.tpl&product_id=210&category_id=19

[usmarine112]

Well, just to be safe I replaced the entire coil.... Still bogged at high rpm's... I did however feel a noticeable difference in acceleration with the new coil... So now my next move is just going to be to buy a new carb!! I've spent the last 3 days and about 20+ hours on this issue and still nothing... My wife is just starting to laugh...lol... It looks like this week I'll be spending some money on gas for my car to go to work.. This scoot has saved me $35 a week on fuel... Hopefully I can get this thing running good or better with the new carb.. I'll keep you posted.. Thanks again to you all with your help / suggestions..

[usmarine112]

Do these carbs have an Air/Fuel Mixture screw as seen on the other carb??? I've also ordered some high quality vacuum lines (I was using goodyear fuel lines) and will be connecting the vacuum lines as you instructed on an earlier posting / diagram.. I will hook the top port of the maniford to the fuel pump alone and then all the other crap to the other port.. Hopefully this will make a difference also. I've also been thinking that the cold air outside 50 degrees and sometimes dropping to 40 degrees could be causing my engine to bog?? I work graves so I mostly run the scooter at night... It gets a little cooler here in the desert about this time of the year (live in AZ)..