Chinese Scooter Club Forum Index

Home | Forum | Arcade

Moped slows down until it cuts out
Goto page 1, 2  Next
 
Post new topic   Reply to topic    Chinese Scooter Club Forum Index -> Body and Electrical Workshop
View previous topic :: View next topic  
Author Message
Mike91



Joined: 22 Mar 2011
Posts: 26
Karma: 0


PostPosted: Tue Mar 22, 2011 9:35 pm    Post subject: Moped slows down until it cuts out Reply with quote

Hey all, I bought my first moped 2 years ago and it's been running fairly well appart from a few replacement parts such as bulbs and spark plugs. Recently I had a problem with my throttle grip, the housing that holds the throttle cable in place cracked so the cable often detached so I replaced it with a throttle grip from a similar moped and that seems to be working fine.

Current Issue: I can pull the throttle all the way back and it will reach about 30 then it slowly edges down to about 10 - 15 mph until I get to the point where I have to pull over because there are several cars behind me trying to overtake at the worst possible times. I'd also like to note I have trouble keeping it running on idle, it cuts out constantly and I often have to push it to the side of the road to kick start it because the electric start just won't get it running. Before I was having issues with the throttle grip/cable I was getting up to 45MPH out of it on a straight but recently it's running condition has deteriorated. Today I replaced the petrol filter as recommended by 2 friends, I also drained my petrol tank and took off the part that connects the hose's to the tank and cleaned the filter inside, I also blew through each hose to check for blockage. My farther mentioned to me that the petrol filter should be getting more petrol flowing than it currently was, at the moment it seems to drip into the filter rather than flow. The majority of people I've asked about it suggested it was fuel starvation and as I'm not very mechanically minded I've done my best to work with their suggestions, I can't get a garage to look at it as most of them seem to have hate towards chinese mopeds.

Here are a few details about my moped, what has been done to it and and the majority of replacement parts added to it. I'd also like to add I'm not very good with engines or mechanical things in general although I've come to know my way around the moped and I can confidently change parts and tweak certain things.

Make and Model: DIRECTBIKE DB50QT-5 50cc Motor Scooter
Engine: 50cc 4-stroke
Modifications: Derestricted from the carburettor (There was a screw or bolt attached to the cap of the carburettor, the guy at the garage used a hack saw to removed a plastic washer along with a few MM of the screw/bolt itself)
Replacement parts: 2 new spark plugs, new front bolt, new casing/housing for rear lights including indicators, 2nd hand throttle grip from a similar moped and today I replaced the petrol filter.
Condition: I've come off the moped once and of course it's been knocked over a few times over the last few years but the only noticeable damage was to the casing.
Mileage: I'm not sure if the clock is in miles or kilometers but it reads 55000 so roughly 34k miles if it's in kilometers.

I hope I've provided enough information about my situation to get some suggestions rolling in and I appreciate anyone that takes their time to read my post and repsond to it.

Thanks, Michael.


Back to top
View user's profile Send private message
JDi



Joined: 08 Nov 2006
Posts: 3838
Karma: +146

Location: No longer a member

PostPosted: Tue Mar 22, 2011 9:53 pm    Post subject: Reply with quote

Sounds like the petcock is failing, you should get a good flow of fuel not a trickle. Swap it out.



_________________
No longer a member
Back to top
View user's profile Send private message
Mike91



Joined: 22 Mar 2011
Posts: 26
Karma: 0


PostPosted: Tue Mar 22, 2011 10:04 pm    Post subject: Reply with quote

Would I be right in saying that's the part that connects the "hose" to the petrol tank? If yes then I took that part out cleaned the filter between that and the tank and then blew through the 2 hose connectors and air seemed to pass through nicely. My dad checked it over with my earlier and we both couldn't figure out what the 2nd hose from the petrol tank was, the first one connects to the petrol filter I replaced and then to the carburretor. The 2nd hose leads directly to a part in the engine under the screw that adjusts the idle revs.


Back to top
View user's profile Send private message
JDi



Joined: 08 Nov 2006
Posts: 3838
Karma: +146

Location: No longer a member

PostPosted: Tue Mar 22, 2011 11:22 pm    Post subject: Reply with quote

The petcock is a vacuum operated fuel valve. Inlet manifold vacuum sucks on a diaphragm which allows fuel to flow. And it's either on or off - no half measures. Either fuel flows well, or it doesn't flow at all. If it's faulty then you get reduced fuel flow.

