Resend my activation email : Register : Log in 
BCF: Bike Chat Forums


Running rich, help me diagnose

Reply to topic
Bike Chat Forums Index -> The Workshop
View previous topic : View next topic  
Author Message

Deropke
L Plate Warrior



Joined: 09 Jun 2021
Karma :

PostPosted: 02:58 - 09 Jun 2021    Post subject: Running rich, help me diagnose Reply with quote


The bike
: Derbi Terra 125cc

Symptoms:

    Running rich (black sparkplug)

    Hesitates initially on throttle often leading to a stall

    Sometimes doesnt start at all, not even bump start. (Now fixed, was ripped manifold intake hose)

    Severly poor performance below 4k rpm

    Poor performance above 7k (redline is @10k, but it struggles to reach it)

    Sometimes idles at higher rpm with no hesitations saddly everytime this has happened the bike was in pieces unable to ride to test performance.


Other notes

    Bike equiped with automatic choke

    Carb only comes with 1 screw to adjust mixture which is slightly rounded, you can screw it, but cant unscrew, seems like it's fully screwed as despite having grip clockwise I wasnt able to move it, but then shouldnt bike not able to start at all if it's fully in


Last edited by Deropke on 21:04 - 09 Jun 2021; edited 1 time in total
 Back to top
View user's profile Send private message You must be logged in to rate posts

jaffa90
World Chat Champion



Joined: 06 Apr 2016
Karma :

PostPosted: 10:05 - 09 Jun 2021    Post subject: Reply with quote

Sounds like the carb needs servicing and check that the exhaust system as well.
 Back to top
View user's profile Send private message You must be logged in to rate posts

Hong Kong Phooey
World Chat Champion



Joined: 30 Apr 2016
Karma :

PostPosted: 10:19 - 09 Jun 2021    Post subject: Reply with quote

https://www.fowlersparts.co.uk/parts/5701280/terra-terra-terra-e3-terra-adventure-e3-2007-2009-terra-e3-terra-adventure-e3-all/carburettor

Carb is still available, some individual parts too, but I'm guessing the pilot screw is not available as an individual part. If that's been butchered then maybe the float height is also wrong.

You might be able to get a Chinese knock off, not sure how good it'll be but at £181 for the full carb, versus parts and labour on fixing there's probably not much in it if you split the difference.
____________________
'81 CG125, '97 FZS600 : '99 CBR600F4, '09 KTM RC8
 Back to top
View user's profile Send private message You must be logged in to rate posts

Easy-X
World Chat Champion



Joined: 08 Mar 2019
Karma :

PostPosted: 11:09 - 09 Jun 2021    Post subject: Reply with quote

Mice in the airbox Wink
____________________
Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter
 Back to top
View user's profile Send private message You must be logged in to rate posts

Robby
Dirty Old Man



Joined: 16 May 2002
Karma :

PostPosted: 14:26 - 09 Jun 2021    Post subject: Reply with quote

The mixture screw only affects idle really, so that is not the source of your problems. The fact that the screw is chewed up, and that the bike is a 125, tells us what someone has fiddled with the carb before to try and make it go faster.

So, carb out, strip and clean, make sure the float height, needle height and jetting are the same as what the factory manual says they should be. Work on getting the mixture screw out and replace it, and make sure that the choke flap isn't just closed all the time.
 Back to top
View user's profile Send private message You must be logged in to rate posts

Deropke
L Plate Warrior



Joined: 09 Jun 2021
Karma :

PostPosted: 21:01 - 09 Jun 2021    Post subject: Reply with quote

Robby wrote:
The mixture screw only affects idle really, so that is not the source of your problems. The fact that the screw is chewed up, and that the bike is a 125, tells us what someone has fiddled with the carb before to try and make it go faster.

So, carb out, strip and clean, make sure the float height, needle height and jetting are the same as what the factory manual says they should be. Work on getting the mixture screw out and replace it, and make sure that the choke flap isn't just closed all the time.


Yeah, bike is a mess. also perhaps any of you know where "13" hose would go to. It has been sealed by previous owner, could be potentially culprit ?https://www.fowlersparts.co.uk/parts/view/863212

It seems like this bike had air problems as airbox been drilled and I just fixed the vacuum leak (the manifold intake hose was ripped, but this only fixed bike not able to start.
 Back to top
View user's profile Send private message You must be logged in to rate posts

Easy-X
World Chat Champion



Joined: 08 Mar 2019
Karma :

PostPosted: 23:25 - 09 Jun 2021    Post subject: Reply with quote

I'd guess the '13' pipe is a breather pipe - a vent from the engine/gearbox/crank (depending where it's attached) not something that should be blocked off as vents excess pressure. It'll likely consist of oil soaked air so either vent straight to atmosphere (and kill all the asthmatic kittens) or any old rubber hose that will fit and route it back to the airbox as it should be. Any leftover hydrocarbons can then be reburnt in the engine.

That being said do you mean the breather has what looks like a little pod filter to vent through rather than actually blocked? It's one of those typical, pointless mods ppl do.
____________________
Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter
 Back to top
View user's profile Send private message You must be logged in to rate posts

Robby
Dirty Old Man



Joined: 16 May 2002
Karma :

PostPosted: 12:51 - 10 Jun 2021    Post subject: Reply with quote

Looks like Easy is right. Typically there is a vent hose from the crankcase (often on top of the gearbox, behind the cylinder) into the airbox. This serves to even out crankcase pressure, and to direct air out of the crankcases into the engine to be burnt. This air contains a bit of exhaust that has blow past the piston, and bit of oil vapour, so you shouldn't be venting it to atmosphere.

I'm assuming the hose is still connected to the airbox and blocked off, but not connected to the engine. Find the stub on the engine that it connects to and plug it back in.

If the airbox was drilled and the inlet manifold stub was broken, then this bike has the textbook signifiers of someone trying to "tune" it. Carb needs to come out for a proper inspection, but also inspect any hoses or rubbers that it connects to, they may also be torn and need replacing.

Chances are that it has the wrong size main jet in. That's the go-to option for children that know nothing about tuning engines. If you can find someone that sells a carb rebuild kit, it may be worth just buying one and replacing all the bits.

Other hint that the person doing it didn't know anything - they tend to try to increase fuel flow in the hope that will make a difference. With most mixture screws, you screw it in for less fuel and out for more fuel. Standard setting is usually around 1.5-2 turns out.
 Back to top
View user's profile Send private message You must be logged in to rate posts

MCN
Super Spammer



Joined: 22 Jul 2015
Karma :

PostPosted: 18:37 - 10 Jun 2021    Post subject: Reply with quote

Air filter plugged (mouses).

Carbonaterorer worn. Needles/Jets.

Mixture setting too rich.
____________________
Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts
  Display posts from previous:   

Post new topic   Reply to topic    Bike Chat Forums Index -> The Workshop All times are GMT + 1 Hour
Page 1 of 1

 
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
You cannot attach files in this forum
You cannot download files in this forum

Read the Terms of Use! - Powered by phpBB © phpBB Group
 

Debug Mode: ON - Server: birks (www) - Page Generation Time: 0.10 Sec - Server Load: 0.17 - MySQL Queries: 17 - Page Size: 62.62 Kb