Connection wise, you have a fuel inlet from the tank, a fuel outlet to the carb, and a vacuum pipe to the inlet manifold between carb and head.



_________________
No longer a member
Back to top
View user's profile Send private message
Mike91



Joined: 22 Mar 2011
Posts: 26
Karma: 0


PostPosted: Wed Mar 23, 2011 12:24 am    Post subject: Reply with quote

Ok, thanks for your response I'll take a look at that first thing tomorrow, would you know if it's a standard part of would it vary from moped model?


Back to top
View user's profile Send private message
Scootin
Moderator


Joined: 09 Oct 2006
Posts: 7236
Karma: +168

Location: St. Johns MI USA

PostPosted: Wed Mar 23, 2011 2:27 am    Post subject: Reply with quote

Pretty standard I believe



_________________
2005 50cc Taishan Sport XT

2006 150cc Hitong SR-150 (2007-2010)

Member since October 2005
Back to top
View user's profile Send private message
NOLA Scott



Joined: 16 Apr 2009
Posts: 1426
Karma: +24

Location: NOLA, baby!

PostPosted: Wed Mar 23, 2011 2:21 pm    Post subject: Reply with quote

My first impression was petcock related as well. I'd actually look at the vacuum line attached to it. Almost sounds like a small leak. On takeoff, the hose has enough integrity to allow you to go, but as you vibrate along at speed, the hole opens a bit, you loose pressure on the petcock, and gas stops flowing. Stopping allows the hole to seat itself again when pressure is removed.

Faulty diaphragms and vacuum bladders did similar things to the water filtration systems I used to work on. That's why I thought of the vacuum line first.



_________________
I can fill up for under $3. What's that SUV take?
150cc Velocity Eagle Style.
50cc NST/Shenke/Jonway/insert brand here on the lam.
Back to top
View user's profile Send private message
Mike91



Joined: 22 Mar 2011
Posts: 26
Karma: 0


PostPosted: Wed Mar 23, 2011 5:45 pm    Post subject: Reply with quote

Ok, I've spent pretty much the whole day trying to fix my moped. I've cleaned all the parts, changed the oil and filtered the petrol to remove any crap that may have found its way into the petrol tank. I went to my local scooter dealership and purchased a petcock which to my suprise is exactly the same as the one that I replaced it with. I put everything back together and I must say if anything the peformance has worsened so I believe that rules out the petcock and the petrol filter. I don't think it's the actual hose leading to the vaccum as I checked all of them for wear and tear, despite the condition of the rest of the moped the hoses seem to be in good condition so under your suggestion I'd have to agree more towards the vaccum itself rather than the parts leading from it.

I'm gonna take a fresh look tomorrow and hopefully I'll find the cause, if it's not the vaccum are there any other suggestions to what it might be?

Thanks for your time and input, Michael.


Back to top
View user's profile Send private message
IanWalton



Joined: 20 Aug 2010
Posts: 575
Karma: +7


PostPosted: Wed Mar 23, 2011 6:40 pm    Post subject: Reply with quote

impressions are still fuel related.

have you verified that you are getting a good fuel supply to the carb ?

by that I mean removing the petrol pipe to the carb and dropping it into a bowl of some sort and removing the inlet manifold vacuum pipe and gently sucking on it ?

if you suck on that inlet manifold pipe, do you need to constantly suck on it or can you suck once strong and hard and then plug the hole with the tip of your tongue and the vacuum holds ?

if you dont get a constant strong fuel flow into the bowl doing this, then you need to look at a fuel line blockage.

if you have to constantly suck on the inlet manifold pipe then you are looking at a split / degraded vaccum system issue.

there are other things that may be at fault, but if we can rule those out first Smile


Back to top
View user's profile Send private message
TJ



Joined: 22 May 2008
Posts: 1195
Karma: +43

Location: Devon/Cornwall UK

PostPosted: Wed Mar 23, 2011 7:07 pm    Post subject: Reply with quote

you can bypass the vacuum petcock directly and block off the vacuum tube for uninteruupted free-flowing goodness Smile



_________________
'99 Kawasaki KLR 250 FOR SALE!
'01 Suzuki GSF600S Bandit :D

"Hrrbleflrg Bunnerwaffles." - Jaspar
Back to top
View user's profile Send private message Send e-mail Visit poster's website MSN Messenger
Mike91



Joined: 22 Mar 2011
Posts: 26
Karma: 0


PostPosted: Wed Mar 23, 2011 7:33 pm    Post subject: Reply with quote

I haven't carried out any tests like that, no, But I'll certainly give that a try and post the results, this won't be until tomorrow though as I lack a garage with sufficient lighting to do something like that right now. Looking at the fuel filter that sits between the carb and the fuel tank, I can see that it is usually a good 3/4 full most of the time. I'd like to add that I've noticed a noise that sounds like a piece of plastic against a fan as it spins. Also I've noticed a rather thick tube sitting at the bottom of the case near the kick start that looks as if it should be connected to something but I cannot find anything that looks like it should connect to in reach, unless a part of the tube has come loose as I've been riding at some point. I can't really say I've given that area enough attention to say if it should or shouldn't be connected to something.


Back to top
View user's profile Send private message
Mike91



Joined: 22 Mar 2011
Posts: 26
Karma: 0


PostPosted: Wed Mar 23, 2011 9:46 pm    Post subject: Reply with quote

Could it be something as simple as the spark plug causing the problem? From my understanding the spark plug ignites the fuel then continues to ignite it as the engine is running, if the spark is strong enough to start the engine but too weak to handle the fuel flow, or if it even cuts out constantly could this cause the symptoms I've described? It may have been a little ignorant of me to not have checked the spark plug but a new one had not long been fitted so I kinda ruled that out as a cause perhaps prematurely. From what I can tell the fuel is flowing so that also leads me to believe the carb could also be the issue. Maybe a build up of stale fuel is preventing the carb from operating smoothly?


Back to top
View user's profile Send private message
Mike91



Joined: 22 Mar 2011
Posts: 26
Karma: 0


PostPosted: Thu Mar 24, 2011 4:30 pm    Post subject: Reply with quote

Today I checked and cleaned the spark plug but to be sure that wasn't the problem I replaced it with a new one and there is no noticeable impact on performance. I did your recommended fuel flow test, I removed the hose from the carb and left it hanging inside a large bottle and then sucked on the hose that was connected to the vaccum. A short soft suck on the hose resulted about half a litre of petrol. I've had a suggestion that it may be the coil, I'm unsure what part that is maybe you guys could shed some light on the matter and help me further rule out the cause.

Thanks for your time, Michael.


Back to top
View user's profile Send private message
IanWalton



Joined: 20 Aug 2010
Posts: 575
Karma: +7


PostPosted: Thu Mar 24, 2011 7:33 pm    Post subject: Reply with quote

ruled out fuel flow issues.

so, next. have you checked the breather pipe from the valve cover ? is this in good condition and working ? when engine is running you should be able to feel air flow.

coil is an integral part of the plug lead, trace the plug lead back to its source and thats the badger, could be breaking down under stress, equaly, the lead could be too, cheap enough to replace.


Back to top
View user's profile Send private message
Mike91



Joined: 22 Mar 2011
Posts: 26
Karma: 0


PostPosted: Thu Mar 24, 2011 10:55 pm    Post subject: Reply with quote

Thanks for your reply, I have to say I'm not too sure what the breather pipe is. Could you shed some light on the matter, obviously I need to know what I'm looking for before I can actually find it. As far as the coil and the leads attached to it are concerned, is there any way to test them for integrity? Like you said, it's cheap enough to replace but I've spent quite a bit in the last few days trying to get this thing in a safe operational state and being a student I have limited funds that I can pump into this job.

Thanks for your time, Michael.


Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Chinese Scooter Club Forum Index -> Body and Electrical Workshop All times are GMT
Goto page 1, 2  Next
Page 1 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2002 phpBB Group
Theme created by Vjacheslav Trushkin
Effex-Media Web Resources

Scooters | Scooter Insurance | Moped Insurance | Direct Bikes | Direct Bikes Reviews


Free Forum Free Top Site List
Make this Forum Ad-Free




31170788